Encephalization Illustration (IMAGE)

American Museum of Natural History

Encephalization Illustration

Caption

This illustration compares the brain sizes of a variety of primates, including humans (top left) and the fossil Chilecebus (bottom middle), based on a new method (phylogenetic encephalization quotient, or PEQ) that takes into account both the body size and the evolutionary relationships of the species. The size of each primate species reflects its PEQ value (large head equals high PEQ, small head equals low PEQ), not its actual brain size or body/head size. For example, a high PEQ (larger heads in this image) signifies a larger than expected brain for an animal of a given body size.

Credit

© Xiaocong Guo/Xijun Ni

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