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Thread: Why do humans have such wide variety of facial features?

  1. #1 Why do humans have such wide variety of facial features? 
    Forum Ph.D. Raziell's Avatar
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    In the animal kingdom, i dont know a SINGLE case where the face of two members of a species looks identical. (EDIT: I mean unidentical that is, oops to simplify, they all look the same to me )

    Humans, with the exception of twins etc. have different faces. Sure you can find look-alikes but theres always some distinct feature that separates them.

    Is this purely an illusion from looking at other humans over time, while if i spent the same life span looking at different snakes for example id notice different faces? Or is there some other explanation?


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    Reptile Dysfunction drowsy turtle's Avatar
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    I could certainly identify my cat just from the face.

    I think it very much depends on the animal in question; larger animals tend to have more variation than smaller. Or it could simply be that we cannot see enough detail to distinguish between smaller animals' faces.


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  4. #3 Re: Why do humans have such wide variety of facial features? 
    Moderator Moderator TheBiologista's Avatar
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    Quote Originally Posted by Raziell
    In the animal kingdom, i dont know a SINGLE case where the face of two members of a species looks identical.

    Humans, with the exception of twins etc. have different faces. Sure you can find look-alikes but theres always some distinct feature that separates them.

    Is this purely an illusion from looking at other humans over time, while if i spent the same life span looking at different snakes for example id notice different faces? Or is there some other explanation?
    We encounter other humans far more frequently than any other species, even if there are no hard-wired behaviours that cause us to look more closely at other humans, we'll still tend to spot the difference more easily.
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    Forum Senior Kukhri's Avatar
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    A 2008 study seems to suggest that human faces may not be hardwired into our brains. Monkeys were reared for 6, 12 or 24 months with no exposure to faces. After exposure to human or animal faces for one month, they were shown images of faces they had seen, and ones they had not. If their eyes spent more time on the novel faces, it was assumed that they recognized the old ones. From this, it was determined that they recognized faces they had seen before, whether it was 6 or 24 months of deprivation. Following this experiment, the monkeys were raised in a general monkey population with exposure to both monkey and human faces. Their preferential recognition of the first faces they were exposed to never changed.

    http://www.pnas.org/content/105/1/394.full
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    Administrator KALSTER's Avatar
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    There actually is a mechanism for recognising faces that is hardwired into our brains. People have been observed that have damage to a certain area of the brain that takes this ability away and stops them from learning new faces. They can still see the features of the face in question such as eye colour or pimples just as we can, but they cannot see it as a "whole". Their vision is not affected in any way. This would suggest that other animals have this same ability and also in regards to general body language and mannerisms, but it might be bit more geared towards faces than other animals, since we have been wearing clothes since early in our development I'd guess. Other animals often have other bodily features, sounds or smells that are also in part or exclusively used for recognition purposes.

    A pertinent part of that PNAS paper:

    "These results indicate the existence of an experience-independent ability for face processing as well as an apparent sensitive period during which a broad but flexible face prototype develops into a concrete one for efficient processing of familiar faces."

    So we all have a hardwired mechanism that gets tuned by early exposure to faces.
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    Forum Freshman asxz's Avatar
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    i think it is more inportant to recognize human faces, to save ourselves from embarrasment. This means that if we meet someone for the first time we will look at them harder than if we saw them on the street.
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    Kalster is quite correct about the hard wiring. And it appears to work only on human faces. Which is not to say that we cannot learn to distinguish animal 'faces'. People who work for long periods with a specific type of animal get really good at recognising individuals. However, we are specially adapted to recognising human faces more than animal, and 'normal' humans will always be much better at human rather than animal faces.
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    Forum Freshman LoKo1Wolf's Avatar
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    Also, even twins have different facial features even if they are not visible to the naked eye.

    Monozygotic twins are the same sex and their traits and physical appearances are very similar but not exactly the same; although they have nearly identical DNA, Environmental conditions both inside the womb and throughout their lives influence the switching on and off of various genes.
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    I think no matter what, genetic makeup will not exactly turn out to be the same. Based on my experience, even if you observe identical twins for the first few times, you won’t be able to make out the difference. But once you get to know them longer and observing their facial buildup, soon enough, you will find that indeed there’s actually a difference.
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    Forum Ph.D. Leszek Luchowski's Avatar
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    It is strange that we are so good(*) at recognizing faces but so helpless when it comes to describing them.

    Try asking a friend to fetch your sister (whom he has never met) from the station and just telling him what her face looks like - no way you can make your description clear enough that he will identify her in the crowd. Unless you add some non-facial characteristics, such as a particular hairstyle, stature (tall/short, slim/fuller) and, ironically enough, clothing.

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    (*) personally, I am not. There must be something wrong with my hardwired face recognition cortex. I have to see a person many times before I can recognize them with any degree of certainty.
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    Forum Cosmic Wizard paralith's Avatar
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    Quote Originally Posted by Will
    I think no matter what, genetic makeup will not exactly turn out to be the same. Based on my experience, even if you observe identical twins for the first few times, you won’t be able to make out the difference. But once you get to know them longer and observing their facial buildup, soon enough, you will find that indeed there’s actually a difference.
    In monozygotic twins, the genetic makeup is the same. However environmental differences between the twins in the womb and growing up will alter their physical features somewhat. For example, it often happens with twins that one ends up consuming more nutrients than the other in utero, so that one is heavier and taller than the other once they're born and throughout the rest of their lives.
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    I think it very much depends on the animal in question; larger animals tend to have more variation than smaller. Or it could simply be that we cannot see enough detail to distinguish between smaller animals' faces.
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    Forum Professor marcusclayman's Avatar
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    Our environment is also very diverse. Hippocrates observed that people who live in relatively moderate climates had more similar features than those who were subject to more dynamic weather patterns.
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    Quote Originally Posted by Raziell View Post
    In the animal kingdom, i dont know a SINGLE case where the face of two members of a species looks identical. (EDIT: I mean unidentical that is, oops to simplify, they all look the same to me )

    Humans, with the exception of twins etc. have different faces. Sure you can find look-alikes but theres always some distinct feature that separates them.

    Is this purely an illusion from looking at other humans over time, while if i spent the same life span looking at different snakes for example id notice different faces? Or is there some other explanation?
    even twins dont resemble each other
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    which contribute uniqueness of face ? viscerocranium?,or softtissues?
    Last edited by sampi25; March 3rd, 2014 at 11:05 AM. Reason: spell
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  18. #17  
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    We recognize it in our own simply because though we might be hardwired to some degree, we also learned to tell distinguishing characteristics to groups of people we've been around. To a large degree when someone gets around a haplogroup of people they are unfamiliar with they have trouble distinguishing between individuals--they actually "all look alike," (a statement of fact...not a declaration of being raciest) the same as the OP says about animals. With time around that same group they learn to tell the difference between individuals.

    Caldara has done a lot of work in this area:
    Roberto Caldara - Google Scholar Citations
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    Forum Cosmic Wizard icewendigo's Avatar
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    dogs: i have a chiwawa and a st-bernard, i cant tell them appart

    i think / would guess we are more tuned to noticing differences in humans by being exposed. a bit like someone not used to chinese words might find similar sounding words virtually impossible to differenciate
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  20. #19  
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    Do humans have that great a variety? How many have you seen with 3 eyes or two mouths? I think we just look at much finer detail in humans. On the other hand there are animals with much greater uniformity. Grey squirrels are virtually identical to each other.
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  21. #20  
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    I was watching a doco on Emperor penguins a couple of days ago. It's obvious that you can tell that some are, marginally, bigger or smaller than others and you can sort of pick up a few differences with the chicks. For all practical human purposes, there are 80000 identical twins. But these animals have no problem meeting up with their mate for each year's breeding season despite not seeing them for months at a time.

    It really depends on what you're hardwired and acculturated to recognise. We have to distinguish like/unlike, tribe/not tribe (though we often do that with footy jumpers nowadays), friend/foe. If it's really vital to survival to discern really fine differences between apparently identical individuals, you'll have acquired ways to do it or you'd have gone extinct.
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