If you believe in evolution you may think that we humans have evolved to have softer facial features over the years compared to common drawings of hard faced early humans.
Women usually have softer features than men, and straight men usually find soft-featured women more attractive.
So what’s the actual survival benefit of having soft facial features? There must be a reason why people find them attractive.
“Hard features” like a pronounced brow ridge can protect the face and eyes from blunt blows to the face. Brow ridges can also give your eyes shade. A bigger, wider jaw allows you to eat tougher food and hold more in your mouth at a time. Wider cheekbones allow for bigger muscles to attach to them. A sloped forehead should be able to take hits better than a vertical one. A more robust face seems stronger.
So what’s the benefit of having a weaker face, especially for women?
Less resources spent on making the features - less bone, less muscle. If they’re not needed (because we’re not fighting in the same direct physical way - knobs on the head is not going to stop a pointy rock between the ribs, because we’re cooking our food, because we can make eye shades) then spending calcium and protein etc on shaping them is just a waste. Better to spend it on longer limbs, or bigger boobs, or whatever else floats your cohorts’ boats.
I don’t think that there is a factual answer to the question, just reasonable hypotheses. Two that I would suggest:
Boniness is linked to starvation. A person who can scavenge enough resources to keep herself well-fed is going to be more desirable. Generally, men prefer women who are rounder (despite the fashion/model industry standard which, it’s been hypothesized, is a result of gay men and their interest in the clothes and how they hang, rather than in the women).
A larger brow and deeper brow ridge reduces the ability to see as much information in a person’s face. Our social/pack nature makes it an distinct advantage to be able to communicate more through gaze, subtle movements of the eyebrow, furled brows, flared nostrils, etc. You’ll note, in addition to the skeletal features that you have picked out, humans are rare for having a white section visible outside of the iris. Most animals go straight from flesh to iris without any gap between.
Definitely unusual, even among primates–Planet of the Apes adds them in their creatures, subtly humanizing them with a rather uncanny result. Dogs have a bit and will use it as part of communication–to the extent wolves have white sclera, it is far less prominent. Horses have it, but I know dookie about how those beasts communicate.
Evolution doesn’t optimize every little detail of living bodies. It is quite common for a trait to arise at random and persist not because it’s an advantage but because it’s not disadvantageous enough to be eliminated. “Soft facial features” needn’t have an advantage if they’re the result of something else that does have an advantage.
Here’s where I point out that humans are neotenous. Look at a picture of a baby chimpanzee, an adult chimpanzee, and an adult human. You’ll see that both the baby chimp and the adult human share certain traits when compared to the adult chimp: relatively large head, smaller jaw, more prominent forehead, smaller brow ridges, and several other features you describe as “soft facial features”. Why would it be advantageous to humans to have more juvenile traits? Or at least not disadvantageous?
Humans have large brains, and they need proportionally larger heads to house them. Due to our brain structure, we need more room in the forehead than the apes do, so retaining a skull more “juvenile” in proportion is necessary. That alone might account for the whole “soft facial feature” thing because it’s hard to change just one detail in a body in isolation - retaining a large braincase with a forehead might mean making the entire skull more “juvenile”.
In addition, though, we started cooking our food a long, long time ago. The primate lineage leading to ours shows progressively smaller teeth and jaws for the most part (*Paranthropus robustus *stands out as an exception to the general rule). That might be due to the use of resources by the body - if you don’t “spend” as much resources building a jaw you can divert those resources to other things, like supporting that very metabolically expensive big brain. Or maybe making the mouth and jaw less robust and into a precision instrument for communication was important enough to drive that trend, with those who communicated better survived better and leaving more descendants. We humans started “outsourcing” some of our digestion to our tools and fire long before we were actually human in the modern sense. We didn’t, and don’t, need large jaws.
Also, men tend to find traits indicating youth attractive in women - more neotenous women might have been more sexually attractive and left more descendants, leading to the species overall tending towards such traits. As a side effect, because, again, it’s almost impossible to make significant changes in isolation, men also became more neotenous in appearance.
But, most likely, all those was driven by a combination of pressures. In other words, all of the above: young looking women were considered more desirable, we needed big braincases which would be attained in part by retaining juvenile skull proportions and our jaws shrank because it no longer was crucial to survival to have massive chewing apparatus and those resources could be spent elsewhere. There isn’t “an” answer, not just one, but several factors involved.
Seeing the whites of a horse’s eyes usually indicates fear, terror and panic. I’m not sure it’s used to communicate as much as a side effect of that emotion.
I would also point out that there have only been a couple hundred fossils of early humans found going back ~7.5 million years ago. Many are just fragments.
So, it’s not a large sample to draw any conclusions from.
This is one of those evolutionary “why” questions where the answer is essentially a side effect of some other evolutionary process rather than a direct benefit itself.
As already mentioned, humans are neotenous compared to other apes. As adults our facial features are more like those of young apes. Our slowed development is probably connected to our comparatively enlarged brains. But as a side effect, that also resulted in relatively reduced facial features.
Neither dogs nor horses have exposed white sclera in the same way that humans do. The white sclera is normally not exposed unless the animal is rolling its eyes. In humans, the sclera is exposed all the time.
It has been suggested that the exposed white sclera in humans serves to enhance social communication by allowing easy detection of where a person is looking.
“More attractive” means greater mating opportunities, which means those genes are going to be passed on far more than their alternatives. Natural Selection seems to be the answer here.
The advantage that softer features give is that other people find them more attractive. That’s how sexual selection works. It doesn’t have to have some underlying reason; it is the reason.
Again, the fact that men have heavier brows and jaws than women is a side effect, not a direct advantage in itself. Male humans are larger and heavier than females probably primarily to be able to compete with other males for access to females (in primitive cultures; of course, civilization has offered other ways to compete for females).
(Sexual size dimorphism in primates tends to be correlated with social system. Gorillas are polygynous and males have harems, and males are much larger than females. Chimpanzees don’t have permanent pairs, and males and females are nearly equal in size. Humans are monogamous to mildly polygynous, and male humans are somewhat larger than females, but not to the degree of gorillas.)
During adolescence, increased testosterone causes males to become bigger and stronger than females. It has the side effect of also causing increased growth of the brow ridges, jaws, and hands and feet.
The fact that males find delicate female facial features attractive is probably due to the fact that that’s correlated with being female, rather than any direct advantage.
None of those are considered legitimate reconstructions by modern paleontologists, which I’m sure you know, and one of those images is a scan from a textbook calling out the image for Othering Neandertals.
(No bet that the image was made by a European, which is an extra layer of irony.)
(That image also portrays Neandertals as hunting rhinos. Does that make sense, or is it a case of “Hey, this weird thing and that weird thing maybe lived at the same time! I betcha they fought, I betcha.”)
So it seems like a package deal: If you want adults who can learn and change in a changing environment, you get flatter faces and reduced brow ridges and narrower shoulders all the other obvious physical traits. Genetics isn’t orthogonal, and packages unlike things into the same overarching phenomenon.
Of course, but Tripolar expressed unfamiliarity with such images. At any rate, Homo erectus and other human ancestors authentically had much more prominent brow ridges and generally less delicate facial features than modern humans, which is apparently what the OP was referring to by “hard-faced.”
Neandertals are known to have hunted (and butchered) rhinos in Europe such as the Woolly Rhino (Coelodonta) and Merck’s Rhino (Stephanorhinus), as well as mammoths, horses, bison, etc.
This is the answer IMO. I’m surprised I had to scroll down so far to see it.
If people find certain features more attractive, that fact becomes its own evolutionary reason - and “softer facial features” doesn’t have any great cost in terms of survival (unlike, say, a Peacock’s tail).
OK, maybe we do need a refresher on sexual selection. I’ll use peacocks here, because they’re the textbook example, but it’s applicable to any case of sexual selection.
Suppose you have a situation where peahens find elaborate tails more attractive than boring tails. It’s easy to see why this would make elaborate tails more advantageous for the peacocks: A peacock with an elaborate tail will have an easier time finding a mate than one with a boring tail, and so he will probably have, on average, more descendants. But why do the peahens find the elaborate tails more attractive? To answer that, let’s consider an unusual peahen who doesn’t care about tails, or possibly even prefers the boring tails. She’s more likely than other peahens to mate with a boring-tailed cock. And so, of her chicks, the males are likely to have drabber-than-average tails. And because all of the other peahens like the elaborate tails, her sons are going to be less likely to be able to get a mate, and so she will, on average, have fewer grandchicks than other peahens. Thus, having similar tastes to other members of her species is an advantage to the female, and having different tastes is a disadvantage.
And how did this originate? Well, it could have originated in any way at all, including possibly just random chance: If you start with a population of peafowl where the females just randomly happen to have a slight preference for fancy-tailed males, then over time, evolution will cause that slight preference to become more and more extreme, which in turn causes the fancy tails to become more and more extreme. The original slight preference for fancy tails might have had some underlying reason, or it might (being only slight) have been just random. In some other population of birds, the slight initial preference might instead have been for males with elaborate plumage around their necks, or brightly-colored beaks, or combs of skin, with just as much reason (or lack thereof) for any of these features.
