Every food crop we eat today was once a wild plant. Over of years, early farmers seeds from the they liked best and them again. , the plants . Their seeds larger, and they no fell to the ground people could them.

Rice was one of the first crops domesticated in Asia. Archaeological suggests that people in the Yangtze River of China began it about nine years ago. From , rice farming south and west, Southeast Asia of years . Today it more than half of the world’s population.

In most of the world, cooked rice grains stay separate. In northeast Thailand and Laos, however, the everyday rice is glutinous, or “sticky”. Despite its name, it contains no gluten. Its stickiness comes from its starch.

Rice starch is made of two main substances: amylose and amylopectin. Ordinary rice contains a mixture of both, but glutinous rice contains almost no amylose. When it is steamed, the amylopectin makes the grains cling together, so the rice can be rolled into a ball by hand and dipped into sauces.

Geneticists have traced this quality to a change in a single gene, which stops the plant from producing amylose. The change appears to have arisen once and then spread as farmers selected and shared the sticky variety.

Why did it become so popular in one region? Researchers point to culture as much as biology. Sticky rice is easy to carry to the fields, stays edible for hours and is closely tied to festivals, offerings and social identity. A crop, in other words, is shaped not only by nature but also by the people who choose to grow it.

Flooded rice paddies are one of the most iconic landscapes of Asia, but they have an unexpected effect on the climate. When fields are kept underwater for long periods, the soil runs out of oxygen. Microbes that thrive in these conditions break down plant matter and release methane, a greenhouse gas that traps far more heat than carbon dioxide over a short period.

Rice farming is estimated to produce roughly a tenth of the methane released by human activity. As the world’s population grows, so does the demand for rice, which makes the problem more pressing.

One promising solution is a technique called alternate wetting and drying. Instead of keeping fields flooded all season, farmers let them dry out for a few days at a time before flooding them again. Field trials in several countries have found that this can cut methane emissions substantially while saving water and keeping harvests stable.

The method is not suitable everywhere. Farmers need reliable control over their water supply, and many small farms depend on rain or shared canals. Spreading the technique therefore requires investment in irrigation as well as training.