Animal populations increase in size in the absence of constraints. Classic ecological examples include extirpation of all native predators (consider white-tailed deer in much of the northern United States, for example, now that humans have removed their predators). In our case, ready access to cheap fossil fuels alleviates constraints such as famine and pestilence. Like all animals that overshoot — that is, outstrip resources — the human animal will undergo a large-scale correction. The longer overshoot persists, the larger the human population becomes, and the greater the requisite correction. The Club of Rome was right, way back in 1972: There are limits to growth, for economies and populations.