Scientists recently found new evidence that ancient Chinese, living 300,000 to 400,000 years ago, would pick their teeth.

It may be the earliest evidence of tooth-picking among humans in eastern Asia.

Scientists from China, Spain and the United States used binocular microscopes and scanning electron microscopes to examine the surfaces of seven fossilized human teeth unearthed in Yiyuan county in Shandong province, on which they found marks left by tooth-picking.

The article was published by Quaternary International, a peer-reviewed scientific journal on Quaternary science, in late March.

"The crowns and roots of the dental fossil showed different degrees of wear, from multiple shallow lines to deep grooves, which are similar to artificial wear caused by habitual tooth-picking," says Xing Song, a researcher from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, and one of the authors.

Evidence of tooth-picking was found only within Homo members. The reason that human ancestors formed this habit could either be to allay periodontal disease, or being just a habit formed as the result of increasing intake of animal protein in the human diet.