Grazing Animals Drove Domestication of Grain Crops by Early Humans

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Large grazing animals have a strong selective force on plants, certain plants have evolved traits to thrive on pastoral landscapes. Spengler and Mueller theorize that yak herding may have helped drive buckwheat domestication in the southern Himalaya. This lone yak in the Lhasa region of Tibet is a significant evolutionary force on the plant communities around where it grazes. (Robert Spengler)

(CN) – Ancient grains and crops may have evolved their ability to reproduce in response to humanity’s farming of them, according to research released Monday.

The study, published in the scientific journal Nature, found that small-seeded annuals such as quinoa, hemp and buckwheat underwent an evolutionary switch with the advent of human domestication.

Rather than carry traits that helped such crops disperse seeds via grazing animals, such as seeds that could survive an animal’s digestive process, the plants evolved to adapt to human farming.

Roughly 5,000 to 7,000 years ago, humans began cultivating large-seeded cereals such as barley, wheat and rice. While scientists have studied such crops extensively, they know less about small-seeded crops and how they evolved.

The wild ancestors of small-seeded crops feature seeds with shells that are indigestible and are only found in small patches. The study’s authors posit that this was not always the case, in that these crops used to grow in dense populations helped by grazing animals such as bison. The crops would then be harvested by humans.

“As humans began to cultivate these plants, they took on the functional role of seed dispersers, and eventually the plants evolved new traits to favor farming and lost the old traits that favored being spread by herd animals,” the study states.

Scientists have tried to understand for more than a century why small-seeded crops, which yield far less edible material than large-seeded crops, became a major food source for humans.

Robert Spengler, co-author and director of the Paleoethnobotany Laboratories at the Max Planck Institute for the Science of Human History, said the research will help scientists better understand how such crops have changed alongside humanity’s farming practices.

“Small-seeded annuals were domesticated in most areas of the world,” Spengler said. “So the ramifications of this study are global-scale. Scholars all over the world will need to grapple with these ideas if they want to pursue questions of domestication.”

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