Was agriculture impossible during the Pleistocene but mandatory during theHolocene? A climate change hypothesis

Several independent trajectories of subsistence intensification, often lead ing to agriculture, began during the Holocene. No plant-rich intensificatio ns are known from the Pleistocene, even from the late Pleistocene when huma n populations were otherwise quite sophisticated Recent data from ice and o cean-core climate proxies show that last glacial climates were extremely ho stile to agriculture-dry, low in atmospheric CO2, and extremely variable on quite short time scales. We hypothesize that agriculture,vas impossible un der last-glacial conditions. The quite abrupt final amelioration of the cli mate was followed immediately by the beginnings of plant-intensive resource -use strategies in some areas, although the turn to plants was much later e lsewhere. Almost all trajectories of subsistence intensification in the Hol ocene are progressive, and eventually agriculture became the dominant strat egy in all but marginal environments. We hypothesize that, in the Holocene, agriculture was, in the long run, compulsory. We use a mathematical analys is to argue that the rate-limiting process Sor intensification trajectories must generally be the rate of innovation innovation of subsistence subsist ence technology or subsistence-related social organization. At the observed rates of innovation, population growth will always be rapid enough to sust ain a high level of population pressure. Several processes appear to retard rates of cultural evolution below the maxima we observe in the most favora ble cases.