Uri Alon of the Weizmann Institute of Science in Israel and other researchers drew the data for the study from three sets of data from pairs of Swedish twins, including one set of twins that was reared apart. To test how generalizable the results are, the group also examined data from a study of 2,092 siblings of 444 Americans who lived to be over 100. Their goal was to identify outside factors that can affect how long someone lives, like infections or accidents, separate from the intrinsic factor of genetics.