Published online by Cambridge University Press: 31 July 2008
Guerrero (1975) has cited a wealth of direct data supporting the hypothesis that timing of insemination is related to the sex of the resulting zygote. It is argued here that if this hypothesis were correct, then parental coital rate would be associated with the sex of the resulting children. It is suggested here that empirical data support this inference and hence support the hypothesis.
It is estimated that if Pmale (the probability that a zygote will be male) declines linearly across the fertile period, that decline is from about 0·57 to 0·45.