More than 10,000 years ago, somewhere in the Andean foothills between Argentina and Bolivia, two wild legume species mixed, probably with the help of some pollinating bees. Their offspring was atypical — a freak of nature that couldn’t remix with its wild ancestors and cousins. The freak plant continued to evolve, first on its own, and then by selection as farmers domesticated it for its tasty seeds that grew, not from its branches like most beans and peas, but beneath the soil. Mer…