[ummonk]

You're making it sound like everything advanced and then receded at the same time across the world. This hasn't been the case since the end of the last glacial period. There have been recedings of local civilizations scattered throughout history, as well as some large scale regional disruptions (e.g. late bronze age collapse, decline of the roman empire), but nothing like periods where everything collapses globally.

[Maursault]

> but nothing like periods where everything collapses globally.

What else but a population bottleneck could explain the lack of any genetic diversity to speak of in humans? No human alive today is more distantly related to you than 37th cousin. Any two random individuals are 99.9% identical. That's weird. For this to have occurred, something must have happened everywhere all at once.[1]

[1] https://https://en.wikipedia.org/wiki/Toba_catastrophe_theor...

[ummonk]

Yeah I don't disagree, which was why I caveated it by saying "since the end of the last glacial period".

Before that, all bets are off, and I personally do consider the Toba catastrophe a possible explanation for the ridiculously low level of genetic diversity in modern humans outside sub-Saharan Africa.

[svnt]

Not necessarily — it could just as easily have been a founder population event, combined with “weird” sexual selection.

[Maursault]

I like this idea. A long time ago, there was one amazingly attractive, irresistibly seductive, incredibly promiscuous and astoundingly prolific breeding individual and sexual athlete: the legendary Don Juan of the late Pleistocene.

[nomel]

With "pockets of", I read this

> It also shows that pockets of architectural knowledge rapidly advanced and then receded all across the known world.

as "individual pockets, all around the world, advanced and receded."

[ummonk]

Oh, you're right. My objection was based on my own misinterpretation of "pockets" as referring to time periods and/or specific architectural knowledge rather than to particular locations.