silvertown1_Natasha Breen_REDA&CO_UIG via Getty Images Natasha Breen/REDA&CO/UIG via Getty Images

Evolution on the Menu

Everything people eat has an evolutionary dimension, but as the history of meat and milk consumption demonstrates, choice is often an overlooked factor. While biology has historically provided the potential for diversity in the human diet, it is culture that has written the menu.

EDINBURGH – While some diet books might suggest otherwise, nature has been very accommodating in its meal plan for Homo sapiens. Whereas other great apes, like gorillas and orangutans, are vegetarian (though some chimpanzees will eat monkey), evolution has made humans “omnivores” and left most culinary decisions up to us. So, when did evolution enable humans to eat meat? Two sources – our species’ family tree and the fossil record – offer clues.

The branches of the human family tree converge as they descend toward the root, revealing common ancestors where branches join. The shared ancestor of humans and chimps lived some five million years ago, and, while we do not know for certain what that ancestor ate, the best guess is that it was mainly, if not exclusively, vegetarian. If five million years ago is the earliest date that human ancestors could have opted for a diet that included meat, what is the latest date by which this might have happened?

One answer to that question can be gleaned from the skeletal remains of “Lucy,” a pre-human fossil ancestor of humans, discovered in 1974. Lucy belonged to a species called Australopithecus afarensis, which lived in East Africa between 3-4 million years ago and is thought to have been the immediate ancestor of our genus, Homo.

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