WE CAN think – and look laterally. The shape of our eye sockets may have given our ancestors an edge when they moved from forests into savannahs, allowing them to quickly and easily scan their new habitat.
Eric Denion at the French Institute of Health and Medical Research in Caen and his team examined 100 modern human skulls and 120 ape skulls – 30 each belonging to gibbons, orangutans, gorillas and chimpanzees. The human eye sockets were much wider relative to their height than those of the apes, and the outer margin was recessed much further back in the human skull. This means that when we swivel our eyeballs sideways, we have a lateral view of the world that is unimpeded by the bones of the skull, unlike other apes (Scientific Reports, doi.org/5rs).
It’s not yet clear if the trait evolved for this purpose or if it simply emerged as a consequence of other changes to our head, such as evolving smaller chewing muscles, says Denion. Another explanation, he says, is that there was a relaxation of the pressures forcing other apes to have recessed eyes: in forests, there is a constant danger of a stray branch damaging the eyes, but this isn’t an issue in the open savannah.
This article appeared in print under the headline “Our savannah eyes beat ape forest view”
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