I question a lot of the info in comment. Specifically the “humans domesticated themselves 6000years ago.” We had characteristics of “domesticating ourselves” long before 6000 years ago. Non-pronounced canines, reduced sexual dimorphism between males and females, are all hallmarks of a transition from a mating system that was “tournament based” (one male wins all the females) to a more pair-bonded species, although it’s a spectrum and humans have behavior related to both.
This was probably co-evolving with the cost of raising a human child. Which we didn’t just magically start doing 6000 years.
Classic example of the bullshit asymmetry principle, where it took me two paragraphs of text to reasonably dispute a one sentence off hand, inaccurate comment
Two notes on language and self-domestication:
- 77kya is very late for the emergence of language (though how far it can be traced is still object of heavy debate and nuance). The tenuous consensus nowadays is that the last common ancestor with the Neanderthal/Denisovan branch had at the very least a partial capability of language. 'Behavioral modernity' is also a bit of a red herring on its own, in light of discoveries like this and how similar Neanderthals were to us in terms of archaeological record.
- Re self-domestication... The concept is very messy and disputed (I've largely given up on its usefulness, in fact). But in any case 6kya is too late, simply because all modern humans are prosocial, as parent comment said.
Source: human evolution PhD, I have worked in faculty of language evolution, prosociality, genetic basis for self-domestication.
Am I right that the common ancestor of sapiens and Neanderthals and Denisovans is -800kya?
And what about the following strong differences between sapiens and Neanderthals/Denisovans: musical instruments, cave paintings, projectile weapons?
I found that the basis has to be there from a long time ago, and one branch makes use of it. The lungfish has limbs, but only some branches of it went terrestrial. An old human ancestor had language capabilities but only some branches used it. Dinosaurs had feathers but only some used it for gliding and flight.
Can you comment on the shrinking brain size that’s observed among humans in the past few thousand years?
Strong differences: it's not so clear these are "strong", for a couple reasons:
1. The archaeological record has disputed some of those claims: spears are supposed to have been part of the hunting repertoire of Neanderthals [1], there are some claims regarding musical instruments (personally I'm skeptical) [3], and cave paintings [2] basically resemble what sapiens where doing about that time, which is just... not very impressive in general.
2- A much more interesting question is hiding in plain sight. It's not as much "did Neanderthals do X or Y relative to what sapiens are known to be capable of?", but rather: "given enough time, could Neanderthals or Denisovans have painted something like the Lascaux cave paintings?". Or, rather: did all these extinct humans species have the same capability for cultural ratcheting, ie transmitting and refining knowledge, that we have proven to have? Sapiens needed a lot of time to create some of our most representative "representative art", let alone other cultural innovations. On the other hand, if there were any differences in capability, what were their nature? What are the implications for language?
Re the basis: for sure! Some of the innate physical and neurological basis for language have been in place for a long time. Which pieces where co-opted, modified or appeared de novo when and for what is the interesting part. Having only the archaeological record and the DNA of these species, it's a hell of a problem.
As for the shrinking brain size: as far as I know there is some doubt about the universality or significance of this claim. It could be due to agricultural diet changes, or holocene climate fluctuations. It also coincides with population size increases, so mutations allowing more efficient brains or just regular old drift are possible. Honestly, I can't say I have a strong opinion on it.
Any thoughts on the tech & culture timeline I provided above? I'm by no means an expert - or even an armchair archaeologist for that matter - so it's difficult to keep track of the age estimates as they evolve.
The changes in the field have done nothing but accelerate and it feels like there's a new development every other week at this point.
Maybe I'd add to this the first engraving by erectus [1] (~500kya) because people tend to forget about it but I think it's quite significant. Other than that, it looks great! I also have a hard time keeping track of every new discovery, specially as I got out of academia. Amazing time to work in human evolution.
Citation for that? There's clear evolutionary selection for language capabilities a long time before that isn't here?