New Study Challenges Long-Held Idea that Our Ancestors Simply Got Bigger Over Time

Key Points:

• New research led by the University of Reading reveals that hominin body size evolution was not a steady increase over millions of years, but featured a major size jump around 2 to 2.5 million years ago with the emergence of Homo rudolfensis or Homo erectus/ergaster.
• The study analyzed 386 fossil specimens across 21 hominin species using statistical models that account for evolutionary relationships, finding that size increases were most pronounced within later members of the genus Homo rather than across all hominins.
• Species such as Homo floresiensis and Homo naledi remained significantly smaller than average for their time, highlighting divergent evolutionary paths within the hominin lineage.
• The significant body size increase in Homo erectus/ergaster coincided with other evolutionary developments, including enhanced bipedal locomotion and dietary shifts toward carnivory, suggesting a link between size and ecological-behavioral adaptations.
• These findings, published in the Proceedings of the National Academy of Sciences, challenge the simplistic view of constant growth and emphasize the complexity of human evolutionary history.