Opinion Anthropogenic Seed Dispersal: Rethinking the Origins of Plant Domestication Robert N. Spengler III 1, * 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 anthro- pogenic 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. The Origins of Agriculture The linked questions of why, how, when, and where people first domesticated plants and animals are among the greatest mysteries in the development of human culture. Understanding how and why humans gained the ability to produce grain surpluses is the key to understanding the special- ization of artistic and intellectual pursuits, as well as the demographic changes that led to the for- mation of cities and empires. Over the past century, scientists have made great strides in answering the questions of when and where plants first evolved in response to human selective pressures [1,2]. However, there remains no clear consensus regarding the why and how ques- tions [2,3]. The lack of agreement may be due to the way these two questions have been framed since Darwin presented the concept of ‘artificial selection’ as opposite to or separate from natural processes [4]. Thinking of domestication as unique from other evolutionary processes effectively makes the why and how questions unanswerable – the greatest trick questions in the sciences. The focus on human agency in the process has left scholars from Pumpelly [5] and Childe [6] to Sauer [7], Cohen [8], Flannery [9], Hayden [10], and hundreds of others searching for rational drivers of human innovation. After 160 years of research into the origins of agriculture, most scholars finally accept that the process was not driven by conscious selection; in accepting this, the scholarly community is poised to reframe the study of evolution under cultivation and focus on the effects of heavy human herbivory on plant communities in the early and mid- Holocene. In this paper, I argue that plant domestication originated through the evolution of those traits which facilitated a stronger mutualistic bond between plants and people, with humans providing seed dispersal services. Evolutionary studies illustrate that mutualism often evolves from a predatory relationship [11,12]. In some cases, plants evolved sugar-rich fruits in order to recruit dispersers, and in other cases, dispersers were enticed by the green foliage that surrounded small, dry-fruited seeds. The pro- cess of plants in the wild evolving new traits in order to change their seed dispersal mechanism is effectively the same process that led to morphological changes in seeds during the first few Highlights Archaeobotanical and genetic evidence demonstrates that the first morphologi- cal changes in all of the earliest domesti- cated 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, do- mestication is best modeled as a natural evolutionary response to herbivory. Early domestication traits gave plants a selec- tive 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 pro- genitors were weakened by megafaunal extinctions. 1 Max Planck Institute for the Science of Human History, Kahlaische Str. 10, 07745 Jena, Germany *Correspondence: spengler@shh.mpg.de (R.N. Spengler III). Trends in Plant Science, Month 2020, Vol. xx, No. xx https://doi.org/10.1016/j.tplants.2020.01.005 1 © 2020 The Author. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Trends in Plant Science TRPLSC 1922 No. of Pages 9