Sexual Dimorphism in Mammals

This review from 1974 examined sexual dimorphism in mammals, focusing on structural and functional differences beyond reproductive organs and psychological aspects. It highlighted that life expectancy and mortality rates varied by sex due to both external hazards and inherent biological differences. Males generally had higher mortality rates due to congenital diseases and external risks, leading to a longer average lifespan for females. Chromosomal and hormonal influences were crucial in developing male and female characteristics, with the Y-chromosome initiating testis differentiation and gonadal hormones influencing further development. The study noted that males typically grew faster but were less mature than females, with puberty occurring earlier in females. Various organs and metabolic processes exhibited sexual dimorphism, with males generally having larger organs and higher metabolic rates, while females had greater immunological competence. The review also discussed differences in brain structure and function, with females having proportionately larger brains and different hormonal influences on reproductive cycles. Overall, the document provided a comprehensive overview of the biological differences between male and female mammals.