International Journal of Epidemiology, 2016, Vol. 45, No. 1
habits that may have been acquired. It ought to assign limits to reasonable doubt. We should learn that the number
of times in which an acquired habit was inherited to any
sensible degree, after some specified number of generations, did certainly not exceed so and so, per cent. We
might also learn that it certainly did exceed some lesser
number. We cannot prove any negative and therefore cannot hope to prove that acquired habits are never inherited,
but we may perhaps find no case of their being inherited in
any appreciable degree, even after many generations. This
seems to have been already done in the case of many artificial mutilations. But as the loss of a limb belongs to a different order of events to the loss of an instinct, it would be
dangerous to conclude that what has been found to occur
in the one case would necessarily occur in the other. It
therefore appears to me that the possibility of experiments
along the lines I have suggested, on creatures reared from
eggs and away from their parents, are well worth considering. It is only through the hard compulsion of unquestion-
15
able facts, that we are likely to forego the wholesome
moral doctrine that the self-denials and toils of the parent
will earn for his children a happier nature than he had himself been gifted with. That they will be congenitally more
disposed than he was to deny themselves harmful pleasures, and to work generously for the good of others. It
must be recollected that we are no longer justified in idly
holding this comfortable belief, and in preaching about it
as if it were unquestionably true.
So far from this being the case the balance of probability seems strongly against its truth. But the question is not
yet solved. The possibility of a child inheriting even the
simplest aptitudes that the parent has acquired against the
grain of his nature, can only be determined by a direct appeal to suitable experiments. The object of this memoir is
to obtain the opinion of experts as to the most feasible experiments for the purpose.
International Journal of Epidemiology, 2016, 15–20
Commentary: Before
doi: 10.1093/ije/dyw004
Weismann and germplasm
there was Galton and eugenics: the biological
and political meaning of the inheritance of
acquired characteristics in the late 19th century
Ruth Schwartz Cowan
Philadelphia, PA 19104, USA
E-mail: [email protected]
Accepted 11 January 2016
Francis Galton was a Victorian gentleman of means, more a
polymath than a disciplined man of science. He was born in
1822 into a distinguished and affluent Birmingham family.
His father, Samuel Tertius Galton, was a banker; his mother,
Violetta Darwin Galton, was one of the many daughters of
Erasmus Darwin, which made her an aunt (and Francis
therefore a cousin) to Charles Darwin. Francis Galton’s paternal and maternal grandfathers had been Quakers and
founding members of the famous Lunar Society of
Birmingham, an association of men who were interested in
what we would now call science and technology.
According to family accounts, Francis was a very bright
and inquisitive boy—but he disliked school and was an in-
different student. As a young man he studied medicine for
a few years and then, over some parental objections, went
to Cambridge; he left 3 years later with only an ordinary
degree, having done poorly in all of his examinations. In
the autumn of 1844 shortly after receiving his degree, his
father died, leaving an enormous inheritance. After that
Galton had no need of gainful employment; until his death,
76 years later, he was free to spend all of his time and a
good deal of his money on his personal interests, almost all
of them (following in the footsteps of his family) either scientific or mathematical. Over the course of his long life,
Galton wrote and published more than 300 papers and 9
full-length books, almost all of which had some
C The Author 2016; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association
V
16
International Journal of Epidemiology, 2016, Vol. 45, No. 1
observational and statistical content. Historians of the
various sciences credit him with having made significant
contributions to the study of African geography, anthropology, anthropometry, psychology, statistics, meteorology, criminology—and, of particular concern here—
genetics, which in Galton’s day was called the study of
heredity.
In 1889, when Galton delivered the essay (published
here in full for the first time) as a talk at the annual meeting of the British Association for the Advancement of
Science, heredity was being investigated by two kinds of
biologists: naturalists and cytologists. The naturalists were
interested for two reasons; one was practical (how can we
breed better domesticated animals and plants?) and the
other was theoretical (evolution by natural selection requires an explanation—which was missing in those
years—of how adaptive traits are passed from one generation of organisms to the next). The cytologists also had
two reasons; they suspected that the cellular and nuclear
structures that they were discovering with their increasingly powerful microscopes (and staining techniques)
might provide that missing explanation—and might also
hold the key to the linked mysteries of reproduction and
embryological development.
Galton, however, was neither a naturalist nor a cytologist; he was interested in heredity for an entirely different
reason, a reason which he had first explored in print in
1865.1 ‘Hereditary talent and character’ was Galton’s first
foray into the study of heredity, and its very first paragraph
holds the key to understanding both the nature and the
depth of his interest in the subject:
The power of man over animal life, in producing whatever varieties of form he pleases, is enormously great. It
would seem as though the physical structure of future
generations was almost as plastic as clay, under the control of the breeder’s will. It is my desire to show more
pointedly than—as far as I am aware—has been attempted before, that mental qualities are equally under
control. (p.157)1
Galton was, as this paragraph makes clear, interested in
the inheritance of human mental qualities for philanthropic reasons; he hoped it would prove possible to improve the human race by controlling its breeding
patterns—just as if humans were domestic animals, like
horses, dogs and sheep, and as if behavioural traits were
akin to physical characteristics.
To put the matter another way, Galton’s argument rests
on two analogies, which he carefully expounds at the beginning of the article: first, that mental traits can be inherited in the same way as physical traits; second, that
heredity in man is no different from heredity in animals. If
this argument and these analogies sound familiar to 21stcentury ears, it is because they are the foundations for both
a scientific discipline and a social movement, each of which
still exists (although considerably altered) in our own day.
The scientific discipline is now called human genetics; the
social movement was then, and still is, called eugenics.
Over the course of his long career, Galton never gave up
his conviction that the best hope for social reform rested
with better knowledge of human heredity and better application of its laws. Galton himself coined the term
‘eugenics’—combining the Greek roots for ‘good’ and
‘ancestry’—in 1883 (pp. 24–25).2 His eugenic convictions,
first articulated in 1865, underlay all his subsequent studies of heredity.
About one-quarter of ‘Hereditary talent and character’
is devoted to developing the empirical evidence in favour
of Galton’s thesis, ‘ . . . that talent and peculiarities of character are found in the children, when they have existed in
either of the parents, to an extent beyond all question
greater than in the children of ordinary persons’. (p.158)1
To do this, he attempts a statistical analysis of several biographical dictionaries. He finds in one such volume that
out of the 605 individuals listed, 102 were relatives of
someone else on the list, with a frequency of 1 in 6. Doing
the same analysis on another biographical dictionary of
eminent men, he finds a frequency of 1 in 11: in a listing of
painters, 1 in 6; for musicians, 1 in 10; for scientists, 1 in
12; among Lord Chancellors (the law being ‘by far the
most open to fair competition of all the professions’) he
finds a frequency of 1 in 3 (p.161).1
The conclusion, he argues, is ineluctable: ‘Everywhere is
the enormous power of hereditary influence forced on our
attention’. (p.163)1 Not one whit of additional evidence is
provided, however; the remaining two-thirds of Galton’s
article is concerned with the practical implications of this
conclusion (can young people be persuaded to find intellectual superiority more romantically attractive than physical
beauty? Can the government be persuaded to give large
cash wedding presents to intellectually superior couples?).
If modern readers find the evidence unconvincing, so too
did many readers in his own day (Cowan, pp.10–20,
60–65; Gillham, pp.169–172).3,4 In subsequent researches,
Galton improved his investigatory methods but never
found any reason to alter his original conclusion about the
enormous power of hereditary influence.
Furthermore, he retained his scepticism, already
announced in ‘Hereditary talent and character’ about the
idea (which was then a part of both biological and political
orthodoxy) that characters acquired during the lifetime of
an individual (characters both physical and mental) could
be inherited. ‘Can we hand anything down to our children’, he asked at the beginning of the second part of the
International Journal of Epidemiology, 2016, Vol. 45, No. 1
article, ‘that we have fairly won by own independent exertions?’ (p.321)1 Probably not, he answers; the sons of soldiers, for example, do not learn to drill any faster than the
sons of other men, nor are the sons of sailors noticeably
more accustomed to the sea than the sons of those who are
land bound. ‘Or are we’, he goes on to ask, ‘no more than
passive transmitters of a nature we have received, and
which we have no power to modify?’ (p.322)1 Probably, he
continues, making a most unorthodox (for his day) suggestion, we should ‘ . . . consider our own embryos to have
sprung immediately from those embryos whence our parents were developed, and these from the embryos of their
parents, and so on forever’. If this suggestion sounds uncannily like August Weismann’s concept of the continuity
of germplasm, that is because it is, with one crucial caveat;
Weismann came to his conclusion (in the 1880s) after decades of careful biological research, but Galton came to his
because it followed, almost logically, from his political
convictions.
Liberalism was the dominant political orthodoxy in
England in the middle years of the 19th century. Victorian
liberals believed that men (and they meant men as a sex,
not as a generic term for humans) were basically the same
at the time of their birth and were only made different
from each other by the effects of their environments and
educations; many liberal reform efforts were, therefore,
focused on relieving poverty and improving access to education. Victorian conservatives, on the other hand, took
the opposite view, holding that men were inherently different from each other at birth, a difference which could not
be overcome by environment and education; this view
made them disinclined to believe that society could be, or
even needed to be, reformed. Galton was a lifelong conservative. ‘It is in the most unqualified manner’, as he wrote
in his book Hereditary Genius, ‘that I object to pretensions of
natural equality’. (p.56)5 As a result, he tended to be sceptical
of the biological notion that underlay liberal reform efforts,
namely that we can pass anything biological down to our
children that we can acquire during our lifetimes.
Since the last decades of the 18th century, that biological notion had been an essential component of the scientific discussion about whether species had evolved over
time. A prominent French naturalist, George Louis Leclerc,
Comte du Buffon (1707-88) had started the argument by
declaring that the fossil record (just then being, literally,
unearthed) could be understood as the degeneration of the
original God-created species as a result of the inherited effects of climate and diet. A generation later, a German
comparative anatomist, Johann Friedrich Blumenbach
(1752–1840) had asserted that the first human beings were
light-skinned and that dark-skinned humans were, therefore, a degenerate form that had arisen when humans
17
migrated to places in which they suffered over-exposure to
the sun. Erasmus Darwin, who was of course the common
grandfather of Charles Darwin and Francis Galton, used
the idea that acquired characters could be inherited to buttress his more progressive concept of evolution in
Zoonomia; or the Laws of Organic Life, which was published in 1794. Subsequently, Buffon’s famous disciple
Jean Baptiste Lamarck, whose major work Philosophie
Zoologique appeared in 1809, followed Erasmus Darwin
in turning his mentor’s vision on its head, seeing evolution
as progressive rather than retrogressive, going from simplicity to complexity while retaining the same proposed
mechanism, a ‘life force’ which allowed organisms to pass
on traits that they had acquired (in response to changing
environmental circumstances) during their lifetimes.6–9
Charles Darwin, perhaps the most observationally acute
naturalist of the 19th century, also believed in the inheritance of acquired characters. In 1865, when Galton wrote
’Hereditary talent and character’, he could not have known
that (since Darwin did not mention it in The Origin of
Species, 1859) but he certainly learned it three years later,
when Darwin published his dense two-volume tome The
Variations in Animals and Plants Under Domestication.
The first volume of The Variations contains huge amounts
of information about the numerous varieties of domestic
animals and plants, information that Darwin had spent
several decades culling from the writings of animal and
plant breeders; there are chapters on dogs and cats, horses,
pigeons, fruits, ornamental trees, cereals and many other
domesticated organisms. The second volume opens with
several chapters in which Darwin tries to discern patterns
of inheritance in all the data he had presented in the first.
Some of these patterns did not involve the inheritance of
acquired characters (hybridization for example) but a very
large number of them did (‘use and disuse’, for example).
In the penultimate chapter of the book, furthermore,
Darwin proposes a physiological mechanism that might
explain all the patterns that he had discovered; he called it
‘the provisional hypothesis of pangenesis’.6 Darwin speculates that every organism may contain a large number of
very small heredity-particles (he called them ‘gemmules’)
which are continuously produced by all the organs of the
body and which continuously circulate throughout the
body. Eventually, he concludes, the gemmules (or some
portion of them) must collect in the reproductive organs,
so that they can be passed on to the next generation. Quite
explicitly, pangenesis allowed for and explained how
acquired characters could be inherited.
Galton had a very strong reaction to The Variations; his
personal copy is filled with marginal notes.7 As a reader of
‘Hereditary talent and character’ might have easily
guessed, he was dubious about the inheritance of acquired
18
characters which was, as he had pointed out, logically incompatible with his conviction that both physical and intellectual traits were innate. Where, for example, Darwin
had written (Vol II, p.24) about cases of a child born with
an injury similar to one that a parent had acquired, Galton
wrote: ‘He might have had an infirm organ to begin with
or . . . his wife, or his wife’s family must have’. On the
other hand, he was enthusiastic about the notion of gemmules, because they could be mathematized; in Hereditary
Genius, which Galton published just a year later, he was
explicit on this point. ‘The theory of Pangenesis’, he wrote,
‘brings all the influences that bear on heredity into a form
that is appropriate for the grasp of mathematical analysis’.
(p.426)5
Until the publication of Hereditary Genius, Darwin and
Galton had not had much of a personal relationship despite their family ties. But Darwin was delighted by
Galton’s appreciation of pangenesis and so, when Galton
wrote to him in December 1869 regarding some experiments that might test the theory, Darwin responded enthusiastically. Galton proposed to transfuse blood between
rabbits of different breeds in order to see whether the traits
of the donor rabbits (particularly coat colour) would appear in the offspring of the recipients. Darwin put Galton
in touch with rabbit breeders and, for the next year, insisted on being kept apprised (by letter) of the progress of
the experiments. To Galton’s delight—and Darwin’s
embarrassment—the results were negative; out of 124 offspring in 21 litters born by transfused rabbit does, not a
single ‘mongrel’ had appeared. Galton presented a full report of his findings to the Royal Society in March, 1871.12
(The correspondence between Darwin and Galton about
the rabbit experiments can be found in Pearson’s Life,
Letters and Labours of Sir Francis Galton, Vol. 2.13)
Darwin reacted to Galton’s report uncharacteristically; he
behaved badly. Galton found himself publicly admonished
for having unwittingly misinterpreted his cousin’s theory. ‘In
my chapter of Pangenesis in my ‘Variations of Animals and
Plants under Domestication’, Darwin wrote in a letter to
Nature, ‘I have not said one word about the blood, or about
any fluid proper to any circulating system’. (p.502)14 Darwin
was nit-picking. What he had actually said was ‘the gemmules in each organism must be thoroughly diffused; nor
does this seem improbable considering their minuteness, and
the steady circulation of fluids throughout the body’,—and
in all the correspondence that he had had with Galton, he
never expressed any doubts about the experimental efficacy
of transfusing blood between breeds of rabbits.10
Galton’s reply to Darwin was a model of British forbearance. ‘I do not much complain’, he replied, a week later, ‘of
having been sent on a false quest by ambiguous language, for
I know how conscientious Mr. Darwin is in all he writes,
International Journal of Epidemiology, 2016, Vol. 45, No. 1
how difficult it is to put thoughts into accurate speech, and
again, how words have conveyed false impressions on the
simplest matters from the earliest times’.15 But Galton never
forgot his annoyance; this explains the first sentence of his
B.A.A.S. speech (‘Feasible experiments have yet to be designed that shall be recognised by experts as satisfactory tests
of the hereditary transmission of acquired habits’) as well as
the fact that he waited until Darwin had died (1882) to discuss the matter again publicly.
Despite the failure of the rabbit experiments, Galton never
gave up his conviction that some sort of hereditary particle
existed: his apologetic letter to Nature ends with the words,
‘Vive Pangenesis’.15 Indeed, between 1872 and 1876 he published two papers in which he developed a variant of the theory (which he called ‘stirp’). Galton understood stirp to be
the entirety of all the hereditary particles in the body, but—
unlike Darwin—he thought that, because of the large number
of particles, the laws of heredity were most likely probabilistic.16,17 Over the course of the next decade, Galton pursued
this hypothesis by undertaking experimental studies of the inheritance of height in ornamental sweet pea plants (the same
plant, ironically, and one of the same traits that Mendel had
studied) and a series of controlled observations on the heights
of children compared with the heights of their parents. His
analysis of those experiments and observations led him to the
discovery of what we now call regression to the population
mean, one of this major contributions to the science of
statistics.18
Stirp theory did not, however, permit the inheritance of
acquired characters. The text of Blood Relationship makes
it very clear that Galton still held to his notion that every
embryo is the direct, physical descendant of another embryo. ‘The span of the true hereditary link’, he wrote,
‘connects . . . not the parent with the offspring, but the primary elements of the two [stirp that is passed from one
generation to the next] such as they existed in the newly
impregnated ova’. (p.400)16
Just a few months before Galton gave his B.A.A.S lecture, August Weismann wrote to Galton acknowledging
that Galton had expressed the central idea of continuity of
germplasm earlier than he himself had done. After thanking Galton for having sent a copy of his most recent book,
Natural Inheritance, in addition to some of his earlier
papers on heredity, Weismann expressed his regret about
not having previously read Galton’s A Theory of Heredity
because ‘ . . . you have exposed in your paper an idea which
is in one essential point nearly allied to my theory of the
continuity of germplasm’. After explaining that an English
translation of his essays was about to appear,19 Weismann
went on to remark that, ‘I shall profit from the next occasion which offers itself to me to give a more extensive
International Journal of Epidemiology, 2016, Vol. 45, No. 1
account of your views and to point out the differences between our views’.20
Weismann does not elaborate on what he thought those
differences might be, but subsequent commentators have repeatedly done so.21,22 Weismann, one of the ablest of the
German founders of cytology, is famous for having given
the inheritance of acquired characters its final coup de grace
by cutting off the tails of newborn laboratory mice and
observing their offspring for several generations without
once finding a newborn tail-less mouse. But Weismann
only did that experiment after first convincing himself,
through his cytological and embryological studies, that the
physical substance responsible for generational continuity
was located in the nucleus of the cell (he called it ‘germplasm’ as opposed to ‘protoplasm’). Galton never located
stirp in the body except to say that it eventually collected in
the reproductive organs; not being a naturalist, let alone a
cytologist, Galton knew nothing about the existence of
cells, let alone about the contents of their nuclei.
Weismann’s version, as a result, had biological meaning in
a way that Galton’s did not. It led to the discovery of the
chromosomes and to the understanding of both mitosis and
meiosis—and, eventually, helped naturalists to understand
the significance of Mendel’s laws. Galton’s concept of continuity was not historically sterile; it laid the foundation for
what we now call biostatistics. Weismann’s concept, however, laid the foundation for what we now call genetics.
Galton’s concept also laid the foundation for what became, early in the 20th century, the eugenics movement.
Galton had never given up his conviction, first expressed in
1865 and embedded in both the title and the content of his
BAAS speech a quarter-century later, that human talent
and character were determined more by nature than by
nurture, and in his old age he was happy to lend his support to the social movement that some of his disciples were
creating.(The pairing of nature and nurture appears in
Shakespeare’s The Tempest (Act 4, Scene 1) but its modern
usage is ascribed to Galton in the title of his book23). The
title of the B.A.A.S paper reminds us that Galton was more
interested in mental habits than in physical traits. The text
also reminds us which organism he cared most about; it
refers, repeatedly, to ‘parents’ and ‘children’, even though
the animals on which he suggests experimenting are chickens, moths and fish. Galton focused on these organisms because they can be bred relatively easily and kept under
controlled environmental conditions; he already knew—
having undertaken a pioneering study of twins in the same
years that he was developing his stirp theory—that human
beings were far from the ideal experimental animals for
this purpose. 24
Galton was a eugenicist even before he coined the
term—and his passionate commitment to the idea that bet-
19
ter breeding would produce a better human being underlay
all of his effort to study heredity and all of his efforts to
deny the likelihood of the inheritance of acquired traits—
as this paper aptly demonstrates.
A note about the persons mentioned
in Galton’s paper
August Weismann (1834-914) has already been identified,
but it is worth noting that Galton spelled his name wrongly
here and continued to make the same mistake in subsequent publications.
Mr Welldon is undoubtedly W. F. R. Weldon
(1860–1906) who started his career as an invertebrate morphologist, but who developed an interest in the statistical
study of variation in the 1890s, becoming a disciple of
Galton’s and a collaborator with Karl Pearson. In the first
decade of the 20th century, when the English Galtonians
waged a fierce battle of words with the English Mendelians,
Weldon and Pearson were the leaders of the Galtonian camp.
Frank Merrifield was an entomologist living in
Brighton, England, in the 1890s. He undertook some
experiments with moths at Galton’s behest, the first of
which are reported in ‘Practical Methods and Enquiries as
to the Method of Breeding Selenia illustraria for the
Purpose of Obtaining Data for Mr. Galton’, Trans.
Entomol. Soc 1887;I:19-14.
It has proved impossible to identify Miss Pridhom.
Mobius is not the mathematician August Ferdinand
Möbius (1790-1868) but rather the zoologist Karl August
Möbius (1825-1908). The work in which he reported his
experiment is a 20-page pamphlet, Die Bewegungen der
Thiere, und ihr psychischer Horizont [The movement of
animals and their psychological horizon] (Kiel, 1873).
Charles Darwin gave a full account of the experiment in
Chapter 3 of The Descent of Man, and Selection Related to
Sex (1871)—which is undoubtedly where Galton encountered it, as he did not read German.
Funding
The research on which this essay is based was done forty
years ago, in 1966-1967, when the author was a pre-doctoral fellow, under an NIH Training Grant on the history
of genetics. The principal investigator was William
Coleman, PhD. (deceased, 1988) then a faculty member at
The Johns Hopkins University, where the author was then
a graduate student.
References
1. Galton F. Hereditary talent and character. MacMillan’s
Magazine 1865;12:157–66, 318–27.
20
2. Galton F. Inquiries into Human Faculty and Its Development.
London: Macmillan,1883.
3. Cowan RS. Sir Francis Galton and the Study of Heredity in the
Nineteenth Century. New York, NY: Garland Press, 1985.
4. Gillham NW. A Life of Sir Francis Galton: From African
Exploration to the Birth of Eugenics. Oxford, UK: Oxford
University Press, 2001.
5. Galton F. Hereditary Genius. London: Macmillan, 1869.
6. Zirkle C. The Inheritance of Acquired Characters and the
Provisional Hypothesis of Pangenesis. The American Naturalist
1935;69:417–45.
7. Green JC. The Death of Adam: Evolution and its Impact on
Western Thought. New York, NY: Mentor, 1961.
8. Burkhardt RW. The Spirit of System: Lamarck and Evolutionary
Biology. Cambridge, MA: Harvard University Press, 1977.
9. Jordanova LJ. Lamarck. Oxford, UK: Oxford University Press,
1984.
10. Darwin C. The Variations of Animals and Plants under
Domestication. 2 vols. London: John Murray, 1868.
11. Located in Galton Papers, Archives, University College London,
London UK.
12. Galton F. Experiments in pangenesis by breeding from rabbits of
a pure variety, into whose circulation blood taken from other
varieties had previously been transfused. Proc R Soc 1870-71;
19:404.
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13. Pearson K. Life, Letters and Labours of Sir Francis Galton. Vol.
2. Cambridge, UK: Cambridge University Press, 1914-30.
14. Darwin C. Pangenesis. Nature 27 April 1871:502–03.
15. Galton F. Pangenesis. Nature 4 May 1871:5–6.
16. Galton F. On blood relationship. Proc R. Soc 1872;21:394–401.
17. Galton F. A theory of heredity. J R Anthropol Inst 1876;5:
329–48.
18. Cowan RS. Francis Galton’s statistical ideas: the influence of eugenics. Isis 1972;63:509–28.
19. Weismann A. Essays upon Heredity and Kindred Biological
Problems. Oxford, UK: Clarendon, 1889.
20. Weismann to Galton, 23 February 1889. In: Pearson K. Life,
Letters and Labours of Sir Francis Galton. III. Cambridge, UK:
Cambridge University Press, 1914-1930.
21. Churchill FB. August Weismann, Development, Heredity and
Evolution. Cambridge, MA: Harvard University Press, 2015.
22. Schwartz Cowan R. Sir Francis Galton and the continuity of
germplasm: a biological idea with political roots. In: Proceedings
of the 12th International Congress of the History of Science, vol.
8. Paris: Albert Blanchard, 1970.
23. Galton F. English Men of Science: Their Nature and Nurture.
London: Macmillan, 1874.
24. Galton F. The history of twins as a criterion of the relative
powers of nature and nurture. Fraser’s Magazine 1875;12:
566–76. Reprinted in Int J Epidemiol 2012;41:905–11.
International Journal of Epidemiology, 2016, 20–23
Commentary: Inheritance of
doi: 10.1093/ije/dyw031
acquired characteristics: eliminating
alternatives in the search for mechanisms.
Commentary on Galton F: Feasible experiments
on the possibility of transmitting acquired
habits by means of inheritance
BG Dias
Emory University School of Medicine, Department of Psychiatry and Behavioral Sciences, Yerkes
National Primate Research Center, Atlanta GA 30329, USA. E-mail: [email protected]
Accepted 11 January 2016
Increasing scientific evidence suggests a role for the inheritance of physiological and behavioural traits across
generations.1–17 By way of clarification, the inheritance
being talked about refers to traits that have first been
acquired by an ancestral generation as a consequence of an
environmental trigger and then subsequently inherited by
the descendant generations. This is in contrast to congenital traits that are inherited from the ancestral lineage.
Several broad conceptual questions dominate critiques
about the inheritance of characters acquired by ancestral
populations and ought to be addressed if such inheritance
is to be proven unequivocally.18–20 Among these: (i) is the
acquisition of the trait in question a case of true biological
inheritance or a consequence of information transmitted
across generations via social means? and (ii) over how
many generations should this acquisition be observed to
C The Author 2016; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association
V