Narrator: This is Science Today. For a long time it has been known that identical twins live longer than fraternal twins, but until now, nobody has known why. Malcolm Zaretsky, a molecular and cell biologist at the University of California, Berkeley, recently found that frequent communication by phone or mail between identical twins keeps them alive longer.

Zaretsky: I looked at various factors, environmental factors, to see what could be responsible for the greater longevity of identical twins. And I found that communication between twin partners was a very significant factor.

Narrator: This finding suggests that meaningful human relationships, and not just genetics, affect our longevity.

Zaretsky: Identical twins who communicated frequently had a mortality rate, which was about 5% less than identical twins who did not communicate frequently, but that was not the case with fraternal twins—their mortality rate was the same whether they communicated frequently or not.

Narrator: For Science Today, I’m Larissa Branin.