Science on Religion

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Religiousness may have a genetic basis

Religion genesThe old debate of “nature vs. nurture” continues well into the 21st century. Both sides claim to have science on their side, and both have statistics to support their case. Regarding the topic of religion, most studies have tended to favor nurture over nature, but Dorte Hvidtjørn and colleagues from the University of Southern Denmark recently looked to twin studies for a genetic influence on religiousness. While they mostly confirmed the importance of environmental factors, they did uncover some overlooked genetic factors on religion.

The researchers chose to conduct a twin study because twins act as a natural control for the environment (they are raised in the same household) and have variable genetic similarities. Monozygotic twins share 100% of their DNA, and dizygotic twins share 50% of their DNA. Consequently, scientists can pinpoint where a similar trait shared by twins comes from - that is, from the environment or from genes.

The researchers chose to study twins living in Denmark because Denmark has one of the most secularized populations in the world. Although Denmark has very low rates of church attendance, 82% of its population officially belong to the Danish National Evangelical Lutheran Church, and the majority continue to have religious baptisms, weddings, and funerals. For this reason, many consider the church of Denmark to mark merely cultural identity, but others would add that in times of crisis (such as hospitalization) Danish patients report increased religious activity.

With this religious background of the Danes in mind, the researchers invited 6,707 Danish twins born from 1970-1989 to participate in their study. Of these, 55% responded and 45% actually participated. The study they participated in aimed at capturing three dimensions pertinent to religion: cognition (principles), practice (activities), and importance (feelings). More specifically, this survey measured belief in God an an afterlife (both categorized as cognition), frequency of church attendance and prayer (both categorized as practice), and the importance of God and finding comfort and/or strength in religion (both categorized as importance).

After running the numbers, the researchers found, not surprisingly, that overall the environment played a larger role in religiousness than genetics for both monozygotic and dizygotic twins. For belief in God, environmental and genetic factors carried equal rate. For belief in an afterlife, genetic factors accounted for only 20% of the variance. Regarding the practice dimension, environmental factors accounted for 80% of the variance for frequency of church attendance, but for frequency of prayer, genetic factors actually played a more significant role than environmental ones (and even the more so the older the person was). Finally, for the importance dimension, the environmental factors dominated the importance of God in one’s life, while finding strength and/or comfort in religion had a split influence of environmental and genetic factors.

All told, of the six measured variables, genes enjoyed a greater influence than the environment in one case (frequency of prayer), had equal influence in two cases (belief in God and finding strength and/or comfort in religion), and had less influence than the environment in the other three cases. The researchers may not swing scientific opinion back to nature as more important than nurture, but they have countered those who side completely with nurture over nature. Perhaps in religion, if not other areas, both matter.

For more, see “Familial Resemblance in Religiousness in a Secular Society: A Twin Study” in the journal Twin Research and Human Genetics.


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