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Are You There, Race? It’s Me, DNA

Some people claim race is a biological reality, whereas others say it is a social construct. Looking at our DNA can help resolve this friction.

What would you say is Liam Neeson’s race?

I ask this question because in this era of the gene, of people swabbing their cheeks to know where their ancestors came from, and of racism glazed over with the shiny patina of science, many people feel confused about race. They have heard that it’s a social construct, but that can be hard to square with rumours that only Black people have sickle cell anemia. And if 23andMe can report on your ancestry, isn’t that proof that race exists at the biological level?

The concept of dividing humans into categories has been with us for a very long time. Greek philosopher Aristotle attempted to classify living things in a hierarchy. According to his thinking, some humans were born to be kings, whereas others were determined to be slaves. In the 1700s, Man was divided into a handful of races: Africans, Asians, Native Americans, and Caucasians (Pacific Islanders were thought of as a fifth race by some). It wasn’t just a horizontal classification, but a vertical one too. Thinking of Africans as biologically inferior to Caucasians certainly facilitated their treatment during the slave trade.

When participants to a focus group in 2004 were asked what exactly is a race, they ended up mirroring a debate that had been happening among scholars, because it’s not an easy concept to define. Physical appearance, especially skin colour, was often mentioned by the participants, but it wasn’t seen as sufficient. If we stop at skin colour, however—a common enough shortcut for anyone trying to categorize an individual by race—we quickly run into a problem:

Women of different races

 

 

 

Figure 1. Four women illustrating physical variation

(from Hubbard, 2017)

 

To what races do these women belong? It turns out they are all from the African continent. From left to right, we have a Namibian, an Egyptian, a Malian, and a Kenyan. If “African” is one race, why do all these women look so different?

A useful definition of a race is a group of people who are perceived as sharing biological features. Importantly, this perception varies by culture, because this is not, please excuse the pun, a black-and-white ruling. If skin colour is used to distinguish race, where is the cut-off? It’s not obvious, because skin colour is on a gradient.

But skin colour, hair colour, eye colour, and other physical traits are all under the control of genes, so doesn’t our DNA have something to do with race?

Our eyes tell us lies that DNA can pulverize

The DNA in our cells is littered with variants, little changes from one individual to the next that are responsible for many of our physical attributes and our predispositions to disease. It’s like we all have the same book, except that my edition has a few typos and local spelling differences that yours doesn’t and vice versa (e.g. “color” versus “colour”). When we add up all of these variants, that is what we mean by “genetic variability”, the number of DNA differences from one person to another.

So do you think there is more genetic variability between these two penguins… or between Taylor Swift and Kanye West?

A photo of a penguin, Taylor Swift and Kanye West
Figure 2. Genetic variation in humans versus penguins

(from Hubbard, 2017)


The answer is surprising. Even though our eyes tell us one thing, DNA analysis reveals the opposite. These penguins are more different at the DNA level than our two human superstars. It turns out that humans are less genetically diverse than many animals, including chimps.

In fact any two unrelated human beings on the planet are 99.9% identical in their DNA sequence. Only 0.1% varies, and here’s the most important takeaway message from all this. It also happens to be the most replicated finding in the scientific literature on human variation.

Of this 0.1% that varies, almost all of it (95.7% to be exact) is found between individuals within the same race. Despite what our eyes perceive, there is more genetic diversity within a race than between races

If you didn’t know that, don’t worry: you’re in good company. Three out of four college students taking an introductory course in biology and genetics also do not know this.

And since skull sizes are being discussed again in certain corners of the Internet, 90% of the variability in their volume also occurs within (and not between) human groups.

This is a big snag in the argument that race is a biological reality. This finding—that there’s more diversity within than between groups—is true for most physical traits, with one prominent exception: skin colour. Why? Because skin colour is under tremendous selective pressure. It varies depending on how far from the equator we are, because a darker skin offers better protection against sunburn, skin cancer and related damages. People with naturally darker skin were better adapted to their environment and were more likely to reproduce. The fact that a Maasai and an Aboriginal Australian both have very dark skin is not because they are part of the same biological race, but rather because both have lived under a very harsh sun for generations. So skin colour is not evidence of race being a biological reality.

But what about sickle cell anemia, I hear you ask. Isn’t that a disease that only affects Black people?

Race and medicine

The truth about sickle cell anemia is more complicated than that. The sickle cell trait is a variant in our DNA that offers protection against malaria. Over many generations, people who were exposed to malaria were more likely to reproduce if they had this trait, so this trait was selected for. When you have two copies of it, however, you can develop sickle cell anemia. So do only Black people carry the trait? No. While it is commonly seen in people of sub-Saharan African ancestry, it can also be found in Mediterraneans, Middle Easterners, and Indians. It is not restricted to one race but rather to many populations that were all exposed to malaria.

But there is another example where race seems to play a role in medicine: the drug BiDil, the first race-based prescription drug in the US which aims to treat heart failure. It was said to be a breakthrough for African Americans, but here’s the twist: the clinical trial that led to its approval only tested African Americans. How can you pretend your drug can only treat one race when you haven’t tested it in another?

One final argument for the existence of biological races is that African Americans have more health problems than White Americans: more likely to have high blood pressure, disproportionately affected by obesity, and at an increased risk for diabetes. But given that there is much more genetic diversity within African Americans than between them and White Americans, it’s unlikely that the answer simply lies in their DNA. As a parallel, single men are more likely to die of heart disease than their married counterparts, but genes don’t make us married or single. If Black was a biological race and if hypertension was only genetic, we would expect Black people all over the world to have the same risk for it, but they don’t. While hypertension is more prevalent among African Americans than in White Americans, the rate in sub-Saharan Africans is lower than either!

Racial health disparities within countries are often due to the physical tax of discrimination, poverty, an increased risk of living near hazardous waste facilities, lack of access to healthcare, and differences in behaviour. And this is important: race is not imaginary simply because it’s not biological. Our perception of it has real consequences on the health of others because of how differently we treat them. As a study from the early 1990s demonstrates, infant mortality is twice as high in African Americans than in their white counterparts… unless you look at members of these groups who are enrolled in the military and receive care at the same army medical centre. For them, infant mortality rates are more or less the same.

Some doctors still use race as a useful proxy, but this assumption carries with it the risk of withholding effective treatment for some and of using ineffective treatment in others. Socioeconomic factors, culture, behaviour, and where a patient’s ancestors came from are more informative. As Francis Collins, the director of the consortium behind the Human Genome Project, once said, “race is a flawed surrogate.”

Race is relative

So what would you say is Liam Neeson’s race? You probably said “white”, but a hundred years ago, the answer would have been “Irish”. In the eyes of North Americans back then, the Irish were a separate race. Racial categories change over time.

Pakistanis and Indians are thought of as belonging to the Asian race (an idea perhaps more common in Britain than in North America), but at the level of their DNA, they are more similar to Europeans than they are to East Asians. Racial categories are not reflective of the underlying biological reality.

Race is a real concept that we use as social beings. As for whether race can be found in our genes, the answer is no. Biological ancestry, however (which is distinct from race), is real. Where our forebears came from can be seen in our DNA (to a certain degree), but ancestry does not map onto race, not even close. We may intuitively think of Europeans, Africans, and East Asians as three circles that barely overlap, like the Olympic rings. Time and time again, however, genetic studies reveal the opposite. They are rings all right, but they almost completely overlap.

We are a lot more similar than we think, and the ways in which we differ have little to do with our ideas of race.

Take-home message:
- There is more variation within a race than between races at the level of our DNA.
- How we define races has varied throughout history and differs from one culture to another
- Studying our DNA reveals that races are not real in a biological sense, but how we treat other races does have an impact on their health because of poverty, stress, and lack of access to healthcare.

Photo credits

Figure 1: Composite from Hubbard (2017) The American Biology Teacher. Individual photo credits from left to right: Nicolas M. Perrault (CC0 1.0 Universal); David Dennis (CC BY-SA 2.0); Ferdinand Reus (CC BY-SA 3.0); Amelia Hubbard.

Figure 2: Composite from Hubbard (2017) The American Biology Teacher. Individual photo credits from left to right: PMATAS (CC BY-SA 4.0); Marcin Wichary (CC by 2.0); David Shankbone (CC by 3.0).


@CrackedScience

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