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Size matters? Study raises questions about when and where soybeans were domesticated

November 18, 2011

If you like tofu, tem­peh, edamame or miso soup, you’re a fan of soy­beans. But the sig­nif­i­cance of this legume goes far beyond a few culi­nary treats–soybeans rank sev­enth among world crops for ton­nage har­vest­ed.

Now, a new study led by researchers at the Uni­ver­si­ty of Toron­to Mis­sis­sauga and the Uni­ver­si­ty of Ore­gon gets at the root of soy­bean domes­ti­ca­tion in Asia, and chal­lenges many of the long-held beliefs about when and where humans first began to domes­ti­cate this plant—and specif­i­cal­ly, increase its seed size.

“Soy­beans appeared to be linked to humans almost as soon as vil­lages were estab­lished in north­ern Chi­na,” says Pro­fes­sor Gary Craw­ford of the Depart­ment of Anthro­pol­o­gy. “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.”

While pre­vi­ous esti­mates had put the domes­ti­ca­tion of soy­bean specif­i­cal­ly in north­ern Chi­na between3,000 and 5,000 years ago, no proof actu­al­ly exist­ed. In a paper pub­lished in the Nov. 4, 2011 issue of PLoS ONE, Oregon’s Gyoung-Ah Lee, Craw­ford and their 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 5000 to 4000 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.”  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,” says 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.

*Images avail­able upon request



For more infor­ma­tion, please con­tact:

Gary Craw­ford
Depart­ment of Anthro­pol­o­gy

Gyoung-Ah Lee
Uni­ver­si­ty of Ore­gon
541- 346‑4442

Nicolle Wahl
Uni­ver­si­ty of Toron­to Mis­sis­sauga