The human body has some underappreciated superpowers. Sure, we might not be fast like a cheetah, but we can sweat better than most. Now, new research has added another power to our repertoire: a really strong bite1.

Compared to our recent ancestors, we can generate almost twice the amount of bite force with the same sized muscles. Not only is our bite strong, it’s efficient too1.

As if that’s not interesting enough, it turns out that this feature was likely an evolutionary accident. But then, that’s how all good superpower origin stories start.

Meat the competition

400,000 years ago there was no such thing as Homo sapiens. Instead, the world was dominated by another human species called Homo heidelbergensis. Their descendants would go on to become us in Africa, Neanderthals in Europe, and Denisovans in Asia2.

Or at least, that’s the simple version of our history. In reality, different groups were evolving different traits in different orders (and sometimes traits disappeared too) until at some point a population earned enough human points to claim the name Homo sapiens. The messiness of this evolution has led to countless debate about how it all fits together2.

Some different views of how Homo heidelbergensis fits into it all2

But of course, you’re here to find out about our biological superpowers, not hear a technical debate over how species should be defined. And for the former, all you need to know is that humans used to look more like Homo heidelbergensis and now humans look more, well, human!

Specifically, H. heidelbergensis had a larger face with thicker bones and a jaw that stuck out more1 (plus a whole bunch of other stuff which isn’t particularly relevant for studying their bite force)2.

One of the H. heidelbergensis used in the bite force study. The more observant of you might notice it’s very similar to a Neanderthal skull, which many H. heidelbergensis were classified as before they got split off into a separate species1

Evolution of our bite

The fact our jaw has gotten smaller and less robust raises a key question. What impact that had on our ability to bite? Could we still compete with our bigger jawed ancestors?

To investigate this, they used CT scans of fossils (and a modern human from Hull) to build computer simulations of different species chewing1.

Interestingly, these simulations revealed that despite our changes in jaw size our jaw muscles were still the same size (relatively speaking). This means that similar levels of force are being applied to a smaller area in humans, creating a higher bite pressure. The changes in jaw size also meant there were differences in how our jaw functioned as a lever1.

Taken together, all of this means that Homo heidelbergensis could produce 184 – 241 Newtons of force. Meanwhile, humans had a whopping ~90% stronger bite force, clocking in at 332 – 477 Newtons1! This is also more forceful than a Neanderthal’s bite.

An evolutionary accident

Our superpowered bite isn’t all good news. In the simulations, biting puts more stress on our bones than in Homo heidelbergensis.

It seems that despite evolving a stronger bite, we didn’t evolve the stronger bones to deal with it. In fact, our face is less robust1.

Strain from biting in humans (top) and H. heidelbergensis (bottom). Red = more strain

If there was natural selection for a stronger bite, there would also be natural selection for dealing with it. The fact this evolution didn’t happen led the researchers to infer the stronger bite was an “accident” and not used often.

Instead, they speculate that some other force drove the evolution of a smaller jaw. The fact that we can now generate stronger bites is just a side-effect. It also seems to be a side-effect our ancestors didn’t use often, as we didn’t evolve to deal with the consequences.

Like any good superhero, we didn’t choose our power. But now we have the great responsibility that comes with great (bite) power.

References

  1. Godinho, R.M., Fitton, L.C., Toro-Ibacache, V., Stringer, C.B., Lacruz, R.S., Bromage, T.G. and O’Higgins, P., 2018. The biting performance of Homo sapiens and Homo heidelbergensis. Journal of human evolution118, pp.56-71.
  2. Stringer, C., 2016. The origin and evolution of Homo sapiens. Phil. Trans. R. Soc. B371(1698), p.20150237.
  3. Anton, S.C., 1990. Neandertals and the anterior dental loading hypothesis: a biomechanical evaluation of bite force production. Kroeber Anthropol Soc Pap71(72), pp.67-76.

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2 Comments

Stephen Carman · 16th October 2018 at 3:13 am

This runs contrary to studies I’ve read that track the jaw muscles of apes being much larger than human jaw muscles. In fact the larger brain of humans was said to be a factor of less pressure on the skull because of smaller jaw muscles. Whether this article tracked humans and compared them to only recent ancestors is not the point. The process of human ancestors adapting by evolving stronger jaw muscles is possibly only a recent advantage. If brain size was indeed a factor of jaw bone and muscle structure then the DNA which produced weaker jaw muscles than apes was the critical point from which we developed. Addressing this point should be fubdamental to this article.

    Adam Benton · 25th October 2018 at 2:50 pm

    The key point isn’t that our jaw evolved to be stronger, but that it didn’t. Its recent increase in strength appears to be a side effect of other changes in the face. Much like the initial weakening of it might be a side effect of other facial changes linked to increased brain size. In other words, much of our jaw’s evolution hasn’t really been linked to its function.

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