A time to plant

Abstract

The emergence of agriculture was one of the most fundamental transformations of the human–environment interaction, and the changes it wrought continue to influence the landscapes and societies that we study today. Anatomically modern humans appeared ∼100 000 years ago. Behaviorally modern humans (those with language capabilities, and thus some capacity for communicating foresight and planning) were present by 30 000–50 000 years ago. Yet evidence for agricultural activity does not appear in the fossil record until some 7000–12 000 years ago, spanning at least seven independent centers in the Old and New Worlds. Why did agriculture not emerge earlier? And why is there a relatively rapid convergence on domestication in sites that are geographically independent? In a new paper [ 1 Richerson P.J. et al. Was agriculture impossible during the Pleistocene but mandatory during the Holocene? A climate change hypothesis. Am. Antiq. 2001; 66: 387-411 Crossref Scopus (403) Google Scholar ], Richerson et al. review some of the prevailing hypotheses for agricultural origins, including population pressure, technological innovation and cultural evolution, arguing that each has the wrong timescale: the characteristic rate of change is too rapid to explain the late onset of domestication relative to behavioral modernity. They therefore conclude that the climatic changes at the Pleistocene–Holocene boundary (reduced climate variability, and increased rainfall and atmospheric CO2) are what made previously impossible agricultural activities possible.