American Scientist

Origins of Intelligence: The Evolution of Cognitive Development in Monkeys, Apes, and Humans. Sue Taylor Parker and Michael L. McKinney. 404 pp. Johns Hopkins University Press, 1999. $55.

At my local bookstore science and pseudo-science make uneasy bedfellows. In one rack headed "Natural History," the latest from Stephen Jay Gould and Richard Dawkins rub shoulders with books on what your dog is really thinking, the secret lives of cats and other similar profitable drivel. Consequently, if I had come across Sue Parker and Michael McKinney's book down at the bookstore—words like "origins" and "intelligence" in its title and a picture of a bonobo pointing at his mouth in a cutesy, intelligent-looking way—I might well have hesitated. Could this be a serious piece of work? There was no need for anxiety. Parker and McKinney have produced a very serious and interesting book indeed.

The first part of the book, written by Parker alone, tackles the question of origins in a developmental sense across primate species. Taking a neo-Piagetian approach, she compares cognitive development in the physical, logical, social and linguistic domains. Although there is a wealth of information here, it will probably be of interest only to those with a specific concern with this issue. There are also problems in this data set—some recognized, some not. One of the acknowledged problems is that many parts are very sparse—many tables showing different aspects of cognitive development compared across species are more than half empty. Unacknowledged problems include a tendency to gloss over alternative interpretations and critical voices in the interests of a coherent story.

Part II is a completely different book—far more stimulating and likely to be of much broader appeal. Parker and McKinney argue for several provocative theses. First, they posit (and this is the only major point of connection between the two parts of the book) that the evolution of primate cognition is a story of progressive addition of more cognitive stages: from monkeys (which rarely show skills beyond Piaget's sensorimotor stage) through great apes (which show preoperational and occasional symbolic skills) to human beings (who, of course, reach the formal operational stage of cognitive development). They extend this observation by brief reference to brain anatomy, stone tools, timing of tooth eruption and so on to claim that the idea that humans have evolved as more juvenile forms of the apes from which we are descended—neoteny—is a myth. Instead, they contend, quite persuasively in my view, that we are more mature apes—"adultified." At base, their argument is that we spend more time developing larger, more complex brains and cognitive behaviors. A neotenized species, like a domestic cat or dog, shows behavior dominated by more juvenile behavior patterns—reflexes and simpler behaviors and not behavioral complexity.

One final windmill that Parker and McKinney tilt at is the idea that evolution cannot be said to tend toward greater complexity. They argue that the tendency of evolution to add to the end of existing body plans will inevitably lead to greater complexity. They also argue that a variety of lines of evidence indicate that there has been an increase in the complexity of organisms over time.

Part II is wonderfully provocative and not a little convincing. Unfortunately, the assessment of evidence is often fairly brief (stone tools are dealt with in just one page). Nonetheless, I recommend it heartily to anyone interested in the evolution of intelligence.—Clive D. L. Wynne, Psychology, University of Western Australia