Is Meat Unhealthy? Part II

Over time, animals adapt to the foods they regularly consume.  This is how archaeologists can, for example, determine that Triceratops was an herbivore and Tyrannosaurus was a carnivore just by looking at the structure of the skeleton.  Adaptations to diet extend beyond skeletal structure, into digestion, metabolism, the brain, musculature, and other aspects of physical function.  What is our evolutionary history with meat?

Human Evolutionary History with Meat: 200 to 2.6 Million Years Ago

Mammals evolved from ancestral "mammal-like reptiles" (therapsids, then cynodonts) approximately 220 million years ago (Richard Klein. The Human Career. 2009).  Roughly 100 million years ago, placental mammals emerged.  The earliest placental mammals are thought to have been nocturnal shrew-like beasts that subsisted primarily on insects, similar to modern shrews and moles.  Mammalian teeth continued to show features specialized for insect consumption until the rise of the primates.

65 million years ago, coinciding with the evolution of the first fruiting plants, our ancestors took to the trees and became primates.  For most of the time between then and now, our ancestors likely ate the prototypical primate diet of fruit, seeds, leaves/stems, and insects (1).  Some primates also hunt smaller animals and thus eat the flesh of mammals, birds, reptiles, amphibians, and fish in addition to insects.  However, the contribution of non-insect meat to the diet is usually small.

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