Genetics, fidelity, and marriage
Fooling around in our genes?
We like to think of ourselves as free thinking beings, making our own decisions and determining our own lives, but is this really true? Genetic work is beginning to show that we all have built in tendencies for how we act.
Genes for traits like eye color and height are easy to understand. But genes for behaviors like depression or gambling make some of us a bit uncomfortable. Is something we do our fault or couldn't we help ourselves because of our genes?
We know genes cause some behaviors in animals. A border collie pup taken from its mother at an early age will instinctively herd sheep (or anything else if they can't find a sheep). No one can look at a border collie at play and not believe that this behavior is "in the genes."
Some simple human behaviors are certainly inborn. The startle and sucking reflexes of a baby are clearly hardwired and so must be due to genes. But what about more complex human behaviors?
The two studies below suggest a link between genetics and monogamy in an animal and genetics and divorce in people. In both, it looks like genetics significantly influences the actions of the subjects in these studies. Maybe genes can make success easier to come by in marriage.
How to turn Don Juan into a nice, stable, suburban husband
In the animal world, most males are like many country song guys -- they love 'em and leave 'em. From a genetic point of view, they increase their chances of spreading their genes by mating with as many females as possible.
One of the fewer than 5% of mammals that stick with one mate is the prairie vole. Once this guy finds a mate, he helps raise the kids, fights off potential suitors, and sticks with her for life. His close relative, the meadow vole, is a different story. He is more typical in that he mates with as many females as possible and pays no attention to the kids.
So what's the difference between these two kinds of voles? Careful examination showed that the prairie vole had a lot more of a protein called the vasopressin receptor in its brain than did the meadow vole. To test whether this was the reason for the difference in behavior, scientists used gene therapy to add extra receptors to the brain of the meadow vole.
The result? Now the meadow vole is more like his cousin -- he sticks with one mate even when others are freely available. It is astonishing that a single gene could have such a huge impact on such a complex behavior.
We don't know whether this applies to humans but we do know that the same pattern exists with monkeys. Monkeys who like to fool around have fewer vasopressin receptors than do more faithful monkeys.
So can we turn those country song guys into more stay at home types? We certainly can't yet do gene therapy on humans like was done in this study. But maybe some sort of drug that works on the vasopressin receptor could be made to turn cheating men into prairie voles.
Of course, even if the vasopressin receptor is important in human monogamy and we come up with some way to tweak it to keep men from cheating, should we? Besides ethical concerns, we'd lose an awful lot of good country music...
It's not you, it's my genes
Is a decision as complicated as divorce determined by your genes? Some research into twins suggests that this may be the case.
Twins are often used as a first step in figuring out if something you're interested in has anything to do with genes. Scientists compare identical twins, who share the exact same genes, with fraternal twins, who share the same number of genes as any other brother or sister. If the scientists find something more common between twins in identical twin pairs, then there may be a gene involved.
A twin study was done to try to figure out if genes might influence marriage and divorce. The researchers found that there was no difference between identical and fraternal twins when it came to deciding to get married. Deciding to get divorced was an entirely different matter.
If one twin in an identical twin pair got divorced, the other twin was much more likely to get divorced when compared to the situation with fraternal twins. In other words, genetics plays some role in divorce.
Of course, if genetics really has an influence on behavior, it shouldn't be surprising that there might be a genetic component to the likelihood of divorce. For example, if monogamy is determined to some extent by genes, then a higher divorce rate in these people would not be all that surprising.