Individual Development and Evolution: The Genesis of Novel Behavior.
Dr. Gottlieb has produced a real "reader." Although they are not without intellectual challenges, the pages nevertheless zoom by so rapidly that the book is done in a matter of just a few hours. I took my copy on a weekend reptile collecting trip to Northwestern Colorado, expecting to make a start on the book during our down time. To my surprise, however, I was finished with it before the trip was over. This would never have happened with anything written about developmental psychobiology by T. C. Schneirla (though his pieces are certainly worth the effort). Hence, my hat is off to Dr. Gottlieb for an amazing bit of scholarship that he refers to as a "small book" (p. 194).
Incidentally, one of the objects of the trip to Moffat County, Colorado, was the sagebrush lizard (Sceloporus graciosus), which can be found in a variety of habitats including flat shrublands and rocky ledges. It is my strong impression that in the shrublands S. graciosus is wary and very fast, with a relatively long flight distance, but on rocks its behavior is quite different, resembling that of S. undulatus, having a short flight distance and a considerable degree of site tenacity. In brief, you can't easily get near them in the shrublands but you can do so in rocky habitat. I mention this because Dr. Gottlieb has much to say about this sort of behavioral variability within a taxon, although he emphasizes mammals and birds. It is probable (but not yet demonstrated) that the differences between adult S. graciosus in shrubland and in rocky areas is a consequence of differential early experiences encountered during ontogeny in their respective habitats. Conceptualization of how such behavioral changes are induced during individual development is the focus of this book.
The exposition comes in two parts. First, Dr. Gottlieb spends about 100 pages tracing the history of conceptions of development, showing how the wretched nature-nurture dichotomy has remained with us in various disguised forms. In whatever form it raises its obfuscating head, this oversimplistic view of ontogeny not only creates nomenclatural confusion, but it also limits the depth and accuracy of empirical research, the sophistication of interpretative arguments, and the reach of evolutionary theory. It is a sad fact that although developmental psychobiologists such as T. C. Schneirla have long since freed themselves from the shackles of the nature-nurture paradigm of thought, numerous other subdisciplines continued to labor under this scourge. Accordingly, it remains necessary in 1992 for expositions such as the present one to be placed before those who have not yet been saved.
The second half of the book does something new in that it explores implications of intellectually sound conceptualizations of development for evolutionary theory. Here is the exciting material. I will use Dr. Gottlieb's (1992) own words to summarize the essence of the argument:
Living differently, especially living in a different place, will subject the animals to new
stresses, strains, and adaptations that will eventually alter their anatomy and physiology
(without necessarily altering the genetic constitution of the changing population). The
new situation will call forth previously untapped resources for anatomical and
physiological change that are part of each species' already existing developmental
adaptability. At some time further down the road it is possible the genetic makeup of the
evolving population may change, but by the time that happens (if it does) the new
behavioral, anatomical, and physiological changes will already be in place. The
neophenogenetic pathway for evolutionary change is thus seen as (1) an alteration of
development leading to a significant change in behavior, followed by (2) a change in
morphology, and, eventually, possibly (3) a change in genetic composition of the
population. Consistent with their view of the strictly genetic determination of the
phenotype, adherents of the modern synthesis would consider the evolution occurred
only if and when step (3) was achieved. From the present point of view, enduring
transgenerational changes in behavior and morphology (i.e., phenotypic evolution) have
occurred by step (2), without the necessity of adding to, subtracting from, or otherwise
changing the original genetic composition of the population. (pp. 176-177)
Clearly, these are bold assertions, bound to stir controversy, but they are also non-Lamarckian and they are based on empirically verified conceptualizations of ontogeny. The book is worth reading for the clarity of these conceptualizations as well as for the uses to which Dr. Gottlieb puts them.
There are two points in the argument that cause me to hesitate. First, although there is evidence for the fundamental notion that experience during ontogeny can bring about significant changes in behavior and morphology that can be supragenetically transmitted to offspring, most of the examples are teratological. This does not dimish their theoretical significance, but it would be useful for other examples to be produced from the domain of adaptive (i.e., fitness enhancing) ethomorphology. Examples from field research would be especially welcome. Second, as Dr. Gottlieb acknowledges, While I am unable to propose a specific molecular mechanism whereby the organism's new experiences activate previous unactivated DNA (to get the expression of previously inactive genes), the present proposal obviously assumes such a mechanism" (p. 196). 1 suggest that these points should not be taken as flaws, but rather as signposts pointing toward productive research issues.
Because the appearance of behavioral neophenotypes must, to some extent, be dependent upon both experience and neural processes, Dr. Gottlieb spends a fair amount of time reviewing the literature dealing with effects of early rearing variables on later neural and behavioral measures. He concludes that "we should expect to see, by and large, greater behavioral plasticity in birds and mammals than in lower vertebrates" (p. 190, citing Jerison, 1969, 1973). Indeed, he ends up remarking that "the present theory of behavioral neophenogenesis is manifestly a theory of vertebrate evolution, particularly of the higher vertebrates (birds and mammals)" (p. 197). Although I understand his reasons for saying so, I hope my earlier remarks about S. graciosus will raise several thoughts: (1) In spite of their relatively low brain weight-to-body weight ratio, these animals exhibit considerable behavioral plasticity, as do other lower vertebrates and many invertebrates, (2) we know little about these processes not because they are insignificant in the lives of the animals, but because they have not been studied by developmental psychobiologists, and (3) an exciting consequence of this "small book" may be to focus new interest on the ontogenies of the most speciose groups of organisms, perhaps giving rise to insights into heretofore unsuspected extracerebral mechanisms of neophenogenesis. After all, environmentally produced transgenerational, supragenetic influences on behavior and morphology can be just as important for adaptation, evolution, and theory whether these influences are mediated by the brain and spinal cord or by other processes.
Jerison, H. J. (1969). Brian evolution and dinosaur brains. American Naturalist, 103, 575-588. Jerison, H. J. (1973). Evolution of the brain and intelligence, New York: Academic Press.
(David Chiszar, University of Colorado)
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|Publication:||The Psychological Record|
|Article Type:||Book Review|
|Date:||Mar 22, 1993|
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