Question

We have discussed the role of meat consumption in hominin evolution as an important source of fuel for our oversized and metabolically costly brain. Do you think the expensive tissue hypothesis has merit? Why or why not? Can you think of any alternative hypotheses to explain the trend towards larger brain size over the past 2.5 million years?

Answer 1

It is argued that a high quality diet is necessary for the evolution of a relatively large brain.However, the change to such a high quality diet, which involved an increased proportion of animal based products, need not have been one of the prime movers in brain evolution.

One of the most memorable theory is the Man the Hunter.This theory argued that increasing amounts of meat in the homind diet lead to increasing levels of cooperation among the males in the hunt, which lead to brain expansion and the associated development of cognition, language and symbolic culture.Ideas of brain evolution centering on dietary quality have not been confined to humans and human evolution. Extractive Foraging Hypothesis to explain the relationships in primates.They argued that a relatively large brain correlates with omnivorous feeding in primates, which requires relatively complicated stratergies for extracting high-quality foodstuffs.Alternatively, they suggested that relatively large brain size is associated with the need for a more sophisticated mental map for the location and exploitation of widely spread high quality food resources.

   However, how do we account for this association?There are two logical possibilities.The first is that thereis a direct causal relationship between diet and brain size.Simplistically, hunting or extractive foraging or mental mapping would be directly selecting for large brain size.If this were true, then diet would be seen as a prime mover or major selective agent, in the evolution of the brain.The alternative would be the prime releaser in brain evoltion.In this sense, diet would release constraints on brain expansionand, given other selective agents or a combination of agets , permit brain expansiion to take place.

   The purpose this contribution is to argue that diet must be viewed in the first instance as a prime releaser in brain evolution.

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