Over the past three millennia, selective breeding has dramatically widened the array of plant domestication traits. However, a close look at the archaeobotanical record illustrates a similar suite of linked traits emerging before humans began selectively breeding food crops. A researchers now summarizes all of these early evolutionary responses in plants, arguing that these shared traits evolved in response to human seed-dispersal services.

Robert N. Spengler. Anthropogenic Seed Dispersal: Rethinking the Origins of Plant Domestication. Trends in Plant Science, 2020 

DOI: 10.1016/j.tplants.2020.01.005

Hightlights:

  • Archaeobotanical and genetic evidence demonstrates that the first morphological changes in all of the earliest domesticated plants were associated with wild seed dispersal strategies that were no longer advantageous under human cultivation.

  • Domestication was/is a natural response of plants to heavy seed predation by humans. Many plants in the wild have formed a similar seed dispersal–based mutualism with animals as a response to herbivory.

  • Rather than viewing domestication as an intentional human-driven process, domestication is best modeled as a natural evolutionary response to herbivory. Early domestication traits gave plants a selective advantage through the recruitment of humans as seed dispersers.

  • Many of the progenitors of our modern domesticated crops relied on animals for seed dispersal. The natural dispersal processes of many of these crop progenitors were weakened by megafaunal extinctions.

Abstract: It is well documented that ancient sickle harvesting led to tough rachises, but the other seed dispersal properties in crop progenitors are rarely discussed. The first steps toward domestication are evolutionary responses for the recruitment of humans as dispersers. Seed dispersal–based mutualism evolved from heavy human herbivory or seed predation. Plants that evolved traits to support human-mediated seed dispersal express greater fitness in increasingly anthropogenic ecosystems. The loss of dormancy, reduction in seed coat thickness, increased seed size, pericarp density, and sugar concentration all led to more-focused seed dispersal through seed saving and sowing. Some of the earliest plants to evolve domestication traits had weak seed dispersal processes in the wild, often due to the extinction of animal dispersers or short-distance mechanical dispersal.

Keywords: domestication, seed dispersal, megafaunal extinction, origins of agriculture, crop evolution

Figure 1
Figure 1 - Map of the Regions or Centers of Domestication Globally, as Proposed and Discussed by Larson et al.