Ancient Bison Herds of the American Midwest and the Domestication of the Lost Crops

August 27th, 2019

How did the ancestors of early agricultural crops spread across space? A research project on the influence of animals on human farming practices.

Vast soy and corn fields dominate the landscape of industrial agriculture in the North American Midwest. Decades ago however, this stretch of land was marked by rich argricultural diversity. But what does the spread of these early domesticated plant species imply about human-animal relations? And how did they influence the emergence of agricultural practices?

The modern agricultural system of the North American Midwest is of unparalleled genetic homogeneity. Its dominant crops are cloned hybrids from a handful of parent lineages. The majority of traits in these maize and soy crops date back only a few decades and are testament to a great acceleration in the use of nitrogen fertilizer and advances in irrigation and mechanized harvesting. Which is to say, the highly curated fields of the American Midwest are the quintessential expression of the Anthropocene, a choreographed display of human environmental engineering which has narrowed down the entire vegetation community to just a few cloned variants within two crop subspecies, bred and—more recently—engineered to maximize productivity under highly regulated growing conditions. Heavy herbicide, pesticide, and fungicide use homogenizes the ecosystem of this landscape further to express an extreme form of human niche construction. It comes at great environmental cost, not least of which is the effect of nitrogen washing downriver to create eutrophic dead zones in the Gulf of Mexico.

However, for over 250 generations, a diverse array of locally adapted crops—almost entirely unknown today—grew in this same region. Sumpweed, maygrass, little barley, sunflower, goosefoot, and erect knotweed are just some of a cast of ancient “Lost Crops” now only present in the archaeobotanical record. Little is known about this early agriculture, but in order to gain greater insight, researchers from the Max Planck Institute for the Science of Human History have joined forces with the Lost Crops Garden Network, a network of American scholars concerned with crop reconstruction. This project proposes that the wild ancestors of these, now lost, crops shared a distinct set of traits, which suggest that their seeds were dispersed via consumption by animals (endozoochoric). Their thesis ist that the megafaunal herds of the Pleistocene and bison of the Holocene were the primary dispersal mechanism for these early-domesticated species, and this project plans to test this hypothesis in the Mississippi region, an ideal natural laboratory given the vast herds of bison that continued to thrive there until the 1850s.

Having consumed the wild plants laden with seeds in their thousands, bison would defecate the seeds into a nitrogen-rich bed of fertilizer, thereby playing an essential role in their germination and dispersal. Their diet and ethology would possibly lead to dense patches of annual plants within the tallgrass prairies, similar to cultivated fields. Human beings may have been capable of harvesting and maintaining such convenient sources of nutrition, a practice that could have led to the domestication of these species and informed subsequent farming practices. If confirmed, this would explain why early agriculture focused on these specific plants. At the same time, it is possible to explain how the current rarity of this species is due to hunting, which disrupted their dispersal mechanism and reduced their number to near extinction in the nineteenth century.

The project hopes to test this novel thesis of the emergence of agriculture and subsequent turn toward industrial agriculture. To do so, the project will carry out three sets of studies in the summer of 2019. The first set involves botanical surveys in tallgrass prairies where herds of bison have been reintroduced. Plant communities will be analyzed and compared to bison-free prairies, to gauge whether bison are a concentration factor. Where possible, dung will be collected and the seeds it contains will be quantified; seed morphology will be documented also. Two more studies will involve controlled experiments with captive bison. One will determine the relationship between their digestive tract and seed germination rates. Another will use bison dung as a growth matrix to test its effect on yield and morphology of Lost Crop progenitors. The results of these experiments could suggest that grazing animals played a central role in the emergence of agriculture, and that human history is a history of multispecies relationships.