How did an ugly grass become one of the world’s most important crops? That’s a question researchers have been asking themselves ever since genetic analysis revealed that the ancestor of corn (right) was a spindly Mexican plant called teosinte (left). The answer is that ancient teosinte grew differently from its modern counterpart, according to a study published in Quaternary International. Researchers made the discovery by growing today’s teosinte in 20.1°C to 22.5°C greenhouses with 40% to 50% less carbon dioxide in the air—conditions more like those 14,000 years ago, before the plant was first domesticated. The plants grew shorter and had the female ears right on the main stem, the way they are in modern corn, instead of on side branches. And most of their seeds matured at once, while modern teosinte seeds mature over several weeks; the scientists kept having to go back to harvest them again and again. If teosinte used to be easier to harvest, domestication starts to make more sense. No sign of a cob, though; that must have come later.

See more ScienceShots.

*Correction, 6 February, 10:45 a.m.: This item has been corrected to reflect the fact that corn was domesticated 10,000 years ago.