From the Guardian:
“Tim Spector of St Thomas’s hospital in London, who led the research, said: ‘The theory is that the orgasm is an evolutionary way of seeing if men can prove themselves to be likely good providers or dependable, patient and caring enough to look after the kids.’
Women who orgasm very easily may be more likely to be satisfied with poor quality men.
‘Perhaps women who had orgasms too easily weren’t very good selectors,’ Professor Spector said. ‘It paid women to be more fussy and this is one way of doing it. The simple fact is that it takes women on average 12 minutes and men two and a half minutes to reach orgasm. Adjusting to that imbalance is a test.’
His team used a national register of twins to ask 4,037 women, aged 19 to 83, about their sex lives and to compare their DNA. About half were identical twins, who share all their genes. The others were non-identical twins, who do not. Assuming twins are brought up in similar environments allows scientists to tease out the differences that are down to genes.”