Inbreeding is supposed to be a bad thing. That’s why researchers were startled to discover the extent of inbreeding evident among residents of the orderly and not-exactly-lascivious Island nation of Iceland.
According to longevity specialist Dr. Nir Barzilai, iceland is one of the most genetically homogeneous countries in the world, “There are a half million Icelandic people in Iceland and they are all offspring of 5 Vikings and 4 Irish women or something like that, so all half a million of them are coming from the same fathers and mothers.”
With the world’s longest male lifespan (79.4 years beating second-ranked Japan’s 79.0), and 11th longest female lifespan, Iceland is clearly doing something right.
Further research showed an even bigger surprise: Inbreeding may have a survival advantage. Marriages between third and fourth cousins in the early 19th and 20th centuries (when adequate records were first kept) actually produced more children and grandchildren than marriages between totally unrelated men and women.
For women born between 1800 and 1824, marriages between third cousins produced an average of 4.04 children and 9.17 grandchildren, while marriages between eighth cousins or more distantly related couples had averages of only 3.34 children and 7.31 grandchildren.
“These are counterintuitive, almost dislikable results,” said Dr. Kari Stefansson, senior author of the paper on the study, published in Feb 2008 in the journal Science.
Dislikable and counterintitive because standard genetics teaches us that children of related couples should have a higher risk of genetic disease. Researchers believe the trend toward a more prodigious relationship with a not-so-distant relative must have some kind of biological basis, though they confess cluelessness as to what biological mechanism could possibly be behind this.
In my mind, the crux of the matter is this: Does this survival advantage stem directly from the genetic consequences of inbreeding, or could marrying your 4th cousin be genetically advantageous for an entirely different reason?
I believe the answers lie in epigenetics, which tells us that genetic changes are not random.
Most longevity scientists still assume survival has to do with avoidance of diseased genes. Epigenetics tells us that survival depends more on the interaction between genes and the environment. This new information turns the whole equation around.
It also helps to explain why inbreeding is so common not just in Iceland, but among primary human cultures as well as animal societies.
The explanation for the increased survival among more closely related individuals may be cultural. Those families who are close-knit enough for third and fourth degree cousins to meet and marry are probably also families that pay more attention to tradition, and that includes traditional foods.
Traditional foods provide our DNA with the information it expects. And only when your DNA gets what it wants can you expect to be all you can be.
Typical and traditional Icelandic foods include:
Notice the lack of vegetables, not terrifically surprising for a nation with a growing season averaging 40 days.