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There are many different versions as to why the man’s chin, but at closer look, none of them is not wealthy. What is the purpose of this, it would seem, is not too important element of our face? Correspondent BBC Earth has decided to conduct its own investigation
All people have a chin, a more or less manifest, but … always clearly useless
In some chin strong, strong-willed, others -.. Soft and even double … But what kind of function it performs in our life?
the thing is, none of us do not seem to enjoy his chin usefully.
there is still no satisfactory explanation why among mammals only homo sapiens has chin
even more confusion makes the fact that, even among primates (including our closest relatives, the Neanderthals) chin gave some reason only one kind, homo sapiens (wise man) .
But this protrusion on her face, we gave up, exactly? Over the past century, scientists have proposed several hypotheses. However, most likely, on the true purpose of the chin, none of them really knows for sure.
Arrange some of the most interesting theories will help us to review the literature that exists on this subject.
“They [ chins] some strange, that, in fact, and drew my attention to them, – says James Pempush from Duke University in the US Durham (North Carolina), a scientist, not a single year spent studying the bottom of the human face -. and no one has yet put forward a convincing hypothesis as to why among all the species of mammals chin, there is only the species homo sapiens. “
In his recently published Pempush report tried to solve this given to us by nature intricate task.
we have some idea of what the chin. Yet it would be superfluous to give here a concise definition.
Simply put, this is a projection along the lower edge of the jaw-bone man. No other mammal chin no protrusion. Chimpanzees and other apes, such as the jaw downwards chamfered.
As the findings of the archaeological excavations, coming our relatives, the Neanderthals, too, had no chin.
Its presence or absence in the skeleton person is used therefore as one of the main criteria differences homo sapiens from homo neanderthalensis.
“This is exactly what makes the appearance of the chin in the anatomy of modern man [ie homo sapiens] so interesting. You can therefore be assumed that the behavior or eating habits of modern (in the sense of the anatomical structure) human ruptured with Neanderthals, which led to the appearance of the chin “, – says Zaneta Thayer of the University of Colorado, in the US Denver
The research community has not yet reached a consensus on the chin function, but in this regard have been nominated three prominent hypotheses.
since it is easier to chew over the past decade ?
One of the assumptions is that our chin supposedly helps us to chew food.
According to this hypothesis, people need more bone in order to cope with the pressures, paired with chewing.
However, comparing the man with the apes, the jaws of which are of a similar shape, we see that this explanation is not satisfactory.
When we chew our jaws apart like a wishbone, and the further they are from each other, the weaker the force of these bones.
so if indeed there was a need to help the person cope with related chewing loads would be more logical to look if more bone is formed not under the jaw, and on its inner wall, next to the language.
This is how the matter The situation in chimpanzees and macaques. They have at their disposal so-called simian projection, ie bone on the side facing the tongue of the lower jaw.
We do not have such a bone. And the one that forms the chin does not make our bone structure more sturdy and therefore better suited for chewing.
Chew – not too heavy
Pempush recalls that, generally speaking, chewing food It is not difficult for us. After all, modern man eats mostly soft, thermally processed food
From this he concludes. “The chin should not be considered part of evolutionary adaptation to facilitate chewing process”
The researcher Flora Gröning out. University of the Scottish city of Aberdeen, UK, agrees with this statement.
Five years ago, she has built a computer model to investigate the mechanical load on the mouth, chin and without.
on based on the results of his study she concluded: “The suggestion that the chin is the result of mechanical adaptation, clear evidence is not”
it helps to talk
According to the second.? hypothesis, chin helps us to speak, as an active participant in speech language needs reinforcement in the form of additional bones under the lower jaw.
But, again, for the speech does not need much power, so not very clear why additional bone man.
But even if there was a need for it, then, as in the case with chewing, for speaking it would be much more useful to “fasten” another bone is not to the bottom of the jaw, and by its internal part, closer to the language.
he helped lure?
The third hypothesis is that the chin there is no immediate function, and there was it as a result of sexual selection as an evolutionary adaptation.
In nature, examples of such adaptations may be branched antlers of male elk or high cheekbones orangutan.
Both of these features were favored individuals of the opposite sex when selecting a partner for mating. Which ensured the stability of these traits in future generations, even if no direct benefit.
And here again there is a problem, says Pempush. In all other mammalian species trait selected from sexual selection appears only in one sex. A chin has both men and women
According to Pempusha three above untenable hypothesis, and no one yet knows exactly why we need a chin. “Anyone who says he knows, on the really disingenuous “.
Most of the proposed so hypotheses then collapses on closer examination, and some just can not be tested, according to the American researcher.
turns out that we, unfortunately, did not come close to understanding why the man’s chin.
and yes, chins seem to us not very functional. But then, it may be wise to go to the other side and examine why they are so prominent?
This is the result of reducing our face?
The chin may be maladaptive element which has emerged as a byproduct of other, real adaptation.
This idea was expressed in 1979 by biologists Stephen Gould and Richard Lewontin. They compared the jaw so that the architecture is called antrvoltom (or spandrel).
This is an architectural element in the dome of the building, which is often decorated with so elaborate, it seems that it was he, and is the starting point of the whole project.
In fact, antrvolty exist only because they are helping to support the dome. In other words, antrvolty – architectural or biological – are, in fact, by-products of some other, more significant changes
“Antrvolt” we have to face may become so convex due to the fact that it was reduced in size, says Nathan Holton from Iowa State University in US.
According to him, his chin was formed due to the reduction of the human skull.
at the homo sapiens species lower jaw is weaker than it was at our extinct relatives of the subfamily hominin.
in the course of evolution, humans have conquered the fire and learned to cook their own food, and then they have eliminated the need for strong jaws. As a result, the total jaw fortress actually declined as unnecessary.
Chin, you may need to support our once very strong mandibles
In the course of evolution in humans change and other anatomical characteristics. For example, missing protruding brow, but there was a depression under the cheekbones, called “canine fossa”.
It is also associated with a decrease in the face, said Holton. “The presence of the chin, possibly also a consequence of this change and then understanding its function is reduced to an explanation of the reasons for reducing the size of a human face.”
Flora Gröning like this idea.; She adds that the chin may need to support our once very strong mandibles
“Neanderthals and homo erectus (” upright man “) had a strong jaw;. they had enough powerful bone in the area of the chin, and their additional thickening is not required “-. she notices
The modern (anatomically) person, on the other hand, the bone is very thin.
“The chin may provide additional resistance to maintain the mechanical strength, but the overall strength it does not increase.”
Just coincidence?
On the other hand, the appearance-antrvolta chin may be due to some random event or an accident, and not be a side . the product of some useful adaptations in other parts of the face
“I doubt that this is an adaptation,” – says Pempush. However, he said, and the first part of the statement – if the chin was caused due to accident – is also proved by nobody. “We currently do not have the appropriate tools”.
The key to understanding the evolution of events
However, if none of the hypotheses regarding the appointment of the chin not gives a satisfactory explanation, and we can not prove the theory antrvolta, why then Pempush many years engaged in this topic?
Although chins really quite strange look, their study helps to highlight those evolutionary processes through which modern humans are arranged . just so and not otherwise
The research in this area also show that evolution -. piece rather diverse
In addition, some characteristics of a person, in the biological world -. It is very rare
Most of our existing features can be found in other species. So chin not only stands out for people on the face, but also sets them apart from all other mammals, including great apes.
And the study of how it arose, can give us the key to understanding other evolutionary events leading the appearance of species homo sapiens.
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