Most modern humans have at least one chin. Some of us are blessed with multiple chins. But only one actually has a solid bone structure behind it. Why?
Cosmos reports on a recent article published by Robert Franciscus in the Journal of Anatomy looking at evolutionary history of chins. One popular theory among physical anthropologists has been chins provide support to chewing as humans age and eat harder foods. But Franciscus and his colleagues found that longitudinal studies of bone growth in chins did not support this hypothesis.
What they propose instead is that human chins became prominent when early humans had higher levels of testosterone, which impacts bone growth, especially in the skull. As humans' aggressive behavior and testosterone levels dropped off, hormonal changes caused this large bone in the front of the human face to become sharper and angular--a chin.
-via Dave Barry | Photo: Andrex99