Good question, David! Studies of identical twins, who share 100% of their genes, reveal that genetics account for around 25-30% of the variation in human lifespan. People born with certain gene variants, like the FOXO3 gene, are predisposed to live longer lives.

Still, lifestyle factors like diet, exercise, and managing stress also substantially impact whether someone reaches their full genetic potential for a long life.

Ultimately, while longevity is partially genetic, day-to-day behaviors and environment play a crucial role in translating genetic tendencies into real-world lifespan. :-)