Abstract

Evolutionary scholars advance two major sorts of hypotheses to explain big events, such as the origin of agriculture. One hypothesis assumes that natural selection is so powerful that organisms are always close to an evolutionary equilibrium with current environment. Thus, any major changes will be a result of external processes having to do with the environment. The other camp imagines that evolution is a slow, halting, and biased process that is limited and directed by internal obstacles that thwart what natural selection favors, for example, a particular somatic arrangement that is difficult to “engineer” quickly. Both kinds of constraints were probably involved in the trajectory leading to agriculture but perhaps at different timescales.