Up From Dragons: The Evolution of Human Intelligence [ハードカバー]

Championing the ascent of reptiles as much as the descent of man, this thoughtful volume on the evolution of intelligence by Skoyles and Sagan is a welcome addition to the nature/nurture neurophilosophy shelf. The authors take us well beyond the 'usual suspects' listing of gross anatomical brain structure and function of the familiar phyla, traveling a welcome breadth of comparative data to include a wide variety of species (including our earlier selves). Rather than merely outline the familiar shopping list(s) of evolving structures culminating in the development of the modern human cerebral cortex, Skoyles & Sagan do not end with the discussion of its distinctive "associative" or "silent" areas of the brain of old (as so many other authors are still content to do). Instead, and throughout the book's eighteen chapters, we are treated to a series of detailed proposals concerned with the continuously adaptive neural architecture of both the intra- and inter-cerebral structures underlying the evolution human intelligent behavior.
Reminiscent of learning the names of Tolstoy's characters in the early pages of 'War & Peace', one meets here parts of the brain rarely mentioned (let alone claimed to be of any significance in explaining who we are and why we behave as we do). Following the publication of this volume, the long overdue and normally restricted cast of human brain features will now include the structure and functional connectivities of the anterior cingulate, the amygdala, the insula, the orbital and dorsolateral prefrontal cortex of the brain (and these are just a few of the characters amongst many others that might have been introduced here). We may still not be able to agree upon how best to measure intelligence (IQ, in my view, still tautologically measuring 'what IQ tests measure'), but the physiological substrates of the brain supporting intelligent behavior are slowly coming to be located and characterized. Many of the examples and theoretical components put forward may perhaps appear predictable to those familiar with modern paradigms in comparative psychology and the study of intelligent systems (both biological and man-made), but the real strength of this book is to be seen in its successfully discussing adaptive neural systems for the technical non-specialist. The story as told here is a great achievement for a book aimed at the popular science reader.

The basic thesis of the book follows the development of the nervous system in the aftermath of the 'KT event' (coincident with the demise of the reptilian dinosaurs), which favored flexible, mobile species with nocturnal, cold-adaptable behaviors, capable of finding shelter and forage. In contrast, species with relatively reflexive nervous systems, whilst satisfactory when situated in a stable, predictable environment, can often fail to adapt to changes within the time course of sudden catastrophic events. En route to the architecture of the modern human brain, we meet the aetiology of social and emotional life and their associated neural substrata in the prefrontal cerebral and limbic cortex (amongst other structures). The level of neuroanatomical detail is sufficient to provide a coherent and consistent story of successive adaptations leading to the development of 'higher intelligence', but the pathway taken argues not for this result deriving solely from phylogenetic mutation (per se), but, and more importantly, from ontogenetic neural plasticity and enculturation despite the SAME genetic makeup.

If this idea is new, and at first glance appears to be an uncomfortable one, don't panic! If the authors are right, your prefrontal brain cortex will soon get to work in generating some reflex inhibition, allowing one to assess (and reassess) the situation, temporarily delay one's actions, and then to organize and activate novel planned behaviors towards worked goals. Whether the modern human can prove him/herself to be intelligent enough to plan the survival of any future catastrophe (whether it be of our own making or another KT-like event) we will have to wait and see. In the meantime we have in this book, an accessible version of a still-emerging story telling how, and as the solution to what challenges, the intelligence of a variety of species (including modern humans) currently evolved to demonstrate.

Excellently referenced throughout, with bibliography aplenty for those wishing to read more of the detailed research literature, my only gripe with this book would be with its lack of visualization aids for those unfamiliar with the brain areas mentioned. Although the text is sufficiently detailed to allow the reader to construct crude schematics for him/herself (as one may have done in the case of Tolstoy's family trees?), both anatomical and flowchart illustrations might be of help in hastening the orientation of those perhaps new to the anatomy and neurophysiology of the brain.
Whether this would indeed have been the book that Carl Sagan would have written in 1977 had he possessed the vast corpus of knowledge concerning the brain now available, one may only guess? It is my own view that Skoyles & Sagan's title serves more than to merely pay homage to 'The Dragons of Eden', in whose memory this book is in part written.

"The only book on our origins that will be read 100 years on". Surely not? But this book hides the nuts and bolts of a new answer to an old question that will reshape the sciences of human nature - below I give details and let you decide whether this is indeed the next big thing.

But first that old question: what turned the human brain -- initially evolved 100,000 years ago to be, and only be, a smart hunter-gatherer -- into a brain that in each of us is superfitted for our hi-tech modern life. The problem is an embarrassment to science. No neurologist or paleoanthropologist can explain why your brain so obviously not evolved to read this, does so, like with so many other nonevolved modern skills, with such great finesse. Human evolution lacks foresight and so could have made no preparation. It is a big question. Evolutionary psychology offers no explanation. But the genius of Skoyles and Sagan provides a clear and plausible account.

Before summarizing what that is, a criticism. You start off thinking this is Dragons of Eden: The 25 year Sequel -- but Carl was a science populariser; this book, though averagely well written, lacks illustrations and has rather too many notes and references - more a book for getting out of the library than buying for a holiday read. That said, you soon realize that, with all respect to Carl Sagan, this book is much more important than anything he wrote.

Request, even buy, and get it, for its explanation of that old problem. Chapter 14 lays out its core story one which fits together the jig-saw puzzle pieces that the authors have earlier assembled in chapters 3-13 that describe the latest findings in neuroscience and paleoanthropology. The synthesis they offer is a radically novel, reductive and unexpectedly powerful new neurobiological and anthropological theory of symbolism.

Two theories intertwine. First, that the radical changes in cognition and behavior that make us unique are piggybacked upon earlier evolved primate cognitions and emotions. Symbols - stand-ins - they show are at the heart of the human revolution. Evolved primate cognitions process innate inputs - but culturally transmitted nonevolved signs can co-opt their innate processes. The co-optation just needs (and humans are good at this) the ability to learn abstract associations. When symbols co-opt innate ape psychology, it is like an engine being put into a new chassis -- ape psychology is refitted thus into doing something radically new -- human psychology with all its nonevolved cognitions. For example, the core process of fear in apes uses the innate inputs of snakes, spiders, angry faces and blood. But humans can uniquely hock on novel sign inputs such as swastikas, the radiation sign, evil eyes and the thoughts of God - and so use them to power the radically new behaviors that make us cultural.

But what enables humans to put a new culturally derived `chassis' on the ape brain? Here is their second theory. Symbolic co-optation arose from the prefrontal cortex working memory acting as an abstract association "catalyst" upon neural plastic networks. Many molecules would meet too rarely to react unless another molecule - a catalyst puts them together. The same with the neural connections that underlie the abstract associations of symbolic cognition - the `catalyst' in this case being the working memory of the prefrontal cortex that can 'tutor' new neural links. And the new associations that it creates happen thanks to the recently discovered phenomena of neural plasticity which allows old cognitions to rewire to do radically new tasks. The theory uses bits of already established science. It is theoretical innovation at its best - clear "mechanical" sound processes with no hand waved `dues ex machine' processes. Simple - yet overlooked - perhaps because of the breadth of knowledge they bring together -- by those whose business it is to invent such ideas.

You have to read the argument to appreciate its explanatory power. For a hint, consider how our social attachment is both different and not different from that of other apes. Both ape and human attachment depends upon the same limbic processes. But in nonhuman apes, the inputs to such process arise entirely from the actual physical presence of another individual -hugging, grooming, facial reactions, and the feel of warmth. Symbolic culture puts new a chassis on these limbic processes by adding new inputs such as wedding rings, name changes, and rituals. In doing so, the new `symbolic chassis' enables our ape limbic brain to create human specific forms of social bonds - such as those of marriage, with distant kin, the supernatural and society. This idea is simply an act of genius since reveals how neuroscience and grammatology so easily fit under anthropology and even such fields as cultural studies.

Further, the authors make the breakthrough of showing how what is a transient and private emotion in other apes could by a simple scientifically analyzable process become one that in humans is resistant to separation (symbols can stand-in for missing people and relationships with them), and embedded in communities (symbols allow societies to define relationships and so build up social complexity). One hates the phrase "scientific revolution" or "new paradigm" but these authors have done it - the core problem of our origins has been found. They call their idea, the missing link of human evolution. And they are right.

The resulting approach is not only elegant, simple and powerful - but the stuff of which I bet further science discoveries will be born. It is the first book that can be properly called `neuropaleoanthropology'. It is the beginning of something big. The oddly titled book - a wrong title if there ever was one -- does what evolutionary psychology should have done, but has not - reveal the biological dragons under our anthropological Eden.

A hundred pages of references, but some very simple concepts elude these two authors. The fundamental question they attempt to examine and answer is how and why human intelligence evolved. Unfortunately for the authors and their readers this question requires that they first master the application of the Theory of Evolution, and here they fail quite dramatically.

Making frequent use of chimpanzees as examples, they uniformly fail to address the question of what made humans evolve a larger and more intelligent brain than the chimps did. Which is really the question they need to answer. Fine, chimps need some smarts for their social lives and so on as they discuss, but last I looked we are not living in small bands like chimps do. And we are considerably smarter. Why are we smarter? How are humans different socially? Does that have anything to do with the question at hand? I assert that it does but the authors never mention it or examine human social structure.

Robin Dunbar has done some interesting and pursuasive work on the issue of grooming (Grooming, Gossip...) asserting that verbal skills evolved to allow social bonding in groups too large to bond by grooming, and that they replaced grooming in humans because we evolved to not have much hair to groom. To me this is a much more logical argument for the evolution of intelligence via verbal skills than the one that these authors make.

The authors instead assert the classic cop-out of evolution, that it was sexual selection driving verbal skills/social skills to increase leading to greater intelligence. Sexual selection has its place of course. But here the authors assert that it drove the evolution of larger brains even at the cost of female fitness (well, they actually fail to mention the cost for females despite it being incredibly obvious). This just is not what sexual selection does. Sexual selection is the evolution of a trait that has fitness costs for the gender being selected, not for the one doing the selection, and the marker indicates the fitness of the individual selected. Here the authors assert that females selected for larger brains, effectively, while paying the fitness cost themselves by dying in labor. They further assert that intelligence itself had no direct fitness benefits beyond the chimp level. Evolutionary Theory says no, that is not a possible scenario. If intelleigence is not a fitness marker for males but was simply a "preference" that randomly arose, if it provides no fitness advantages to humans (and given that it has a fitness cost for females) as they assert, then we would be chimps. Because these factors together select out the females that prefer intelligent males. If they had grasped the Theory of Evolution they would have known this.

The dust jacket claims that this book destroys the work of Pinker and others in the area of evolutionary psychology. Instead it shows that these two have a lot of knowledge of details but very little ability to understand or apply the most basic concepts involved in the question they seek to answer. To attempt to refute evolutionary pscyhology one needs at least a sound grasp of evolution, and these authors do not have one.

Finally, by rejecting evolutionary psychology they have remained ignorant of the work of scholars like Dunbar and many others that could have greatly informed their quest to answer the question at hand.

Humans did not evolve greater intelligence than chimps because we were just like chimps but the females decided they liked smart boys. That is their arguement in simplified form and it is not even a weak one, it is a clearly wrong and not even theoretically possible one.