Ancient teeth pose a mystery: What made those strange grooves?

New research on ancient human remains suggests the habitual usage of betel nuts, a plant seed with mind-affecting properties that is popular in parts of Asia despite the health risks it presents.

<img src='https://npr.brightspotcdn.com/dims3/default/strip/false/crop/1296x863+0+0/resize/1296x863!/?url=http%3A%2F%2Fnpr-brightspot.s3.amazonaws.com%2F87%2F13%2F83b654e1463696ae2836e32aa68a%2Fbetel-nut9-8-2.jpg' alt='A woman cracks the hull of a betel nut with her teeth to get to the meat to chew.'/><p>New research on ancient human remains suggests the habitual usage of betel nuts, a plant seed with mind-affecting properties that is popular in parts of Asia despite the health risks it presents. </p><p>(Image credit: Claire Harbage/NPR)</p><img src='https://media.npr.org/include/images/tracking/npr-rss-pixel.png?story=g-s1-144054' />