I'd like my world to have humanoid protagonists, while still reinforcing that they are ultimately not human, but have simply evolved in a similar way due to convergent evolution. To provide a constant small reminder of that, I'd like to introduce one or more subtle cosmetic differences to these humanoids that separate them from us -- distinct from and prior to the more rapidly mutable differences in bone structure, pigmentation, and face shape that characterize different ethnicities.

Now I could just give all my humanoids three eyes and vampire fangs, or what have you, and the sky would be the limit. But to keep things as realistic as possible, and to provide the constraints needed to make this a valid StackExchange question, I'd like to conservatively ground the cosmetic difference(s) in actual human evolution, whether by taking up a trait that we once had but lost, or one we didn't develop but that we know (whether from genetics, primate biology, etc.) would have been a very plausible turn.

Here's some more selection criteria here, to help narrow things down. The differences should be ...

  • Visible, and easily communicable through text.
  • Plausibly constant across all ethnic groups and the entire history of anatomically modern human(oid)s.
  • Not a significant change to human(oid) function. Primarily cosmetic.
  • Not so extreme as to make the humanoids seem totally alien.
  • Not a tail. Already know that one!

In the event of two answers that meet the above criteria equally well, I'll select one based on A) the number of possible differences given, and B) the apparent strength of the argument that the difference(s) are plausible within an otherwise human-ish evolutionary path. Thanks for your time.

  • $\begingroup$ Are these things totally alien, or from some terrestrial vertebrate lineage? What do you envision their ancestors to be like>? $\endgroup$
    – Willk
    Jul 29, 2018 at 1:27
  • $\begingroup$ @Willk: The humanoids are intended to be very close to human. They evolved on an earth-like world and had ancestors similar to our own. $\endgroup$
    – Random
    Jul 29, 2018 at 1:38
  • 1
    $\begingroup$ If these are aliens ("evolved on an earth-like world"), then "persistant[sic] cosmetic difference into human evolution" is highly misleading, since... they aren't human. $\endgroup$
    – RonJohn
    Jul 29, 2018 at 5:14

4 Answers 4


An easy thing to change would be pupil shape. Humans, of course, have circular pupils, largely because we are generally specialized and are not a prey animal. Small cats (not lions etc.) have vertical slit pupils that allow them to hunt in dim light while also not being blinded in bright sun. Prey animals (goats, horses) have rectangular pupils that allow them to see farther around. There is really no reason humans couldn't have either kind of pupil, seeing as our ancestors were both foragers and fairly easy prey, so your hominids could very well have slit eyes. The normal range of color would be available, you could mention that some people's pupils tilt inward or outward if you wanted to, and it's a quick and easy way to remind readers that your characters aren't quite human. People talk about eyes a lot.

Another easy one would be skin patterns. Many animals with fur have patches of color, if not in their fur then in their skin. Of course, human skin tones evolved as early humans moved into new environments with varying sun exposure, but there is no reason that, once individuals of different tones interbred, they would not create paint or even calico patterns, as is sometimes seen in cats, dogs, and horses. You could even say that early interbreeding led to patches, speckles, or stripes, with any one of them being favored and thus sexually selected for, leading to a present population with really any pattern you'd like. This could be an interesting way to divide the society if you wanted to, with a sort of pattern-racism, or perhaps cosmetics to alter or enhance one's patterns. This could also be highly visible, such as white spots on a black person or black spots on a white person, or quite subtle, as with shaded stripes.

Natural mohawks/manes. In human evolution, we retained our head hair while losing most of our body hair to protect our heads from direct sun while allowing our bodies to cool through sweat. It is perfectly plausible that a slightly altered evolutionary line would have led to a loss of hair slightly further up the head and/or retaining hair further down the spine. Your hominids could have Mohawk-style hair that might continue down the spine to the shoulders, or really to anywhere you like. This wouldn't really affect their functioning, though it might lead to new and interesting fashions or clothing. It is highly visible and easily commented upon. All variations in hair type and color could be easily transferred as well.

I'd be slacking if I didn't mention large canines. Humans lost their oversized canines sometime after splitting with chimpanzees, so it was definitely pretty recent in our history. Humans are some of the only carnivorous or omnivorous land mammals that do not have canines larger than the rest of their teeth, and certainly the only ape lacking them. While it is true that humans no longer bite each other to acquire mates and drive off enemies, there is no reason your hominids could not have retained this trait. Perhaps it has even become a place for fashion, with gilded or inlaid tooth rings (I'm thinking something like those seen on some elephant tusks). Just a thought. Larger canines shouldn't have a functional impact on humans in a modern-ish society, though you could probably make them impactful if you wanted to.

Ear shape could also be changed. Some humans have pointier or boxier ears than others anyway, so it would be no great leap for your hominids to have evolved elf-like pointed ears or right-angle edged ears or even something more bizarre, like curled or folded ears. Again, that should have no functional impact, unless you went so far as to give them all cat/dog ears that stick out and swivel or some such, but it would allow for different jewelry styles if nothing else, which would let you remind readers of the difference whenever you felt the need.

A slightly less cosmetic change could be different hand shapes. The most basic would be having, say, six fingers on each hand. Practically speaking, six fingers would be no more or less helpful than five, so you're not talking any real functional difference, but it would be noticeable and could be commented on.

A bit less explainable but still quite possible would be wild hair colors. Of course, in today's world, lots of humans have wacky hair color, but most of them don't grow it that way. Your hominids could have hair in shades of blue, green, red, orange... really anything. The evolutionary explanation for this is where it gets tricky, but it's not completely out of the ball-park. Many birds have amazingly vibrant plumage, almost always due to sexual selection on males, so if you can imagine a vibrant red and yellow gorilla beside the vibrant red and yellow rain-forest birds, this could totally work. You could also just sort of hand-wave it by saying the hominids, after splitting with the apes (assuming that's the evolutionary track you're using) began selecting for more vibrant colors and evolved wild hair patterns on their own. These would almost certainly be male traits, as in birds, and would almost certainly be a fashion/class indicator. Could be interesting implications for the use of hair dye or wigs.

  • $\begingroup$ pupil shape has really strong functional effects. Slit eyes makes for poor day vision for instance. $\endgroup$
    – John
    Jul 29, 2018 at 15:30
  • $\begingroup$ Yes, there are some differences in vision for different pupil shapes, but these could be easily ignored and are minor effects in a semi-modern human-like world. You would not say that a cat has significantly poor day vision, so there's no reason to say these hominids would either. $\endgroup$
    – Aziri
    Jul 30, 2018 at 5:14
  • $\begingroup$ cats do have poorer day vision caused by slit pupils, the shape of the pupil correlates with the shape of the fovea, slit pupils create multiple focal points on the eye. Interestingly we do not see vertical slit pupils in any tall animals, there may be some interaction with the sun and horizon. sciencedirect.com/science/article/pii/S0960982206011961 $\endgroup$
    – John
    Jul 30, 2018 at 5:43
  • $\begingroup$ Sure, and yes, there is some correlation between pupil and average height/predator-prey activity, but unless you've found something I missed, I stand by my statement that altering pupil shape would not significantly impact the functioning of these hominids, assuming a world quite similar to ours. $\endgroup$
    – Aziri
    Jul 30, 2018 at 16:42
  • $\begingroup$ The change in focal points are the biggest issue, the ability to focus on far points is essential to the hominid lifestyle, especially as vision based pursuit predators. Cats are functionally nearsighted. $\endgroup$
    – John
    Jul 30, 2018 at 17:34

Having a colored sclera would be an easy one. having black or dark sclera is unheard of in humans but fairly common in chimps. there is a reason it is used as a quick and easy movie method for showing an alien nature.

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the function of the white sclera is supposedly to make it easier for us to tell where another human is looking (advantage in teaching offspring), but dark scera and light iris could produce the same benefit while looking totally alien.


Seeing as you removed prehensile tails from the possible answers, I give you...prehensile feet. Similar to chimps.

Being able to practise precise foot movements and toe grips across your humanoid population would easily remind your readers that they are not human. According to one study around 8% of the current human population still has a more primitive bendy foot. Some of that fairly large number could be because of modern lifestyles and wearing shoes causing certain foot ligaments to not tighten up as much as possible, allowing a form of regression.

Your characters could retain the use of their feet for gripping things. All your humanoids would be able to use their feet as an extra hand, not just the very few humans who have practised in our world. Plenty of stories and videos of people painting and eating etc with the aid of their feet. Instead of being an oddity as in our world, it would be the norm in yours.

If you require more humanlike scenes, modern social constructs could have made these humanoids less dependent on using their toes/feet instead of their fingers/hands. Or some actions are considered impolite for the hands but not the feet or vice versa. (Similar to some cultures not eating with a certain hand, and enter a room with a certain foot first).

Eg. Both hands are full and they open the door with their feet. A sigh of relief after taking off their social conforming shoes. Shaking of the head at that uncultured person waving their feet while they talk. Typing with both hands and feet...typing with feet while sorting paperwork on table etc.

You could literally "do two things at once"!


Take your pick from any number of hominins that once roamed our Earth and work from that.

Neandertals or Homo Erectus or any of the others would give you a massive amount of differences which are mostly cosmetic if you assume their culture evolved similar to ours..


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