A nearly complete 13,000- to 15,000-year-old skeleton of a woman has the oldest recorded case of impacted wisdom teeth ever documented, say scientists at the Field Museum in Chicago.

The teeth may also point to a key shift in human nutrition.

For years, it was believed that Magdalenian Girl, excavated in France in 1911, was a girl because her wisdom teeth had not erupted. Wisdom teeth usually come in between 18 and 22 years of age.

However, new high-quality digital X-rays revealed that the skeleton had impacted wisdom teeth that had failed to erupt at the normal time. Therefore, Field Museum scientists concluded that Magdalenian Girl was actually a 25- to 35-year-old woman.

The finding is significant because impacted teeth are believed to be the result of dietary changes historically associated with later developments in human cultures. Impacted teeth typically did not occur during the Stone Age due to a coarse diet that required more chewing and higher bite forces. This likely stimulated the growth of the jawbone, creating more room for wisdom teeth to erupt, the scientists explained.

"Finding impacted wisdom teeth 15,000 years ago indicates that the human diet might have already changed, some would say 'deteriorated,' earlier than previously thought," Robert D. Martin, Field Museum provost and primatologist, said in a prepared statement.