Soybeans originated in China, specifically in regions along the Yellow River and the Huang-Huai Valley in the central part of the country. The wild ancestor of the modern soybean, a scrambling vine that still grows across East Asia, was first gathered and gradually domesticated there between 6,000 and 9,000 years ago.
The Wild Ancestor and Where It Grew
The cultivated soybean descends from a wild plant that looks almost nothing like what you’d find in a bag of edamame today. Wild soybeans produce tiny, black seeds with roughly 8% oil content. Through thousands of years of human selection, domesticated soybeans developed large, yellow seeds with about 25% oil content, along with significantly higher protein concentration. Genomic studies have identified over 400 genes unique to the cultivated form that are absent in its wild relative, including genes involved in seed development, oil production, and protein storage.
The wild form still grows across a wide band of East Asia, from northeastern China down through Korea and Japan. But genetic and archaeological evidence points to the middle reaches of the Yellow River basin as the place where people first began deliberately planting and selecting soybeans.
The Earliest Archaeological Evidence
The oldest known soybean remains come from the site of Jiahu in Henan province, China, dating to roughly 9,000 to 8,600 years ago. These were small seeds, not yet showing signs of the size increase that marks full domestication. At the nearby site of Yuezhuang, soybeans appeared alongside broomcorn millet, foxtail millet, and rice around 8,000 years ago, suggesting that early Chinese farmers were already growing soybeans as part of a diverse crop system.
The process from wild gathering to full domestication was slow. Charred soybean seeds from Japan show that noticeably larger, fully domesticated-size seeds appeared there by about 5,000 years ago, and in Korea by about 3,000 years ago. In other words, it likely took several thousand years of gradual selection before soybeans looked like what we’d recognize today.
How Soybeans Spread Across Asia
From their center of origin in China, soybeans radiated outward across the continent over millennia. Researchers have identified at least seven distinct germplasm pools, or regional populations, that developed as the crop adapted to different climates and farming traditions: northeast China, central and south China, Korea, Japan, Taiwan and South Asia, northern India and Nepal, and central India. Each of these regions became a secondary center of diversity, where local farmers developed their own landraces suited to regional conditions.
Soybeans likely reached Japan from China between the 6th and 8th centuries AD, carried along with the spread of Buddhism and its vegetarian dietary traditions. Korea appears to have adopted the crop earlier, based on the archaeological record of large-seeded soybeans there by about 1,000 BC. In each new region, soybeans became the foundation for distinctive fermented foods: miso and soy sauce in Japan, doenjang in Korea, and a wide variety of fermented pastes and sauces across Southeast Asia.
Early Processing and Use
Raw soybeans are difficult to digest and contain compounds that interfere with nutrient absorption, so early consumers had to develop processing techniques. Fermentation became the key method across East Asia. At the Jiahu site, the same village that produced some of the earliest soybean remains, chemical analysis of pottery jars has confirmed that residents were producing fermented beverages from rice, honey, and fruit as early as 7,000 BC. This fermentation knowledge, originally applied to grains and fruit, was eventually adapted to soybeans.
Before more sophisticated techniques developed, early grain fermentation relied on chewing starchy material to break down its sugars (the enzymes in saliva kickstart the process) or on malting, where grains are sprouted to convert starches naturally. Over time, Chinese food producers developed controlled mold-based fermentation, the technique that still underpins soy sauce, tofu, and tempeh production today.
The Journey to the Western World
Soybeans remained almost exclusively an Asian crop until surprisingly recently. The first recorded introduction to North America came in 1765, when Samuel Bowen, a former seaman who had worked for the East India Company, brought soybean seeds from China to Savannah, Georgia, by way of London. Starting in 1766, he planted them on his plantation at Thunderbolt, Georgia. A few years later, in 1770, Benjamin Franklin sent soybean seeds from London to the botanist John Bartram in Philadelphia.
Despite these early introductions, soybeans didn’t gain serious traction in American agriculture for more than a century. Between 1898 and 1928, USDA scientists collected roughly 3,000 soybean samples from Japan, China, Korea, and India. In 1929, the USDA sent researchers William Morse and P. Howard Dorsett on an extended expedition to Japan, Korea, and northeast China to gather even more varieties. That effort laid the genetic foundation for the American soybean industry that eventually exploded in the mid-20th century.
Where Soybeans Grow Today
The geography of soybean production has shifted dramatically from its origins. China, where the crop was born, is no longer the dominant producer. Brazil leads the world with about 180 million metric tons per year, accounting for 42% of global production. The United States follows at roughly 116 million metric tons (27%), and Argentina ranks third at about 48.5 million metric tons (11%). Together, these three countries in the Americas produce roughly 80% of the world’s soybeans, a striking reversal for a crop that spent most of its 9,000-year history confined to East Asia.