For my MSc I undertook a biological analysis of the transition to agriculture in Neolithic societies. A paper resulting from this work was published in Australian Biologist in 1993, and re-published in the journal of the Australian College of Environmental and Nutritional Medicine 19(1) in April 2000.
Why humans adopted agriculture is a thorny question for anthropologists. It is well understood that for pre-industrial farmers the "obvious" benefit - a regular large food supply - was often not forthcoming and would not have stacked up against the dangers of nutritional deficiency and reliance on a single crop. For ancient farmers it wasn't even a labour-saving strategy: they worked harder for food than their hunter-gatherer competitors. Mark Cohen in 1977 asked "If agriculture provides neither better diet, nor greater dietary reliability, nor greater ease, but conversely appears to provide a poorer diet, less reliably, with greater labour costs, why does anyone become a farmer?"
The question of why humans adopted farming is problematic from a biological point of view as well. It's part of the larger problem of using ethology, the evolutionary study of animal behaviour, to understand what people do. Why did a species that evolved as hunter-gatherers make this dramatic lifestyle change in the Neolithic? Why did this lifestyle eventually dominate? If farming has fitness benefits, why do so few species do it? The danger of farming is that you may put effort into producing food that a competitor ends up eating. A safer strategy is to put your effort into hunting or gathering, and protecting the food thus obtained from conspecifics.
My suggestion was that if the products of agriculture produce pharmacological reward, this would override an evolved psychological tendency not to farm. A similar suggestion had already been made by the anthropologist Robert Braidwood, who claimed that alcohol was the motivation for early cereal cultivation. More recent research has revealed that pharmacologically-active substances other than alcohol are present in common cultigens.
Evolutionary psychology (EP) provides a good framework within which to understand the argument. EP proposes that behaviour is produced by domain-specific mental organs which evolved to deliver adaptive responses to our environment of evolutionary adaptedness (EEA). Behaviour is controlled at a proximate level by neural reward circuits which define the range of behaviour an animal can perform. For humans the EEA is taken to be the Pleistocene, ending with the adoption of agriculture and appearance of complex societies in the Neolithic. Our modern environment has changed rapidly, presenting novel stimuli which can bring about non-adaptive behavioural responses. A feature of our modern environment is the wide availability of technologies for achieving psychological reward independent of reproductive advantage. My suggestion was that these cultural artifacts constitute a significant subset of the novel stimuli identified by evolutionary psychology as causing non-adaptive behaviour. By artificially inducing reward, these artifacts reduce the (subjectively perceived) relative importance of competing for and achieving reproductive success. Attenuation of individual competition supports the emergence of social structures which depend on subsets of the population foregoing resources for the benefit of non-kin.
A key explanation of the origins-of-agriculture problem is in
Mark Cohen (1977)
The food crisis in prehistory. overpopulation and the origins of agriculture.
My paper on this topic is
Greg Wadley and Angus Martin (1993)
The origins of agriculture: a biological perspective and a new hypothesis.
Australian Biologist 6: 96-105, June 1993
The ethological view of a mismatch between neurophysiological mechanisms of reward and the modern availability of pharmacological reward was first articulated by Nesse:
Nesse, R. M. (1994)
An evolutionary perspective on substance abuse.
Ethology and Sociobiology, 15: 339-348
Hillman et al (2003) agreed that pharmacological reward might motivate the maintenance of agriculture, though not its initial adoption:
Hillman G, Hedges R, Moore A, Colledge, S., and Pettitt, P. (2001)
New evidence of Lateglacial cereal cultivation at Abu Hureyra on the Euphrates
Holocene 11 (4): 383-393