gee, supermarkets not needed

https://scitechdaily.com/the-shocking-diet-that-fueled-human-evolution/

The transition from grasses to these high-energy plant tissues would make sense for a species growing in population and physical size, Fannin says. These underground caches were plentiful, less risky than hunting, and provided more nutrients for early humans’ expanding brains. Having already adopted stone tools, ancient humans could dig up tubers, bulbs, and corms while facing little competition from other animals. “We propose that this shift to underground foods was a signal moment in our evolution,” Fannin says. “It created a glut of carbs that were perennial — our ancestors could access them at any time of year to feed themselves and other people.”