Sometime around 12,000 years ago, our hunter-gatherer ancestors began trying their hand at farming.
First, they grew wild varieties of crops like pea, lentil and barley, and herded wild animals like goat and wild ox. Centuries later, they switched to farming full-time, breeding both animals and plants, creating new varieties and breeds. Eventually, they migrated outward, spreading farming to parts of Europe and Asia.
The earliest farmers lived in the Fertile Crescent, a region in the Middle East including modern-day Iraq, Jordan, Syria, Israel, Palestine, southeastern Turkey and western Iran. And scientists had long assumed these early farmers were a homogenous group that traded and intermingled, swapping farming tools and tricks — as well as their genes. In other words, farming was long believed to have been started by one group of ancestral humans.
But a new study suggests something different – that multiple groups of people in the Fertile Crescent started agriculture, and these groups were genetically distinct from one another. That is, they didn't intermingle at the time, at least not for a few thousand years. "They lived more or less in a similar area, but they stay highly isolated from each other," says Joachim Burger, an anthropologist at the Johannes Gutenberg University Mainz, in Germany and co-author of the new study.
Burger and an international team of scientists analyzed ancient DNA from the remains of four individuals that lived about 10,000 years ago on the eastern edges of the Fertile Crescent – the Zagros Mountains on the border between Iraq and Iran. They compared the DNA of these individuals with that of skeletons that were a couple of thousand years younger and had been found way on the other end of the Fertile Crescent, a region that includes modern-day Turkey.