[Openurmind]

This is something I have also supported for many years now. it's not that it went extinct, it became something different and no longer a pure strain through hybridization. Prime examples of this can be found in other species also like the ancient aurochs.

https://en.wikipedia.org/wiki/Aurochs

And for early human species, in the Altai Denisova Cave complex they have found the proof of this much more likely theory of course.

https://www.sciencedaily.com/releases/2019/09/190926073340.htm

https://www.sciencealert.com/we-finally-have-some-idea-of-when-the-mysterious-denisovans-walked-the-earth

[SunkenCiv]

This is entertaining (it’s only partially in reply, my mind wanders) — I uploaded my raw DNA file (Ancestry kit) and it turned up Neandertal (which is what I was interested in), Denisovan, Kennewick Man (!), and a raft of other really old DNA matches, apparently from some prehistoric ancestors who lived by some dirty patch of ice in the middle of nowhere.

Archaic DNA project:
http://www.y-str.org/p/ancient-dna.html

This one may require signing up for GEDmatch, a semi-useful site, membership is free last I knew:
https://www.gedmatch.com/AP/ap_group_list1.php