Science Matters

Is race a real thing?

Boyce Rensberger

(2/2023) You’re not a racist. You know that deep down inside, all people are pretty much the same, no matter the color of their skin or the shape of their eyelids. But you are curious about differences among the groups that we call races.

Why do most people from Europe have pale skin? Why is the hair of most Africans tightly curled? Why do most Africans and most Europeans — and their descendants in this country — have eyelids shaped alike but so different from an Asian’s eyes?

Do these variations reflect deeper, more fundamental differences between people usually call races? Scientists have long asked the same questions and, after centuries of probing and failed attempts to set up a workable classification system, today’s researchers generally agree on three conclusions:

• There are many more differences than the ones we usually think about. Most of those other differences are more than skin deep.
   
• Many of these differences have been good for the human species. They have opened the doors to evolutionary change that allowed us to occupy most of the globe.
   
• The third conclusion, and probably the hardest to grasp is this: There is no biological basis for race. We all use the word as if it meant something obvious. We sometimes imagine that Blacks, Whites and Asians belong to different groups that developed long ago. We continue to use "race" to refer simplistically to cultural or social groups. And that’s fine, but according to nearly all anthropologists today, any presumed biological basis for "race" is a presumption invented to fit a misunderstanding about how human beings evolved.

Centuries ago, European scientists argued that races were natural divisions of the human species imposed by a supernatural creator or by natural selection. Some even argued that races represented a series of evolutionary stages, some "more advanced" than others. The thinkers of old knew of very few differences among peoples and did not understand how evolution works. In fact, the concept of race was developed long before 1859, when Charles Darwin published his discoveries about how evolution works.

In 1735, Carl von Linne, the Swedish naturalist better known as Linnaeus, said there were four races. Over the years, dozens of other classifications have been proposed, some arguing that there are as many as 31 or even 37 races. In other words, scientists could never agree on how to define a race.

Today’s researchers know of many differences under the skin that do not correspond to racial categories used in popular culture. Even today, the more that researchers study people worldwide, the more they realize that if they take into account all the hidden differences, there is no correspondence to what we commonly call race.

If you consider each feature by itself, you see that a person of one socially defined race can be more like a person of another "race" than that person is like someone of their own race. Take blood for example. African Blacks may have any of four major blood types: A, B, O and AB. The same is true of European Whites and of Asian peoples. If you’re a type O, your blood is more closely related to that of any other type O person — regardless of race — than it is to a type B or type A of your own race.

If you need a blood transfusion, you want a donor of the same blood type, not the same skin color. That’s also true of organ transplants. Your closest genetic match for a donated kidney, for example, could easily be somebody of another "race."

Still, many of us think skin color is a major factor in pigeonholing people. It is true that most Africans and their descendants have skin that is darker than that of most Europeans and their descendants. But millions of people in India, once classified as members of the "Caucasoid," or "White," race, have darker skin than most Americans who call themselves Black. Does their black skin mean they should be grouped with black Africans? Or does their straight hair mean they should be grouped with Europeans? Also, some supposedly "Negroid" people living in Africa today (such as the !Kung San, once called Bushmen) have skin no darker than that of many Italians and Greeks. And there are people in New Guinea who are as black and woolly haired as any African but have no known ancestral links to Africa. And what about the so-called Australian "aborigines," who have very dark skin and straight, sometimes blond hair?

Here’s yet another angle to think about. If you want to classify all black Africans in one group, how do you deal with the fact that within Africa live several kinds of people with much more dramatic differences than skin color? There are the world’s smallest people, the Mbuti pygmies of Zaire, who average 4 feet 7 inches and whose size is like that of a group in the Philippines called the Negritos. And there are the world’s tallest, the Tutsi of neighboring Rwanda, who average 6-feet-1—close to the average for the very pale-skinned Scandinavian peoples.

And there are deeper differences among Africans. One, for example, explains why East Africans dominate marathon running while West Africans dominate sprints. The two populations have actual differences in muscle physiology, even different ratios of what are called "fast twitch" and "slow twitch" muscle cells. East African muscles are more like those of Scandinavians, who excel at distance events such as cross-country skiing. There are other differences as well.

Genome sequencing among sub-Saharan Africans has revealed a startling fact. There are more genetic differences between any two groups of Africans than there are between Europeans and Asians or between Europeans and any group of Africans. If we want to impose racial categories on Africans, we would have to say there are several different races of black Africans.

All these findings have led most anthropologists to conclude that it makes no sense to think that races are biological categories. The overwhelming conclusion of researchers, in short, is that no single physical feature distinguishes any race. You can classify traits but not people. People are bundles of differing combinations of traits.

Biologists say most of these differences arose as a result of natural selection. This is the phenomenon that Darwin discovered in the 19th century, and it explains a lot about how evolution happens. In a nutshell, it means that if a mutation — a change in a person’s genes — happens to produce a useful feature, the person with that change is more likely to be healthier, live longer and, most important for evolution, have more children. Since the change is in the genes, the children inherit it. Because the change gives each person an advantage in survival, eventually those with the change will outnumber those without it.

Skin color is a good example. People whose ancestors came from the tropics have dark skin. And the farther people lived from the equator, the lighter their skin. Southern Europeans are usually darker than northern Europeans. In Africa, the darkest skins are near the equator, but at the north and south ends of the continent, people’s skins are lighter. In southern India, closer to the equator, many people are as dark as the blackest Africans, while northern Indians are about as light-skinned as southern Europeans.

Whatever the skin color, it is all due to different amounts of a brown substance in skin cells called melanin. Freckles have extra melanin. Sun tanning stimulates melanin synthesis in skin.

That north-south spectrum evolved in response to the sun’s intensity. Too much sun causes sunburn and skin cancer. Too little deprives the body of vitamin D. Without this vitamin, bones grow crooked, resulting in a disease called rickets. In the tropics, the sun is so strong that enough gets through dark skin to make all the vitamin D a person needs.

When dark-skinned people first migrated out of Africa and into northern climates, they may well have suffered rickets, which can also deform the pelvis, making childbirth dangerous or impossible. But because skin color can vary slightly even within a family, lighter-skinned children would be less affected. As a result, they would probably have more surviving children than their darker relatives. And those children would be even more likely to have to have lighter-skinned children of their own.

This is Darwin’s natural selection at work. Less well-known is another of Darwin’s ideas—sexual selection. In a nutshell, it means that if some physical trait is seen as attractive by the opposite sex, individuals with it will be more likely to find mates and to reproduce. In crude terms, ugly people will be less likely to find mates and pass on their genes than will beautiful people. And, of course, the definition of beauty varies from culture to culture.

Most visible differences among people have no practical advantage. For example, nobody knows why Asian people have a special form of upper eyelid. The thin lips of northern Europeans and many Asians have no known advantage over the full lips of many Africans and Middle Eastern peoples. Why do white men go bald so much more often than the men of other backgrounds? Such differences are trivial in a biological sense. In fact, geneticists have estimated that the variations in genetic makeup that account for racial differences occupy only about one out of a thousand of our genes.

So, were there ever pure races? Until the mid-20th century, many researchers assumed that so-called pure races did once exist. Those early thinkers had great trouble figuring out who belonged in which race and decided that was simply because migrations and intermarriage had mixed up, or blended, the once-distinct traits.

Today, most anthropologists hold that pure races never existed, not in any biological sense. They think that human beings have always been migrating and intermarrying, spreading new genes worldwide. Traits such as skin color have always shaded gradually from region to region. Genes useful in all parts of the world would spread quickly — those, for example, that might improve the immune system. Surely the fastest to spread in prehistoric times were the genes that improved the brain. In fact, anthropologists who study fossil skulls of the earliest human beings agree that a fully modern brain evolved long before any of today’s so-called races came into existence.

Genes useful only in some regions would tend not to become common when carried to other places. Dark skin, for example, is not an advantage in cold climates. Light skin is a disadvantage in tropical climates. So skin color genes could not flow far and persist, at least not until the age of large hats, long sleeves, and milk fortified with vitamin D.

The bottom line is that biology does not support the idea of races as natural categories, not now nor in the past. There is no one trait, or group of traits, that can be used to define any race. People have tried to do this using visible features such as skin color and facial form but have ignored all the unseen genetic variability. We all use "race" for social or cultural groups—and that’s fine--but those categories all have blurry edges.

The great lesson from anthropology, biology and genetics is that all people are the same in all essentials but highly diverse in a few things. The same is true of nearly all other known species. These differences have arisen not because there are biologically distinct groups of people but simply because genes sometimes change from one generation to the next, and because we are a hopeful, migratory species whose intelligence has allowed us to survive in almost every environment on Earth.

Boyce Rensberger retired to New Midway after more than 40 years as a science writer and editor, mostly for The New York Times and The Washington Post. Write him at boycerensberger@gmail.com.