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What does the sagittal crest on KNM-ER 1805 suggest about its chewing muscles?

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An illustration of Homo habilis, an early human ancestor, shown walking upright with a hairy body and ape-like features. A scale beside the figure indicates height in inches and centimeters. — Homo habilis Artist's rendering of *Homo habilis*, which lived from 2 to 1.5 million years ago.

The sagittal crest found on the KNM-ER 1805 skull, along with a prominent crest oriented across the rear of the skull, indicates that the individual possessed powerfully developed chewing and neck muscles.1

While this pattern of cresting is similar to that seen in robust australopiths, it is not typically found in the genus Homo. Because of this and other anatomical anomalies, there has been disagreement among scientists regarding the classification of this specimen, though it is frequently discussed alongside other fossils grouped as Homo habilis.1