At a time when many people around the world are living into their tenth decade, the longest longitudinal study of human development ever undertaken offers some welcome news for the new old age: our lives continue to evolve in our later years, and often become more fulfilling than before.

Begun in 1938, the Grant Study of Adult Development charted the physical and emotional health of over 200 men, starting with their undergraduate days. The now-classic Adaptation to Life reported on the men’s lives up to age 55 and helped us understand adult maturation. Now George Vaillant follows the men into their nineties, documenting for the first time what it is like to flourish far beyond conventional retirement.

Reporting on all aspects of male life, including relationships, politics and religion, coping strategies, and alcohol use (its abuse being by far the greatest disruptor of health and happiness for the study’s subjects), Triumphs of Experience shares a number of surprising findings. For example, the people who do well in old age did not necessarily do so well in midlife, and vice versa. While the study confirms that recovery from a lousy childhood is possible, memories of a happy childhood are a lifelong source of strength. Marriages bring much more contentment after age 70, and physical aging after 80 is determined less by heredity than by habits formed prior to age 50. The credit for growing old with grace and vitality, it seems, goes more to ourselves than to our stellar genetic makeup.