Researchers from the University of Washington's Learning and Brain Sciences division put babies in a room with an adult they had never met before. When the researcher would drop a piece of fruit and then pretend to not be able to get it, more than half the babies grabbed the fruit to give it back to the researcher.
When the babies were hungry, still more than a third gave the fruit to the adult. This kind of behavior seems to be uniquely human. While some primates will share to help out other in some situations, it's almost unheard of for a hungry animal to give up food to another.
The researchers say the trait can be molded by how children see their parents react negatively or positively to being altruistic,