Given the evidence that already exists, I would be surprised if he considered the idea just speculation.
The fact that men have a greater variance in ability than women has been repeatedly confirmed. Depending on which characteristic of intelligence is being measured, the variance among men is generally 1.07 to 1.17 times as great as the variance among women. Vocabulary is an extreme, there the variance is 1.4 times greater among men than women. See http://precedings.nature.com/documents/3238/version/1/files/... for verification of that.
The open and difficult question is how much of the over-representation of men at the top echelons of society can be attributed to this variation of ability versus sexism. While the question is going to offend and be controversial, I agree with Summers that the principle of academic freedom says that academics should be free to ask it.
The fact that men have a greater variance in ability than women has been repeatedly confirmed. Depending on which characteristic of intelligence is being measured, the variance among men is generally 1.07 to 1.17 times as great as the variance among women. Vocabulary is an extreme, there the variance is 1.4 times greater among men than women. See http://precedings.nature.com/documents/3238/version/1/files/... for verification of that.
The open and difficult question is how much of the over-representation of men at the top echelons of society can be attributed to this variation of ability versus sexism. While the question is going to offend and be controversial, I agree with Summers that the principle of academic freedom says that academics should be free to ask it.