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81 Klein suggested that the chance mutation of a gene 50,000 years ago may have led to the evolution of the fully modern human brain in Africa; the spread of modern humans throughout the world was tied to that “dawn of culture.” Although the human form remained remarkably stable after that ime, behavioral change accelerated dramatically. Humans were trans- ormed from a relatively rare and insignificant mammal to a geologic force. The explosion of technology in the past 10,000 years shows that cultural actors can unleash limitless accomplishments, proposed anthropologist Carel van Schaik, all with Stone Age brains.'* Hominid brains did enjoy an extraordinary increase in size from about 600,000 years in the past to about 30,000 years ago. Although some scien- ists argue that larger brains are a highly unusual anatomical complex— and a reproductive liability—they have been maintained for hundreds of housands of years." Researchers have confirmed the common assumption that a larger brain makes it easier to adapt to the challenges of a new environment. That larger brain may be more responsive to problems—and opportunities. S. Ohno, a Japanese biologist, suggested that our cave-dwelling ancestors were pro- vided with intellectual potential that was in great excess of what was needed to cope with the environment of the time.” These findings do not prove that the evolution of brains like ours was inevitable. Evolutionary psychologists argue that the human mind is a col- lection of special-purpose circuits produced by natural selection to solve the problems of survival and reproduction. The evolution of cognition is neither the result of an evolutionary trend nor an event of even the lowest calculable probability, declared Owen Lovejoy, but the consequence of selection for unrelated characters such as locomotion and diet." Nobel Prize winner William Calvin saw the evolution of intelligence as being an unforeseen consequence of neural machinery that has been selected for some other reason. Our intelligence arose primarily through the refinement of some brain specialization, such as that for language. The transition to a cognitively fluid mind was neither inevitable nor preplanned, archaeologist Steven Mithen found; evolution simply capitalized on a window of opportunity that it had blindly created by producing a mind with multiple specialized intelligences.” De Duve supported the believers when he wrote that increasingly complex polyneural networks appear to be strongly favored by the fact that a more effective brain is advantageous under any circumstance. Others challenge this view; as many species on Earth have survived longer than humans, intelligence is not a necessary adaptation. Intelligence must first arise by chance and in degrees, commented science educator John Mauldin, then The Debate Goes on The Debate Goes on