His approach can include altruistic behavior by defining individuals' utility appropriately.

The existence of altruistic behaviors has been a difficult problem for evolutionary theorists from the beginning.

Recent studies have shown chimpanzees engage in apparently altruistic behavior within groups.

Over the years, I have witnessed several incidents of altruistic behavior in dogs.

Because of this an altruistic behavior can take hold by the following reasoning.

However, such altruistic behavior cannot be recognized in large groups.

Perhaps even more than the drive toward independent achievement, shy people long to make connections to others often through altruistic behavior.

Yet in many social animals altruistic behaviour can be found.

It is more difficult to understand the mechanism through which altruistic behaviour initially developed.

I worked in the area of altruistic behavior, trying to understand what it is that makes a person helpful to somebody else.