Now, all it takes is a spit swab for scientists to find out how old you are, according to new research published online yesterday (June 22) in PLoS One. Scientists at the University of California, Los Angeles, identified 88 methylation sites on the DNA from saliva swabs that strongly correlate with age, since methylation patterns shift as people grow older. Narrowing down their search, the team built a predictive model based on just two genes and were able to correctly predict the subject's age within five years. “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,” first author Sven Bocklandt said in a press release. Forensic investigators could use the new tool to pinpoint a suspect's age, the authors write, and it could be used in routine medical screening to predict the risk of age-related diseases.