The term has two almost opposite, but often confused, meanings: to provide someone with what they need, and to prevent things from changing.
Homo-sapiens was never sustainable. No species is - 99% of them have gone extinct. Eventually the human-race will be, unless we choose otherwise, wiped out by some ice age, a meteor, a supernova, etc.
The idea that we can harken back to some prehistoric time where life was sustainable and we all lived in tranquility like hobbits isn’t grounded in reality. Only Knowledge can save us. Only Progress is sustainable.