Answer to Question #281167 in Human Anatomy and Physiology for Ejg

Question

The Expensive Tissue Hypothesis is an important concept that accounts for which major morphological change in the hominin family tree?

What major selective pressures and resource niches are hypothesized to have led to these changes? Be sure to include specific species and their morphological features that support this hypothesis.

a paragraph for each, please

Answer 1

The expensive tissue hypothesis (ETH) relates brain and gut size in evolution specifically in human evolution. It suggests that in order for an organism to evolve a large brain without a significant increase in basal metabolic rate as seen in humans, the organism must use less energy on other expensive tissues.

ETH suggests that in humans, this was achieved by eating an easy-to-digest diet and evolving a smaller, less energy intensive gut.

The human brain stands out among the mammals because its relative size compared to the rest of the body is unusually large compared to other animals. The human brain is about three times larger than that of our closest living relative, the chimpanzee. For a primate of our body size, the relative size of the brain and that of the digestive tract is rather unexpected; the digestive tract is smaller than expected for a primate of our body size.