A genetic argument has been made for why individuals should reproduce with people outside of their immediate family based on the idea that a more diverse gene pool leads to fewer genetic illnesses. I am wondering whether this same logic could be reasonably extended to support the genetic benefits of reproducing with individuals outside of one's race (at least at the macro level).
-A curious adult from Pennsylvania October 6, 2010 Great question! It does make sense that having kids with a different ethnic group would be a good idea genetically. After all, we know that having kids with a close relative can be downright dangerous! See, each of us has a few hidden genes that can cause deadly diseases. But this isn't usually a big deal because we always carry two copies of each gene: one from each parent. As long as one of the two gene copies is good, you don't usually get sick. So bad genes only cause problems if both parents pass it down to their kids. And this happens more often when parents are closely related. The more closely related two parents are, the more likely they are to share the same bad genes. In these cases, each child can have up to a 1 in 4 chance of getting the disease. For this reason, marrying close relatives (inbreeding) is forbidden in many countries. Good examples of the effects of inbreeding are the old royal families of Europe, like the Habsburgs. The Habsburgs ruled large parts of Europe for centuries. After many marriages between first cousins and even uncles and nieces, King Charles II was born. Because of all the "bad genes" he inherited, Charles had physical and mental disabilities and probably could not have children, ending the Habsburg rule. Since having a child with a close relative is risky, you might think that that having one with as distant a relative as possible is the least risky. And the least distant relatives are those of different ethnic groups. To some extent this is true. But as you get less and less related, the advantages become less and less. This is because there tends to be far more variation within an ethnic group than between them. The reason for this is that very few genetic differences distinguish different races but a whole bunch distinguishes height, intelligence, etc. So marrying outside your ethnic group won't have as many advantages as you might think. Now this isn't to say there are no advantages. There are for a few bad genes that happen to be more common in certain groups. For example, cystic fibrosis (CF) is much more common in Europeans than in other groups. So a child with European parents is more likely to end up with CF than is a child with an African and an Asian parent. Or even a European and an Asian parent.

Different skin colors:
President Obama posing with
Colombian singer Shakira and
her Argentine boyfriend Antonio.
Photo by Movimiento ALAS.
What this all means is that while there is probably some benefit to having kids outside of your ethnic group, it is probably pretty small. But there definitely can be advantages in some cases.For example, there are certain traits from different ethnic groups that can prove useful when mixed. A good example of such a trait is skin color, which is thought to have evolved differently between races. Places with strong sunlight are favorable for people with dark skin, as the dark color in their skin (melanin) protects them from sunburn and skin cancer. Light skin is an advantage in countries with little sunlight. This lets the sunlight get into the skin better to make Vitamin D. Now imagine that a light-skinned man from Northern Europe marries a dark-skinned woman from Africa, but they live in Mexico. The father would get burned by the sun all the time, while the mother might need to take vitamin D pills. Their children however, would have the perfect skin for Mexico's climate, as their skin color would be in between mom and dad. Of course this "advantage" is dependent on the family moving to a new environment (which is how natural selection and evolution work). And there are undoubtedly similar advantages I could come up with for people within the same ethnic groups. But if you and your family stay put, then the biggest advantage is probably a slightly decreased risk for genetic disease. What this all means is that there is a big benefit to having kids outside of your family. And while there is probably some benefit to having kids outside of your ethnic group, it is probably pretty small. Dr. Hinco Gierman

Inbreeding can cause severe
problems as evidenced by
Charles II, the last Habsburg king.