Why did ancient humans have scratchy teeth?

Between 1.2 million and a few hundred thousand years ago, early human ancestors like Homo and Neanderthals relied mainly on meat and other animal foods for nutrition, while earlier ancestors like Australopithecus ate mostly plants.

Dental wear patterns in Homo antecessor suggest their diet included gritty foods like underground plants contaminated with soil or bone marrow, rather than primarily meat, because meat causes less wear than plant silica or quartz particles.

Fossil teeth from Homo antecessor show more and shorter scratches than those from Homo heidelbergensis and Iberian Neanderthals, indicating that their food was tougher to chew, possibly because they did not use fire to cook or process food as extensively.

Fossil teeth from early human ancestors show fewer scratches over time, suggesting their diets became softer, possibly because they started using better stone tools or cooking food with fire.

Fossils of Homo antecessor show more scratches on their cheek teeth than later human ancestors, which suggests they ate more unprocessed, gritty foods like raw meat, tough plants, or bone marrow without cooking or using tools to prepare food.