More specific evidence that evolution has shaped human social behaviour in the recent past comes from a third major social transition, from agrarian to modern economies.
This transition is usually known as the Industrial Revolution. Before the Industrial Revolution, almost everyone in agrarian economies but the rich lived near the edge of starvation. Whenever any improvement in farming technology raised productivity, more children were born, the extra mouths ate up the surplus and semi-starvation soon reigned again. This harsh regime is known as a Malthusian economy after the Revd Thomas Malthus, who described it in his 1798 ‘Essay on the Principle of Population’. As it happened, the Malthusian regime was nearing an end at the very time Malthus was writing because of the vast increase in productivity that was the essence of the Industrial Revolution.
The cause of the Industrial Revolution is the central issue of economic history, yet economic historians have arrived at no consensus as to what that cause or causes may have been. Their preferred candidates are institutions of various kinds, or access to resources. For a quite different explanation, step back to Malthus for a moment. It was from Malthus that Darwin derived the idea of natural selection.
Darwin perceived that if people were struggling on the edge of existence, as Malthus described, then a person with the slightest advantage would have more children and bequeath this advantage to them. ‘Here then I had at last got a theory by which to work,’ Darwin wrote in his autobiography.
If the English population provided the example from which Darwin intuited the idea of natural selection, that population was surely being subjected to the same force. The question then is what traits were being selected for. The economic historian Gregory Clark, of the University of California, Davis, has documented four behavioural changes in the English population between 1200 and 1800 AD.
The level of violence declined, literacy increased, and so did work hours and the propensity to save. The effect of these changes, Clark notes in his 2009 book Farewell to Alms, was to transform the violent peasant population of 1200 into the disciplined workforce of 1800. Because the nature of the people had changed, productivity soared, and for the first time an increase in population failed to drag down the standard of living.
Clark not only documents the behavioural change in English society but also provides a plausible mechanism of hereditary transmission. From the study of wills he finds that the well-off had more surviving children than the poor. Since the size of the English population remained fairly constant, many children of the rich must have dropped in social status, diffusing the genes and values that had made their parents wealthy into the wider-population.
The same process presumably occurred in other agrarian populations, which is why the Industrial Revolution spread so easily to other European countries and later, after political obstacles had been removed, to the countries of East Asia.
With all three transitions, an evolutionary change is plausible but remains a hypothesis nonetheless: proof awaits discovery of the relevant genes. ...
Persistently poor countries, particularly those that are still tribally organised, have not been through the Malthusian wringer experienced by agrarian populations and may therefore find the transition to a modern state that much harder.