We're the Only Animals with Chins
theatlantic.com
theatlantic.com
Any time there's a special feature on a bone, usually a muscle attaches to it. I googled, and found out that the mentalis muscle attaches to the chin.
Interestingly, wikipedia says "In conjunction with orbicularis contraction, the mentalis muscle allows the lips to 'pout.' Externally, mentalis contraction causes wrinkling of the chin skin, as used in expressions of doubt or displeasure. It is sometimes referred to as the 'pouting muscle.'" [Emphasis mine]
Humans have complex facial expressions, and I would say that the pout is part of the repertoire. When someone is pouting, they are in extreme emotional distress, on the verge of sobbing. Having such an obvious "tell" would be beneficial to a social species, probably leading to conciliatory behavior and promoting de-escalation and group cohesion during conflict.
I did some cursory googling to see of the mentalis is involved in speech production, but found nothing at my level. Offhand I can't think of any particular speech sounds I can make when my lips are in pout formation.
> Others have suggested that the chin is an adaptation for chinwags: It resists the forces we create when speaking. After all, speech is certainly a feature that separates us from other living animals. But there's no good evidence that the tongue exerts substantial enough forces to warrant a thick chunk of reinforcing bone. “And any mammal that also communicates vocally or suckles or engages in complex feeding behaviors that involve the tongue are probably experiencing similar stresses and strains, and they're not getting chins,” says Pampush.
Nor should we think that extra structure for complex sounds are needed for a language or comprehensibility. Consider the Silbo Gomero Language, which is "a whistled form of a dialect of Spanish." It "has only 2 vowels and 4 consonants, according to the official nomination document submitted during the UNESCO convention." (Quotes from Wikipedia.)
Verbalized Morse code is another example of how simple vocalizations are all that are needed for a comprehensible language.
A language which evolved from an earlier language, e.g. Italian, or is based on another language, e.g. Silbo Gomero, doesn't need complex sounds to get started, and often replaces "words" in the source language with rules, i.e. replaces lexical and phonological complexity with inflectional and grammatical complexity. But perhaps the very first language to ever be invented will rely on many different sounds and on many different words made from those sounds, but have a simple grammar. A recent study showed the likely dispersal of language from an initial point somewhere in Africa by counting the phonemic diversity, i.e. number of different speech sounds, in various languages around the world. [1] Perhaps the very first language had over a hundred different sounds to compensate for lack of grammar rules.
Perhaps a chin is needed to speak that very first language. Perhaps it had far more clicks than Khoisan, as well as the usual array of consonants, vowels, and tones. Maybe a chin helps with many of the clicking-like sounds.
[1] http://archive.cosmosmagazine.com/news/human-language-spread...
We know that other primates communicate with each other. This form of communication includes different sorts of warning calls, and perhaps also vocalizations for identification.
Any human language would have developed from a similar sort of proto-language, without an a-ha moment when two humans finally invented the language. (And if there was such a moment, then the chin would have had to evolve first, for some other reason.)
Therefore, I don't think it makes much sense to say "very first language" or "invented."
Let's suppose it's meaningful to talk about the first truly human language. In that case, the population of the original speakers would be small. According to the paper you gave, "phoneme number decreases as a population gets smaller." Thus, it would suggest the first language had a low phoneme count.
The problem is, that guideline isn't useful for the timescale we're talking about. It's believed there was a genetic bottleneck some 50,000 to 100,000 years ago (see https://en.wikipedia.org/wiki/Population_bottleneck#Humans ). All living humans come from a relatively small and relatively recent population, which means all of the diverse languages of Africa come from an originally quite small population, which therefore would have had a lower phoneme number.
Thus, on the flip side, what happens when populations get larger and isolated? Proto-Indo-European shows that it only takes a few thousand years to develop German and Celtic from the same language, and we know modern language can have sounds that weren't in the parent languages.
So while the principle might be useful for migrations within the last 10,000 years, that's still quite recent in the evolution of humans.
u (actually whole range from o to u), v/w, probably f.
Even "r" - http://www.avspeechtherapy.com/2014/02/06/tips-to-pronounce-...
They do purse their lips, but that's a different set of muscles.
As an observation, https://en.wikipedia.org/wiki/Chin quotes:
> Enlow, Donald H. (1982). Handbook of facial growth. Philadelphia: Saunders. p. 283. ISBN 0721633862. "In the human mandible, a prominent chin marks this region, a distinctive feature that characterizes the face of modern man (and also, for reasons yet to be studied, the elephant)."
and further qualifies "although this leads to debate over the use of the term."
The Atlantic author does a followup on this topic, at http://www.theatlantic.com/notes/2016/01/no-really-other-ani... , saying:
> “For these reasons, it is generally agreed that whatever the biological situation occurring on the front of the elephant lower jaw, it is fundamentally different from the condition in humans,” says James Pampush, who recently reviewed the various possible origin stories for the human chin. “It may provide some insights into the situation in humans, but to call it a 'chin' stretches the definition.”
However, that addresses a different topic. In common speech we use "hair" to refer to refer to hair on a mammal, made primarily of keratin, and to a chitinous seta on an insect. Thus, "hair" does not depend on a shared evolutionary history, though I think Pampush would prefer that to be the case.
If that were the case then "chin" would, by definition, only apply to humans.
He says it's fundamentally different, and I think I can see how that's the case, seeing how elephants can actually close their mouth/trunk onto their chin (giving it an obvious use), and also considering the structural difference where the elephant's chin is a direct continuation of the line where teeth are resting. It's more of an extended lower jaw than a separate protuberance like in humans. That being said, I'll keep on calling it a chin.
In my experience, leg and body control make or break a RNC, not head/neck grip: https://en.wikipedia.org/wiki/Rear_naked_choke#.22Body_Lock_... . It's way easier to escape a RNC that neglects leg/body control whether or not they've passed the chin: https://www.youtube.com/watch?v=JR2e0IsqhrQ , and the chin is an important part of the last-ditch defense.
...which is a long way of saying, I'd rather fight a dude with no chin, and if there were some option to temporarily remove my chin while grappling, I'd still decline, for performance reasons :)
I'd love it if a more experienced MMA player could chime in to confirm or deny our suspicions.
http://www.npr.org/2016/01/29/464893281/why-do-humans-have-c...
In short. It's unlikely to be for protection, or for sexual selection, or to aid in speech. Go to the interview detailed explanations.
Most of the comments here offer reasons that are even mentioned in the articles as plausible.
Others have suggested that the chin is an adaptation for chinwags: It resists the forces we create when speaking. After all, speech is certainly a feature that separates us from other living animals. But there's no good evidence that the tongue exerts substantial enough forces to warrant a thick chunk of reinforcing bone.
That's not my first thought at all. I think it has absolutely to do with speech, but not for that reason. I think it's to create more space for the tongue to move around and make different sounds.
Just another SWAG, of course, but I'm surprised not to see this idea floated.
You might be interested in reading their original paper, "The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme", available from http://faculty.washington.edu/lynnhank/GouldLewontin.pdf .
Does any other animal fall as commonly & dangerously as humans?
I have fallen and busted my chin a few times, but never my nose. How about yourself?
"Nearly forty years ago, Susumu Ohno proposed that one or two rounds of whole genome duplication took place close to the origin of vertebrates. The refined version of this proposal, known as the two round (2R) hypothesis, assumes that the genome of jawed vertebrates has been shaped by two rounds of whole genome duplication that took place after the emergence of urochordates and before the radiation of jawed vertebrates. [...] Of special interest in this connection is the proposal of Olinski et al. [ 45••] that the four sets of MHC paralogons and the four sets of neurotrophin paralogons were derived from a single contiguous region on an invertebrate proto-chromosome (Figure 2). Interestingly, two of the neurotrophin paralogons [46] are located on 12p11–p13 and 19q13–q14 that encode the NKC and LRC, respectively." http://www.ncbi.nlm.nih.gov/pubmed/17707623
http://www.skullsunlimited.com/userfiles/image/variants_larg...
It's true that it's part of a slope inwards towards the body, but in most pictures I could find it looks like it is definitely the same sort of phenomenon talked about in the article. At certain angles it's pretty remarkably a chin: https://boneclones.com/images/store-product/product-1169-mai...
To my untrained eye, looking through mammal skulls the slope of the chin/not-chin area seems to have more to do with the angle of the teeth than anything.
Actually, even other primates like this Siamang seem to have something pretty similar to human chins: http://www.store.dinosaurgeorge.com/images/Siamang%20Gibbon%...
I know there is no proof of this. But we accept many things as true because it seems very likely. I think chins fall into the same where the above explanation should be accepted as probably true until proven otherwise. Other explanations just don't seem nearly as plausible. Even the 'attractiveness' argument doesn't seem compelling to me as you're talking about every society on earth. Did every community of humans on every continent find chins attractive? Not likely.
> A different explanation portrays the chin as a bit of the jaw that got left behind while the rest shrunk back. As early humans started cooking and processing our food, we made fewer demands upon our teeth, which started shrinking as a result. They gradually retracted into the face, while the part of the lower jaw that held them did not (or, at least, did so more slowly). Hence: chin.
> Stephen Jay Gould and Richard Lewontin, who coined the concept of evolutionary spandrels, liked this hypothesis. So does Nathan Holton from the University of Iowa, who studies facial evolution. “It seems that the appearance of the chin itself is probably related to patterns of facial reduction in humans during the Pleistocene,” he says. “In this sense, understanding why faces became smaller is important to explaining why we have chins.”
> “But why did the lower border of the jaw also not shrink?” Pampush asks.
It then elaborates on the diversity of hypotheses:
> It may seem frustrating to have so many imperfect competing hypotheses, but that's part of the joy of chins: They reveal something about how scientists think about evolution. Some see the sculpting power of natural selection in everything, and view chins as surely some kind of adaptation. Others see natural selection as just one of many evolutionary forces, and so gravitate towards a spandrel-based explanation. “The chin is one of these rare phenomena in evolutionary biology that really exposes the deep philosophical differences between researchers in the field,” says Pampush.
Allows your head to pivot up and down from the hinge of the top of your spinal column, but also allows for the front/variable length bit (the front of your neck) to be protected when needed.
e: Expanding on this a bit, the only other animal that comes to mind that stands like us that I can think of is the Meerkat. Why don't they have chins? Maybe it's that they only stand in situations, not for movement; or maybe it's that they aren't in situations where they can/have to fight back vs predators (not that they don't have predators, but that human vs wolf is a bit more even than meerkat vs lion, more of a chance for the human to prevail and more of a chance for a human with the optional-neck-guard to eek out a win where a chinless compatriot wouldn't).
http://colinramsay.co.uk/chinorno/
Unfortunately you can never win, because the chimp question is a bit of a stumper.
Is the author an Elephant?