While genes and lifestyle play their respective role in the aging process, deeper research further delineates between the two. Living past 100 may be in the genes, says Scientific American. "A glance at your family tree may indicate whether you have a familial tendency toward longevity. Research suggests that exceptional longevity—living one to three decades beyond the average U.S. life span of approximately 80 years—runs strongly in families... Genetic factors can contribute to the degree of longevity in at least two important ways: An individual may inherit certain genetic variations that predispose him or her to disease that decreases longevity; other gene variants may confer disease resistance, thereby increasing it."