Political Genetics
If the decision to vote is based in part on genetics, James H. Fowler reasoned, identical twins should behave more alike than fraternal twins, because identical twins share all of their DNA, whereas fraternal twins share only half on average.
The researchers matched data from the Southern California Twin Registry with publicly accessible electronic voter registration and turnout records from Los Angeles County. Their analysis of voting histories for 326 identical and 196 fraternal twins suggests that genetics was responsible for 60% of differences in voting turnout between twin types.
Fowler also investigated a larger, more nationally representative database from the National Longitudinal Study of Adolescent Health, or Add Health. This study not only asked if participants voted but also inquired about participation in other political activities, such as whether they contributed to campaigns or attended political rallies or marches. The researchers’ data on 442 identical and 364 fraternal Add Health twins indicate that genetics underlies 72% of differences in voting turnout and roughly 60% of differences in other political activity. Preliminary results from the Twins Days festival in Twinsburg, Ohio, also support the findings.
Fowler hypothesizes that the drive to vote or participate in politics may be linked with genes underlying more ancient behaviors, such as innate dispositions toward cooperation.
Robert Plomin analyzed Fowler’s data, and concluded that genetics was responsible for 40%, not 60%, of differences in voting turnout between twin types. 40% is also the average estimate of heritability seen in twin studies of personality.
Evan Balaban cautions that about two thirds of identical twins share the same bloodstream while fetuses, so greater similarities between twins could be attributable not only to sharing genes but to sharing more similar levels of hormones and other compounds each fetus produces during development.