In the United States’ Declaration of Independence, it states that “all men are created equal.” This may be true in the way that we deal with one another, but unfortunately, health and physiology would beg to differ. Our health and the way that our bodies work is significantly influenced by our genetics, and sometimes those genetics make some groups more susceptible to specific diseases than others. Many of these diseases are diseases which are based entirely in genetics, and others are influenced by the genetics.
Some genetic diseases have become more prevalent in an ethnicity through something called heterozygote advantage. To give a quick run-down on Mendelian genetics: each person has two copies of a gene-one from their mother and one from their father. A simple gene will come in one of two flavors: either recessive or dominant. Dominant traits will always be the one that shows itself, unless both copies are recessive, in which case, the recessive trait can express itself. So, someone could express a dominant trait, but also possess a silent, recessive version. Most genetic diseases are recessive. This may seem odd at first, but consider that in the times when these diseases couldn’t be cured, you would need to live to reproductive age. That is much less likely to happen if the disease would kill you young, and couldn’t be dormant. But even though Gregor Mendel’s pea plant experiments showed that having a dominant and a recessive is the same as having two dominants, we now see that to not be true. Some diseases actually convey some survival advantage, so long as there’s a dominant version to keep it from killing the person. As such, people who are heterozygous for the trait—that is, possessing both a dominant and a recessive copy—are more likely to survive.
The most classical example of a heterozygote advantage is sickle cell anemia. When both copies are recessive, sickle cell anemia results in red blood cells that are shaped like sickles, instead of disks. As such, these deformed red blood cells cannot carry the oxygen they are supposed to, as well as being more prone to getting stuck inside capillaries than other blood cells. This disease is purely genetic—you have it at birth or you don’t, and there’s no way to get rid of it. However, not every child is equally as likely to get the disease. In fact, those of African descent are almost 175 times more likely to carry the trait than those of European descent. It shouldn’t come as much of a surprise that the first explanations were racially charged. However, eventually, these explanations died away, and more in depth epidemiology came to be the focus. In fact, this disease isn’t just common in Africans. The Caribbean, the Mediterranean, India and the Arabian Peninsula also show elevated levels of this trait. Eventually, the key was found in malaria. It appears that being heterozygous for the trait increases your likelihood of living through malaria—the protozoa can’t attach to the red blood cells as well with the sickle cell trait. So, in places were malaria is prevalent, so is the sickle cell trait. You have an evolutionary edge over the next guy—so long as you don’t get killed by sickle cell anemia, but get its benefits, you win out.
But sickle cell isn’t the only example of this. Cystic Fibrosis is a disease which is most common in those from Scandinavia and the Celtic Islands; those from mainland Western Europe show elevated levels when compared to Africans and Asians. It turns out the Cystic Fibrosis affects the sodium-ion channels that regulate the salt-water ratio in the cells. Conveniently, or not so conveniently, cholera attacks those channels, forcing water to flood out of the cells and into the intestines, resulting in the characteristic dehydrating diarrhea by which cholera kills. If the channel doesn’t work, then neither will cholera. Once again, if the channel is so broken that it never works, you won’t really need to be resistant to cholera—survival is mostly impossible without medical assistance. However, if you are resistant to cholera, but don’t have Cystic Fibrosis, you’re going to outlive your neighbor.
Other genetic diseases have become prevalent through genetic bottlenecks. This is especially common in small ethnicities that are averse to marrying outside their kind. A bottleneck occurs when a small genetic population is inbred such that “bad genes” which usually would be diluted to not being a problem are forced to be reproduced—the usual statistics do not apply anymore. Such is the curse that has befallen the Ashkenazi Jews—a race of Jews in Eastern Europe and Germany. Because these poor people haven’t suffered enough, they get to have a higher prevalence towards many autosomal diseases such as Tay-Sachs Disease (a disease which kills by about the age of 6), Gaucher Disease (a blood disease), Usher’s Disease (degenerative deafness and blindness), and Type C hemophilia (a version of the disease that is not linked to gender). Several diseases that are thought to be at least partially influenced by genetics are also more common in Ashkenazi Jews, such as Parkinson’s Disease, breast and ovarian cancers, and congenital deafness. This idea is the same logic behind explaining many of the diseases common to European royals.
There are, of course, those diseases which are influenced by both genetics and environment, but the genetics of some groups prove to be especially influential. Native Americans are ripe with many of these conditions. Stereotypes tell us that Native Americans fall hard to alcohol—but is it true? Well, researchers at the University of Indiana suggest that Native Americans are more likely to lack protective genes against alcoholism, public health surveys by California State University suggest that Native Americans crave ever increasing amounts of alcohol more often when compared to other races, and the CDC and Indian Health Services report that 1 in 10 Native American deaths is alcohol related. It is hard to explain these facts without some appeal to genetics. Other similar conditions are diabetes (more common in African Americans, Hispanics, Native Americans, Native Hawaiians and Pacific Islanders), and breast cancer (extremely uncommon in Native American, but more common in Caucasians).
Finally, there are diseases which seem to be more common in some groups when compared to others for no logical reason. Pernicious anemia, an inability to process iron efficiently, is one of these, which is significantly more common in those of Celtic descent. Others of these diseases include PKU (absolute intolerance to protein common in Scandinavians and Celts) and heart disease (inexplicably common in Pacific Islanders).
So, family history matters when it comes to your health. Sometimes it doesn’t seem quite fair—like the Native Americans and Ashkenazi Jews needed more problems that aren’t their fault. But, sometimes nature decides that being fair isn’t on the radar.