Understanding Taxa by Comparing Brains

UNDERSTANDING TAXA BY COMPARING BRAINS PAUL PIRLOT* The article by Bullock [1] on Understanding Brains by Comparing Taxa deals with a relatively recent trend in the neurosciences—that is, a comparative approach toward animals with a broad spectrum of behaviors. As a neuroanatomist and student of vertebrate evolution who has been following that line of thought for 20 years, I am delighted to see that, at long last, an authority in neurophysiology so openly recognizes both the significance of what is fundamentally an evolutionary viewpoint and the importance of morphological studies of brain structures to that perspective . However, some interesting aspects of the current situation in the field were not considered in the article referred to. Behavioral Neuromorphology To investigate the brains of species possessing distinct ways of life from a comparative point of view has been defined as the objective of a hybrid discipline called neuroethology. More specifically, the task of neuroethology derives, as Bullock [1] aptly remarks, from the fact "that important neural, particularly anatomical, differences exist even between species of the same order, for which we lack plausible behavioral correlates" [1, p. 519]. Bullock then tries to illustrate both the desirability and the scarcity of such correlations, reviewing a sample of recent publications in which at least a limited effort in the direction of neuroethology can be detected. This reflects great progress in comparison with an attitude that was quite common not so long ago, which amounted to assuming that there were only five modes of life worth considering among the five classes of vertebrates. As a matter of fact, this past year, a Spanish scientist who mav know a little about aquatic animals but surely The author currently works under grant A0778 from the Natural Sciences and Engineering Research Council of Canada. He is grateful to Mrs. Jessica Pottier for her work on the manuscript. *Address: 288 Richford Road, Abercorn, Province Quebec JOE IBO, Canada.© 1986 by The University of Chicago. AU rights reserved. 0031-5982/86/2904-0485$01.00 Perspectives in Biology and Medicine, 29, 4 ¦ Summer 1986 | 499 knows a lot less about brains was telling me (as a compatriot of Ramón y Cajal, I guess) that all neuroanatomy can do is to compare a frog with a iish (sic), leaving for the twenty-first century such more subtle comparisons as those between species of the same class: some "scientists" in some countries still wallow in nineteenth-century concepts. But even in progressive circles, information may be incomplete. Considering Bullock's laudable effort to update neurology with respect to ethology, it would be easy to draw a substantial list of articles in which various authors have already done in neuromorphology exactly what he suggests they ought to do. faking mammalian neuroethology alone, one finds papers from about 1950 on in which the comparative approach is explicitly resorted to, and papers from the late 1950s or mid-1960s in which neuroanatomists explicitly seek to correlate brain structures with behaviors in nature. Bullock mentions a dozen species of vertebrates, including man, used in comparative neurology by authors who paid at least some attention to behavior. Actually, in the past 15 years alone, and within a limited circle known to me, more than 100 mammalian species have been included in several dozens of ethologically oriented investigations in the sole field of comparative neuromorphology. In two other papers by Bullock [2, 3] no reference was made to those publications either. Another important contribution to the field was also overlooked: a 1972 symposium edited by Masterton et al. [4, 5] in which 3 dozen biologists (out of more than 50 participants) expressed their views on brains, behaviors, and the evolution of taxa. I his raises the broader question of why neuromorphological research has so long failed to make full use of the comparative approach—despite the existence of at least one internationaljournal of comparative neurology . The main reason is that a comparative approach in morphology is closely linked with the study of evolution, whereas neurology as a whole has long been almost exclusively a medical domain—that is, one in which evolution is not of prime importance: only a few interspecific comparisons of animal brains have been...