Twins and Religion
In a 2005 study, researchers analyzed reports on the religiosity of twins in adolescence compared with adulthood. The intent was to calculate, by means of a statistical model, the relative importance of genetic factors versus environmental influence at those two stages of life. For adolescents, they learned that genetics - in other words, dispositions for certain personality traits - accounted for only 12 percent of their religious identity, and a shared upbringing contributed 56 percent. (If you include a third category, which captures all the unique events that shape a twin’s life, these three numbers add up to 100 percent.) Conversely, 44 percent of adults’ religiosity could be attributed to genetics, and 18 percent had to do with their environment.