Monday, 14 March 2016

Meat scarcity limits brain growth

Having considerable knowledge of anthropological history, I have long been sceptical of demands for veganism even on grounds of reduced greenhouse gas emissions. Free-market economics unanimously if without the tiniest fanfare says that vegetable protein even if it emits much less greenhouse gases is incomparably more labour- and land-inefficient than animal protein. History backs up this fact, showing that only on the best soils available to ancient farmers in Mesoamerica and Andean South America could humans de facto abandon animal food near completely, and even there it meant major nutritional deficiencies. Today, the best plant proteins come from regions that gained the majority of their protein from the rich seas of East Asia, nourished by rivers with huge sediment loads from the Asian mountains.
It is clear form this map that Australian-made (directly and indirectly) greenhouse pollution is tipping the planet to dangerous climate change. 1.5˚C above the “virgin” temperature mean is known to be the maximum level sustainable before irreversible ecological changes. Note the negative anomalies on the east coasts of the Northern Hemisphere due to continental westerly flow.
Now, as the results of Australia’s dreadful performance in greenhouse emissions and their reduction become even clearer, there will no doubt be major calls to abandon animal-based foods because their production involves an enormous carbon footprint from land clearing in Australia. However, the ideal of eliminating animal foods is one which I have long been sceptical of for nutritional reasons. Documentation – although implicit – of nutrient deficiencies in Eurasia being eliminated by increased affordability of meat after industrialisation is something I have been long aware of, for instance from being lectured about the minimum in human height before the Industrial Revolution.

This month, Nature authors Katherine D. Zink and Daniel E. Lieberman in their ‘Impact of meat and Lower Palaeolithic food processing techniques on chewing in humans’ are providing clear evidence that brain growth to present sizes in humans would be very difficult on anything approaching a vegan diet. They argue that, even after cooking developed, masticatory demands under a strictly vegan diet would be too high for brain growth to anything like present cranial capacities of races native to RoW (the world outside of Australia and Southern Africa). Time in ‘Sorry Vegans: Here’s How Meat-Eating Made Us Human’ shows masticatory energy consumption to be almost fifty percent greater under a vegan diet than under a diet that was one-third meat (smaller than the actual proportion of meat in the diet of almost all documented Enriched World hunter/gatherers).

If we glance Richard Lynn’s studies of race differences in intelligence, it is extremely tempting to believe that, indeed, protein scarcity remains the limiting factor in brain growth. Observed genotypic IQs of Bushmen, Pygmies and Australian Aborigines range from 55 to 65, whereas those of RoW peoples range from 80 to 110. It’s indeed possible that these differences between ASA and RoW peoples are understated because:
  1. with most preindustrial RoW peoples, nutrient deficiencies are likely to affect IQ
    • however, Lynn’s data do suggest diet may have more effect on ASA peoples than RoW because variation between different studies is considerable among Australian Aborigines (52 to 74, which may reflect nutritional effects)
  2. partial desocialisation, or the elimination of cooperative breeding, which is the normal process upon movement of a cooperative species to more nutrient-rich soils (e.g. among the family colonising Eurasia Paridae from Africa) may influence RoW peoples especially in the Western Hemisphere, and produce less high IQ values
    • Lynn’s data do suggest possibility of partial desocialisation in the extratropical Americas as phenotypic IQs of Native Americans in Canada and the US are no higher than in Latin America
    • With Native Americans in Chile and Argentina, who lived on the richest soils of any subcontinent but were subject to a relentless “hierarchism as a revolt against nature” that made its flora and fauna the most undomesticable in the world and precluded civilised agricultural societies, no IQ data exist.
    • Cranial capacity data suggest higher IQs than other Native Americans, but not so high as Southern Cone Native Americans’ very rich soils, fertile seas and very largely animal-protein-based diets imply
  3. if what Zink and Lieberman say is true, it’s highly plausible that growth of intelligence was consistently limited or rolled back to the point of a bottleneck upon ancient African soils as humans exhausted the available animal protein. Protein scarcity woudl select for lower genotypic IQ, but this bottleneck was removed upon movement to richer European or Asian soils.
For all its unanswered questions, Time and Nature’s study remains fascinating for what they suggest about the history of human encephalisation.

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