Incidentally, KgT, hopefully you noticed that you imply a timeframe very different from the one I named. Hundreds of millions of years ago, the time frame I specified, it is doubtful that mammals were living the Fred Flintstone lifestyle to which you allude. That far back, the period I specified, mammals looked a lot more like mice or shrews than like the cave dwelling hominids you invoke. And yes, that far back, selection swords were already shaping males as roaming hunters as they had no need to be huddled, still, with several pups, in a protected underground nesting site, providing milk...