• The human chin is an evolutionary oddityWestend61/Getty Images The human chin is an evolutionary oddity Westend61/Getty Images Humans are the only primates with a chin, leaving biologists to wonder why we acquired this unique feature. • According to a new analysis of head anatomy in apes, it probably didn’t evolve for a specific reason of its own but instead emerged as a side effect of other changes driven bynatural selection. • “There has been a tendency to assume that every feature that differs significantly between species has been shaped by natural selection for a specific purpose, but this ‘purposeful’ view of evolution is inaccurate,” saysNoreen von Cramon-Taubadelat the University at Buffalo in New York state. • “Evolution is often messier and less directed than people expect or assume.” Read moreWhat made us human? • The fossils redefining our evolutionary origins Read more What made us human? • The fossils redefining our evolutionary origins In simple terms, the chin is a bony projection of the lower jaw that extends beyond the front teeth.
Article Summaries:
- A new comparative study of 532 human and 14 ape skulls shows that the human chin likely arose as a by‑product of other evolutionary changes rather than a distinct adaptation. Researchers measured 46 anatomical distances, mapped them onto an ape phylogeny, and applied a quantitative genetic model to test for selection. They found only three chin‑related traits under direct selection; the rest appeared neutral or linked to other traits. The authors argue that upright posture, larger brains, and reduced front teeth led to a smaller lower face, causing the lower jaw to project forward and create the chin. The work highlights how selection on one body region can produce secondary features.
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