U. TORONTO (CAN) / U. OREGON (US) — New research challenges many of the long-held beliefs about when and where humans first began to domesticate soybeans—and specifically, increase its seed size.
“Soybeans appeared to be linked to humans almost as soon as villages were established in northern China,” says Gary Crawford, an anthropology professor at the University of Toronto Mississauga. “Soybean seems to be a plant that does well in human impacted habitats. In turn, humans began to learn how tasty soybean was and how useful it was.”
A and C are from Dahecun, China (5,500 to 5,000 years old); B is from Jiahu, China (about 8,000 years old); and D is from Pyeonggeodong, South Korea (3,500 to 3,200 years old).
While previous estimates had put the domestication of soybean specifically in northern China between 3,000 and 5,000 years ago, no proof actually existed. In a paper published in the open-access journal PLoS ONE, University of Oregon’s Gyoung-Ah Lee, Crawford, and colleagues report that soybean was probably domesticated at least three separate times.
Soybean’s early use dates from 8,600 to 9,000 years ago in northern China. It’s still a mystery whether it was a crop at that time because the seeds are similar to wild ones. Selection for large seeds, evidencing artificial selection by people, took another 5,000 to 4,000 years.
In Japan, evidence of domesticated soybeans dates from 5,000 years ago, says Crawford, and these soybean seed specimens are the largest seed specimens found in East Asia at the time.
Soybean samples similarly reveal evidence of selection for larger size soybeans at 3,000-year-old sites in Korea. This indicates that soybean was being domesticated in Korea too.
“It means that people were recognizing the characteristics of plants and . . . recognizing that plants are malleable. These people were the first biotechnologists; they were keen observers,” adds Crawford.
For example, wild soybean plants have small seeds and tend to grow as vines, whereas domesticated soybeans were selected to put more energy into growing larger and more seeds (instead of stems and leaves).
“What we did not expect to see was the early record for soybean in Korea, as well as Japan,” says Crawford. “Both of those areas did not launch into agriculture the way China did, or as early. But it looks like wild soybean gravitated to these [villages] as they did in China, and people found them to be an attractive resource.”
Today, soybean is the world’s foremost oilseed source and the major source of protein for domesticated chickens and pigs. But Crawford believes the study does more than shed light on a simple seed.
“Domestication and agriculture marks the passage into a more modern, but pre-industrial human relationship with the environment,” notes Crawford. “Agriculture was and is fundamental to who we are as a people. It marks the transition out of the relatively simple hunting-gathering way of life into who we are today.”
The Australian Research Council, Social Sciences and Humanities Research Council of Canada, National Science Foundation of China, and the National Science Foundation in the United States supported the research through various grants to the co-authors.
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