Light and Sexual Periodicity

Abstract

IN the North Greenland (Peary) Expedition, evidence of sexual periodicity in the Eskimos was observed by Cook.1 Thus, with the onset of the sunless winter, sexual desire fails and menstruation during the long period of darkness is absent. But with the dawn of spring a phase of sexual excitement or prœstrum ensues, menstruation returns, and the majority of the children are bom nine months after the return of the ‘sun’. The girls marry at fourteen or fifteen years of age, but the menstrual flow does not begin until they are nineteen or twenty years old. Children are ‘suckled’ for four to six years, and on the average one child is born every four years. Stieve and others, too, have noted that in the long polar night Eskimo women neither menstruate nor conceive. If this hiatus in the sexual cycle be due to absence of light, it must be of ‘sunlight’, for moonlight is present in the polar night. Light and heat rays seem essential for maintenance of the sexual cycle.