I'm becoming leery of seemingly-definitive terms like "warfare" and "wiped out", not to mention the definition of "species", the more I learn about hominid evolution.

The truth seems to be a lot fuzzier than a nice tidy genealogical chart, and it's useful to keep in mind that the names of hominid "species" are, for the most part, just the names given to a handful of individual fossils out of the billions who must have lived. They're just random snapshots in time of what was certainly a process of wide genetic variation and recombination of gene pools, as groups continually split off and diverged, then became reunited and combined genes again. Our genetic "line" more closely resembles the Mississippi at flood than the deceptively mathematical lines of a genealogical chart.

So if you can't really define a hominid species with precision, how you can define "extinction", and then blame it on "warfare"? No doubt divergent tribes fought upon meeting up again generations later, but war among hominids is almost always followed by genetic mingling. War would rarely have led to extinction among hominids, I think. A more likely picture is that the main line of the flood has continually reabsorbed the more successful offshoots. It's more like an amorphous cloud of seething DNA that kind of swarmed and straggled its way to where we are now.

I don't think we need to borrow unnecessary guilt by making up stories about the wretched cousins we wiped out; they're still here, where it counts, in the DNA.