June 28, 2020
An international team of researchers led by UNM and University of California, Santa Barbara is investigating the use of maize by the earliest humans in Central America.
Radiocarbon dating of the skeletal samples shows the transition from pre-maize hunter-gatherer diets, where people consumed wild plants and animals, to the introduction and increasing reliance on the corn. Maize made up less than 30 percent of people’s diets in the area by 4,700 years ago, rising to 70 percent 700 years later.
Maize was domesticated from teosinte, a wild grass growing in the lower reaches of the Balsas River Valley of Central Mexico, around 9,000 years ago. There is evidence maize was first cultivated in the Maya lowlands around 6,500 years ago, at about the same time that it appears along the Pacific coast of Mexico. But there is no evidence that maize was a staple grain at that time.
The first use of corn may have been for an early form of liquor.
“We hypothesize that maize stalk juice just may have been the original use of early domesticated maize plants, at a time when the cobs and seeds were essentially too small to be of much dietary significance. Humans are really good at fermenting sugary liquids into alcoholic drinks. This changed as human selection of corn plants with larger and larger seeds coincided with genetic changes in the plants themselves, leading eventually to larger cobs, with more and larger seeds in more seed rows,” Prufer explained.
To determine the presence of maize in the diet of the ancient individuals, Prufer and his colleagues measured the carbon isotopes in the bones and teeth of 52 skeletons. The study involved the remains of male and female adults and children providing a wholistic sample of the population. The oldest remains date from between 9,600 and 8,600 years ago and continues to about 1,000 years ago
The analysis shows the oldest remains were people who ate wild plants, palms, fruits and nuts found in tropical forests and savannahs, along with meat from hunting terrestrial animals.
By 4,700 years ago, diets had become more diverse, with some individuals showing the first consumption of maize. The isotopic signature of two young nursing infants shows that their mothers were consuming substantial amounts of maize. The results show an increasing consumption of maize over the next millennium as the population transitioned to sedentary farming.
Prufer noted, “We can directly observe in isotopes of bone how maize became a staple grain in the early populations we are studying. We know that people had been experimenting with the wild ancestor of maize, teosintle, and with the earliest early maize for thousands of years, but it does not appear to have been a staple grain until about 4000 BP. After that, people never stopped eating corn, leading it to become perhaps the most important food crop in the Americas, and then in the world.”
Maize from El Gigante Rock Shelter shows early transition to staple crop
More information: D.J. Kennett at University of California, Santa Barbara in Santa Barbara, CA el al., “Early isotopic evidence for maize as a staple grain in the Americas,” Science Advances (2020). DOI: 10.1126/sciadv.aba3245 , advances.sciencemag.org/content/6/23/eaba3245 Provided by University of New Mexico
Phys.org has the report here; https://phys.org/news/2020-06-document-maize-mesoamerica.html