I thought it would have been the standard Homo S.S. response when encountering a new tribe to either:

a) Trade.
b) Wipe out all the men and children and take the women as mates (even if they or the offspring are sterile).

Plenty of human tribes have got driven into the mountains and away from more fertile lands by larger more cooperative populations. We have done it to each other, so why not to our closest cousins?