Our happy hour fact to amaze your drinking buddies with.

The best way to predict longevity may simply be by comparing how old a person looks relative to his or her actual age.

In 2001, researchers in Denmark photographed 1,826 pairs of twins over the age of 70 and subjected the duos to various physical and cognitive tests. The team later rated the photos it took based on what the pictured individual's age appeared to be. After seven years, death records showed that the perceived ages were the best indicator of which member of each pair of twins would live longer.

Professor Kaare Christensen of the University of Southern Denmark, who headed the study, believes that rather than giving expensive, less accurate genetic tests, doctors would be better off assessing their patients' longevity by simply eyeballing them.

Of course, plastic surgery throws a huge wrench into this plan. If it didn't, Dick Clark could be used as a human time capsule.