Most scientific communities, ranging from archaeology to botany to molecular biology, grant an extraordinary importance to the study of agricultural origins because food surpluses made possible by agriculture have fueled major cultural developments, culminating in the emergence of urban societies and advanced civilizations around the world. Identifying the regions where plant domestication arose is crucial for our understanding of why and how agriculture emerged. The current consensus is that agriculture arose independently in eight regions of the world after the termination of the last Ice Age, 12,000 years ago. Numerous explanations have been proposed for the beginnings of agriculture, which rely mostly on the influence of the ecological changes that occurred globally at the end of the last Ice Age. Another favored explanation is processes operating within human social systems involving the emergence of power and prestige.
The emergence of agriculture was extremely difficult, on account of the unreliability of the climatic conditions. In addition to punctual events (flooding, hurricane, volcano explosion, draught) the climate seems to go from one extreme to the other over the millennia. There is now confirmed evidence that the sun does not shine with unvarying brightness. The climate of the northern North Atlantic has warmed and cooled nine times in the past 12,000 years, in step with the waxing and waning of the sun. Since the last Ice Age, there is a 1500-year oscillation of climate, including the Little Ice Age of the 17th century, give or take half a millennium. These variations may have a tremendous influence on burgeoning agricultural economies.
Several problems concerning human paleohistory are under discussion. First is the reason for the disappearance of the Mousterian culture: the Lower Paleolithic represented by the Neanderthals vanished precisely when it was in its golden age. Second is the debate over the antiquity of the human presence in the New World. Third is the cultural development in North America: how comes that the many attempts made to lift the cultural level from the American Hunter to that of the American Villager aborted? Fourth is the reason for the disappearance of the Mayan civilization: it had gone before the arrival of the Spaniards. Finally, the passage from the Upper Paleolithic to the Neolithic period does not appear to be a revolution as was assumed, but a slow adaptation to communal living. Why the settling down? Was it for farming purposes or for cultural reasons? Or were the people forced to assemble, as American Villagers, to defend themselves against Nomads? Why did most agricultural fixation points remain at that level of cultural development and never developed further?
J. Diamond1 emphasizes that members of primitive cultures are at least as intelligent than members of the higher Western Culture, yet their achievements have been poor. Diamond attributes this failure to circumstances. There is no denying that opportunities favor cultural development but the moral quality of the culture itself bears on the final outcome also. Most striking is the remark made by Diamond of frequent violent deaths among members of these primitive cultures and his reluctance to take this absence of security into account, at least as being part of the explanation.
In 1987, Colin Renfrew advanced the theory of farming-language, which held that farmers who had grown strong on domesticated crops, wheat and barley in the West, rice in the East, maize and tubers in the Americas, armed with seeds and language, displaced the indigenous hunter-gatherers. According to this theory, crops were the engines of linguistic dispersal, and culture, biology and language marched together in lockstep. This explanation appears valid for some Empires but it cannot be a universal explanation for the reason that the postulated strength of the farmers over the hunters is a myth. The health of the native inhabitants of Florida was excellent until the Spaniards imposed their rule: the forced adoption of the regimen of the invaders resulted in a considerable weakening of the health of the indigenous population. The Cheyennes, living in the North American Great Plains, were superb human specimens, whose health was far better than that of the white farmers who dislodged them. Secondly, the crops developed may not always be suitable for growth in the new environments: it took 3000 years for the northwest Indian farmers (Aryans) to develop a monsoon-tolerant wheat that could grow in south India, populated by Dravidians. The rice–growing Austronesians left Taiwan about 4500 years ago to reach Polynesia about 1500 years later. Yet, they abandoned rice during their travels. Furthermore, the contemporary Polynesians, an Austronesian offshoot, originated from Indonesia and their expansion predates that of the Austronesians. According to most linguists, European languages and crops come from different homelands. A group may adopt an outside language without adopting the accompanying genes: this is how Hungarian and Turkish languages spread in Europe, millennia after farming was practiced there.