The human skull is the species’ most unique anatomical feature. A cavity large enough for a big brain and a flat, slender face set humans apart from their closest relatives.
The evolutionary adaptations that allowed for human development came with tradeoffs, however. Scientists have long assumed that humans traded jaw power for brain capacity. New research shows that assumption is only partially correct.
A new study, published this week in the journal PeerJ, suggests the human jaw packs a powerful and efficient bite — but one that comes with considerable risk.
“We found that humans have high biting leverage, which some previous studies have noted, but we also found that humans are at risk of dislocating, and possibly damaging, the jaw joint during powerful molar biting,” lead study author Justin Ledogar, a researcher at the University of New England, said in a news release. “Additionally, we found that the human facial skeleton is generally weaker during biting than chimpanzees, which is not surprising given our small faces.”
The findings confirm the hypothesis that a greater supply of smaller, softer — butchered and cooked — food items diminished the need for big, powerful bites. The twist is that the human jaw adapted while maintaining a forceful chomp.
Researchers say humans’ surprisingly powerful — but unstable — bite is a secondary byproduct of natural selection for a function other than chewing food.
While scientists are now certain Homo sapiens‘ flat face was adopted for reasons other than biting, they’re not sure what those reasons are.
“Because the need to bite powerfully is very unlikely to have led natural selection to favor a facial configuration that puts the feeding system at risk of being compromised, the flat faces of modern humans are probably unrelated to such behaviors,” said Ledogar, who conducted the research while earning his doctorate at the University of Albany.
“We suspect that limitations on producing high bite forces may have characterized the origins of our genus,” Ledogar added. “Going forward, it will be important to examine the various hypotheses that attempt to explain human facial flatness. There are a few different ideas, but we’re really not sure what was driving this unusual characteristic.”