Once you've worked out a good way to leach out the tannins, acorns actually become a really useful food. There are a variety of possible methods - boiling, prolonged immersion in running water, or repeated mashing and rinsing cycles.

The American west coast is probably the most famous example of where they were widely used, with all three methods of processing in use according to local resource availability.

Long-term storage was achieved by drying and grinding into flour, oak groves were actively managed, and yields were enhanced by regular burning of undergrowth.

They were a nutritious, reliable, and low-risk source of calories with widespread availability, and the processing was time-consuming but not particularly difficult. Before the genocide, they'd have been the staple foodstuff for most people in an area stretching from the Cascades down to roughly where San Diego is today.