Long before early humans in North America grew corn and beans, they were harvesting and cooking the bulbs of lilies, wild onions and other plants, roasting them for days over hot rocks, according to a Texas archaeologist.
The evidence for this practice has long been known of in fire-cracked rock piles found throughout the continent, but archaeologists have tended to ignore it "because a new pyramid or a Clovis arrow point is much sexier," said archaeologist Alston V. Thoms of Texas A&M University.
In two reports published online this week in the Journal of Anthropological Archaeology and the Journal of Archaeological Science, Thoms reported that cooking on hot rocks first became a substitute for cooking on hot coals about 9,000 to 10,500 years ago, then had a sudden jump in popularity about 4,000 years ago.
The reason for the changes: population growth that required the exploitation of new food resources.
"Whatever they were eating before did not require prolonged cooking," Thoms said. But beginning about 10,000 years ago, "people couldn't live off the cream of the land anymore." The megafauna that had been a prime food source -- such as the woolly mammoth -- were becoming extinct, and other mammals were becoming harder to find. People had to turn to plants.