Sex ratio: a biological perspective of 'Sex and the City'.
The primary sex ratio in humans differs remarkably from the theoretically expected equality of 1:1, and may be as high as 170 males to 100 females. A number of environmental, physiological and genetic factors have been observed to impact on the primary sex ratio: sexual behaviour, variation in hormonal concentrations, natural disasters, environmental pollutants and timing of conception. Nevertheless, no biological mechanism or interaction of factors has suitably explained this phenomenon, or that of the prenatal vulnerability of the male, the suspected higher sex ratio in spontaneous abortion and the male excesses in adult diseases related to the intrauterine environment. Knowledge of the environmental effects and causes of natural variation in the primary sex ratio will make possible its manipulation, which will have public health implications as well as cultural and social consequences.
Pergament
Eugene
E
Department of Obstetrics and Gynecology, Northwestern University, Chicago, IL, USA. pergament@northwestern.edu
Toydemir
Pinar Bayrak
PB
Todydemir
Pinar Bayrak
PB
Fiddler
Morris
M
D001755:Blastocyst / Q000502:physiology; D004190:Disasters; D004785:Environmental Pollutants / Q000494:pharmacology; D005260:Female; D005306:Fertilization / Q000502:physiology; D006728:Hormones / Q000097:blood; D006801:Humans; D008297:Male; D012744:Sex Ratio; D012725:Sexual Behavior / Q000502:physiology; D013997:Time Factors
D004785:Environmental Pollutants; D006728:Hormones