Why Do Tortoises Live So Long?

The term longevity is sometimes meant to refer only to especially longlived members of a population, whereas life expectancy is always defined statistically as the average number of years remaining at a given age.

- 

Longevity is best thought of as a term for general audiences meaning 'typical length of life' and specific statistical definitions should be clarified when necessary.

This is a very complex question. Turtles and tortoises have been on planet Earth even before the dinosaurs. They are that old. The difference between a turtle and a tortoise is that the turtle stays in the water while the tortoise stays on land. But both creatures have one thing in common: they live to a ripe old age, from 120 years to almost 200 years! There's an evolutionary answer and a biological answer according to livescience.com.