Are there preconceptional determinants of mammalian sex? A response to Boklage (2005)

Boklage (2005, Hum Reprod 20,583-587) wrote: 'Changes in, or mediated by, the epigenetic environment of embryogenesis provide the most plausible prospects for causes of changes in secondary sex ratio'. Without impugning this notion, I suggest here that other causes of variation in secondary sex ratio antedate fertilization or, in other words, that there are circumstances under which unequal numbers of male and female zygotes are formed. It will be documented here that this suggestion has repeatedly been made on the basis of data on many mammalian species (golden hamster, sheep, mouse, white-tailed deer, American bison, springbok, domestic cattle and Barbary macaque). It may be acknowledged that the causes of this hypothesized preconceptional variation are not established. I have suggested one (parental hormones around the time of conception). But the truth of that hypothesis is not germane to the thrust of the present argument--which is to document the strong suspicions that such preconceptional determinants do, indeed, exist. Efforts should be made to confirm or discredit these suspicions.