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Origins of the human brain
BOOK
REVIEWS
Homo sapiens a wise guy? Origins of the Human Brain edited by J-P. Changeux and J. Chavaillon Oxford University Press, Symposia of the Fyssen Foundation, 1995. 545.00 hbk (xiii + 321 pages) ISBN 0 19 852307 6
E
volutionary biology and neuroscience have had a somewhat fitful relationship. On one hand, neuroscientists are at least implicitly interested in the evolutionary context of the systems they study, because in order to understand how a system works it helps to have some idea about what it was designed to do. But, because neuroscientists tend to focus on the details of mechanism, their forays into evolutionary explanation have been largely confined to speculation, or to limited interspecific comparisons that tend simplistically to invoke the SC& natcm as an evolutionary model. On the other hand, the evolutionary biologists’ idea of doing behavioural neuroscience has been, typically, to correlate behaviour with no more sophisticated a variable than brain size. Because brains got here by evolution, and because there is intriguing neural diversity that goes far beyond mere brain size, there is a clear need to bridge this interdisciplinary gap. Recent developments, including the advent of powerful, new comparative methods, have started to make this happen. It was therefore a disappointment to me that this edited book, the outcome of a symposium of the Fyssen Foundation in 1990, barely mentioned the comparative method, and ignored much new work in evolutionary cognitive neuroscience. In part, this reflects the focus on origins of the human brain; but that is something we will never understand unless we develop general principles of brain evolution from comparative studies of diverse groups of animals. It is a cliche to say of an edited book that its quality is uneven, but that is the strong im pression here. Too much of the first section, on anatomy, consists of settling old scores in tired debates about fossil cranial endocasts. These debates seem to reflect more about the participants entrenched positions concerning what ‘must’ have been important in hominid evolution than about what the evidence can actually tell us. The field is long on assumption and speculation, and short on data, mainly because there’s not very much you can tell from a lump of fossilized gunk that intruded into a brain case a couple of million years ago. This is a problem acknowledged by Tobias in his more critical chapter. Holloway, however, seemsto assume that the first hominids must have had brains superior
506
to that of the common ancestor with chimps, and that chimps are a suitable model for the latter: ‘It would be a remarkable reversal of the evolutionary process if the Taung specimen’s lunate sulcus were in a position even more primitive...than in Pan’ (p. 47). Well, no it wouldn’t actually, because chimpanzees are not our ancestors but are highly derived in their own right. Misappre hensions and assumptions such as these riddle several contributions in the first part of the book. Rakic, on the other hand, a neuro biologist, shows the evolutionists the way with avery interesting discussion of develop mental mechanisms of neocortical evolution and its anatomical and functional consequences -this is essential reading for comparative biologists hoping to interpret species differences in neocortex size. Section two of the book is devoted to genetics. There are three good reviews by experts in the fields of molecular genetics, mitochondrial DNA and homeobox genes, rc spectively. The trouble is that any relevance that these areas may have to understanding brain evolution is entirely inchoate. Section three, on ‘Culture’, also has some interesting contributions, though again of marginal relevance to brains. Hinde’s chapter on the re lationships between biological heritage and culture could provide a link; human behavioural universals vary adaptively (not really a paradox) reflecting the interaction between learning predispositions and environmental input. This perhaps parallels Rakic’s expo sition of the way in which genetic scaffolding and sensory input interact to determine brain wiring during development, the sort of parallel 1would have liked to see made more of by the editors in this book. Other contributions, on palaeolithic art, on writing and on tool diversity, would be harder to link in. The final section, on ‘Intelligence’, is again diverse, though more consistently interesting. Weiskrantz, for example, reviews work on neurological syndromes affecting aspects of conscious perception, and askswhat level of consciousness non-human nervous systems might be capable of. Huberman’s models of cooperative problem-solving are interesting, but the absence of competition within them limits their relevance to evolution. Pinkerpresents concise and powerful arguments that language is a specific neuro-cognitive adap tation, not a ‘spandrel’ or a cultural invention, and Premack reviews his work on intentionality in primates and human children - here, a fundamental distinction is made between learning, which almost any organism is capable of, and reasoning, for which more complex nervous sytems are required. The patchiness and diversity of this book make it difficult to recommend to any particular readership; the best chapters mainly review work that specialists will already know about, while generalists may be put off by the lack of overall coherence or theme. The
rather uninformative discussions at the end of each chapter would probably have been better replaced by a linking editorial in each section; there are real prospects for interdisciplinary links between the subject areas dealt with by many of the contributors, but unfortunately this book does not develop them. Robert Barton Dept
of Anthropology, Durham,
UK
University DH13HN
of Durham,
Diijihvu, all over again Species Diversity in Space and Time by ML. Rosenzweig Cambridge University Press, 1995. f50.00/$74.95 hbk, f17.95/$27.95 pbk (xxi + 436 pages) ISBN 0 52149618 7
A
I1ecologists desiring an inexpensive and informative time-travel adventure should read this attractively produced volume. Its goal is to catch the essence of (maybe particularly or only American) ecology’s diversity phase of the 1960sand 1970s to present it as both a history and a laudatio to Robert MacArthur, and to propose new applications and challenges. The book provides ideas and interpretations about why patterns exist, and embellishes these with curve-fitting theory. Its major conclusion can be briefly summarized. Diversity (essentially speciesrichness, a term Rosenzweig dislikes) is seen as the summation of immigration, speciation and extinction rates. Species-area relationships constitute a substantial fraction of the diversity puzzle, with the unknown role of regionally varying productivity contributing a primary hindrance to some grand synthesis. The book, however, remains almost totally devoid of mechanistic understanding at the species level, while invoking such well-trodden subjects as niche metrics and habitat diversity. As time travel, it’s an enormous success. Reading this folksy account rekindled long-departed personal doubts about the value of non-mechanistic ecology. I was nurtured in that same glorious era as Mike Rosenzweig yet I retain little nostalgia. I’ve never met an ecologist or paleontologist who doubted that patterns exist in nature when viewed at large spatial or temporal scales, and that they were capable of tantalizing the imagination, as MacArthur readily acknowledged. Species Diversity in Space and Time reviews many such patterns and has its merits as a history, as much for describing the excitement of the 1960s about diversity, as for illustrating why that interest’s demise was only minimally lamented. TREE
uol.
IO,
no.
I.2 December
1995
REVIEWS
Homo sapiens a wise guy? Origins of the Human Brain edited by J-P. Changeux and J. Chavaillon Oxford University Press, Symposia of the Fyssen Foundation, 1995. 545.00 hbk (xiii + 321 pages) ISBN 0 19 852307 6
E
volutionary biology and neuroscience have had a somewhat fitful relationship. On one hand, neuroscientists are at least implicitly interested in the evolutionary context of the systems they study, because in order to understand how a system works it helps to have some idea about what it was designed to do. But, because neuroscientists tend to focus on the details of mechanism, their forays into evolutionary explanation have been largely confined to speculation, or to limited interspecific comparisons that tend simplistically to invoke the SC& natcm as an evolutionary model. On the other hand, the evolutionary biologists’ idea of doing behavioural neuroscience has been, typically, to correlate behaviour with no more sophisticated a variable than brain size. Because brains got here by evolution, and because there is intriguing neural diversity that goes far beyond mere brain size, there is a clear need to bridge this interdisciplinary gap. Recent developments, including the advent of powerful, new comparative methods, have started to make this happen. It was therefore a disappointment to me that this edited book, the outcome of a symposium of the Fyssen Foundation in 1990, barely mentioned the comparative method, and ignored much new work in evolutionary cognitive neuroscience. In part, this reflects the focus on origins of the human brain; but that is something we will never understand unless we develop general principles of brain evolution from comparative studies of diverse groups of animals. It is a cliche to say of an edited book that its quality is uneven, but that is the strong im pression here. Too much of the first section, on anatomy, consists of settling old scores in tired debates about fossil cranial endocasts. These debates seem to reflect more about the participants entrenched positions concerning what ‘must’ have been important in hominid evolution than about what the evidence can actually tell us. The field is long on assumption and speculation, and short on data, mainly because there’s not very much you can tell from a lump of fossilized gunk that intruded into a brain case a couple of million years ago. This is a problem acknowledged by Tobias in his more critical chapter. Holloway, however, seemsto assume that the first hominids must have had brains superior
506
to that of the common ancestor with chimps, and that chimps are a suitable model for the latter: ‘It would be a remarkable reversal of the evolutionary process if the Taung specimen’s lunate sulcus were in a position even more primitive...than in Pan’ (p. 47). Well, no it wouldn’t actually, because chimpanzees are not our ancestors but are highly derived in their own right. Misappre hensions and assumptions such as these riddle several contributions in the first part of the book. Rakic, on the other hand, a neuro biologist, shows the evolutionists the way with avery interesting discussion of develop mental mechanisms of neocortical evolution and its anatomical and functional consequences -this is essential reading for comparative biologists hoping to interpret species differences in neocortex size. Section two of the book is devoted to genetics. There are three good reviews by experts in the fields of molecular genetics, mitochondrial DNA and homeobox genes, rc spectively. The trouble is that any relevance that these areas may have to understanding brain evolution is entirely inchoate. Section three, on ‘Culture’, also has some interesting contributions, though again of marginal relevance to brains. Hinde’s chapter on the re lationships between biological heritage and culture could provide a link; human behavioural universals vary adaptively (not really a paradox) reflecting the interaction between learning predispositions and environmental input. This perhaps parallels Rakic’s expo sition of the way in which genetic scaffolding and sensory input interact to determine brain wiring during development, the sort of parallel 1would have liked to see made more of by the editors in this book. Other contributions, on palaeolithic art, on writing and on tool diversity, would be harder to link in. The final section, on ‘Intelligence’, is again diverse, though more consistently interesting. Weiskrantz, for example, reviews work on neurological syndromes affecting aspects of conscious perception, and askswhat level of consciousness non-human nervous systems might be capable of. Huberman’s models of cooperative problem-solving are interesting, but the absence of competition within them limits their relevance to evolution. Pinkerpresents concise and powerful arguments that language is a specific neuro-cognitive adap tation, not a ‘spandrel’ or a cultural invention, and Premack reviews his work on intentionality in primates and human children - here, a fundamental distinction is made between learning, which almost any organism is capable of, and reasoning, for which more complex nervous sytems are required. The patchiness and diversity of this book make it difficult to recommend to any particular readership; the best chapters mainly review work that specialists will already know about, while generalists may be put off by the lack of overall coherence or theme. The
rather uninformative discussions at the end of each chapter would probably have been better replaced by a linking editorial in each section; there are real prospects for interdisciplinary links between the subject areas dealt with by many of the contributors, but unfortunately this book does not develop them. Robert Barton Dept
of Anthropology, Durham,
UK
University DH13HN
of Durham,
Diijihvu, all over again Species Diversity in Space and Time by ML. Rosenzweig Cambridge University Press, 1995. f50.00/$74.95 hbk, f17.95/$27.95 pbk (xxi + 436 pages) ISBN 0 52149618 7
A
I1ecologists desiring an inexpensive and informative time-travel adventure should read this attractively produced volume. Its goal is to catch the essence of (maybe particularly or only American) ecology’s diversity phase of the 1960sand 1970s to present it as both a history and a laudatio to Robert MacArthur, and to propose new applications and challenges. The book provides ideas and interpretations about why patterns exist, and embellishes these with curve-fitting theory. Its major conclusion can be briefly summarized. Diversity (essentially speciesrichness, a term Rosenzweig dislikes) is seen as the summation of immigration, speciation and extinction rates. Species-area relationships constitute a substantial fraction of the diversity puzzle, with the unknown role of regionally varying productivity contributing a primary hindrance to some grand synthesis. The book, however, remains almost totally devoid of mechanistic understanding at the species level, while invoking such well-trodden subjects as niche metrics and habitat diversity. As time travel, it’s an enormous success. Reading this folksy account rekindled long-departed personal doubts about the value of non-mechanistic ecology. I was nurtured in that same glorious era as Mike Rosenzweig yet I retain little nostalgia. I’ve never met an ecologist or paleontologist who doubted that patterns exist in nature when viewed at large spatial or temporal scales, and that they were capable of tantalizing the imagination, as MacArthur readily acknowledged. Species Diversity in Space and Time reviews many such patterns and has its merits as a history, as much for describing the excitement of the 1960s about diversity, as for illustrating why that interest’s demise was only minimally lamented. TREE
uol.
IO,
no.
I.2 December
1995