I thought everyone knew this?
The profs measured the intelligence of 2,500 brothers and sisters and pronounced that males show a greater propensity for being both geniuses and morons than their female siblings.
Agreed, saying it is what got Larry Summers into so much trouble at Harvard but then it being something which the Harvard faculty insists it is impermissible to say bolsters rather than reduces the likelihood of its being true.
The distribution of attributes (whether it be height, intelligence, speed, strength, whatever) in males is wider than it is in females. Longer tails to the distribution if you like.
The most interesting (entirely unproven I might add) explanation for this came from a female biologist back when Summers was in all that trouble. It\’s exactly to do with the XX and XY. Y is such a truncated little thing that if there\’s a problem (read mutation?) with the sole X then there\’s no other copy of a gene to cover for it. Women, having two X\’s, are more likely (for a lack of a functioning gene in both X\’s is less likely than in just one) to have another copy of a gene that can take over. Thus, women are more likely to be "average", men more likely to be at the extremes of a distribution.*
Summers\’ problem was that he then mused that perhaps (and it very much was a perhaps) this explained the gender imbalance amongst Ivy League professors, especially in the hard sciences, where the people are drawn from the third and fouth standard deviations from the mean. Because there are more men in that pool. I don\’t think he would have got into so much trouble if he\’d pointed to the other end of the distribution, the population of those in homes for the feeble minded.
* Please note, I\’m absolutely certain that this will read wrongly to anyone who actually knows about this area of biology but the general gist should be clear.