Next time you stroke your chin when you're puzzled, ask yourself the question "Why do I have a chin"?
Scientists have been stroking their chins asking the same question but unlike us, they're come up with a scientific answer. It seems our chins developed because the size of our skulls and noses shrunk as we evolved to become more human over time.
In other words, our chins were the inevitable result of our evolution from hulking humans that fought hard to survive to modern humans that don't work as hard to stay alive. But more specifically, it seems our chins grew larger because our noses grew smaller.
It's a little known fact our chin is unique to humans. Neither the Neanderthals, one of our human ancestors, nor our current primate cousins such as chimpanzees have chins (you can look at the pictures), but exactly why modern day humans have chins has escaped scientists.
A recent study by Dr. Nathan Holton and his team from the University of Iowa shows the prominence of the chin may simply be a side effect of the rest of the face evolving to be smaller.
It suggests chins emerged as a secondary trait caused by a gradual shift in hormonal balances related to our change from isolated social creatures. This study also reveals evidence to suggest the emergence of the chin has more to do with our social skills than it does the way we eat.
The prominent human chin "is a secondary consequence of faces getting smaller," said Dr. Holton.
"It really seems like a lot of changes in the modern human face are really due to a reduction in size, so if we can explain that, we can explain a lot".
Dr. Holton said one possibility explaining our smaller faces is that hormonal changes associated with reduced violence and increased cooperation had the side effect of "domesticating" the human face, thus shrinking it.
He and his colleagues are also looking at evidence that points to the nose as the main reason for our smaller faces. As overall body size shrank, nasal cavities didn't need to grow as large to provide enough air for survival. As a result, the face then didn't have to grow as large to support the nose, said a report in Medical Daily.
Dr. Holton said the emergence of the chin seems more closely linked to lifestyles changes that occurred around 80,000 years ago. Humans left Africa during this time and began to shift from their isolated hunter-gatherer ways to more socially connected groups.
To form these social networks, humans (especially males) needed to be less aggressive. The consequence was males began to produce less testosterone.
This biological change produced a visible change in our facial appearance, causing the actual face to shrink up to 15 percent in size, according to the study.
Researchers now believe our chin was a secondary result of humans developing smaller faces. And because our faces were now smaller, the jawbone became more prominent.
That's food for thought (now, stroke your chin).