The study in Genes, Brain and Behavior found those more likely to be generous had a gene variant not in the DNA of those less likely to be less generous.

In the Hebrew University of Jerusalem experiment, 203 online "players" were each allocated the equivalent of $12 and asked to choose to either keep it or give away all or part of it to an another anonymous player. Reactions were compared to DNA samples and the researchers found those who had certain variants of the AVPR1 gene gave away an average of 50 percent more money that those not having the variants.

"The experiment provided the first evidence, to my knowledge, for a relationship between DNA variability and real human altruism," study researcher Ariel Knafo said in a statement.

Knafo and the other researchers -- R. P. Epstein, Gary Bornstein and Salomon Israel -- suggest the gene AVPR1 is involved in producing a receptor for the hormone, arginine vasopressin, which is linked to social bonding.