We have tools that don't require us to find sites that may have been destroyed. For one, genetic studies constrain human population levels assuming any descendants were related to either living people or sampled remains. That constrains population levels quite a bit. Moreover, we can roughly track human habitation on landscapes by how much fire they used as well as changes in flora and fauna. Recent results have even demonstrated direct detection of ancient humans from environmental DNA they left behind in skin cells and such, but that's quite new.

All of these different lines of evidence greatly constrain the types of 'civilizations' that were possible to highly localized ones with small populations, or that were completely and utterly wiped out with no surviving material culture, technology, or descendants.

That's to say it's not impossible, but highly unlikely. Any explanations all those lines would have to be parsimonious and no one's brought forth good evidence for such a narrative.

First, define civilization. It's pretty much common sense that human tribes had their own sets of customs and rules, even back then. Is that enough to have "civilization"? Is getting out of Africa a prerequisite to have "civilization"?

At one point in our history, humans developed language and could tell each other stories about major events in their lives. If developing an oral legacy is your definition of having "civilation", your question is unanswerable because there's no way we can prove conclusively which ancient humans had those capabilities and which didn't.

At some later point, we developed writing. Mural inscriptions and stone tablets are the first examples we have of humanity's communicative abilities. Is using the written word enough to have "civilization"?

Taking the other extreme, it's pretty much assumed that until the European exploration phase in the 15th-16th century, humans lived within their own local/continental society. Is being in contact with people on the other side of the globe a prerequisite to have "civilization"?

> First, define civilization.

A layer of systems built by organisms atop their natural biology, where new members of an species are inducted into those systems by “choice” and not biological requirements.

Example: Bees and termites build nests, but that’s part of their natural biology: They can’t practically survive without it.

Humans “choose” to build houses, but a human infant could survive and grow to adulthood without one, albeit with less convenience.

Good point. I guess somewhere between building monuments (but do mural inscriptions/drawings count ??) and building cities ?

Basically it comes down to lack of archeological evidence. We have lots of cave paintings (and many other things) from 50-100k years ago and they depict a caveman lifestyle not civilization.

We also find tons of tools and fossils such dating back to 200k years ago and there's no evidence of civilization there too. Rather the evidence is pretty clear on how primitive those people were.

Note that advanced, wide-ranging social relationships (i.e. civilisation) do not leave obvious archaeological traces.

We only think it does because we conflate civilisation with technologies of violence and bureaucracy, and those indeed leave clear archaeological traces.

They leave genetic traces, and we’re fairly sure about the migration patterns of all people currently alive on Earth through those.

All of us are very closely related as far as species go, so there must have been a serious population bottleneck at one point. We’re all more similar to each other than two chimpanzees.

> All of us are very closely related as far as species go, so there must have been a serious population bottleneck at one point. We’re all more similar to each other than two chimpanzees.

Is this true of Africans as well? I would expect there to be much more variety in humanity's original homeland than in the rest of the world.

It's true of Africans as well, but you can divide humans by the little variation we have, and it turns out there are a dozen or so groups in sub-Saharan Africa, and one group pretty much everywhere else.

Why ? Isn't it typically the animals that get disconnected from the rest that are then able to diverge ?

Humans haven’t been around long enough for that to happen. The most divergent groups outside Africa are that way because we met our distant relatives like Neanderthals, but it seems in our case they were just incompatible enough it didn’t add that much.

Africans esp the San have much more diversity than everyone else but IIRC it’s still remarkably low for our current population size.

"Primitive" is relative, we have evidence of tools and tool manufacturing industries more sophisticated than what any other animal uses dating back a whopping 2 600 000 years ago :

Oldowan, also : ~first (non-sapiens) Homo, ~beginning of the current Ice Age (~50 interglacials so far),

and maybe even 3 300 000 years ago (Lomekwian) - also note that even going that far back, Australopithecus *still* doesn't have other remaining descendants than us.

> "Primitive" is relative, we have evidence of tools and tool manufacturing industries more sophisticated than what any other animal uses dating back a whopping 2 600 000 years ago :

That's kind of the point though with regard to early humans and proto-humans and civilization, isn't it? We've found plenty of evidence of basic stone tool manufacture and use of fire and intentional burials from much earlier eras.

But we haven't found evidence of what we call civilization - and traces of iron tools and irrigation works and cities and monuments ought to be easier to discern than small cut flint if early humans flourished with them over those periods - until the last 10-15k of human existence.

I figured (related to previous poster) that the lack of evidence of domesticated animals was a decent indicator that there were no big civs in the past interglacials