Much controversy exists over the origins of domesticated maize/corn in the Americas. Archaeological evidence is examined to try and unearth the truth.
The deliberate cultivation of food and animal husbandry for human sustenance began only 10,000 years ago. Hunter-gatherers moved from their nomadic lifestyle to a more settled one, where crops could be grown. The reasons for this sudden change are many and complex; however, there is little agreement amongst the theorists.
It is interesting to note that for millions of years our ancestors were hunters and gatherers and yet between 10,000 and 3,500 years ago, all over the world they started to grow crops – rice in China, wheat in the Middle East, potatoes in the Andes and maize in the Americas. There is much controversy about the domestication of maize and the relationship between teosinte and domesticated maize.
Teosinte – the wild ancestor of domesticated maize?
There is evidence to suggest that teosinte (Zea Mexicana) is the wild ancestor of domesticated maize. However, they are very different plants in that teosinte has long branches which end in tassels and maize has short branches which end in ears.
John Doebley et al (1999) believes that it was modification of a particular gene over many centuries, which allowed the teosinte to develop into maize. This, he believes, took place in southwestern Mexico, in the deciduous forests of the Balsas Valley. The teosinte was modified by selecting the preferred plant seeds. Piperno and Pearsall (1998) also produced evidence that domesticated maize originated in the tropical lowlands. K. Pope et al (2001) discovered maize dating to 5100 BC in San Andres on the Gulf of Mexico.
Mesoamerica and maize
Mesoamerica is important for the initial domestication of maize. Kent Flannery’s excavation in the Valley of Oaxaco, Mexico and investigations thereafter, give us much information on the move by the hunter-gatherers from foraging to cultivation. The hunter-gatherer moved from one area to another following seasonal foods. They would follow the ripe cactus fruit, mature grasses, deer and rabbits. Genetic change occurred in the ancestor of maize – teosinte – which made it more productive and it took a more important place in the diet. Thus, the hunter-gatherer began neglecting familiar foods in favour of maize.
It was soon discovered that teosinte grew well with beans and squashes. Wild beans began to be collected at Guila Naquitz around 7000 BC. Runner beans and squashes naturally grow around the base of teosinte and they were probably domesticated together. These three foods became the classic food crop in the Americas.
The Arrival of the Europeans and their discovery of maize
When Europeans landed in the Americas, they found maize growing from Argentina all the way up to Canada. Botanish Georg Beadle theorises that a teosinte from 13,000 BC to 6,000 BC slowly transformed into a primitive corn due to intensive gathering of plants. Beadle (1981) believes that there was a gene mutation in teosinte which made what were originally hard fruit cases of the grass into shallow softer cups which contained husks which protected the kernels. This made teosinte easier to thresh. This edible maize/corn did not scatter when touched but could be removed by threshing.
Domestication of maize
Beadle says this domestication of maize may have taken place simultaneously in many areas over a period of one hundred years. He believes the process probably started as a result of gathering wild teosinte which resulted in the plant modifying itself so the seeds were in bunches and therefore did not scatter easily. This form of teosinte would then have grown in campsites and middens. Eventually, humans would select those plants which suited their needs and so slowly a genetic change turned the teosinte into edible maize. The maize became dependent on human planting and the humans became dependent on maize as a staple food.
Early evidence of domesticated maize
he dry caves and dry highland open sites of the Tehuacan Valley in southern Mexico provide the best evidence for early maize cultivation. These examples, and those from the Tlapacoya valleys in Mexico, date to around 5000 BC. Richard MacNeish (1970, 1978) began digging at Coxcatlan in order to try and discover the origins of domesticated maize. He excavated approximately thirteen sites in Tehuacon. In five of these he found remains of ancient maize.
The earliest maize cobs were found in the lowest occupation levels in San Marcos Cave; the ears of corn are less than 20mm long. It is thought that the mature plants would have grown to about 1.2m with one to five maize bearing branches. Each plant would produce between ten and fifteen small cobs. It was originally estimated by MacNeish that the age of these finds was between 5000 and 3500 BC but recent AMS radiocarbon dating puts the corn cobs from San Marcos and Coxcatlon Caves at 2700 BC.
MacNeish found that as the game population in the area declined between 8000 and 4500 BC, so the people relied more heavily on wild plant foods. The inhabitants of the rock shelter came back each season and may have started plant cultivation. Certainly, by 3000 BC, maize cultivation (amongst other foods) was practiced, and people lived in more permanent settlements. By 1500 BC, there was a settled village life based on maize/bean/squash agriculture. This change in food reliance has also been found in other areas.
Maize, bean and squash agriculture
There is evidence that some of the different hybrid forms of maize were introduced from other areas where dry cave communities advanced, at the same time as the community in Tehuacan. The highland lakes of the Valley of Mexico may have experimented with domesticating maize during the fourth millennium BC, as they appear to have acquired a sedentary way of life before the Tehuacan region. As can be seen, there are may hypotheses about the first domestication of maize, but as yet, there is no sure evidence which has been gained from the archaeological site in the Americas.