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One neglected inference from Gregory Clark's master work A Farewell to Alms: a brief economic history of the world - is that before the industrial revolution the effect of average societal intelligence was broadly the opposite of what it is today - the higher the average intelligence, the lower the per capita standard of living.
In the modern world, after the industrial revolution, it has been exhaustively shown by Richard Lynn and co-workers, and multiply confirmed, that there is a positive correlation between average intelligence and economic measures such as GDP and per capita income.
(More exactly that high average IQ - or perhaps a high IQ of the ruling elite - is nearly always necessary for economic success in the modern world - however, this tendency can be blocked by adverse economic ideologies, such as Marxism/ Maoism, which kept China poor for several decades.)
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But, before they underwent the industrial revolution, China and Japan probably had the lowest standard of living per capita in the world - the average Chinese was perhaps the poorest in the world; with the mass of the population almost exclusively on rice, and a very small amount per day - despite that the population laboured almost every waking hour. (See also Ron Unz reference below)
By contrast, in Africa at about the same time, it is probable that the amount of food per person was among the highest in the world, and most African people had far more leisure than people in China or Japan.
Western European societies seem to have been somewhere in between - higher standard of living than China/ Japan but less than Africa; more hours of work than Africa but less than China/ Japan.
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If it is assumed that the rank ordering of average general intelligence, as measured by performance in IQ tests, was then as it is now - with China/ Japan highest; Western Europe intermediate, Africa lower - then this represents an inverse correlation between intelligence and per capital standard of living.
Clark explains the reasons why this would be the case - which is that higher intelligence and a more conscientious personality were selected-for in complex agrarian societies (because higher intelligence and the ability to work had for long hours both improved reproductive success); and these selection pressures and the higher average intelligence led to things like increased productivity of food, improved hygiene^, and reduced violence; which combined to increase the population density until the population was constrained by starvation (China/ Japan) and starvation mixed with infectious disease (Western Europe).
(^High standards of hygiene - as was normal in medieval Japan - therefore reduces the mortality rate from infectious disease, which drives down standard of living by increasing population density.)
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This is the 'Malthusian Trap' which affected all pre-modern societies in the long term, population could only increase at the cost of reduced standard of living - although average material conditions could be improved over the short term of a few generations after a drastic population cull, or qualitative jump in productivity - before population density increased, and the Trap resumed. This happened in England after the Black Death halved the population - a couple of hundred years of improved average prosperity resulted.
But Africa had extremely high mortality mainly due to diseases, and to a lesser extent violence; which meant that for the survivors of endemic infectious disease and violence there was enough land, enough to eat, and little need for long hours of intensive hunting, gathering or agricultural work.
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So, broadly speaking, comparing between societies in the pre-modern world, high average intelligence led to lower average standard of living: intelligence was negatively correlated with standard of living;
Despite that within pre-modern societies, and looking at individuals, higher intelligence was positively-correlated with a higher standard of living (and higher average reproductive success from reduced child mortality).
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(Many of these correlations now go the opposite direction in modern societies: between societies, higher intelligence is now associated with higher wealth, as I have just described; within societies higher intelligence is still associated with higher wealth - which is the same as for pre-modern societies; but, both between and within societies, higher intelligence is now associated with lower reproductive success, via lower fertility.)
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References
http://www.econ.ucdavis.edu/faculty/gclark/a_farewell_to_alms.html
http://www.theamericanconservative.com/articles/how-social-darwinism-made-modern-china-248/
