A paper showing a strong genetic contribution to social responsibility was published in the December 22 issue of Proceedings of the Royal Society: Biological Sciences, 271, 2583-2585, entitled "Genetic and environmental contributions to pro-social attitudes: a twin study of social responsibility."
The study compared identical twins with non-identical twins to see how much they agreed on 22 questions, such as "I am a person people can count on," "It is important to finish anything you have started," and "Cheating on income tax is as bad as stealing," using a scale from 1 (strongly disagree) to 5 (strongly agree). Answers are known to predict real-life behavior such as whether a person votes in elections or volunteers to help others.
The twins came from the University of London Twin Register. There were 174 pairs of monozygotic (identical twins, who share all their genes) and 148 pairs of dizygotic (non-identical twins, who share only half their genes). If monozygotic twins agree more than dizygotic twins it suggests that morality has a biological basis and is part of our evolved psychology.
The answers of the identical twins were almost twice as alike as those of the non-identical twins. The results showed that genes account for 42% of the individual differences in attitudes, growing up in the same home for 23%, and differences within the same home for the rest.
The study also found that genes had a stronger influence on males than females (50% vs. 40%) and that home upbringing had a stronger influence on females (40% vs. 0%). This suggests parents may watch over the behavior of daughters more carefully than they do for their sons.
In previous research Rushton has shown that genes influence people's levels of altruism and aggression--including feelings of empathy like enjoying watching people open presents and acts of violence such as fighting with a weapon. Rushton has also demonstrated that the male sex hormone testosterone sets the levels of aggression and altruism.
When asked about his findings Prof. Rushton noted, "They join a host of recent research in showing that both genes and upbringing influence almost every human behavior. It is especially interesting to see that this applies to moral attitudes." He said that he agreed with George Eliot's sentiment: "What do we live for, if it is not to make life less difficult for each other?"
If your reaction is that identical twins share more social environment keep in mind that a great many of twins studies have been done, including on twins reared apart. My impression from reading on twins studies and comparison across these studies is that the common experiences of identical twins as compared to non-identical twins and non-twin siblings do not end up counting for that much. So Rushton's use of this data to draw the conclusions he reaches about hereditability is sound in my opinion.
What is most important about this result? When something is genetic then it becomes manipulable using genetic technologies. Once people can control what genetic variations their offspring can have will they choose genetic variations that make their children more or less altruistic, more or less empathetic, more or less desirous to see justice done (with different levels of brain rewards for carrying out altruistic punishment), or more or less prone to being aggressive?
Once genetic variations for behavior and cognition become choosable by parents they will make choices that differ from what would happen from chance combination of their genes to produce offspring. So human offspring will change somehow as a result. The question is how?
My guess is that in different cultures the average decision made will be different. So cultures will become more unalike as humans make average different decisions about behavioral characteristics in their offspring.
Abstract: Although 51 twin and adoption studies have been performed on the genetic architecture of antisocial behaviour, only four previous studies have examined a genetic contribution to pro-social behaviour. Earlier work by the author with the University of London Institute of Psychiatry Adult Twin Register found that genes contributed approximately half of the variance to measures of self-report altruism, empathy, nurturance and aggression, including acts of violence. The present study extends those results by using a 22-item Social Responsibility Questionnaire with 174 pairs of monozygotic twins and 148 pairs of dizygotic twins. Forty-two per cent of the reliable variance was due to the twins' genes, 23% to the twins' common environment and the remainder to the twins' non-shared environment.
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|Share |||Randall Parker, 2005 January 07 01:55 PM Brain Altruism|