The meaning is, however, found in the original context. stcredzero:

When we lived as hunter gatherers

That's a reference to ancestral environment.

One should note, though, that studies of murder rates amongst hunter gatherer groups

That's a reference to present-day hunter-gatherers, with the implication that what we see among modern groups so described is what happened among humans generally in the Paleolithic, when hunting and gathering were the only ways that people had yet invented for getting their food. This is the fallacy that taw is talking about when he says:

We have precisely zero samples of any real Paleolithic societies unaffected by extensive contact with Neolithic cultures.

To which stcredzero replied by quoting:

Bushman society is...

And so on.