Eli5 : why do humans look different but animals and other species look the same?
In: Earth Science
Not sure the premise of this is right. Isn’t it just that the more time you spend with a species, the more you’re able to differentiate between individual animals of that species?
Pet owners have no problem telling their pet apart from others of the same species.
Actually, until a certain age, human children can distinguish between different animals quite well (in addition to people of other races). However, at some point that skill gets refocused only on people who look like their caretakers.
Most animals are fairly specific to their environment, and are adapated to that. Part of what’s made humans the most successful animal (insects aside) is our adaptability – our ability to survive in (almost) any environemrnt. We have spread all over the planet, and our physicality has changed according to the diferent environments (eg darker skins in sunnier climates) – and then we have moved and mixed again and inter-bred – hence there is large gene-pool from which we are made, and hence our different looks.
Some farmed and domesticated animals exhibit something similar, where artificial breeding has resulted in different breeds of the same animal, with different characteristics and looks. Think how different so many dogs look – even dogs of the same breed.
Because you probably never had a reason to learn how to differentiate animals between each others as they do not belong in any social group you’re in and you don’t require that kind of knowledge.
Honestly, probably because as humans, we’re more adept at distinguishing the differences in human features. If you spend a lot of time around animals you do become able to recognize individuals – ie, my cat looks very different and unique compared to any other calico. But essentially, like recognizes like – it’s more important for humans to be able to distinguish between other humans from an evolutionary standpoint
In addition to the points others have made (humans have a lot of diversity from spreading all around the world, you can distinguish animals with practice but the method may be counter intuitive to a human), I’ll add this:
We are social creatures. It’s one of our most important survival skills. So have a ton of extra features to communicate with other humans (blushing, eyebrows, visible whites in our eyes, etc.) And a diversity of appearance to make us easily identifiable is an adaptive trait. Plus, a huge amount of our brain is dedicated to interpreting other people – their behavior, assistance, etc. – so we are hard wired to be good at it.
To animals, we all look the same. Hell, even a lot of humans will commonly mistake people for other people, even when those people don’t really look very similar at all. Species tend to be very good at distinguishing between other members of their own species, whatever that species may be, but not very good at distinguishing between members of other species, cos those circuits need to be able to remember a lot of stuff and need to be good at paying close attention to detail, so they’re very specialised.
Part of it is that we rapidly spread into every imaginable ecosystem on the planet, faster than evolution could cause us to drift far enough apart to create new human species. Every human now alive descends directly from one of 3,000-10,000 ancestors who survived a population bottleneck about 70,000 years ago, which is an eyeblink in evolutionary time for a species like us. That narrowed our potential for speciation quite a lot.
However, a larger part of it is in how your brain works. We have an entire section of our brain dedicated solely to recognizing faces. It’s one of the few which sort of works as intended immediately after birth, as anyone who has ever smiled at an infant only for them to smile back can attest. They can only do that because they are recognizing faces on an instinctual level. What this means in a practical sense is that your brain is incredibly good at identifying faces, and indentifying differences between them. Why we do this is obvious – being able to tell people apart is a powerful survival trait – but it’s very narrowly focused. It works best on human faces because it’s been trained almost entirely on them, to notice the kinds of differences which are common between human faces.
So there isn’t much variation between humans, but that which exists is super obvious to us because it needed to be to promote survival.
They don’t. There’s as much variation between dog faces, horse faces, elephant faces are there are between human faces. Your brain just isn’t wired to pick up those differences as strongly. Humans actually have a specific part of the brain (the fusiform gyrus) devoted to facial recognition of other humans. It’s why we see faces in everything from the clouds to stains on wallpaper. Our brains just hone in on specific shapes and tell us we’re looking at a face, even if those shapes are just two dots and a curved line 🙂 and we’re *very* good at picking out subtle differences between them. Sometimes, people sustain damage to that part of their brain and lose the ability to distinguish faces. But that doesn’t mean that familiarity doesn’t make a difference. People who work with animals are definitely better than the average person at at picking up the subtle differences of their animals’ faces. It’s just not as hardwired into us as distinguishing human faces.
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