The radiocarbon dates from burned rock middens (plant baking facilities) on the Edwards Plateau show a marked increase in frequency during the Late Prehistoric period (after A.D. 800). Although preservation bias plays a role in this pattern (older materials less likely to be preserved for dating), the increase in plant baking seems clear. Put unkindly, people were forced to bake lots of nasty roots because they had no other choice. More and more people in the region forced some groups to move into less-than-favored locations and resort more and more to eating less-desirable foods. From Black and Creel, 1997, “The Central Texas Burned Rock Midden Reconsidered” in Black et al. 1997.