Evolution of hominin body size

Proceedings of the National Academy of Sciences—A study finds trends of increasing body size throughout hominin evolution. Changes in body size were critical components of hominin evolution, influencing brain size, locomotion, and range expansion. However, little consensus exists on how hominin body size evolved. Some hypotheses favor a general overall increase in body size, whereas species with small stature, such as Homo floresiensis, provide counterexamples. Jacob Gardner, Chris Venditti, and colleagues applied Bayesian modeling of evolutionary lineages among 386 specimens of 21 species of hominins. The authors modeled progression of body size over time. Within a single framework, the authors tested multiple hypothesized models of hominin body-size evolution. The modeling showed strong evidence for a marked increase in body size in late Homo species excluding Homo habilis, and moderate evidence for a general size increase over time across all hominin species of up to 0.99 kilograms per million years. Uncertainties in body-size evolution may have arisen due to variation in the methods of body-size estimation, incomplete skeletal samples, and ambiguity regarding species assignment of fossil specimens. According to the authors, the framework accounts for the nonindependent evolution of lineages, variation in body size within species, and other sources of uncertainty, providing clarity on transitions in Homo body-size evolution.

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Homo heidelbergensis. José Luis Filpo Cabana, CC BY-SA 4.0, Wikimedia Commons

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Article Source: PNAS news release.