Can humanity lead itself out to pasture?

A few more thoughts on how the steady evolution of human norms toward peacefulness, self-control and respect for life tracked by Steven Pinker in The Better Angels of Our Nature could go wrong.

One weakness in Pinker's analysis of our social evolution, as far as I can tell so far, is that while he sometimes identifies an adverse trend, or an adverse offshoot of a positive trend, he doesn't consider the potential dangers that such trends might pose. Stephen J. Gould, as I recall, recounted the story of a moose-like creature for which natural selection favored the growth of ever-larger antlers, which attracted females of the species. Competition led to the antlers growing to absurd height and weight, which ultimately, or so the hypothesis went, led to the species' extinction.  While Pinker is careful to stipulate that the positive behavioral developments he tracks are not products of biological evolution, could not social evolution go off-track in similar ways?