[djf]

I have heard speculation that during the last third or so of the last great ice age, worldwide population fell to the 10-20K range.

I guess we're talking about 12-15 K years ago.

[blam]

"I guess we're talking about 12-15 K years ago."

I think you're thinking of the Last Glacial Maximum(LGM), 18-23,000 years ago. That was an extremely cold period and this Journey Of Mankind shows an extreme shrinkage of humans worldwide during that period. I've not seen any population figures associated with that period though.

[aruanan]

I have heard speculation that during the last third or so of the last great ice age, worldwide population fell to the 10-20K range.

You mean the last glacial period that ended about 11 or so thousand years ago before our current interglacial period of the present ice age that we're in right now?