Xenophobia Will Actually Impede Human Evolution

I relish the ability to relate biology to other fields in these posts, but it’s not often that I find meaningful and relevant reasons to do so. Today is different. Having done some interesting reading this past weekend, I’ve come to realize that, politics aside, xenophobia is fundamentally bad because it actually creates evolutionary disadvantages, which will hurt our descendants down the road.

To start, we should get some biology vocabulary squared away. Evolution refers to change in the genetic makeup of biological populations over time; its main mechanism is natural selection, the process by which traits that increase survivability in a given environment spread throughout the population. Natural selection results in adaptations: structural, physiological, and behavioral traits that enhance an organism’s chances of survival and reproduction in its environment.

A map of the flow of human genes over time from National Geographic

So, how does xenophobia tie into evolution at all? Through eugenics, a pseudoscience that purportedly aims at improving the genetic quality of the human population. During the Progressive Era in US history, eugenics was considered a method of preserving and improving the dominant groups in the population. Historically, immigration bans have been used as a means of enforcing eugenics. The Immigration Restriction League, founded by 3 Harvard grads in 1894, sought to bar “inferior races” to prevent dilution of what they saw as superior American stock. Eugenic considerations helped justify anti-miscegenation laws, strengthened existing laws against race-mixing, and boosted forced sterilization efforts.

This sort of artificial selection for “desirable” traits can, from a biological standpoint, create persistent problems. Consider, for example, the English bulldog. Harry Pettit of New Scientist notes that these dogs have “difficulty breathing, moving and mating. These traits are a result of how we have selectively bred the dogs to promote characteristics like its shortened muzzle and stature. Decades of heavy inbreeding have caused further problems, including autoimmune diseases and allergies.” English bulldogs as a breed have incredibly low genetic diversity, which means that it would be incredibly difficult to reverse their inborn problems.

The ills we perpetrated on the English bulldog can also befall human beings. European royal families have proven a prime example of this. Through the marriage of close relatives, these families have passed on genetic diseases such as hemophilia, porphyria, and Crohn’s disease, which might have been prevented through other marital arrangements. When parents are closely related, the chances of passing on genetic diseases carried on recessive alleles increases. Conversely, when both parents are distantly related (i.e. from different human populations), we see the opposite. Therefore, genetic mixing will cause some genetic disorders to become less and less common.

A photograph by Martin Schoeller for National Geographic’s “The Changing Face of America

As Scott Solomon of Aeon puts it:

We are a restless species … Today, 244 million people in 2015 [were] living in a country other than the one in which they were born. The biological implications of this massive experiment in interbreeding we are now witnessing will not be known for generations. But applying what we know about genetics and evolution can help us predict our future, including whether humans will be able to continue adapting to the constantly changing conditions on Earth.

Biological adaptation is a result of natural selection, and natural selection requires diversity. Think of natural selection like a sieve separating one generation from the next. Only the genes from those individuals that are well suited to their environment at that time will reproduce, passing their genes through the sieve to the next generation. Changing conditions alter the shape of the sieve’s holes and thereby which genes can pass through. The more variation there is in the population, the better the chances that some genes present in a generation will be able to pass through the sieve and be inherited by future generations. Unfortunately for us, humans are not very diverse…

As environmental conditions change, species have only two options: adapt or become extinct. In our rapidly changing world, we should weigh our options. We can’t stop evolution entirely, but we can limit our adaptation by keeping ourselves isolated (as per the eugenics advocates). Or we we can cast off xenophobia, increase genetic exchange, and bolster our collective ability to withstand the challenges ahead.

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