📏 Human ancestors had ‘men’ much greater than ‘women’

The first human ancestors had marked differences of size between males and females. A recent study sheds light on the social behavior of these ancient hominines.

The research carried out by Adam D. Gordon, anthropologist at the University of Albany, reveals that the males of Australopithecus Afarensis and A. Africanus were much larger than the females. This disparity suggests an intense competition between males for access to partners, a trait observed in some primates current.

The study, published in theAmerican Journal of Biological Anthropologyuses an innovative method to bypass the limits of incomplete fossils. She compares these ancient Australopithecus to modern primates, revealing more pronounced size differences than in current humans, even gorillas. The results indicate that these species probably lived in social systems where the competition between males was fierce. This dynamic could explain the imposing size of males, while the smaller females were perhaps adapted to metabolic constraints linked to reproduction.

This discovery questions the previous interpretations of sexual dimorphism in these species. It also opens up new perspectives on the diversity of evolutionary pressures that have shaped our ancestors, long before the emergence of Homo sapiens.

What is sexual dimorphism?

Sexual dimorphism designates the physical differences between males and females of the same species, beyond the reproductive organs. These variations can concern the size, color, or the presence of specific structures such as horns or feathers.

In primates, marked dimorphism is often linked to competition between males for access to females. The larger or stronger males generally have an advantage in these confrontations, which can influence the social structure of the group.

In the case of Australopithecus, the big difference in size between sexes suggests a society where some dominant males monopolized females. This scenario contrasts with that of modern humans, where size differences are less pronounced and the social structures more egalitarian.