Global human population expansion is rooted in a remarkably successful evolutionary innovation. The neolithic transformation of the natural world gave rise to a symbiosis between humans and their domesticated plant and animal partners that will expand from a current 20 per cent to 60 percent of terrestrial biomass by the middle of the coming century. Such an increase must necessarily be accompanied by a concomitant decrease in wildlife biomass. We suggest that current trends in population growth are unlikely to abate (...) for three reasons: first, there are intrinsic biological pressures to reproduce regardless of social engineering; second, the character of the domestic alliance makes it a formidable competitor to wildlife; and third, the timeframe before population doubling is, from a biological perspective, virtually instantaneous. This paper draws from a wide body of research in the biological and social sciences. We neither condone nor endorse this picture of inexorable population increase. Rather, we appeal for a change in the nature of the discussion of population among environmentalists, to focus on the question of how best to manage what wildlife will be left on the margins of a domesticated world. (shrink)