Scholars have long recognized the emergence of agriculture as a turning point in the history of humankind. Pinpointing its origins, however, has proven quite complicated. But researchers generally agree that somewhere between five and 10 thousand years ago, societies in more than half a dozen regions around the world domesticated a number of different plants. Mexico is one such region, and two sets of findings reported today in the Proceedings of the National Academy of Sciences are shedding new light on the rise of its predominant grain crop, maize.

In the first study researchers from the University of Michigan and the Smithsonian Tropical Research Institute in Balboa, reanalyzed maize cobs and sediments that had been excavated in 1966 from Guil Naquitz cave in the eastern valley of Oaxaca. Using the previously unavailable accelerator mass spectrometry dating technique, the team determined that the cobs are about 6,250 years old--nearly 700 hundred years older than the previous record holders-- making them the oldest known in the New World. The results of the second study, however, reveal that these cobs do not represent the origin of domesticated maize. Bruce F. Benz of Texas Wesleyan University studied the morphology of the maize cobs and ascertained that the grain had already been subjected to genetic manipulation by that point.

Despite the new advances, the question of when people began domesticating maize remains. Yet even that information will provide only a small piece of the agriculture origins story. Different crops appear to have arisen in different places at different times, not only in Mexico, but all over the world.