Distasteful as it may seem to men, it's women who are responsible for the intelligence of the human race. According to a controversial theory, our female ancestors were smart enough to pick brains over brawn when choosing a mate. They spurned the local Hercules or Adonis, and plumped instead for the man with a sparkle in his eye that hinted at wit and intelligence. Humanity should be grateful, men especially. For if these female ancestors had preferred bright red rumps, men might still be sporting these and keeping company with gorillas and chimps in Africa. Where did this bold idea come from? It has its origins in IQ studies. The average IQ of men and women is pretty much equal. But look closely at intelligence and you find some strange differences between the sexes. For a start, men have a broader range―there are more mentally subnormal males, and more geniuses. And the pattern hasn't changed as far back as the records go. What's more, mothers are more likely to transmit their mental disabilities to their children than fathers. It was clues like these that, 30 years ago, led Robert Lehrke of Brainerd State Hospital in Brainerd, Minnesota, to suggest that many genes for intelligence are concentrated on the X chromosome.
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