There are several factors in play here.

First, the "selfish gene" approach. We will desire sex with the partner most likely to produce strongly surviving offspring.

Then the Gordon Gecko. Women will desire the mate best able to provide for offspring (in current Western society, the richest or the most socially or politically powerful).

Then the paranoid man. He will seek women least likely to have had previus partners lest his genes do not take in that the woman may already be pregnant. Here lies the Victorian fascination with virginity, and the foundations for today's institutional peadophilia.

Then the 60s - the change of sex from being for procreation to recreation. The LAST thinking you wanted was a fertile mate, for babies were a sex life disaster.

Then the powercrazed: The powerful of both sexes wish to control others including thier sex partners, so desire such partners to be inexperienced, hence immature, hence youthful - hence slim and free of body hair or odour.

The need for a robust physique to combat illness has been displaced by medical advance, so mass is no longer a survival trait.


Compare the way paleness is prized in agricultural societies, since it betokens a person of enough power that another can labour for them - but the 60s and since, the suntan indicates enough money to holiday in the sun. Then the sunbed and Easyjet - the suntan becomes the derided "tango".