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:
- 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)
- 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