Published online by Cambridge University Press: 31 July 2008
Reproductive performance of the human female is simulated by Monte Carlo methods. The results clearly suggest the operation of natural selection on the length of the female menstrual cycle, brought about by differential fertility. It is argued that the selection pressure towards a shorter cycle, with a selective advantage of approximately 1% per day of shortening, is balanced by internal physiological determinants preventing excessive shortening, so the result is a situation of stabilizing natural selection.