The Season of Birth in Man

Abstract

A critical study of the available data from the countries of the Old World and South America conclusively shows that the incidence of birth is seasonally determined. It has been suggested by others that the factor most likely to be responsible is temperature. The season of natality in the northern New World is now largely culturally determined. Canada still shows remnants of the European season of birth coexisting with the newer pattern so typical of the USA. Puerto Rico has gradually changed from a northern Old World pattern to the one conspicuously reminiscent of the continental USA. The season of birth in Mexico appears to be a reflection of cultural patterns, both general and more local, such as the effect of migration and agricultural practices. It has been suggested that the change that Canada has been undergoing in its season of natality is a reflection of improved standards of living, better heating and lighting, and the unifying effect of better mass communications. Similarly, Puerto Rico shows the results of improved mass communications between her and the continental USA. coupled with the possible effect of migration. The seasonality of birth appears to be increased by illegitimacy, poverty, war, depression and subspecific differences. The caucasoid group indicates the lowest amplitude when compared to others living in the same region. Isolated noncaucasoid groups tend to show lower amplitudes than when they coexist with caucasoid society.