Sci & Educ (2009) 18:469–501
DOI 10.1007/s11191-008-9149-3
Gaia Theory in Brazilian High School Biology Textbooks
Ricardo Santos Do Carmo Æ Nei Freitas Nunes-Neto Æ Charbel Niño El-Hani
Published online: 21 February 2009
Springer Science+Business Media B.V. 2008
Abstract Gaia theory proposes that a cybernetic system including the biota and the
physicochemical environment regulates environmental variables at a global scale, keeping
them within a range that makes Earth inhabitable by living beings. One can argue that this
theory can play an important role in school science, since it bears upon current environmental problems, contributes to cross-disciplinary learning, and may help students
understand the nature of science. Nevertheless, discourses about Gaia include both scientific and non-scientific ideas, and, consequently, this theory has been seen as
pseudoscience, or even antiscience, as an unwarranted view, entangled with mysticism. But
an informed view about the contributions and risks associated with Gaia as part of science
education depends on a general analysis about the treatment of this theory in school
knowledge. Here, we offer the first analysis of this sort, critically evaluating how Gaia is
addressed in a representative sample of Brazilian textbooks (n = 18). We present data
about the presence or not of Gaia theory among the contents covered by the textbooks, the
presence of the claim that Earth is living, whether and how they use analogies to justify this
claim, the discussion of evidence for and against Gaia, and the treatment of its relevance to
current issues. Gaia theory is explicitly addressed in ca. 39% of the analyzed textbooks.
There is a general script that the textbooks that explicitly name the theory follow when
discussing Gaia. First, they argue that life affects the environment, and support this
argument by means of examples, then, explain what the Gaia theory proposes, discuss
evidence in favor either of the idea that Earth is living or Gaia theory in general, introduce
one or more analogies to justify the claim of a living Earth, and, finally, offer remarks on
the current importance of Gaia. Three analogies used by Lovelock himself were found in
R. S. Do Carmo C. N. El-Hani (&)
Research Group on History, Philosophy and Biology Teaching, Department of General Biology,
Institute of Biology, Federal University of Bahia, Salvador, Brazil
e-mail: [email protected]
R. S. Do Carmo
e-mail: [email protected]
N. F. Nunes-Neto C. N. El-Hani
Graduate Studies Program in History, Philosophy and Science Teaching, Federal University of Bahia,
and State University of Feira de Santana, Salvador, Brazil
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the analyzed textbooks, Gaia as a superorganism, the analogy between Gaia and a redwood
tree, and between Gaia and the Greek goddess of Earth. The most frequent was the
superorganism analogy. The idea of a control system including the biota and the physicochemical environment and any discussion about theoretical and empirical advances
resulting from Gaia theory were absent from most analyzed textbooks, which focused
mainly on the claim of a living Earth. Although Gaia can contribute to the understanding of
environmental issues, the treatment found in most of the analyzed schoolbooks puts so
much emphasis on the idea that Earth is living and is so close to an animistic understanding
of the Earth system that it is likely that it will bring no true contribution to the development
of adequate conceptions about that system and the connections between human activities
and the environmental crisis.
1 Introduction
Gaia theory1 bears upon current and consequential environmental problems, such as global
warming, and, accordingly, its connections with the now prestigious Earth System Science
(ESS) have been acknowledged by books on this field, such as Jacobson et al. (2000),
despite complaints about the fact that Gaia has been often neglected by scientists working
with ESS (Margulis 2004; Tickell 2004). In their book directed towards ESS researchers,
teachers, and students, Jacobson and colleagues make several prestigious references to
Lovelock and Gaia (see, e.g., Jacobson et al. 2000, pp. 12–13), recognizing that they
offered important orientations for the construction of an integrated view of the Earth
system:
The task of integrating the spheres and the biogeochemical cycles emerges as a
necessary if daunting challenge. Disciplinary science has provided little in the way of
precedent for us, although substantial guidance is provided by the pioneers like
Arrhenius, Vernadsky and Lovelock who presaged these global developments.
(Jacobson et al. 2000, p. 11)
That Gaia can be seen as an integral part of the understanding of the Earth system now
under construction is reinforced by an examination of The Amsterdam Declaration on
Global Change, which opens with the following statement:
1
Gaia is dubbed both as a hypothesis and a theory in the literature. In its initial stages of development,
Lovelock himself referred to Gaia as a hypothesis, but more recently he has been also calling it a theory. In
our view, a misconception about the nature of hypotheses and theories underlies this change in vocabulary.
It seems that Lovelock changed from calling Gaia a ‘hypothesis’ into calling it a ‘theory’ due to the idea of a
progressive linearity according to which hypotheses can become theories, as evidence for them accumulates
(see, e.g., Lovelock 1995). As it is well known, however, theories and hypotheses are distinct forms of
knowledge and do not turn into each other. In our view, Gaia should be systematically treated as a theory,
i.e., a set of claims about the empirical world related in a systematic manner and playing the role of
explaining and predicting phenomena or patterns observed in nature by elucidating processes or mechanisms
responsible for their production or causation. Moreover, as a theory, Gaia should also show heuristic power,
being capable of guiding investigations conducted by a community of practicing researchers. We conceive a
hypothesis, in turn, as an explanation for a specific phenomenon or pattern, which should lead to predictions,
then submitted to empirical test. In this paper, we will use the expression ‘Gaia theory’ throughout, limiting
the use of ‘hypothesis’ to quotations of other authors.
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Gaia Theory in Brazilian High School Biology Textbooks
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The Earth System behaves as a single, self-regulating system comprised of physical,
chemical, biological and human components. The interactions and feedbacks
between the component parts are complex and exhibit multi-scale temporal and
spatial variability. (Moore III et al. 2001, p. 1)
This is a statement remarkably similar to claims we find in works related to Gaia. We can
thus appreciate Lovelock’s amusement when he observed:
I wonder how many of those who signed the declaration knew that they were putting
their names to a statement of Gaia theory. (Lovelock 2004, p. 1)
In our view, Gaia theory has an important role to play in school science, at several
educational levels, as a result of its environmental bearings, and also other features and
contributions (see below). It comes as no surprise to us, then, that this theory can be
already found in textbooks. As just an example, consider, for instance, its presence in the
textbook ‘‘Environmental Science: A Global Concern’’ (Cunningham and WoodworthSaigo 1995), which intends to offer a comprehensive presentation of environmental science
for non-science majors, at the college or advanced placement high school level. But, as we
can see in a review of this textbook, Gaia raises grave concerns as a school subject:
The so-called Gaia hypothesis is not so much a hypothesis as a body of conjecture. It
has a basis in scientific observations, but the observations have been extrapolated to
support unscientific conclusions and have become entangled with cocktail-party
mysticism. This seems to be the reason why the Gaia conjecture, although it has
nothing to contribute to a beginner’s understanding of environmental science, has
shown up in various environmental-science texts. It is trendy, and some writers
evidently think that its overtones of supernaturalism will make it appealing to
readers. (Rodel 1995)
This review interests us because it clearly illustrates what we take to be a central tension
when considering the prospects of introducing Gaia as a school content. Rodel denies that
Gaia can play any role in promoting students’ understanding of environmental science. We
believe, however, that Gaia can indeed contribute to the understanding of environmental
issues, even though it should be surely treated as a controversial theory. Even a strong
critic of this theory, such as James Kirchner recognizes that ‘‘Gaia’s proponents have done
a great service by championing the need to consider the Earth as a coupled system’’
(Kirchner 2002, p. 404). Nevertheless, it can really be the case that, as addressed in
schoolbooks, Gaia can end up being not only worthless, but even hazardous to students’
and teachers’ conceptions about environmental matters. In fact, we cannot come to a
conclusion about whether Gaia is to be part of school science or not without an informed
view about how it is represented in school knowledge, including its treatment in schoolbooks. We performed, however, extensive bibliographical surveys2 and could not find any
general analysis about how Gaia is addressed in textbooks (or, else, in science education,
generally speaking) at any educational level or country. Therefore, the present paper offers,
as far as we can know, the first analysis of this topic.
We do not intend to offer here a general review of the treatment of Gaia in textbooks all
around the world. Rather, we intend to critically evaluate whether and how Gaia is
2
The surveys were made through ERIC search tool (http://www.eric.ed.gov—Education Research Information Center) with ‘Gaia’ as a keyword, and ISI Web of Science databases with ‘Gaia’ and ‘teaching’ (and
derivatives) or ‘education’ (and derivatives) as keywords. We also performed Google searches with the
combinations of keywords ‘Gaia and education’ and ‘Gaia and teaching’.
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addressed in a representative sample of Brazilian textbooks. This sample is quite representative of the universe of Brazilian high school textbooks, since we analyzed all
materials submitted by publishing companies to the Brazilian National Program for High
School Textbooks (El-Hani et al. 2007), a huge governmental program that includes a
critical evaluation of these materials and purchases textbooks for students all over the
country (reaching at 2007 the figure of 9.1 million textbooks distributed to 6.9 million
students at more than 15,000 high schools3).
1.1 Gaia Theory
Preliminary ideas about a self-regulating Earth system were first introduced by the English
scientist James Lovelock in a little known paper given in 1968 at a meeting of the
American Astronautical Society. Gaia theory itself was initially presented to the scientific
community in 1969, in a conference held in Princeton about the Origins of Life on Earth
(Lovelock 2000a). A more developed version of the theory was addressed in a letter
entitled ‘Gaia as seen through the atmosphere’ sent by Lovelock (1972) to the editors of the
journal Atmospheric Environment. The initial sketches of the theory grew out of Lovelock’s researches in co-operation with philosopher Dian Hitchcock, about the detection of
life in other planets, for NASA (National Aeronautics and Space Administration) during
the 1960s. Gaia theory was considerably developed in 1974 and subsequent years by
Lovelock’s collaboration with North-American microbiologist Lynn Margulis, who,
according to Lovelock (2001, p. 258), ‘put flesh in the bare bones of my skeleton of Gaia’.
They published papers in Icarus (Margulis and Lovelock 1974), Tellus (Lovelock and
Margulis 1974a), and Origins of Life and the Evolution of the Biosphere (Lovelock and
Margulis 1974b), where they proposed that living beings are able to profoundly change
their environment in order to keep physicochemical variables in a state adequate for
themselves.
In its initial stages of development, the theory was harshly criticized by the scientific
community. Its scientific status was often put into question (Postgate 1988; Kirchner 1989,
1993). Ideas related to Gaia—some but not all of them indeed advocated by Lovelock—
were enthusiastically received, however, by spiritualist and environmentalist groups,
becoming an integral part of so-called ‘new age philosophy’ (e.g., Badiner 1990; Sahtouris
2000). In particular, those groups were attracted by Lovelock’s most controversial statements, such as the claim that Earth is a living system, while not paying much attention to
other central ideas of the theory, such as the proposal of a cybernetic system that could
regulate environmental variables at a global scale. As Gaia became more and more
accepted by those groups, the scientific community became increasingly suspicious of its
claims about the functioning of the Earth system (see, e.g., Tickell 2006).
Since the 1980s, and particularly in the 1990s, the theory grew to be more and more
accepted by the scientific community. Currently there are many researchers who attempt to
develop and test Gaia theory, contributing to its increasing scientific respectability, particularly with regard to its potential input to studies and debates about ongoing climate
change (see, e.g., Schneider et al. 2004). Nevertheless, that there is remaining suspicion
about Gaia is indicated by the fact that many papers published by authors associated with
Earth System Science (ESS) do not refer to Gaia (e.g., Johnson et al. 1997; Moorcroft
3
See http://portal.mec.gov.br/seb/index.php?option=content&task=view&id=648&Itemid=666, for more
information on the Brazilian National Program for High School Textbooks.
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2006. See Margulis 2004; Tickell 2004, for critiques of this situation), even though ESS
clearly works with concepts closely related to this theory (see above).
Today, Gaia is supported by a significant body of evidence (e.g., Lovelock and Lodge
1972; Charlson et al. 1987; Lovelock 2000a), and this certainly plays a role in boosting its
acceptance by the scientific community. Moreover, the construction of increasingly
complex models based on mechanisms proposed by Gaia has significantly contributed to
the recognition of the theory, since Watson and Lovelock (1983) developed their ‘Daisyworld’ model (see also Lenton and Lovelock 2000).
The term ‘Gaia’ designates both the theory and the physical system it intends to
describe and explain. This is a cybernetic system that can be defined as
… a thermodynamically open system at the Earth’s surface comprising life (the
biota), atmosphere, hydrosphere (ocean, ice, freshwater), dead organic matter, soils,
sediments and that part of the lithosphere (crust) that interacts with surface processes
(including sedimentary rocks and rocks subject to weathering). (Lenton and van
Oijen 2002, p. 684)
Generally speaking, Gaia theory can be conceived as a theory about the functioning of
Gaia systems (cf. Lenton 2004), which are part of planetary systems with abundant life
(including Earth and any other putative planet that may harbor life).4 According to this
theory, the coupling of organisms and their environment is strong enough to have greatly
influenced the way the life-environment system evolved on Earth. From this perspective,
biological evolution and the evolution of the physicochemical environment are not two
independent processes, but, rather, two aspects of the same process. As Lovelock (1990, p.
100) writes, Gaia is ‘‘the theory of an evolving system—a system made from the living
organisms of the Earth, and from their material environment, the two parts being tightly
coupled and indivisible’’. Gaia theory states that the connections between organisms and
their environment constitute a huge number of negative and positive feedback loops, which
form, in turn, a highly complex network. This network is a cybernetic adaptive control
system (the Gaia system), and it leads to the regulation of environmental variables at a
global scale (temperature, atmospheric chemical composition, ocean pH and salinity,
among others). Consequently, these environmental variables are kept within a range that
makes Earth inhabitable by living beings. Their regulation is seen as an emergent property
of the Gaia system as a whole (Lenton 1998).
The claim that Earth is a living organism is the statement that most people undoubtedly
associate with Gaia and take to be Lovelock’s most significant and identifiable thesis.
Nevertheless, this appraisal of Gaia theory often entails a neglect of a very important idea
included in it, namely that of a coevolving cybernetic system involving the biota and the
physicochemical environment. Furthermore, there are signs that the idea of a living Earth
can be less central to the theory than most people think. Even though the formulation of
Gaia as a theory about a ‘superorganism’ capable of acting so as to optimize the conditions
for life on Earth is present in many of Lovelock’s writings and can be still found in recent
works of other authors, since the mid-1980s Lovelock himself has been oscillating between
this claim and the idea that Earth is quasi-living (see Lovelock 1985, 1986, 2000b). More
importantly, many researchers who ground their work on Gaia rarely or never use the idea
that Earth is living (e.g. Volk 1998; Wilkinson 1999; Kleidon 2002; Lenton and van Oijen
4
Hereafter, the expression ‘system Gaia’ refers to the particular system assumed to exist on Earth,
according to the Gaia theory, since it is the single representative of this category, in our current state of
knowledge.
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2002), and some even criticize this claim. Margulis herself once declared: ‘‘I reject Jim’s
statement ‘The Earth is alive’; […] I do not agree with the formulation that says ‘Gaia is an
organism’’’ (Margulis 1996, p. 54). Wilkinson (1999), in turn, argues that the most
accepted understanding of Gaia theory among scientists ascribes to life a significant regulatory effect on the global environment, but avoids the ideas of a superorganism and also
of optimization of physicochemical conditions.
We stated above that Gaia theory has an important role to play in school science. It is
time now to offer some arguments in support of this claim. With regard to environmental
issues, it is worth considering that predictions derived from Gaia theory play a role in
models about climate change and are, thus, relevant to the understanding of current
environmental problems. Based on Gaia theory, Lovelock and Lodge (1972) and Margulis
and Lovelock (1974) ascribed several functions to gases of biological origin, such as
methane, nitrogen dioxide, ammonia, including functions related to temperature regulation.
It was subsequently verified that compounds such as methane do play a role in mechanisms
involved in the regulation of physicochemical variables such as atmospheric oxygen
concentration and global average temperature (Watson et al. 1978, 1980). Even more
remarkable, however, are the consequences of a series of researches derived from Lovelock et al.’s (1972) claim that dimethyl sulphide (DMS), among other gases, was involved
in the mass transfer of sulfur from the oceans to the atmosphere and continents. It was
shown that some algae (in particular, Emiliana huxleyi, which has a wide distribution)
release DMS to the atmosphere, where DMS suffers oxidation and originates a non-sea salt
sulphate aerosol (NSS–SO42-), which came to have an unexpected role in the cycle of
water and, also, in the regulation of global temperature. A compound derived from the
oxidation of this salt acts as a cloud condensation nucleus, contributing to the condensation
of water vapor and, consequently, to the formation of clouds. The clouds, then, raise the
planetary albedo, and this results in a decrease of solar irradiation and, thus, in a decrease
of the production of DMS by the phytoplankton (Charlson et al. 1987). This idea is
currently known as the CLAW hypothesis5 and gave rise to an important research theme
known as ‘cloud-algae link’. It postulates the existence of a negative feedback loop
between oceanic phytoplankton and the global climate, and has been extensively investigated in recent years, particularly with regard to the importance of DMS to the global
biogeochemical cycle as well as to global warming (e.g., Andreae and Crutzen 1997; Simó
2001; Kloster et al. 2006). We currently know that the oceanic and atmospheric processes
involved in this feedback mechanism are complex (Kloster et al. 2006) and several aspects
of DMS oxidation in the atmosphere have not been well understood yet (Andreae and
Crutzen 1997; Malin 2006). Nevertheless, it is clear that the cloud-algae link has an
important role to play in models of global climate.
Gaia may also contribute to science education efforts aiming at cross-disciplinary
learning, since it combines in its formulation ideas from biology, geology, chemistry,
physics, etc. For instance, the role of DMS in both cloud condensation and the sulfur cycle
offers a good example of how Gaia theory can help in understanding a topic such as the
biogeochemical cycles in a manner which is both significantly integrated and gives
emphasis to the interconnection between living systems and physicochemical processes.
Finally, as a controversial theory under development, Gaia may also help students
understand some aspects of the nature of science (NOS) through an examination of its
convoluted history (see also Baker 1993).
5
From the initials of the authors of the paper in which it is presented, Charlson, Lovelock, Andreae, and
Warren.
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Nevertheless, Gaia theory entered spheres of human culture other than science, due to
its philosophical, metaphysical, and political connotations (Markoš 1995), and discourses
about Gaia include both scientific and non-scientific ideas (Haigh 2001). From this perspective, one can question the very idea of introducing it into school knowledge, as Rodel
(1995) does, since it might lead to unscientific conclusions. And, even if one takes the
position that it should be part of school knowledge, as we do, it is quite important to be
very careful about its treatment, since it might lead to an introduction of contents alien to
science education, such as new age philosophy, or, as Rodel writes, ‘‘cocktail-party
mysticism’’. After all, we consider that school knowledge is built by means of the didactic
transposition of academic knowledge and, thus, partly derives its legitimacy from a relative
proximity to the latter (Chevallard 1991; Lima-Tavares and El-Hani 2001; Guimarães et al.
in press).
2 Methods
Eighteen biology textbooks submitted by publishing companies to the Brazilian National
Program for High School Textbooks (El-Hani et al. 2007) constituted the sample analyzed in
this study (see Appendix 1).6 We built a protocol to standardize the analysis of the high school
textbooks. Among the topics included in the protocol, this paper focuses on the following:
Does the textbook explicitly address Gaia? Does the textbook discuss the relevance of Gaia to
current issues? Does the textbook claim that Earth or biosphere is living? Does the textbook
employ analogies to justify the claim of a living Earth/biosphere? Does the textbook present
evidence for or against the idea that Earth or biosphere is living or, alternatively, for or aganist
Gaia theory in general? The complete protocol is shown in Appendix 2.
The protocol was filled in for each textbook, providing the raw data for the analysis
reported here. To increase the reliability of the analysis, we made several independent
cross-checks of the raw data and interpretations. The nature and size of the sample of
analyzed textbooks give external validity to our study in relation to Brazilian textbooks,
but we cannot guarantee that our results can be extrapolated to textbooks from other
countries.
3 Results and Discussion
Among the 18 analyzed textbooks, only five explicitly addressed Gaia theory (T4, T6, T10,
T17, T18). Nevertheless, two textbooks (T11,7 T15) seemed to respectively ground their
treatment of some contents on Lovelock’s view about Earth as a living being (in particular)
and Gaia theory (generally speaking), even though they do not openly name the theory. This
can be a silence with meaning, since it is possible that the authors intended to avoid naming
such a controversial theory. Therefore, a first result of our study is that Gaia theory is
explicitly addressed in ca. 28%, or, if we also consider the two latter textbooks, in ca. 39%
6
In this program, textbooks are certified by an evaluation team gathered by the Ministry of Education (for
more details on the textbook evaluation, see El-Hani et al. 2007). The procedures and data discussed in this
paper are not part of that evaluation and, thus, represent independent results.
7
This is an Italian textbook adapted to use in Brazilian schools. In the sample of 18 analyzed textbooks, 16
were written by Brazilian authors, and only two were adaptations from textbooks from other countries. The
second one is T12, which is an adaptation of a North-American textbook.
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of the sample of analyzed textbooks. We consider this to be a significant representation of
Gaia theory in Brazilian high school biology textbooks, particularly if we take into account
that Gaia is not among the traditional contents covered by school knowledge in the country.
It is also interesting to notice that among the textbooks that address Gaia we find materials
that were both approved and disapproved by the critical evaluation that is part of the
Brazilian National Program for High School Textbooks (cf. El-Hani et al. 2007).
An overview of the first five textbooks shows that their approaches to Gaia are significantly similar, even though there are a number of differences between them. Tables 1
and 2 summarize our findings. We will organize the presentation of our results in four
parts: (1) a general analysis of the treatment of Gaia by the five textbooks that openly
address it; (2) a discussion of each of these textbooks in turn; (3) we will consider whether
and how analogies between Earth and other entities used by Lovelock to support his claim
of a living Earth appear in the seven textbooks mentioned above; (4) we will discuss
whether and how these textbooks address major theoretical and empirical advances
resulting from Gaia theory.
3.1 A General Script in the Treatment of Gaia by the Textbooks
There is a general, characteristic script that the textbooks that explicitly name the theory
follow when discussing Gaia, even though they explain it at different lengths. Initially, they
argue that life affects the environment. Then, they attempt to lend support to this argument
by means of examples. This is followed by an explanation of what the Gaia theory proposes. Subsequently, evidence in favor either of the idea that Earth is living (in T4, not
Earth, but the biosphere) or Gaia theory in general is discussed. Then, one or more
analogies are introduced to justify the claim of a living Earth (with the exception of T17).
And, finally, they comment on the importance of Gaia theory in the current state of affairs,
with an emphasis on environmental issues (with the exception of T4 and T10).
The claim that Earth or the biosphere is a single living entity is an important common
feature in four textbooks that address Gaia explicitly, with the exception of T17. Among
the two other textbooks that mention ideas related to Gaia, T11 also present that claim
(Table 2). Generally speaking, the textbooks do not give much attention to the description/
explanation of the cybernetic system postulated by the Gaia theory. A relevant difference
in their approach to Gaia is found in the evidence offered by each textbook to lend support
to the idea that life affects the environment, or to the claim that Earth is living (Table 2, see
also below).
3.2 Analysis of Textbooks that Openly Address Gaia Theory: T4, T6, T10, T17, T18
3.2.1 T6: Cheida’s Textbook
T6 differs from the other analyzed textbooks in two relevant features. First, instead of
addressing Gaia only in sections about ecology, as the other textbooks do, it also employs a
different context to discuss the influence of life over the environment and introduce ideas
related to that theory. In its first chapter—‘How everything began’—dedicated to the study
of the origins of the universe and life on Earth, the textbook explicitly explains Gaia theory:
[Life] originated approximately 3.8 billion years ago, as soon as Earth was sufficiently cool, and since then it has been evolving. Nevertheless, our planet shows a
high concentration of oxygen, a low concentration of carbon dioxide, and an average
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477
Table 1 Gaia theory in Brazilian high school biology textbooks
Textbooks
Does the
textbook
explicitly
address
Gaia?
Does the
textbook
claim that
Earth/
biosphere
is living?
Does the
textbook employ
analogies to
justify the claim
of a living Earth/
biosphere?
Does the textbook
present evidence for
or against the idea
that Earth/biosphere
is living or Gaia
theory in general?
Does the
textbook
discuss the
relevance of
Gaia theory to
current
issues?
T1
Amabis and Martho No
(2005)
No
No
No
No
T2
Borba and Cançado No
(2005)
No
No
No
No
T3
Borba, Crozetta and No
Lago (2005)
No
No
No
No
T4
Boschilia (2005)
Yes
Yes
Yes
Yes
No
T5
Carvalho (2005)
No
No
No
No
No
T6
Cheida (2005)
Yes
Yes
Yes
Yes
Yes
T7
Coimbra et al.
(2005)
No
No
No
No
No
T8
Faucz and
Quintilham
(2005)
No
No
No
No
No
T9
Favaretto and
Mercadante
(2005)
No
No
No
No
No
T10 Frota-Pessoa (2005) Yes
Yes
Yes
Yes
No
T11 Gainotti and
Modelli (2005)
Yes
No
Yes
No
No
T12 Laurence (2005)
No
No
No
No
No
T13 Linhares and
Gewandsznajder
(2005)
No
No
No
No
No
T14 Lopes and Rosso
(2005)
No
No
No
No
No
T15 Machado (2005)
No
No
No
Yes
No
T16 Morandini and
Bellinello (2005)
No
No
No
No
No
T17 Paulino (2005)
Yes
No
No
Yes
Yes
T18 Silva-Júnior and
Sasson (2005)
Yes
Yes
Yes
Yes
Yes
temperature of 13C, which make it ideal for known living beings, because of life
(T6, p. 9. All translations of textbook passages from Portuguese were made by the
authors of the present paper).
It also speculates that our planet would be similar to Mars and Venus if it did not have life:
If Earth did not have life, it would be like Mars or Venus. In these planets, the
average temperature is very high, there is almost no atmospheric oxygen, and the
concentration of carbon dioxide is extremely elevated. These environmental conditions are incompatible with terrestrial life. (T6, p. 9)
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Cheida (2005)
T6
No
Yes. It mentions the selfregulation capacity of the
biosphere to support the
claim that it is living
organism.
Does the textbook
discuss the relevance
of Gaia theory to
current issues?
Yes. It appeals to a list of Yes. ‘‘Gaia theory
Yes. ‘‘When we imagine Yes: the superorganism
Yes. ‘‘In this book
offers reasons for
properties or conditions
metaphor; Gaia and the
Earth as a gigantic
(The Ages of Gaia),
understanding
for life in order to
redwood tree; Gaia and the
living being, with its
James Lovelock
Earth as a living
support the claim of a
Greek goddess of Earth.
own mechanisms of
makes a series of
being that
living Earth: a living
control and
observations about
currently has its
being ‘‘(1) has defined
organization, and think
the planet as a
health affected by
boundaries and exterior
that its ecosystems are
living entity: the
the harmful actions
limits; (2) takes in energy
like organs, when one
Gaia theory’’.
of mankind’’.
(directly from the Sun or
of them is sick, the
from food); (3) excretes
equilibrium of the
wastes; (4) maintains a
whole is threatened’’.
constant internal
medium, despite external
conditions’’.
Yes: the superorganism
Yes. ‘‘According to the
Yes. ‘‘The Gaia
metaphor.
hypothesis, the
hypothesis […]
biosphere shows the
claims that
same characteristics of
organisms and
a living being: it is
environment not
capable of selfonly interact, but
regulation, i.e., it takes
are also capable of
in energy for its
modifying the
functioning’’.
physical medium so
that it becomes
more adequate to
the existence and
perpetuation of
life’’.
Boschilia (2005)
T4
Does the textbook present
Does the textbook employ
analogies to justify the claim evidence for or against the
of a living Earth/biosphere? idea that Earth/biosphere is
living or Gaia theory in
general?
Does the textbook
explicitly address
Gaia?
Textbooks
Does the textbook claim
that Earth/biosphere is
living?
Table 2 Overview of the treatment of Gaia theory in Brazilian high school biology textbooks that address it (either explicitly or not)
478
R. S. Do Carmo et al.
No
No
T11 Gainotti and Modelli (2005)
T15 Machado (2005)
No
No
Yes. ‘‘… our planet keeps No
itself alive due to the
continual exchanges of
chemical elements
between the biosphere,
lithosphere,
hydrosphere, and
atmosphere’’.
Yes: the superorganism
Yes. ‘‘The Gaia
Yes. ‘‘The theme
metaphor.
hypothesis takes as a
‘harmony in nature’
starting point the idea
has resulted in a
that our planet is like
variety of
an organism, because it
conceptions,
regulates its own
sometimes
constitution, with the
subjective and
help of living beings’’.
gratuitous. The
most interesting is
the Gaia
hypothesis, the
name of a goddess
in Greek
mythology that
represented Earth’’.
No
No
Does the textbook
discuss the relevance
of Gaia theory to
current issues?
Yes. It mentions the role of No
algae in cloud nucleation.
Yes. It appeals to the
existence of chemical
exchanges between the
biosphere, the
lithosphere, the
hydrosphere, and the
atmosphere.
Yes. It mentions the
regulation of ocean
salinity.
Does the textbook present
Does the textbook employ
analogies to justify the claim evidence for or against the
of a living Earth/biosphere? idea that Earth/biosphere is
living or Gaia theory in
general?
T10 Frota-Pessoa (2005)
Does the textbook claim
that Earth/biosphere is
living?
Does the textbook
explicitly address
Gaia?
Textbooks
Table 2 continued
Gaia Theory in Brazilian High School Biology Textbooks
479
123
Yes. ‘‘This amplitude No
of the biological
control up to a
global level is the
basis of the Gaia
hypothesis […],
from James
Lovelock […] in
collaboration with
the microbiologist
Lynn Margulis’’.
T17 Paulino (2005)
Does the textbook claim
that Earth/biosphere is
living?
Does the textbook
explicitly address
Gaia?
Textbooks
Table 2 continued
123
No
Does the textbook
discuss the relevance
of Gaia theory to
current issues?
Yes. It mentions Lovelock Yes. ‘‘The Gaia
hypothesis
and Margulis’
suggests the
conclusions about the
importance of
peculiar chemical
discovering and
composition of Earth
preserving the
atmosphere and the mild
controls that
conditions of
allows biosphere
temperature and pH in
to adjust itself to
our planet. It also
certain amounts of
emphasizes the
substances such as
interactions between the
carbon dioxide…
activities of living beings
Thus, humans
and the physicochemical
should not only
environment.
strive for reducing
pollution by all
means, but also for
preserving the
integrity and large
scale of the
buffered system
that maintains life
on Earth’’.
Does the textbook present
Does the textbook employ
analogies to justify the claim evidence for or against the
of a living Earth/biosphere? idea that Earth/biosphere is
living or Gaia theory in
general?
480
R. S. Do Carmo et al.
Does the textbook
explicitly address
Gaia?
Does the textbook claim
that Earth/biosphere is
living?
T18 Silva-Júnior and Sasson (2005) Yes. ‘‘The idea of the Yes. ‘‘James Lovelock
[…] elaborated in the
importance of these
1970s the Gaia
interrelationships
hypothesis, according
was taken to an
to which planet Earth
extreme by the
behaves as a single
English scientist
living being’’.
James Lovelock,
who elaborated in
the 1970s the Gaia
hypothesis’’.
Textbooks
Table 2 continued
Yes: the super-organism
metaphor; Gaia and the
redwood tree.
Does the textbook
discuss the relevance
of Gaia theory to
current issues?
Yes. ‘‘… Gaia
Yes. It refers to many
hypothesis has the
homeostatic, regulatory
merit of calling
mechanisms that control
attention to the
Earth conditions. In
delicate equilibria
particular, the textbook
that govern life on
stresses the contribution
Earth and the
of photosynthesizing
necessity of
organisms to the stability
studying and
of atmospheric chemical
knowing them
composition.
better, so that we
can interfere with
them the least
possible’’.
Does the textbook present
Does the textbook employ
analogies to justify the claim evidence for or against the
of a living Earth/biosphere? idea that Earth/biosphere is
living or Gaia theory in
general?
Gaia Theory in Brazilian High School Biology Textbooks
481
123
482
R. S. Do Carmo et al.
Finally, the following conclusion is offered:
It seems that the activities of living beings, along with natural phenomena, make our
planet have lower temperature and carbon dioxide concentration. Therefore, even
though many claim that Earth modifies life, it seems that life also molds Earth. (T6,
p. 9)
Later, the textbook revisits the origins of life, stressing once again how planets differ from
each other depending on the presence or absence of living beings, and poses the following
question to the students:
Suppose that […] mankind colonized Mars. After many years, the atmospheric
composition and the climate of the planet were modified. In which planet of the solar
system did this sequence of facts apparently happen? (T6, p. 15)
The following answer is given to the teacher:
On Earth, where it is shown that the presence of life also modifies the planet. On
Earth, this is shown by the average temperature and the concentration of oxygen and
carbon dioxide. (T6, p. 52, teacher handbook)
Gaia is also explicitly discussed in the end of a chapter entitled ‘Ecological succession and
biomes’. T6 transcribes a passage from Lovelock’s book ‘The Ages of Gaia’, and then
proposes an activity to the students:
In this book, James Lovelock makes a series of observations about the planet as a
living entity: the Gaia theory. Discuss the text with your group, make a research, and
search for arguments in favor of and against this theory. (T6, p. 418)
Here we can see the second and major difference between the way T6 and other textbooks
address the Gaia theory: the proposal of activities aiming at deepening the students’
understanding of arguments/evidence that can justify or refute the theory.
In another activity, T6 poses the following question: ‘‘The Earth as a gigantic living
being? From where did you take this ingenious idea?’’ (T6, p. 444). The answer given to
this question stresses the idea of Earth as a superorganism:
The idea is called Gaia theory and was proposed by the English scientist James
Lovelock. He imagined Earth as a gigantic organism that, as every living being,
possesses homeostatic mechanisms […]. The name was a homage to Gaia, the
goddess of Earth for the ancient Greeks. (T6, p. 444)
We will come back to the superorganism metaphor in Sect. 3.3.
3.2.2 T17: Paulino’s Textbook
T17, in turn, deserves attention for the general good quality of his treatment of Gaia, in
comparison to the average treatment found in the analyzed materials. This textbook begins
its discussion of Gaia by means of a text adapted from Odum (1988):
… it is a consensus that, as the abiotic environment controls the activity of living
beings, the latter also influences the abiotic environment in many important ways.
The physical and chemical nature of inert materials is always being altered by
organisms, which give back to the environment new compounds and energy sources.
(T17, vol. 3, p. 175)
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Gaia Theory in Brazilian High School Biology Textbooks
483
Then, the textbook offers two examples of situations in which the activity of living beings
influences the environment. One of them concerns the influence of marine organisms on
the constituents of sea water and seafloor. Another refers to the fact that plants growing on
sand dunes radically change the soil, making it quite different from the original substrate.
In another passage, Lovelock and Margulis are explicitly mentioned, in connection with
a comparison between the atmosphere and surface temperature of Earth, Mars, and Venus
(see Table 3). T17 explains that ‘‘the table contrasts the Earth atmosphere with a hypothetical lifeless atmosphere and with the atmospheres of Mars and Venus, where if there is
life, it is certainly not controlling the planet’’ (T17, vol. 3, p. 176). This claim is consistent
with Lovelock’s argument that life originated on Earth before the Gaia system, which
would have only appeared when bacteria colonized a great part of the planet. As Lovelock
(1995, p. 72) explains, ‘‘sparse life hanging on in oases could never have the power to
regulate or oppose the unfavorable changes that are inevitable on a lifeless planet. Sparse
life would only be found at the birth or death of a Gaian system’’.
According to T17, the composition of the Earth atmosphere, the average temperature in
our planet, and the stability of pH on the Earth surface
… cannot be explained without the critical activities of buffering of relatively simple
life forms and the continuous, coordinated activity of plants and microbes, which
diminishes the fluctuations of physical factors that would take place in the absence of
well-organized living systems. (T17, vol. 3, p. 175)
About the Earth atmosphere, the textbook comments that it ‘‘… did not develop its
capacity of sustaining life merely through casual interaction of physical forces, for life to
evolve later, adapting to these conditions’’ (T17, vol. 3, p. 176). It stresses that ‘‘… since
the beginnings, organisms played an important role in the development and control of a
geochemical environment favorable to themselves’’ (T17, vol. 3, p. 176). This is—T17
explains—the basis for Gaia theory:
This amplitude of the biological control up to a global level is the basis of the Gaia
hypothesis […], from James Lovelock […] in collaboration with the microbiologist
Lynn Margulis. (T17, vol. 3, p. 175. Emphasis in the original)
It is important to highlight that this textbook does not state that Earth is a living being.
Moreover, it offers a rather precise description of the cybernetic system postulated by the
Gaia theory:
Table 3 Planetary atmospheres: their compositions (from Lovelock 1995)
Gas
Planet
Venus
Earth without life
Mars
Earth as it is
0.03%
Carbon dioxide
96.5%
98%
95%
Nitrogen
3.5%
1.9%
2.7%
79%
Oxygen
Trace
0.0
0.13%
21%
Argon
70 ppm
0.1%
1.6%
1%
Methane
0.0
0.0
0.0
1.7 ppm
Surface temperatures C
459
240–340
-53
13
Total pressure, bars
90
60
0.0064
1.0
123
484
R. S. Do Carmo et al.
… a complex control system, which functions as a chemostat, something analogous
to an environmental control system that maintains a building inhabitable. This
control system (‘‘Gaia’’) turns Earth into a complex but unified cybernetic system.
(T17, vol. 3, p. 176)
Albeit somewhat circular in its claim that the ‘control system’ described by Gaia turns
Earth into a ‘cybernetic system’, this is the passage among the analyzed textbooks that
offers the account that comes closest to a proper explanation of this central idea of the
theory.
T17 also makes it clear to teachers and students that Gaia is still a controversial theory:
All this is only a hypothesis. It has not been shown yet any real control network that
could satisfy many skeptical scientists, even though the majority accepts a strong
biological influence over the atmosphere. (T17, vol. 3, p. 176)8
The textbook concludes its discussion of Gaia by stressing the potential role of this theory
in promoting more conscious behaviors and attitudes, which might help to preserve the
integrity of the cybernetic system that maintains life on Earth (T17, vol. 3, p. 176).
3.2.3 T4: Boschilia’s Textbook
T4, in turn, shows the worst treatment of Gaia among the analyzed textbooks. It presents a
comparative table similar to Table 3, but with different data (due to mistaken values found
in this textbook). It also mentions explicitly Lovelock and Margulis, and describes Gaia as
follows:
The Gaia hypothesis, formulated by the North-American (sic) scientists James
Lovelock and Lynn Margulis, claims that organisms and environment not only
interact, but are also capable of modifying the physical medium so that it becomes
more adequate to the existence and perpetuation of life. (T4, p. 472)
Thus, the textbook not only misidentifies Lovelock as a North-American scientist (he is
English!), but also limits the content of the theory to the idea that living beings alter the
environment in a manner that favors their own existence.
3.2.4 T10: Frota-Pessoa’s Textbook
Among the textbooks that discuss Gaia, T10 offers the most negative appraisal of this
theory. This textbook discusses it in a chapter about biogeochemical cycles. After
explaining carbon, oxygen, and nitrogen cycles, it introduces the theory in a section
entitled ‘‘The Gaia hypothesis emphasizes the harmony between environment and living
beings’’ (T10, vol. 2, p. 102). Gaia is treated as a subjective and unwarranted (albeit
interesting) idea:
8
This passage also suggests that T17 is committed to a misconception about the nature of hypotheses and
theories we mentioned above, namely that a hypothesis is a rather speculative idea that can turn into a theory
when there are better grounds to accept it. It also shows signs of a naı̈ve realism while considering the
prospects of showing a ‘real control network’, instead of theoretically and empirically supported models to
which scientists might adhere (not only due to internal factors, such as the theoretical and empirical
consistency of the models, but also to external factors, related to the social nature of the scientific community and to the embedment of this community into larger societies).
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Gaia Theory in Brazilian High School Biology Textbooks
485
The theme ‘‘harmony in nature’’ has resulted in a variety of conceptions, sometimes
subjective and gratuitous. The most interesting is the Gaia hypothesis, the name of a
goddess in Greek mythology that represented Earth. (T10, vol. 2, pp. 102–103.
Emphasis in the original)
At best, Gaia would be an allegoric or even wrong idea that might be useful, to the extent
that it can stimulate scientists to test it:
Gaia hypothesis, advocated by renowned scientists, is regarded by many as an
allegoric interpretation of real facts. It is not useless for this reason. Even wrong
ideas can be useful, if they lead people to think and make observations, in order to
approve or refute them. (T10, vol. 2, p. 103)9
3.2.5 T18: Silva-Júnior and Sasson’s Textbook
Finally, T18 addresses Gaia in more detail than most of the textbooks, but in a rather
confusing way, which may bring difficulties to students’ understanding. The textbook
considers Gaia in an introductory text to a chapter entitled ‘‘Ecology and ecosystems’’. It
initially states that ‘‘… the environment exerts a great influence over living beings and, at
the same time, is modified by them’’ (T18, vol. 3, p. 302), and offers two examples of these
interactions. One of the examples concerns the relationship between the photosynthetic
activity of algae and oxygen concentration in a pond. It is explained how an abiotic factor,
light, interferes with the metabolism of living beings, algae, and this in turn influences the
concentration of another abiotic factor, oxygen concentration. After these examples, we
find the following statement:
The idea of the importance of these interrelationships was taken to an extreme by the
English scientist James Lovelock, who elaborated in the 1970s the Gaia hypothesis.
(T18, vol. 3, p. 302. Emphasis in the original)
The most peculiar feature of its treatment of Gaia is the explanation of the content of the
theory in four distinct ways in just two pages. First, the textbook refers to a superorganism
with the capacity of regulating its climate and temperature. Then, Earth is treated as a
super-ecosystem:
Earth, according to this idea, would be a super-ecosystem, with many mechanisms of
regulation and homeostasis […], which would moderate extreme temperatures and
keep constant the composition of the atmosphere and oceans. (T18, vol. 3, p. 303)
Next, the textbook emphasizes the capacity of the biosphere of controlling planetary
dynamics:
Our biosphere would manage, thus, to self-regulate and keep itself healthy, through
the control of the physical and chemical environment. (T18, vol. 3, p. 303)
Then, it expands on explaining self-regulation by the biosphere as follows:
Ultimately, according to Gaia hypothesis, the biosphere would be a highly integrated
and very precise control system. This control, however, needs not be external, as the
thermostat that controls the temperature of a refrigerator, but is internal, […]
9
An interesting feature in this passage lies in the treatment of wrong ideas as playing a role in the
construction of scientific knowledge.
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R. S. Do Carmo et al.
involving hundreds of thousands of feedback mechanisms and a diversity of interactions. (T18, vol. 3, p. 303)
After that, T18 introduces yet another idea, that it is not the entire Earth that is living, but
just part of it, in connection with Lovelock’s analogy between Gaia and a redwood tree
(see Sect. 3.3):
Gaia hypothesis does not claim that the entire Earth is living, or that it is ‘consciously
directing’ its own activities. (T18, vol. 3, p. 303)
Even though T18 offers a more detailed account of Gaia than the average treatment in the
analyzed textbooks, this combination of distinct explanations is not sufficiently consistent
and can be detrimental to students’ understanding. Indeed, there are important tensions in
the text, as, for instance, that between the descriptions of Earth as a superorganism and as a
super-ecosystem, in which concepts related to distinct levels of biological organization are
treated indiscriminately as analogues of our planet.
T18 also considers arguments against Gaia:
Although the idea of treating Earth as a ‘‘superorganism’’ is seductive and appealing,
most ecologists are reluctant to accept Gaia hypothesis. There are several arguments
against it. For instance, geological events of the past, such as comets colliding with
Earth, huge volcanic eruptions and ice ages, which happened from time to time,
deeply modified the aspect of the planet. This is not in accordance with the notion of
a homeostasis mainly accomplished by living beings. Geological factors also mold
the planet, not only biological factors. (T18, vol. 3, p. 303)
This is at first a positive feature, since it is important to make it clear to teachers and
students that Gaia is indeed a controversial theory, offering arguments and evidence for
and against it. Nevertheless, the counter-arguments offered by T18 are not well chosen,
since they are not convincingly against Gaia. First, Gaia theory does not claim that only
biological factors shape the planet, and, therefore, the statement that geological factors do
so is no argument against it. Secondly, one can even argue that these arguments are rather
in favor of the theory, which might explain, for instance, how it was possible that 30 or
more planetesimals hit Earth some 65 m.a. and, yet, life survived (Lovelock 1995, 2000b).
The claim that Earth harbors a self-regulating system can be used as a basis to explain how
Earth recovered its homeostasis after those impacts and also after geological cataclysms in
general. T18 misses the point that perturbation is a conditio sine qua non for homeostasis.
There is no homeostasis (regulation) in a system that is not submitted to perturbation from
external forces. In order to recover a given state (self-regulate), a system has to be displaced from that state, which means that it has to be perturbed.
Finally, T18 emphasizes the relevance of Gaia theory to current environmental problems, stating that ‘‘nevertheless, Gaia hypothesis has the merit of calling attention to the
delicate equilibria that govern life on Earth and the necessity of studying and knowing
them better, so that we can interfere with them the least possible’’ (T18, vol. 3, p. 303).
3.3 Analogies Used to Support the Claim of a Living Earth
We also analyzed the textbooks from the standpoint of a number of analogies that
Lovelock employs in several of his works to support the idea of a living Earth. While
presenting these analogies, he often takes Gaia to be synonymous with Earth. This is one of
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487
the ambiguities that mark his writings and lead to a number of confusions, since the term
‘Gaia’ is also used to describe a cybernetic system that is not the same as Earth, as we saw
above. Lovelock uses the following analogies: (1) Gaia and organisms: the idea of Gaia as
a superorganism; (2) Gaia and the redwood tree; (3) Gaia and the Greek goddess of Earth;
(4) Beehives and self-regulating systems: Earth as quasi-living; (5) Gaia and bacteria.
Analogies 1–3 are more frequent both in Lovelock’s writings and in the general literature
about Gaia, while the other two are rarely used, mostly by Lovelock himself.
Here, it is necessary to say some words about three of these analogies (2, 4, and 5).
Lovelock ascribes great importance to the analogy between Earth and the redwood tree,
since it helps, in his view, ‘‘to swallow the notion that anything as large and apparently
inanimate as the Earth can in any way be said to be alive’’ (Lovelock 1995, p. 27). He
usually emphasizes three similarities between those two entities: first, that both are
‘undoubtedly alive’, although they are composed of more than 97% of dead matter; secondly, as the tree, which has a thin layer of living cells—the cambium—that guarantees its
life and growth, Earth similarly has just a layer of living organisms on its surface; thirdly,
the tree bark and the Earth atmosphere play both the essential role of protecting living
matter present on the surface.
As to the analogy with a beehive, Lovelock writes:
It is possible, of course, to […] look on (sic) Gaia not as alive, but still as something
special, able to regulate itself in a way like a living organism. […]. Perhaps neoDarwinists might accept ‘‘quasi-living’’ as a category for Gaia and for ecosystems,
beehives, and other systems that contain organisms and exhibit self-regulation.
(Lovelock 2000b, p. 31)
The analogy between Gaia and bacteria appeared as a response of Lovelock to critical
comments by evolutionary biologists who stressed, among other aspects, that Earth is not
capable of reproduction, a key requirement in a neo-Darwinist account of life (see also
Lima-Tavares and El-Hani 2001). Lovelock claims that there is no doubt that bacteria are
living beings, even though in his view they have no sense of purpose, cannot move by their
own will, or do not ‘make love’ (Lovelock 2000b). Therefore, he concludes, Earth can also
be said to be living, even though it does not, for instance, make love, just as bacteria do not
do either. It is evident, however, that Lovelock’s argument misses the point completely,
since the criticism has nothing to do with sexual reproduction, but concerns reproduction in
general, and bacteria obviously reproduce by asexual means.
In these analogies, Lovelock emphasizes similarities and neglects several important
differences between Earth and other entities. To properly sustain the claim that Earth or
even the cybernetic system described by his theory is a living system, it would be necessary, however, to consider both analogies and disanalogies between the compared
entities, and, furthermore, to examine whether the idea of a living Earth is consistent with
definitions or explanations of life proposed in the literature. Lima-Tavares and El-Hani
(2001) made a systematic analysis about this latter issue and concluded that Earth cannot
be treated as living on the grounds of two definitions of life—found in neo-Darwinist
biology and biosemiotics—and it might be regarded as a living system, according to the
theory of autopoiesis (Maturana and Varela 1980), to the extent that it can be characterized
as an autopoietic system. In his discussions about Gaia, Capra (1996), for instance, follows
this line of reasoning to consider Earth as a living entity. Nevertheless, Lima-Tavares and
El-Hani (2001) observe that this argument can also be taken as showing that an account of
life as autopoietic is not specific enough to characterize living beings, since there may be
other autopoietic, but non-living systems, such as Earth itself. In sum, the argument for a
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R. S. Do Carmo et al.
living Earth based on autopoiesis may be understood both as a reason to support the idea
that Earth is living and as a basis for questioning the very autopoietic definition of life.
Lovelock (2000b) himself considers definitions of life while discussing the claim that
Earth is living. He states that thermodynamics offers an account of living organisms as
dissipative systems that makes it possible to perceive a similarity between living organisms
and Earth, supporting his metaphor of a superorganism: both show the capacity of reducing
internal entropy at the expense of an increase of entropy in the environment. But it is
possible that a thermodynamic definition of life is also not specific enough, since dissipative systems are not exclusively found in the living world, as convective currents, for
instance, illustrate (Korzeniewski 2001; Meyer et al. 2007). Nevertheless, according to
Lovelock (1965, p. 568), ‘‘Life differs from the other phenomena so classified (as dissipative systems) in its singularity, persistence, and in the size of the entropy decrease
associated with it’’. His argument is, therefore, not simply focused on the presence or not of
entropy decrease, but, rather, on different degrees of entropy decrease in living beings and
in other dissipative systems. This is an interesting argument, but it can still be controversial
as a way of distinguishing living and non-living entities and processes. It is plausible to
assume that living organisms are placed at one extreme of a spectrum of entropy decrease,
whereas non-living entities, such as flames or convective currents, are situated at the other.
It is also clear that Gaia would not be placed in either of these extremes, since it is certainly
not a typical living organism, and Lovelock is in fact insisting that it is not a non-living
entity. But how can we decide where to put a boundary between living and non-living
entities and processes in such a spectrum? It is certainly necessary to have a non-arbitrary
criterion to do so. Lovelock draws a line in the spectrum of entropy decrease in a point X so
that Gaia is situated in the class of living entities, while flames and convective currents are
among non-living processes. But we could easily draw a dividing line X0 placing Gaia
outside the domain of living systems. Both would be arbitrary distinctions in this spectrum.
Therefore, it is not so straightforward to advocate the thesis that Gaia or Earth is living by
dividing the spectrum of entropy reduction as Lovelock does. It seems that, when he
divides the spectrum so as to fit his idea that Earth is living, he is indeed presupposing this
very idea. But this simply begs the question. An independent criterion, other than degree of
entropy decrease, is necessary to justify where to put that dividing line. Then, the only way
to escape the arbitrariness of this proposal is to independently characterize Gaia or Earth as
a living system. But this just means that we are back with the original problem.
Maybe, the best thing to do is to avoid the characterization of Gaia or Earth as a living
system, as Odling-Smee and colleagues suggest:10
All versions of the Gaia hypothesis that insist that ‘‘she’’ is alive are […] misleading,
mystical, and counterproductive. However, at the heart of the Gaia hypothesis there
are two other simpler ideas that are potentially valuable. The first is that organisms
alter their environments in ways that may benefit themselves. The second is that the
many ways in which organisms do alter their environment may ultimately contribute
to some very large-scale self-regulating feedback cycles that have had the effect of
providing the services necessary for life over a very long time. (Odling-Smee et al.
2003, pp. 335–336)
10
It is likely that the Gaia system is more fruitfully treated as a ‘superconstruction’, instead of a ‘superorganism’, as Odling-Smee et al. (2003) suggest with regard to both ecosystems and the Gaia system. We
refer the readers to the original work for more details (see Chapter 8, Sect. 8.4.4).
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Most of the analyzed textbooks, however, are quite far from an approach of the claim of a
living Earth informed by the problem of defining life. That is, they simply do not discuss the
concept of life in the context of their treatment of the Gaia theory, despite the fact that most of
them are committed to Lovelock’s claim that Earth or the biosphere is a living entity. T6 is the
only exception. It appeals to a list of properties or conditions for life in order to support the
claim of a living Earth. Nevertheless, this is an approach to define or explain life that shows
several shortcomings (for discussions, see Rizzotti 1996; Emmeche 1997; Meyer et al. 2007).
First, there is no clear and unambiguous way of establishing how many and what types of
properties one should include in such a list. Second, there are no reasonable criteria to choose
one list among several available in the literature (e.g., Monod 1971; Mayr 1982; De Duve
1991, Koshland 2002). Third, to list properties is not the same as defining a concept. To define
life, we should offer an explanation of the coexistence of a set of properties in living beings
(Bedau 1996). For instance, if one builds an account of life within the network of concepts
included in a specific theory, that theoretical framework can offer resources to explain the
coexistence of properties ascribed to living beings, and, consequently, such a theoreticallygrounded account of life can show explanatory significance. This is what Lovelock tried in his
appeal to thermodynamics. Unfortunately, none of the analyzed textbooks that claim that
Earth or biosphere is living attempted this move, falling short of offering to teachers and
students more than a mere commitment to Lovelock’s claim of a living Earth.
Even textbooks that do not mention the Gaia theory explicitly can nonetheless put
forward the claim that Earth is living. T11 offers a case in point. In an introduction to the
biogeochemical cycles, it writes:
We can even say that our planet keeps itself alive due to the continual exchanges of
chemical elements between the biosphere, lithosphere, hydrosphere, and atmosphere.
(T11, p. 461)
It is clear from this statement that contents related to Gaia are present in this textbook, even
though the theory is not explicitly named and none of the above analogies are used.
We found no instances of analogies 4 and 5 in the analyzed textbooks. Most of the
textbooks, however, focus on analogies 1–3, which are more frequent in Lovelock’s
writings and the literature about Gaia, to support the claim of a living Earth.
3.3.1 Gaia and Organisms: The Idea of Gaia as a Superorganism
The first analogy was observed in four textbooks (T4, T6, T10, and T18). T6 employs the
metaphor of a superorganism six times. An example is found in a chapter entitled
‘‘Environmental disequilibria’’, in which the textbook stresses the destabilizing action of
mankind, arguing that:
When we imagine Earth as a gigantic living being, with its own mechanisms of
control and organization, and think that its ecosystems are like organs, when one of
them is sick, the equilibrium of the whole is threatened. (T6, p. 419)
The textbook comes back to the idea of Earth as a superorganism in its last section, entitled
‘‘Mankind: plague or defense?’’, which has the goal of nurturing students’ environmental
awareness:
Mankind, more than any other species, has altered Earth environments, acting truly
as a plague. The planet is at disequilibrium, as a sick patient, and its illness can be
fatal or not. (T6, p. 449)
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It goes on to argue that the recovery of Earth will be very slow and we cannot wait it to
happen without the help of mankind, which should keep itself ‘‘… as a true system of
defense for Earth’’ (T6, p. 449. Emphasis in the original). Finally, it claims that, ‘‘as in the
case of an organism’s health, which depends on its internal equilibrium, Earth can balance
itself. This depends on mankind, the thinking part of nature’’ (T6, p. 449).
This shows how far T6 takes the metaphor of Earth as a superorganism, treating
environmental problems as analogous to diseases, and environmental equilibrium, to
health. We find these analogies in Lovelock’s (e.g., 1995, 2000b) works themselves. It
seems that the author of this textbook believes that these ideas may play an important role
in nourishing ecological awareness. Nevertheless, they can also promote an inadequate
view about the nature, causes and solutions of environmental problems. This becomes
clearer when we analyze how T4 addresses the view of the biosphere as a superorganism:
According to the hypothesis, the biosphere shows the same characteristics of a living
being: it is capable of self-regulation, i.e., it takes in energy for its functioning. Thus,
all the elements, such as the clouds, the atmosphere itself, the oceans, the forests, and
the rains, are responsible for the maintenance of Earth temperature, and biomes are
capable of adjusting themselves even in the face of modifications introduced by man.
(T4, p. 472)
This passage makes it clearer that there are important risks to the development of ecological awareness related to the metaphor of Earth as a superorganism with the same
capacity of balancing itself as typical living organisms. Gaia theory has been indeed
interpreted so as to result in a neglect of the impact of human activities on the environment,
due to a supposed capacity of biomes to adjust themselves in the face of anthropic impacts.
It is clear, however, that this interpretation takes the theory too far, since it is also the case
with living organisms that there is a threshold beyond which they cannot regulate themselves anymore in the face of environmental perturbations. Lovelock (e.g., 1985, 1995,
2006) himself insists that the Gaia system is currently at a precarious equilibrium and his
theory rather suggests that, if we keep disturbing the Earth control system to the extent that
we have been doing for the last two centuries, it is likely that it will suffer great oscillations, chaotic changes, or even a total collapse, and this will certainly threaten our survival,
and, perhaps, Earth biomes as a whole. Anyway, it is clear from textbook passages such as
the one we just quoted that, despite these caveats, Gaia theory can be still interpreted so as
to make us more complacent about our impact on Earth ecosystems. This is yet another
feature to be concerned about when transposing Gaia theory to school scientific
knowledge.
T18 employs the metaphor of Earth as a superorganism three times. In one of its
descriptions of Earth, we find:
This superorganism, according to Lovelock, has the capacity of regulating its climate
and its temperature, eliminating its wastes, and fighting its own diseases. (T18, vol.
3, pp. 302–303)
Although not so strikingly, this passage brings with it the same dangers discussed above, in
connection with the T4 treatment of this metaphor.
T10 also characterizes the Gaia theory in terms of the superorganism metaphor:
Gaia hypothesis takes as a starting point the idea that our planet is like an organism,
because it regulates its own constitution, with the help of living beings. (T10, vol. 2,
p. 103)
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The superorganism metaphor is, in fact, one of the reasons for the author of this textbook to
be suspicious about Gaia, very much in the same way as it has been a source of doubts
throughout the history of the theory.
3.3.2 Gaia and the Redwood Tree
The second analogy is found in two textbooks (T6 and T18). In a chapter entitled ‘‘Health,
disease, and health promotion’’, T6 strives for explaining the similarities between Gaia and
the redwood tree that Lovelock points out, as a basis for a movement from contents related
to human health to a discussion about ‘‘the health of a being called Earth’’ (T6, p. 444):
The redwood tree is indeed a gigantic tree […]. Although it is an extraordinary living
being, 97% of its body is dead! […] The only living part is a thin layer of cells below
the bark (cambium), leaves, flowers, and seeds […]. Planet Earth is also like that: a
great part of its matter is inanimate and only a small part is composed of living
organisms. It is just this small part, however, that keeps it alive. Moreover, life
happens between the atmosphere that protects it from the external medium and a
layer of rocks that isolate it from the internal medium, as in the case of the redwood
tree, in which the layer of life is protected from the external medium, above the cork,
and below, by the wood, ensuring life. (T6, p. 444)
T18 offers a similar explanation:
Gaia might be compared to a tree, which is constituted by 99% of cork and wood,
dead matter. The tree keeps itself alive through interactions between its small living
portion and its dead parts, and […] between itself and the external environment. […].
Almost as a whole, Earth consists of non-living matter, covered by a very thin film of
life, the biosphere, which interacts with the non-living part, regulating the whole set.
(T18, p. 303. Emphasis in the original)
Lovelock’s writings directly influenced T6 and T18 authors, as shown by these almost
verbatim quotations of his explanation of this analogy.
3.3.3 Gaia and the Greek Goddess of Earth
Even though a cursory reference to the origins of the name ‘Gaia’ in the Greek goddess of
Earth is found in other textbooks, T6 is the only one that indeed explores this metaphor. To
understand its arguments, it is necessary to describe some elements of the Greek myth
about Gaia, the goddess who personifies Earth (Brandão 2004). According to the myth,
Antaeus was a giant, son of Poseidon and Gaia, who was extremely strong as long as he
remained in contact with the ground (i.e., Earth, his mother). But Hercules discovered his
secret and, in combat, raised him from the ground, keeping him aloft until he died. T6
states that humans correspond analogically to Antaeus, and Earth, to the goddess Gaia.
Thus, ‘‘as in the Greek myth, the human species is weakened when it distances itself from
nature’’ (T6, p. 373). The textbook then describes several environmental problems as a
consequence of the detachment of Antaeus from Gaia, and asks: ‘‘How to think and act
differently? How could Antaeus reconnect with his mother Geia?’’ (T6, p. 373).11
11
Geia and Gaia are variant names for the same goddess in Greek mythology.
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3.4 An Important Absence: Theoretical and Empirical Advances Resulting from the
Gaia Theory
In only two cases, the analyzed textbooks refer to important advances resulting from the
Gaia theory, going beyond their reliance on the idea that Earth is a living being. T15
mentions the role of algae in cloud nucleation. This happens in the discussion of two
distinct subject matters: algae and oceans. The textbook acknowledges the role of algae not
only in the water but also in the oxygen cycle, recognizing the interrelationship between
these two biogeochemical processes:
Diatom algae and dinoflagellates are responsible for the production of approximately
70% of atmospheric oxygen. Additionally, phytoplankton releases dimethyl sulphide
(DMS), a compound that reacts with water to form sulfuric acid (H2SO4). According
to scientists, H2SO4 functions as a ‘condensation nucleus’ for the assembling of
clouds, balancing the water cycle and Earth climates. (T15, p. 210)12
Despite its mostly negative appraisal of the theory, T10 mentions models developed by
advocates of Gaia in order to account for the regulation of salinity in the oceans:
For instance, the amount of salt in the oceans had to be always increasing, since the
salt brought from the continents by the rivers has no way to come back. The
advocates of the Gaia theory suggest that ocean salinity is kept constant by a
feedback mechanism. There are bacteria that concentrate the salt in salt mines where
they live. As the rivers bring more and more salt, more salt mines are formed, and,
thus, the salinity in the sea never reaches one tenth of the saturation level. (T10, p.
103)
We can conclude, thus, that a missing element in most textbooks is a discussion about
major theoretical and empirical advances resulting from the Gaia theory, which might
indeed contribute more to the understanding of environmental science than the mere
reference to the idea of a living Earth, which strongly prevails in the treatment of Gaia in
the analyzed textbooks. Furthermore, when taken by itself, this latter idea seems so close
to animism that it can indeed lead Gaia to be entangled with non-scientific ideas, as
Rodel (1995) and others argue. It is regrettable, then, that theoretical and empirical
advances such as those related to the cloud-algae link, i.e., to the role of DMS in the
water and sulfur cycles, as well as in climate regulation, are almost entirely absent from
the textbooks. After all, these developments from the Gaia theory would allow teachers
and students to appraise how this theory, albeit being controversial and far from being
generally accepted by the scientific community, has been leading to advances in scientific understanding. Generally speaking, most of the analyzed textbooks miss an
opportunity to stimulate teachers and students to understand scientific knowledge under
construction, what they could do if they addressed the Gaia theory in a manner that
showed both that it is under development and is quite polemical, and, yet, has already
led to new ideas about how the Earth system functions, which can contribute to our
understanding of environmental issues.
12
T15 refers to sulfuric acid as the compound that operates as a condensation nucleus for the formation of
clouds, and not to a non-sea salt sulphate aerosol (see above). The possible involvement of sulfuric acid in
this mechanism is, indeed, under consideration by the scientific community.
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4 Concluding Remarks
The analyzed textbooks address Gaia theory mainly in the context of ecology teaching. In
this context, the theory could play a role in promoting a better understanding of environmental matters by students and teachers. Nevertheless, what we see in most analyzed
textbooks (with T17 as the only exception) is a treatment of Gaia focused mainly on the
claim of a living Earth, usually without taking into account the central idea of a coevolving
cybernetic system involving the biota and the physicochemical environment, or any theoretical and empirical advance resulting from the Gaia theory. Thus, even though Gaia can,
in our view, contribute to the understanding of environmental issues, it is true that, in most
of the schoolbooks we analyzed, it is treated in a manner that puts much emphasis on the
idea that Earth is living and is quite close to an animistic understanding of the Earth
system. This treatment can indeed lead to little more than a mystical view with no true
contribution to the development of adequate conceptions about the Earth system and the
connections between human activities and the environmental crisis. It is even the case that
this is a potentially misleading and dangerous view, as we can see, for instance, in the use
of the metaphor of Earth as a superorganism with environmental problems as analogous to
diseases, which can suggest that environmental problems caused by human beings might
be self-correcting (see above). It would be interesting to verify if the same kind of treatment prevails in textbooks published in other countries, and, thus, if they succeed or not in
encouraging teaching and learning about Gaia theory in such a manner that it can play a
beneficial role in science education.
We are not alone in believing that Gaia can play such a beneficial role. Baker, for
instance, mentions two potential inputs from Gaia to science education:
A study of the Gaia Hypothesis in a biology course illustrates to the students the
development of a current scientific hypothesis, and the creative integration between
different aspects of biology and between biology and other disciplines which often
result in the development of new and novel hypotheses. (Baker 1993, p. 115)
In fact, the contribution that Gaia can bring to the understanding of environmental issues is
also limited by the fact that the theory is not used by the analyzed textbooks as a ground for
a cross-disciplinary treatment of contents, which can easily follow from its very structure.
In our view, this is an opportunity lost, since this theory can lead to an integrated discussion of contents from biology, geology, physics, and chemistry. In particular, teaching
about biogeochemical cycles, geological ages, global changes (e.g., climate change), and
origins of life may be improved by appealing to ideas from Gaia theory. Consider, for
instance, biogeochemical cycles. All analyzed textbooks that address this subject13 offer
explanations which do not establish any connection between the several cycles and typically do not consider the participation of living beings. The contributions of Gaia theory to
the treatment of biogeochemical cycles become clear when we consider that it gives
emphasis to these two important aspects, as one can see in its explanations about the cloudalgae link (see above).
To discuss Gaia theory in the science classroom can also contribute to students’ and
teachers’ understanding of the nature of science (NOS). But this can only happen if it is
clear that Gaia is a theory that is still being developed and gives room to several scientific
controversies. Nevertheless, this is not clear in most of the analyzed textbooks. Gaia cannot
be treated in school knowledge as if it was a theory largely accepted by the scientific
13
T3 is the only analyzed textbook in which biogeochemical cycles are not addressed.
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community. Rather, it should be explicitly treated as a controversial theory and, in this
manner, it may allow teachers to address in their classrooms the central role of scientific
controversies in the history of science, something that can foster a more sophisticated view
about NOS. In our sample, only two textbooks stimulated students to engage in an
appraisal of Gaia as a controversial theory (T6 and T17), and another one offered a
judgment of the theory as a false, unwarranted one (T10), leaving little room for students to
reach their own conclusions. The other textbooks ascribed to Gaia or ideas derived from it
the same status they attributed to other scientific contents, suggesting that Gaia theory is as
accepted today as any other theory in science. However, it is also important to emphasize
that the degree of controversy surrounding Gaia is much smaller today than in its initial
stages of development, in the 1960 and 1970s. Therefore, Gaia offers a good opportunity to
teach that a theory is a historical entity, and its acceptance by the scientific community can
increase or decrease along its history.
We believe that, in order to properly transpose Gaia theory to school scientific
knowledge, it is essential to give emphasis to the central idea of an adaptive control,
cybernetic system through which physicochemical environment and biosphere evolve in a
coupled way, and the consequent evolution of feedback mechanisms leading to self-regulation of several environmental variables by the Gaia system. Additionally, we consider
that it is crucial to avoid giving so much emphasis to the claim of a living Earth as the
analyzed schoolbooks do. It is also important to consider recent developments in Earth
System Science (ESS) related to pressing environmental problems, such as global warming, putting them in connection with Gaia theory, as we see in Jacobson et al. (2000), and
Margulis (2004) and Tickell (2004) stress it should be done.
Even though it is clear to us that Gaia should not be addressed in school science in the
manner we observed in most of the analyzed schoolbooks, we still think it is worth looking
for other, more fruitful ways of discussing this theory at high school (and other educational
levels). Accordingly, a future goal of our research is to develop and test didactic materials
and teaching sequences that address environmental issues from the perspective of both ESS
and Gaia, while avoiding promoting any view close to an animistic understanding of the
Earth system. Our idea is to focus on two claims that are, in our and others’ views (e.g.,
Wilkinson 1999; Odling-Smee et al. 2003) particularly valuable, namely that organisms
alter their environments in ways that may benefit themselves, and that the environmental
changes brought about by organisms may also contribute to very large-scale self-regulating
feedback cycles that are part of the cybernetic system described by Gaia theory.
Acknowledgments We are indebted to the Brazilian National Council for Scientific and Technological
Development (CNPq) for support during the development of the research reported in this paper. We also
thank Michael Matthews and two anonymous referees that examined a preliminary manuscript and offered
very helpful contributions to the final version of the paper.
Appendix 1: List of Analyzed Textbooks
T1
T2
T3
T4
T5
Amabis, J.M. & Martho, G.R.: 2005, Biologia, Moderna, São Paulo.
Borba, A.A. & Cançado, O.F.L.: 2005, Biologia, Positivo, Curitiba.
Borba, A.A., Crozetta, M.A.S. & Lago, S.R.: 2005, Biologia, IBEP, São Paulo.
Boschilia, C.: 2005, Biologia sem Segredos, RIDEEL, São Paulo.
Carvalho, W.: 2005, Biologia em Foco, FTD, São Paulo.
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T6 Cheida, L.E.: 2005, Biologia Integrada, FTD, São Paulo.
T7 Coimbra, M.A.C., Rubio, P.C., Corazzini, R., Rodrigues, R.N.C. & Waldhelm,
M.C.V.: 2005, Biologia—Projeto Escola e Cidadania para Todos, Editora do
Brasil, São Paulo.
T8 Faucz, F.R. & Quintilham, C.T.: 2005, Biologia: Caminho da Vida, Base, Curitiba.
T9 Favaretto, J.A. & Mercadante, C.: 2005, Biologia, Moderna, São Paulo.
T10 Frota-Pessoa, O.: 2005, Biologia, Scipione, São Paulo.
T11 Gainotti, A. & Modelli, A.: 2005, Biologia, Scipione, São Paulo.
T12 Laurence, J.: 2005, Biologia, Nova Geração, São Paulo.
T13 Linhares, S. & Gewandsznajder, F.: 2005, Biologia, Ática, São Paulo.
T14 Lopes, S. & Rosso, S.: 2005, Biologia, Saraiva, São Paulo.
T15 Machado, S.W.S.: 2005, Biologia, Scipione, São Paulo.
T16 Morandini, C. & Bellinello, L.C.: 2005, Biologia, Atual, São Paulo.
T17 Paulino, W.R.: 2005, Biologia, Ática, São Paulo.
T18 Silva-Júnior, C. & Sasson, S.: 2005, Biologia, Saraiva, São Paulo.
Appendix 2: Protocol Used to Standardize the Analysis of High School Biology
Textbooks
1. Does the textbook explicitly address Gaia?
( ) Yes
( ) No
2. Does the textbook discuss ideas that can be straightforwardly related to Gaia, even if it
does not name the theory?
( ) Yes
( ) No
a. Reproduce here the relevant passages that show the treatment of ideas related to Gaia
by the textbooks, if you answered ‘‘yes’’ to each of the above questions.
3. What is the epistemological status ascribed to Gaia in the textbook?
( ) theory
( ) hypothesis
( ) another one: which?
4. Is it possible to discern in the textbook the historical context in which Gaia was built?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, reproduce here the relevant passages.
5. Does the textbook treat Gaia in a cross-disciplinary fashion?
( ) Yes
( ) No
a. When it addresses Gaia, does the textbook make it explicit its relevance as a way of
integrating scientific knowledge produced in the context of the disciplines related to
that theory?
( ) Yes
( ) No
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b. Is it possible to conclude from the analysis of different subject matters within biology
that the textbook is successful in using Gaia as an integrating approach to biological
knowledge?
( ) Yes
( ) No
c. Transcribe the passages that justify your answers.
6. Lovelock (1995) claims that the increasing attention given to Gaia theory in the 1980s
and 1990s results from the construction of the Daisyworld model. Does the textbook
address the Daisyworld model?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, how is this model addressed?
b.1 Is any other model related to Gaia, besides the Daisyworld model, presented in the
textbook?
( ) Yes
( ) No
b.2 If you answered ‘‘yes’’, inform which other model(s) is(are) presented?
7. Some epistemological issues related to the name given to the theory, ‘Gaia’, have been
discussed in the literature (Lovelock 1990; Margulis 2004). Does the textbook offer
any comments about the name ‘Gaia’?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, transcribe the relevant passages.
b.1 Is the name ‘geophysiology’’ (also proposed for the theory by Lovelock 1986, 1993,
1995, 2000b) mentioned as a possible alternative to the name ‘Gaia’?
( ) Yes
( ) No
b.2 If you answered ‘‘yes’’, transcribe the relevant passages.
8. Does the textbook discuss the relevance of Gaia to current issues, particularly
environmental problems?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, transcribe the relevant passages.
9. Does the textbook address the notion of emergent properties in connection with Gaia
(as Lovelock does in several of his writings, e.g., Lovelock 1972, 1990)?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, does the textbook explain what are emergent properties? If so,
what is the explanation given to this notion?
( ) Yes
( ) No
b. Transcribe the passages that justify your answers.
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10. Does the textbook claim that Earth or biosphere is living?
( ) Yes
( ) No
a. If you answered ‘yes’, reproduce here the relevant passages.
11. Does the textbook employ analogies to justify the claim of a living Earth or
biosphere?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, which analogy(-ies) does the textbook use to justify the claim
that Earth or biosphere is living? Identify the analogies, count their occurrences, and
reproduce the relevant passages.
( ) Gaia and organisms: the idea of Gaia as a superorganism.
( ) Gaia and the redwood tree.
( ) Gaia and the Greek goddess of Earth.
( ) Beehives and self-regulating systems: Earth as quasi-living.
( ) Gaia and bacteria.
12. For Lovelock (2000b), the concept of Gaia is closely related to the concept of life,
which he believes is not clearly understood up to the present day. Lovelock also
states that a thermodynamic approach can bring substantial contributions to attempts
to clarify what is life. Furthermore, thermodynamics is also regarded by him as
important to understand the Gaia system. Does the textbook put forward any remark
about thermodynamics in connection with Gaia?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, transcribe the relevant passages.
b. Does the textbook offer any definition for life related to thermodynamics (when
discussing Gaia or elsewhere)?
( ) Yes
( ) No
c. Is any other definition of life presented in the textbook?
( ) Yes
( ) No
d. If you answered ‘‘yes’’, which definition(s) is(are) presented? Does the textbook
connect it (them) with Gaia? How?
13. Does the textbook offer any argument or evidence against Gaia?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, transcribe the relevant passages.
14. Does the textbook discuss any difficulty to obtain empirical support for the existence
of the Gaia system?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, transcribe the relevant passages and discuss the difficulties that
are mentioned.
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15. Does the textbook offer any argument or evidence for Gaia?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, transcribe the relevant passages.
16. In some of his writings, Lovelock emphasizes the strength and resistance of Gaia
(e.g., Lovelock 1995, 2000c). He opposes this view to that of a fragile and delicate
Earth, as we see in some environmentalist discourses. Not surprisingly, these
arguments led to controversies about Gaia in environmentalist circles.
a. Does the textbook address this view about Gaia?
( ) Yes
( ) No
b. Does the textbook discuss controversies about Gaia in environmentalist circles?
( ) Yes
( ) No
c. If you answered ‘‘yes’’, transcribe the relevant passages.
17. Kirchner (1989, 1993) states that Gaia is a not a single hypothesis, but a set of
different although interrelated hypotheses, ranging from strong to weak ones. The
strong ones are: Homeostatic Gaia, Teleological Gaia, Optimizing Gaia, and
Geophysiological Gaia. The weak ones are: Influential Gaia and Coevolutionary
Gaia. Without losing from sight the need of didactic transposition (Chevallard 1991)
in a high school textbook, is it possible to identify one or more of these distinctions in
the treatment given to Gaia?
( ) Yes
( ) No
a. If you answered ‘‘yes’’, transcribe the relevant passages.
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Author Biographies
Ricardo Santos do Carmo is a biology student at Universidade Federal da Bahia, Brazil. He currently has a
grant for scientific training from the National Council for Scientific and Technological Development
(CNPq). His research interests are in science education research, philosophy of biology, and theoretical
biology.
Nei Freitas Nunes-Neto is a master degree student in the Graduate Studies Program in History, Philosophy
and Science Teaching (Universidade Federal da Bahia and Universidade Estadual de Feira de Santana).
During the development of the research, he had a master grant from the National Council for Scientific and
Technological Development (CNPq). His research interests include philosophy of biology, theoretical
biology, and science education research. He published the paper ‘‘Gaia, teleologia e função’’ (Gaia, teleology, and function) in Episteme (2006), in collaboration with Charbel Niño El-Hani.
Charbel Niño El-Hani is Professor of History, Philosophy, and Biology Teaching at the Institute of
Biology, Universidade Federal da Bahia, Brazil, and Researcher of CNPq (National Council for Scientific
and Technological Development). He is affiliated with the Graduate Studies Programs in History, Philosophy, and Science Teaching (Universidade Federal da Bahia and Universidade Estadual de Feira de
Santana) and in Ecology and Biomonitoring (Universidade Federal da Bahia). His research interests are in
science education research, philosophy of biology, biosemiotics, theoretical biology, and animal behavior.
His recent publications include ‘‘Towards a multi-level approach to the emergence of meaning processes in
living systems’’, in Acta Biotheoretica (2006), in collaboration with João Queiroz; ‘‘A semiotic analysis of
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the genetic information system (2006), in Semiotica in collaboration with João Queiroz and Claus Emmeche; ‘‘Semiosis as an emergent process’’ (2006), in Transactions of the Charles Sanders Peirce Society, in
collaboration with João Queiroz; and ‘‘Multicultural Education, Pragmatism, and the Goals of Science
Teaching’’, in Cultural Studies of Science Education (2007), in collaboration with Eduardo Mortimer. He is
a member of editorial boards of Brazilian and international journals in science education and philosophy of
science.
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