Sexual Dimorphism in Mammals

This review from 1974 examined sexual dimorphism in mammals, focusing on structural and functional differences beyond reproductive organs. 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 environmental exposure, 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 affecting further development. The study noted that males typically grew faster but were less mature than females, who reached puberty earlier. Various organs and metabolic processes exhibited sexual dimorphism, with males often having larger organs and higher metabolic rates, while females had greater immunological competence. The review also discussed the impact of sex hormones on organ size, metabolic activity, and reproductive functions, emphasizing the complex interplay between genetics and hormones in shaping sexual dimorphism across different mammalian species.