Many familiar grains today, like quinoa, amaranth, and the millets, hemp, and buckwheat, all have traits that indicate that they coevolved to be dispersed by large grazing mammals.
Many familiar grains today, like quinoa, amaranth, and the millets, hemp, and buckwheat, all have traits that indicate that they coevolved to be dispersed by large grazing mammals. During the Pleistocene, massive herds directed the ecology across much of the globe and caused evolutionary changes in plants. Studies of the ecology and growing habits of certain ancient crop relatives indicate that megafaunal herds were necessary for the dispersal of their seeds prior to human intervention. Understanding this process is providing scientists with insights into the early domestication of these plants.
The domestication of small-seeded annuals involved an evolutionary switch from dispersal through animal ingestion to human dispersal. Those are the findings of a new study by Robert Spengler, director of the Paleoethnobotany Laboratories at the Max Planck Institute for the Science of Human History, and Natalie Mueller, assistant professor of anthropology at Washington University in St. Louis, published in Nature Plants. Spengler and Mueller demonstrate, by looking at rangeland ecology and herd-animal herbivory patterns, that the progenitors of small-seeded crops evolved to be dispersed by megafaunal ruminants. Although today the wild varieties of these species grow in small, isolated patches, the researchers illustrate that heavy grazing of these plants by herd animals causes dense patches to form near rivers or other areas that the animals frequent. In ancient times, these dense patches of plants could have easily been harvested, just like modern farmers’ fields – explaining how and why ancient people might have focused on these specific plants. This study provides an answer for this long-standing mystery of plant domestication.
Image: Large grazing animals have a strong selective force on plants, certain plants have evolved traits to thrive on pastoral landscapes. Spengler and Mueller theorize that yak herding may have helped drive buckwheat domestication in the southern Himalaya. This lone yak in the Lhasa region of Tibet is a significant evolutionary force on the plant communities around where it grazes. (Credit: Robert Spengler)