Geneticists of University of California, Los Angeles, have developed a new saliva test which can accurately predict a person's age.
A newly patented test based on the research, for example, could offer crime-scene investigators a new forensic tool for pinpointing a suspect's age.
"Our approach supplies one answer to the enduring quest for reliable markers of aging," said principal investigator Dr. Eric Vilain, a professor of human genetics, pediatrics and urology at the David Geffen School of Medicine at UCLA.
"With just a saliva sample, we can accurately predict a person's age without knowing anything else about them," he added.
Vilain and his colleagues looked at a process called methylation - a chemical modification of one of the four building blocks that make up our DNA.
"While genes partly shape how our body ages, environmental influences also can change our DNA as we age," explained Vilain.
"Methylation patterns shift as we grow older and contribute to aging-related disease," he added.
"Methylation's relationship with age is so strong that we can identify how old someone is by examining just two of the 3 billion building blocks that make up our genome," said first author Sven Bocklandt, a former UCLA geneticist now at Bioline.
The study has been published in the online edition of the Public Library of Science (PLoS) ONE.