

Why we have chins - diodorus
http://www.sciencedaily.com/releases/2015/04/150413183745.htm

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will_brown
Aside from the chin...look at the picture of the modern human skull compared
to the Neandethal-era skull. Notice Neandethal-era skull has a perfect bite
and the modern human skull has an overbite. The overbite is the direct result
of humans developing/using eating utensils (this fact may have actually been
from a recent HN front page post).

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nsxwolf
Can't get over how Lamarckian this sounds. How long have we been eating with
utensils? Long enough for such a radical change? And is an overbite really
such a disadvantage that it would select you right out of the gene pool?

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JoeAltmaier
Human physical genetic changes have accelerated in the last 50,000 years.
Probably accompanying new pressures brought by living in social groups. But
since the fork was only invented 400 years ago, maybe utensils is a reach.

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Phlarp
Surely "utensils" includes more than just modern style metal forks? I don't
think it's a stretch to say that the use of tools of any kind in the eating
process could remove specific evolutionary pressures that would otherwise
inhibit some individuals from reproducing.

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scotty79
First thing that came to my mind is that chins might be better as attachment
for facial muscles giving more expressive or efficient face expressions or
talking.

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sheensleeves
My first thought was that a chin may take a punch better...

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troels
Quite the opposite. A punch on the chin will knock you out easily.

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sheensleeves
Not to argue, but is being knocked out bad? It seems like a common occurrence
to a fight is go to unconscious. Some people have strong chins. Would they do
better in a no rules fight historically, if they didn't go down?

~~~
jessaustin
Getting knocked out in an athletic competition is one thing. Getting knocked
out when a neighboring tribe is attempting to kill all your men and old folks,
enslave everyone else, and steal everything of value, would probably have been
something else.

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sheensleeves
If you're unconscious, you're not a threat any more.

Live to fight another day.

~~~
jessaustin
Inter-tribal resource wars might be fought by primitives, but they're not
fought by _idiots_. Nor are they fought by chivalrous knights. The throats of
unconscious warriors will be cut. Even if a throat was missed in all the
chaos, what is the evolutionary advantage to a male of living on after all
fertile females have been abducted?

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randomname2
_" Our study suggests that chin prominence is unrelated to function," Holton
says, "and probably has more to do with spatial dynamics during development."_

Just as a sidenote on this theme, it's interesting how according to studies
chin prominence correlates with perceptions of leadership ability, confidence
and sexual attractiveness in men. Apparently chin implants are as popular as
breast augmentations these days:

[http://www.reuters.com/article/2012/05/03/us-chinimplants-
id...](http://www.reuters.com/article/2012/05/03/us-chinimplants-
idUSBRE8420XF20120503)

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diodorus
Here's a link to the original article ("The ontogeny of the chin: an analysis
of allometric and biomechanical scaling"):

[http://onlinelibrary.wiley.com/doi/10.1111/joa.12307/full](http://onlinelibrary.wiley.com/doi/10.1111/joa.12307/full)

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keithwhor
Would like to point out that we're not the only species with chins.

Elephants have chins, too. [1]

(This is my favorite fact at parties. I'm a blast.)

1\. [http://en.wikipedia.org/wiki/Chin](http://en.wikipedia.org/wiki/Chin)

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ratsz
Do elephants have a chin since they use their trunk as an eating utensil?

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dasmithii
My instinct is to see chins as shields to the Adam's apple. I have no
explanation for why primates have less prominent chins, though.

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whoopdedo
How about chicks dig guys with a manly chin.

Don't know how you can call yourself an evolutionary biologist if you so
easily overlook sexual selection.

~~~
wodenokoto
Because you need to ask why they dig a manly chin.

Long hair makes sense because it is a crude history of our health. Symmetry
also makes sense, as it is a sign of healthy, strong genes. Being rich enough
to afford to waste stuff also makes sense (and explain a ton of weird human
and animal behavior)

But if a chin serves no purpose what so ever, why would it become a sex
symbol? They're not big enough to work like antlers (look how much energy I
can accrue to grow these big ass antlers!) so why would they start to grow in
the first place?

~~~
whoopdedo
It is unclear whether sexual selection impedes or facilitates natural
selection [1]. Sexual selection can happen just because. A female who prefers
chins will give birth to sons with chins and daughters who like chins. It's a
positive feedback loop that doesn't need cooperation from natural selection to
give it fitness.

At one time in the past there may have been a reason that the men with chins
were more successful than other humans. The correlation may have been
coincidental though. Maybe the men with no-chins happened to be living in a
part of the world that suffered a famine. Or if there was a direct
relationship, the sexual preference remained after the natural advantage was
no longer relevant.

The study does a good eliminating mechanical advantage as a reason for having
a jaw. (And that's all it says.) But the speculation about why the jaw exists
(inserted by the news writer and has nothing to do with this study) seems less
certain to me. Why did chins not simply get smaller with the rest of the
skull? Something encouraged chin growth in humans. But to say what you'd have
to study skulls from the past to see exactly how the chin changed over time.

[1] [http://www.cell.com/current-
biology/abstract/S0960-9822%2811...](http://www.cell.com/current-
biology/abstract/S0960-9822%2811%2901397-2)

