From something I wrote I quote another scientist:
From the materialist point of view our human brains are the product of evolution — an ape-like brain grown larger and more sophisticated. Physically a human brain is three times the size of a chimpanzee brain, and uses considerably more energy. Our brain represents 2 percent of our body weight but uses 20 percent of the oxygen we breathe. However, our brains are not merely enlarged ape brains — there are other differences. Our brains contain neural structures, enhanced wiring, and forms of connectivity among nerve cells not found in any animal.1 Our neurons continue dividing well into adulthood and have a 10-fold higher density than chimps. The human brain is something new, something different, as can be seen by the things we do that animals don’t.
In fact our differences are likely to be greater than our similarities. David Premack, the late psychologist at the University of Pennsylvania said:
In examining claims of similarity between animals and humans, one must ask: What are the dissimilarities? This approach prevents confusing similarity with equivalence. We follow this approach in examining eight cognitive cases — teaching, short-term memory, causal reasoning, planning, deception, transitive inference, theory of mind, and language — and find, in all cases, that similarities between animal and human abilities are small, dissimilarities large. 2
Are the dissimilarities so large as to make Darwinian evolution of our brains and abilities impossible? Our brains have vastly more ability than is needed for survival, most notably the capacity for language and abstract thought. We are orders of magnitude beyond anything animals can do.
Let’s consider language. As a thought experiment, imagine what life required about 500,000 years ago (noting the irony of the experiment as you do so). The people alive then were hunters and gatherers. Their tools were Acheulean hand-axes and sharpened wooden spears. Fire was used for cooking. Listen to David Premack again:
I challenge the reader to reconstruct the scenario that would confer selective fitness on recursiveness. Language evolved, it is conjectured, at a time when humans or protohumans were hunting mastodons…Would it be a great advantage for one of our ancestors squatting alongside the embers, to be able to remark, “Beware of the short beast whose front hoof Bob cracked when, having forgotten his own spear back at camp, he got in a glancing blow with the dull spear he borrowed from Jack”?
Human language is an embarrassment for evolutionary theory because it is vastly more powerful than one can account for in terms of selective fitness. A semantic language with simple mapping rules of a kind one might suppose that the chimpanzee would have, appears to confer all the advantages one normally associates with discussions of mastodon hunting or the like. For discussions of that kind, syntactical classes, structure-dependent rules, recursion and the rest, are overly powerful devices, absurdly so. 3
- David Premack, “Human and animal cognition: Continuity and discontinuity,” Proceedings of the National Academy of Sciences, 2007, vol. 104 no. 35, pp 13861–13867.
- Premack, ibid.
- Premack, D. “‘Gavagai!’ or the future history of the animal language controversy.” Cognition 19: 207-296.