Final answer:
The ancestors of domesticated seed plants were weedy generalists that thrived in disturbed environments. These plants were genetically modified over time by early agriculturalists through the process of artificial selection, favoring traits such as larger seeds.
Step-by-step explanation:
According to Bruce Smith, the ancestors of domesticated seed plants were A) Weedy generalists that thrived in disturbed environments. These early 'weedy' plants likely grew in places altered by human activity and were the progenitors of many crops we cultivate today. Agriculture likely began when humans started favoring certain plants, assisting their growth by weeding around them and planting or transplanting them in more convenient locations. Early agriculturalists recognized valuable traits in plants and selected for those that yielded more product or offered better nutrition when cared for. The process of domestication involved selecting and planting seeds from the most desirable specimens, leading to rapid genetic modification, especially in annual plants with traits such as larger seeds. Artificial selection, as termed by Darwin, played a critical role in the development of the various crops that now form the foundation of human diets.