AMERICAN ZOOLOGIST
Volume 4, Number 2
May 1964
REFRESHER COURSE ON BEHAVIOR
GENETICS: INTRODUCTORY REMARKS
ERNST CASPARI
Department of Biology, University of Rochester, Rochester, N. Y.
The refresher courses which the ASZ has long time ago. I want to take this opporsponsored since 1956 have a purpose differ- tunity to call attention to an idea which is
ent from that of the usual symposia. The not at present regarded as part of behavior
latter are supposed to present the most genetics, but which may have some bearing
recent findings in a field to an audience of on future developments. In the first decade
experts, while the refresher course is sup- of this century, Richard Semon published
posed to give the teacher an integrated a book on the "mnerae" in which he specisurvey of a particular area, including the fically compared heredity with memory. He
older findings together with the most recent introduced the term "engram" for the physiones. It is intended to enable a teacher ological correlate of memory in the nerve
of biology to get acquainted with the more cells, and speculated that not only nerve
recent developments in a well-established cells but also germ cells have the ability to
field, or with the facts and aims of a rela- preserve and transmit engrams. We would
tively new field which was not taught at say today that both germ cells and nerve
the time when he was a student.
cells can conserve and transmit informaBehavior genetics may appear to belong tion. Semon, however, went one step furto the latter group of fields. Only in 1960 ther with his analogy; he postulated that
did the first book on this topic appear. At the engrams in the germ cells, just as those
the Genetics Congress in Montreal in 1958 in the nerve cells, are produced by influit was impossible to arrange a symposium ences coming from the environment, and
in this field because of lack of material, and that in this way they constitute a racial
actually only two papers falling within memory. This trend of thought led him
this area were submitted as contributed pa- logically to consequences which postulate
pers. Since that time, behavior genetics has a Lamarckian theory of evolution, and the
experienced a very encouraging growth. At book accordingly fell into oblivion in the
the Genetics Congress in The Hague in 1920s when evolutionists came to reject
1963, a symposium on this topic was organ- completely Lamarckian concepts. In all
ized which was very well attended, and fairness it should be mentioned that at Sesufficient contributed papers were submit- mon's time little was known about the
ted so that a complete session on behavior mechanism of memory, and almost nothgenetics could be organized. The question ing about the structure of the genetic mamay therefore be asked why it took behavior terial. Today, we know the mechanism
genetics such a long time to become a recog- whereby coded information is kept and
nized specialty in genetics, and why inter- transmitted in the genie material, but we
est in this field has grown so conspicuously do not know much more than Semon did
in the last six years. I feel that a historical about the storage of information in the
survey of this type may be of interest in brain. Recent observations, particularly
those of Hyden and collaborators on the
the context of this refresher course.
role of RNA in the learning process, seem
Relationships between genetic and be- to indicate that the chemical basis of coding
havioral phenomena were pointed out a
(97)
98
ERNST CASPARI
involved in the two phenomena may be
quite similar.
Geneticists at an early date became aware
of the fact that certain genes with morphological effects have pleiotropic effects on the
behavior of the animals carrying them.
Sturtevant's (1915) observation that the
gene "yellow" in Drosophila affects the mating behavior of the males is a very early
example. There was, however, a tendency
to ascribe these behavioral effects to genie
effects on the sensory or on the effector
organs. Sturtevant, for example, proposed
that the effect of y on mating behavior may
be due to a general muscular weakness of
yellow males. From the point of view of
present-day behavior geneticists we can say
that such pleiotropic effects on sensory and
motor organs certainly exist; but they may
be regarded as trivial, since the main interest centers on the effects of genes on the
activity of the nervous system. As far as the
effect of the gene "yellow" in Drosophila is
concerned, it has been shown by Bastock
(1956) that it consists in definite quantitative changes in certain components of the
mating behavior pattern.
The interest of psychologists in the genetic interpretation of behavioral characters
arose early in connection with the naturenurture controversy. While this controversy has played a certain role in the development of biological concepts, it has
been particularly hotly debated in its application to behavioral and psychological
concepts. In general, the attitude of many
psychologists in the first part of this century
was inclined to deny the importance of
genetic factors for behavior, trying to interpret all findings in terms of experience and
learning. In this way, most psychologists
worked on the relation between environmental factors and behavior, assuming that
individual differences, such as those caused
by genetic factors, may be neglected. The
whole nature-nurture problem as applied
to behavior was, and still is, highly encumbered by emotional overtones, particularly
since it was quite clear from the beginning
that this problem has an important bearing
on practical problems, such as the organiza-
tion of schools. This appears very clearly
from the first systematic investigation on
the genetics of a behavioral character; a
successful selection experiment for performance of rats in a maze showed clearly that
the ability to learn, i.e., to modify behavior
as a result of environmental conditions, is
itself under the control of genes (Tryon,
1940). This study was published in the
Yearbook of the National Association for
the Study of Education.
Much of the early material bearing on
behavior genetics was derived from the
clinical field. The occurrence of many mental diseases in families was known for a
long time, and an interpretation on Mendelian lines was attempted quite early.
Here again, the investigations gave rise to
numerous controversies which have not yet
been resolved. Still, some of the best investigated cases of behavior genetics are
derived from human pathology, such as
phenylketonuria. We will mention them
only briefly in our present discussion, since
our main attention should be centered on
problems of interest to zoologists. It should
not be forgotten, however, that behavior
genetics is a truly interdisciplinary field in
which zoologists, psychologists and psychiatrists have an equally legitimate interest.
As is so frequently the case, much of the
impetus which behavior genetics has gained
is due to the efforts of one man who decided
early in his life to devote his work completely to its analysis. J. P. Scott (1943)
started out by analyzing the behavioral effects of mutants of Drosophila systematically. He proceeded to the much more exacting task of genetically analy/.ing behavioral
differences among mouse strains and finally
among dog breeds. His efforts, at first rather
isolated, received support from developments in other fields. The theory of evolution developed the concept that sexual
isolation is the most important single factor
in species formation. Through the work
of Dobzhansky and his collaborators it became apparent that mating behavior and
mating preferences constitute one of the
most potent single factors in the establishment of sexual isolation. In addition, the
BEHAVIOR GENETICS
simultaneous development of ethology, particularly the work of Lorenz, Tinbergen,
and their students, indicated that behavioral differences are just as important for
taxonomic considerations as morphological
ones, and that in evolution, behavioral differentiation frequently precedes the differentiation of associated structures. It has, in
brief, become obvious that behavior genetics occupies a central position for our understanding of the evolutionary processes
of animal species.
Since most of its behavioral activities are
of obvious adaptational value to the species,
the analysis of their genetic basis opens up
an approach to the problem of the evolution of adaptedness and of adaptation, one
of the most challenging problems of present day biology.
99
REFERENCES
Bastock, M. 1956. A gene mutation which changes
a behavior pattern. Evolution 10:421-439.
Fuller, J. L., and W. R. Thompson. 1960. Behavior
Genetics. New York and London, Wiley and Sons.
Hyden, M. 1962. A molecular basis of neuron-glia
interaction, p. 55-69. In F. O. Schmitt, [ed.],
Macromolecular specificity and biological memory. MIT Press.
Scott, J. P. 1942. Genetic differences in the social
behavior of inbred strains of mice. J. Hered. 33:
11-15.
. 1943. Effects of single genes on the behavior of Drosophila. Am. Naturalist 77:184-190.
Semon, R. 1904. Die Mneme als erhaltendes Prinzip
im Wechsel des organischen Geschehens. (Four
editions between 1904 and 1914.)
Sturtevant, A. H. 1915. Experiments on sex recognition and the problem of sexual selection in
Drosophila. J. Animal Behaviour 5:351-366.
Tryon, R. C. 1940. Genetic differences in maze
learning in rats. p. 111-119. In 39th Yearbook,
Natl. Soc. for the Study of Education, Bloomington, 111. Public School Publ. Pt. I.