In essence, we are not the most numerous, we are not the longest lived, we are not the most immune to disease, we are not the fastest growing and we haven't been dominant for long.
Our niche is certainly being exploited to the full, but then, we've never really had a challenge for it, and any challenges are likely to come from without, not within. Oddly enough, maybe that's why we evolved into a warlike mentality? Because, at some level, humanity needed the drive to evolve, and if it were not an arms race with predators, it would be a mind race with other tribes? I hesitate to speculate because it's too easy to try and personify evolution and give it a 'purpose'...