Evolution

Human Grass Diet Could've Led to Larger Brains

3 to 3.5 mya

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A new comprehensive analysis of early human teeth reveals that early human species like Australopithecus afarensis ("Lucy") changed what they ate about 3.5 million years ago, expanding their ape-like diet of leaves and fruit to more human-like fare of grasses, sedges, and succulents. This set the stage for a modern human diet of grains and the evolution of larger brains, according to researchers.

Four new studies, involving two dozen researchers, of carbon isotopes found in fossilized tooth enamel from a wide range of human ancestors in Africa from four million to 10,000 years ago show a surprising increase in the consumption of grasses and grass-like plants.

h/t Charles WT

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  1. Large brains are expensive in terms of energy. Grass lacks the necessary dense calories and the human digestion system lacks the extra structures to support the bacteria needed to break down the cellulose. That makes the majority of it nothing more than indigestible fiber.

  2. …carbon isotopes found in fossilized tooth enamel from a wide range of human ancestors in Africa from four million to 10,000 years ago show a surprising increase in the consumption of grasses and grass-like plants.

    Considering the first campfire was about a million years ago, 2.5 million years after this change, they would have had to consume the grass raw. Raw grain swells in the digestive tract, causing distress and blockages. It has phytic acid which blocks calcium, iron and other important minerals from being absorbed. It’s just generally indigestible.

    The better answer is the one we already know. Ruminants that eat those grasses incorporate those preferentially-absorbed isotopes into their bodies. Meat from those animals would also raise the isotopes in the humans eating them. So they started eating grazing animals.

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