Washington, Jul 26 (IANS): While rationalists may not agree, acts of generosity come naturally to humans, claims a new research.

Commonplace acts of generosity, like tipping the waiter, where no future return is likely, is seen as misplaced by biologists and irrational by economists.

However, computer simulations by scientists at University of California Santa Barbara, surprisingly show that generosity emerges naturally from the evolution of cooperation, the journal Proceedings of the National Academy of Sciences reports.

This means that human generosity is likely to rest on more than social pressure or cultural conformity, which existing theories propagate.

It is instead built into human nature, according to a California statement.

"When past researchers carefully measured people's choices, they found that people all over the world were more generous than the reigning theories of economics and biology predicted they should be," said study author Max M. Krasnow, post-doctoral scholar at California's Center for Evolutionary Psychology.