Hamilton's rule—the mathematical relation quantifying the idea that genetically related subjects are more likely to help each other, even at the expense of their own survival—has been observed in many animal species, but it had yet to be tested in financial decision-making contexts. Now, in a new study published in the Proceedings of the National Academy of Sciences, MIT Sloan School of Management Prof. Andrew W. Lo and Hebrew University School of Business Prof. Moshe Levy have found strong support for this rule in an experiment involving monetary transactions among human subjects with varying degrees of genetic relatedness.