A mystery concerning how some of North America’s first farmers survived on a diet that appears manifestly inadequate may have been solved.
The ancestral Pueblo people who lived in what is now known as the Four Corners region of the southwestern United States shifted from a nomadic to a settled lifestyle centred on crop-growing around 400BCE.
The primary crop cultivated was maize (known in the US as corn), which accounted for an estimated 80% of calorific intake.
During the ensuing 800 years – a stretch known as the Basketmaker II period – the settlers’ diet contained very little meat. This was perhaps a cultural choice. Basketmaker II people became efficient turkey farmers, but the birds were raised primarily for their feathers, used in the manufacture of blankets, and for certain ritual purposes. They were not eaten.
The nutritional components of Basketmaker II cuisine has been well established through a number of analyses, including radio-isotope sampling conducted at burial sites. A study published in 2013, for instance, found that while maize comprised the massive bulk of food intake, it was accompanied by small amounts of wild plants, including yucca, and – more so in men than women – occasional bits of wild rabbit.
Over all, the Pueblo menu should have been dangerously low in a number of essential nutrients, particularly niacin, tryptophan and lysine – the lack of which leads to a range of ailments, including pellagra, an often fatal disease that results in diarrhoea, dermatitis and dementia.
However, no Basketmaker II human remains ever tested have shown evidence of such an illness. This fact leads to the obvious conclusion that the people must have been able somehow to access the crucial nutrients. There is evidence that at least one community boiled maize in limestone, which would have made some amino acids locked up in the corn more biologically available – but even then the amounts would still have been too small to meet dietary needs.
Now, however, archaeologist and biological anthropologist Jenna Battillo from the Southern Methodist University in Texas may well have found the answer to puzzle.
It turns out to be an organism that today is considered a menace by commercial maize farmers: a fungus called Ustilago maydis, or, more prosaically, corn smut.
Analysing “human paleofaeces” found at a Basketmaker II site known as Turkey Penn Ruin in Utah, Battillo found plentiful evidence of U. maydis spores. This, she writes in a paper published in the Journal of Archaeological Science: Reports, indicates that the fungus was included as an intentional part of the diet.
There is considerable later evidence to back up the suggestion. The fungus, which forms distinctive lumps or “galls” on maize heads, is today a popular food in Mexico, where it is known as huitlacoche. It is also popular among some communities in Central America.
Battillo cites a number of studies that found corn smut was historically considered a delicacy among southern and meso-American societies, including the Aztec, Maya and Hopi.
U. maydis causes loss of vitality and weight as well as cosmetic disfigurement in maize and is therefore hated by commercial growers. About 4% of the US crop is lost to the fungus each year – well down from the estimated 80% that blighted farms in the nineteenth and twentieth centuries.
For the Basketmaker II people, however, the fungus infection was very positive – indeed, quite literally, a lifesaver.
Battillo reports that corn smut alters the nutrient content of corn. It increases the protein levels from as low as 3% to as high as 19%. It also dramatically boosts the levels of lysine, and introduces 16 other essential amino acids. The only one missing is tryptophan, for which no data is available – Battillo suggests limestone boiling and input from other minor food sources might have been sufficient to provide the average four milligrams a day required to maintain health.
And while the new research seems to answer the question of how Basketmaker II people supplemented their nutrient-poor maize diet, it still leaves another matter unresolved.
The evidence, says Battillo, cannot determine whether the early farmer communities intentionally introduced or encouraged corn smut on their plants, or whether infections happened by accident and were simply tolerated.
In either scenario, she concludes, “the ubiquity of the spores in paleofaeces from Turkey Pen Ruin strongly supports intentional consumption”.
