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Thread: Why expressive brows might have mattered in human evolution

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    Why expressive brows might have mattered in human evolution



    Highly mobile eyebrows that can be used to express a wide range of subtle emotions may have played a crucial role in human survival, new research from the University of York suggests.


    Like the antlers on a stag, a pronounced brow ridge was a permanent signal of dominance and aggression in our early ancestors, which modern humans traded in for a smooth forehead with more visible, hairy eyebrows capable of a greater range of movement.


    Mobile eyebrows gave us the communication skills to establish large, social networks; in particular to express more nuanced emotions such as recognition and sympathy, allowing for greater understanding and cooperation between people.


    The study contributes to a long-running academic debate about why other hominins, including our immediate ancestors, had gigantic brow ridges while anatomically modern humans evolved flatter foreheads.


    Senior author of the paper, Paul O'Higgins, Professor of Anatomy at the University of York, said: "Looking at other animals can offer interesting clues as to what the function of a prominent brow ridge may have been. In mandrills, dominant males have brightly coloured swellings on either side of their muzzles to display their status. The growth of these lumps is triggered by hormonal factors and the bones underlying them are pitted with microscopic craters - a feature that can also be seen in the brow bones of archaic hominins."


    "Sexually dimorphic display and social signalling is a convincing explanation for the jutting brows of our ancestors. Their conversion to a more vertical brow in modern humans allowed for the display of friendlier emotions which helped form social bonds between individuals".


    Using 3D engineering software, the researchers looked at the iconic brow ridge of a fossilised skull, known as Kabwe 1, held in the collections of the National History Museum.


    It belonged to a species of archaic hominin - Homo heidelbergensis, who lived between 600,000 and 200,000 years ago.


    The researchers discounted two theories commonly put forward to explain protruding brow ridges: that they were needed to fill the space where the flat brain cases and eye sockets of archaic hominins met, and that the ridge acted to stabilise their skulls from the force of chewing.


    Professor O'Higgins said: "We used modelling software to shave back Kabwe's huge brow ridge and found that the heavy brow offered no spatial advantage as it could be greatly reduced without causing a problem. Then we simulated the forces of biting on different teeth and found that very little strain was placed on the brow ridge. When we took the ridge away there was no effect on the rest of the face when biting.


    "Since the shape of the brow ridge is not driven by spatial and mechanical requirements alone, and other explanations for brow ridges such as keeping sweat or hair out of eyes have already been discounted, we suggest a plausible contributing explanation can be found in social communication."


    According to the researchers, our communicative foreheads started off as a side-effect of our faces getting gradually smaller over the past 100,000 years. This process has become particularly rapid in last 20,000 years and more recently, as we switched from being hunter gatherers to agriculturalists - a lifestyle that meant less variety in both diet and physical effort.


    Co-author of the paper, Dr Penny Spikins from the Department of Archaeology at the University of York, said: "Modern humans are the last surviving hominin. While our sister species the Neanderthals were dying out, we were rapidly colonising the globe and surviving in extreme environments. This had a lot to do with our ability to create large social networks - we know, for example, that prehistoric modern humans avoided inbreeding and went to stay with friends in distant locations during hard times.


    "Eyebrow movements allow us to express complex emotions as well as perceive the emotions of others. A rapid "eyebrow flash" is a cross-cultural sign of recognition and openness to social interaction and pulling our eyebrows up at the middle is an expression of sympathy. Tiny movements of the eyebrows are also a key component to identifying trustworthiness and deception. On the flip side it has been shown that people who have had botox which limits eyebrow movement are less able to empathise and identify with the emotions of others.


    "Eyebrows are the missing part of the puzzle of how modern humans managed to get on so much better with each other than other now-extinct hominins."




    Read more at: https://phys.org/news/2018-04-eyebro...ution.html#jCp

    http://nature.com/articles/doi:10.10...559-018-0528-0

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    1 out of 1 members found this post helpful.
    Interesting, particularly this:

    "For our species losing the brow ridge probably meant looking less intimidating, but by developing flatter and more vertical foreheads our species could do something very unusual – move our eyebrows in all kinds of subtle and important ways.

    Although the loss of the brow ridge may have initially been driven by changes in our brain or facial reduction, it subsequently allowed our eyebrows to make many different subtle and friendly gestures to people around us.

    Historically speaking, these marked changes in the face occurred at a time when the emergence of important social changes began to take place. Mainly the collaboration between distantly related groups of humans."

    I don't think we realize enough how important collaboration was in the development of human technology and advancement of all kinds.


    On a side note, the eyes and brows are the first thing I look at, and then the mouth, in getting a sort of "first glance" impression of people. You can tell an awful lot about a person from that initial analysis.


    Non si fa il proprio dovere perchè qualcuno ci dica grazie, lo si fa per principio, per se stessi, per la propria dignità. Oriana Fallaci

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    That is indeed interesting, and could have been integral to the development of social cohesion. It probably help to communicate the intentions of others better.

    In pictures, I've been told I tend to "smile" more with my eyes, than my mouth.

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    Im a mouth smiler. Btw since people with Botox tend to have lower sympathy due to the muscles behind the brows being weaker, it would be nice to know whether someone can change psychologically just by strengthening certain facial muscles.

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    1 out of 1 members found this post helpful.
    Quote Originally Posted by Jovialis View Post
    That is indeed interesting, and could have been integral to the development of social cohesion. It probably help to communicate the intentions of others better.

    In pictures, I've been told I tend to "smile" more with my eyes, than my mouth.
    I think you can fake "mouth" smiles much more easily than "eye" smiles. There's nothing nicer or more charming than a "twinkle" in someone's eyes. :)

    It's funny how eyebrow shapes go in and out of style as well. Those, imo, awful pencil browns that were in fashion in certain eras of the 20th century gave way to more natural brows like Elizabeth Taylor's or, later on, Brooke Shields.

    \
    I mean, why did women like Marlene Dietrich think this made them more attractive? Is it easier to translate different "emotions" when they're thinner, or the opposite?



    In the 50s, women like Elizabeth Taylor and Audrey Hepburn and Grace Kelly went the other way...very groomed, but thicker.






    Not a fan of the scraggly eyebrow, but I do wish mine were fuller.



    Probably sexist, so apologies, but I don't like it when men groom their eyebrows too much.

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    Quote Originally Posted by Angela View Post
    I think you can fake "mouth" smiles much more easily than "eye" smiles. There's nothing nicer or more charming than a "twinkle" in someone's eyes. :)

    It's funny how eyebrow shapes go in and out of style as well. Those, imo, awful pencil browns that were in fashion in certain eras of the 20th century gave way to more natural brows like Elizabeth Taylor's or, later on, Brooke Shields.

    \
    I mean, why did women like Marlene Dietrich think this made them more attractive? Is it easier to translate different "emotions" when they're thinner, or the opposite?



    In the 50s, women like Elizabeth Taylor and Audrey Hepburn and Grace Kelly went the other way...very groomed, but thicker.






    Not a fan of the scraggly eyebrow, but I do wish mine were fuller.



    Probably sexist, so apologies, but I don't like it when men groom their eyebrows too much.
    There's definitely something a lot more genuine about what a person's eyes can tell you.

    I agree, I'm not a fan of Dietrich's eyebrow-look either. Audrey Hepburn, and Liz Taylor's look was an improvement.

    For me, I don't groom my eyebrows. I think it looks weird for a man to have them in such precise shapes imo.
    Last edited by Jovialis; 11-04-18 at 03:59.

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