Just a passing thought, but I wonder if they were refugees? Last survivors of the losing side of some ancient, nonviolent conquest/displacement? Forced to live in a marginal environment due to an influx of more aggressive, more adaptable homo sapiens?
The history of mankind is brutal, merciless slaughter. Run to the hills. Run for your life.
If I understand correctly, there wasn’t much difference in lifestyle between Neanderthals and Homo Sapiens until about twenty thousand years ago. Then suddenly there was an explosion of advancements in tools, weapons, clothing and especially art and Homo Sapiens vaulted ahead.
It’s still a mystery what got switched on in our heads but I guess the alien monolith from 2001 zapping our ancestors and turbocharging their brains is as good as any.