A replica Paranthropus boisei skull and jaw. Image: DurovaAncient human ancestors ingested tiny rock particles found in soil and dust along with the plants they ate, wreaking havoc on the tough tissue layer protecting teeth, scientists say.



"We agree that phytoliths can mark enamel, [but] we don't think they're responsible for removing tissue from it," says study leader Peter Lucas, a dental anthropologist at Kuwait Univ.

Gary Schwartz, an enamel expert at Arizona State Univ.'s Institute of Human Origins, praised the study for actually testing a common scientific assumption among anthropologists: that food items cause small-scale damage on teeth, which over time scratches and pits the enamel, wearing it down to the point where the teeth are no longer protected and begin to erode.

"This study shows pretty nicely that [phytoliths] just aren't hard enough to do that," says Schwartz, who was not involved in the study.




"It may still be that phytoliths still make it unpleasant to eat because you're causing changes to your tooth, but it's not like they are the primary thing causing your teeth to disappear," says study team member Amanda Henry, a physical anthropologist at the Max Planck Institute for Evolutionary Anthropology.

The team says that the experimental findings could help resolve a mystery surrounding the fossils of an ancient hominin known as Paranthropus boisei.






But based on their findings, Lucas and his team propose an alternative hypothesis. Perhaps, they says, the wear on P. boisei's teeth was caused by drought or by sand carried in by seasonal winds from the Arabian Peninsula.

"It would mean you're seeing the environment and not the diet," Henry says.



Schwartz says the new findings suggest "we may need to be [cleverer] in reconstructing diets in the fossil record."

Henry says the results could have implications for living mammals as well. However, Henry adds that more studies are needed to understand how applicable the findings are to the real world. "The scale that we're talking about here is tiny.”