Geneticists at the University of California, Los Angeles, have discovered a way to use saliva to reveal how old you are.

The researchers used saliva samples contributed by 34 pairs of identical male twins between the ages of 21 and 55. They scoured the men’s genomes and identified 88 sites on the DNA that strongly correlated methylation to age. They replicated their findings in a general population of 31 men and 29 women between the ages of 18 and 70.

Next, the scientists built a predictive model using two of the three genes with the strongest age-related linkage to methylation. When they plugged in the data from the twins’ and the other group’s saliva samples, they were able to correctly predict a person’s age within five years — an unprecedented level of accuracy.

A newly patented test based on the research could offer crime-scene investigators a new forensic tool for pinpointing a suspect’s age.

Ref.: Eric Vilain, et al., Epigenetic Predictor of Age, PLoS ONE, 2011; [DOI: 10.1371/journal.pone.0014821]