In what ways do humans anatomically differ from other great apes like orangutans, gorillas, chimpanzees or bonobos? What evolutionary pressures drove these changes? What advantages do they provide?
Let me start with a few which you can comment on or add to:
1: Having a small amount of fur and sweating mean unusually effective cooling which enables persistence hunting and more hours of activity.
2: Bipedalism freed up two limbs to carry objects and use tools. There may be other advantages like a higher vantage point but the environment can provide that too.
3: I vaguely remember hearing that human shoulders are unusual in their range of motion and the way they apply strength. Is this accurate? What would be the benefits of that?
My guess is that it would have been useful to manipulate objects at eye level or above. It would also have been useful to carry heavier objects on the head or shoulders. It could also have been extremely useful for throwing rocks and spears. Rocks may not be great as an offensive weapon but they could dissuade predators. Spears would have been revolutionary stand-off weapons, the equivalent of today’s cruise missiles. Since early spears would likely have been made of wood with a fire-hardened tip, is it possible that spear use could go back a million years or more?
4: The part of the body which differs most is likely the brain; That’s what leads to non-anatomical differences. I’m guessing the prefrontal cortex is the part of the brain which shows the greatest difference. Are there subcomponents of the PFC which show even greater difference than the PFC as a whole?
Anything else?
“Humans” here can be used in the sense of hominids. If you mean specifically homo sapiens sapiens, please use that term or “HSS”.
Our muscles are attached at different points, giving us different leverage. That’s the main reason why the other great apes are all stronger than us, but the human setup is another reason why we’re better than them at throwing things.
Any idea around what time we got better at throwing things? Yes, I realize it’s not like there was an official date when the switchover happened so it’ll have to be approximate.
Are there any other animals which are anywhere near as good at throwing things with their arms? How good is human hand-to-eye coordination compared to other great apes? Is it mainly down to the utility of chucking rocks and spears?
The problem is that really one would need to compare ourselves to other hominids which is unfortunately no longer possible. Most of the differences noted above happened well before modern humans arrived.
While not perfect consider we are:
Eukaryota/Metazoa/Chordata/Craniata/Vertebrata_Euteleostomi/Mammalia/Eutheria/Primates/Catarrhini/Hominidae/Homo
Catarrhini contains both apes and old world monkeys but the extinct members Hominidae is our closest relatives.
Other apes and old world monkeys have continued to evolve after we split from our common ancestors so it is problematic to frame the question in the context of when “we got better at …” as that position assumes that regressions or advances didn’t happen among our close relatives.
As an example Homo heidelbergensis used spears, but it is unclear if that is from a common ancestor or if they are a direct ancestor to us. Evidence suggests that neanderthals do seem to be descended from heidelbergensis but we do not know when abilities like spear throwing developed or if they were novel.
Male gorillas can tell when a female is in heat - i.e. ovulating, something they also do every 28 days. They do not appear to have a pair bonding, but rather the main silverback typically has exclusive rights, although it is not unknown for multiple males to mate with a receptive female.
Started with Homo erectus around two million years ago.
Nope. It is one of those things we are uniquely good at. Our tremendous endurance is almost as unique, matched or exceeded by only a very, very few animals.
From what I understand, homo erectus is the first hominid you could mistake for a human if you saw them from some distance. Looking at reconstructions of what they looked like, it reminds me of people I’ve seen.
It was also the first species to be fully upright, to routinely hunt and to grow the same size as HSS. Are there more convincing possible pressures for bipedalism?
Would throwing rocks have been a serious hunting tactic (as opposed to defense) or would it have to be spears? Spears suggests a higher minimum level of sophistication than rocks.
Humans have much smaller guts than apes. We discovered how to manage fire and cook food until it is soft and much easier to digest and get calories into the body. Anyone who tries a raw food vegan diet gives their guts a lot of work to do. Avoid getting into an elevator with them.
Humans are adapted to an upright posture so they can run and engage in ‘endurance hunting’ of prey. Basically you chase ‘Bambi’ for miles until they become exhausted, then use a sharp tool to make them ready for the cooking pot. Apes are not good at running marathons and being hairy makes it difficult to sweat and regulate they temperature in the open sun of grass lands. They prefer shady forests.
I would guess humans have better distance vision for the same reason.
Human females disguise their fertility. This encourages long term pair bonding.
Human females have a menopause creating a class of infertile grandmothers that participate in sharing child rearing.
Human babies have a much longer dependency on their parents and birth problems because of their big heads.
Humans have bigger brains to go in the bigger heads. A big brain allows for much more complex social relationships and co-operative behaviour. Apes exist in extended family groups and troops. But they do not co-operate on a large scale like humans. Planet of the Apes it is not.
Humans have opposable thumbs to help grip objects, throw weapons and make use of tools,make clothes and fire. Play the piano. that sort of thing.
Humans have larger voice box adapted to making sounds so we can communicate by spoken language. Apes cannot make the sounds to carry a language of any sophistication. This allows humans to share knowledge, information and to co-operate and co-ordinate their actions.
It comports well with persistence hunting, too: You can use sticks before you have the trick of hitting anything with them reliably if you use them to spook animals into continuing to move, quite possibly in a given direction. This wears them out faster, which means you can kill them faster, and, possibly, kill them in a place of your choosing.
This is all speculative, of course, but if we’re willing to accept modern professors playing around with rocks as information about how people might have crafted hand axes, it isn’t too out there.
I just wanted to come back to this statement - Chimps use purposefully-modified spearsto hunt, so how sophisticated do you have to be ? Throwing the spears is just a step up from stabbing with them - now, chimps have also been documented using crude stone tools (but not hunting with them, only for plant food processing/digging), so I think there’s not much difference in sophistication between the two, at that point.
They have to be sophisticated enough to get a better chance of passing on their genes by securing food reliably or defending against predators using tools.
There are not many items in the chimp toolbox. Prodding termites out a hole with a twig or cracking a nut with a rock really don’t cut it.
I’ve read that a lot of the changes between us and other apes are directly related to our evolution as a persistence hunter- in particular they’re changes to adapt us to long-duration running.
That was probably caused by climate change in Africa favouring open plains with lots of grazing animals to hunt. Early humans gave up foraging in the forest and went walkabout and evolved to take advantage of this change., the great apes meanwhile, stayed in the jungle.
Of course, there are other theories: Here is how one author and movie director imagined it happening.
All the great apes have opposable thumbs. In fact, that is a feature of being a primate. But we have a precision grip, unlike the other apes. The other apes have long fingers and relatively small thumbs. Those work well for hanging from branches, but not so well for the kind of precision work we are capable of.
This arose at least 2M years ago and maybe as long ago as 3M years.
