TAKE a bunch of lap dancers, some lustful men and a fistful of dollars, and you have the best evidence yet for the controversial idea that women send out signals which reveal their fertile periods.

Last month, biologist Randy Thornhill challenged the orthodoxy that women do not undergo regular bouts of hormone-induced oestrus, or “heat”, when they are at their most fertile – something most female mammals experience (New Scientist, 15 September, p 18). Now a study of the tips men give to lap dancers, conducted by a colleague of Thornhill’s, lends further support to the argument for oestrus.

Geoffrey …