Revisiting Body‐Size Differences in Early Australopithecines: Insights from Postcranial Data

Hominins in Unequal Proportions

When looking into the past, the size of a bone can speak volumes about the lives of long-dead ancestors. And when one sex towers over the other, it raises questions not just about biology, but about behavior, reproduction, and the struggles of early life.

New research by UAlbany anthropologist Adam D. Gordon finds substantial sexual dimorphism in some of our early human ancestors. Credit: Ken Zirkel,the Museum of Natural History

A new study¹ led by biological anthropologist Adam D. Gordon offers a fresh take on sexual size dimorphism—the physical size difference between males and females—among Australopithecus species. Using an innovative statistical approach that accounts for fragmentary fossil remains, Gordon reveals that Australopithecus afarensis and Australopithecus africanus displayed dramatic sex-based size differences—more extreme than anything seen in modern humans and even exceeding those in gorillas in some cases.

“In the case of A. afarensis, males were dramatically larger than females—possibly more so than in any living great ape,” said Gordon.