31 Surprising Signs You'll Live to 100, Including Your Diet and Whether or Not You're Outgoing

Consider this: In the 20th century, the average life expectancy shot up 30 years — the greatest gain in 5,000 years of human history. And this: Centenarians — folks who make it into the triple digits — aren't such an exclusive club anymore, increasing 51% from 1990 to 2000. How to account for these dramatic leaps? Advances in health, education and disease prevention and treatments are high on the list, and that makes sense. But what you may not know is that seemingly unimportant everyday habits, or circumstances in your past, can influence how long and how well you'll live.

Here, science-based signs you're on a long-life path, plus tips on how to get on track.