The recent spate of white supremacy marches has rekindled many questions as to why such groups and ideologies still exist.

These questions become all the more troubling when you consider how science has proved that humans are biologically the same.

“Broadly thinking about what part of the world people’s ancestors might have come from is fine, but to take it to the next step and say that somehow different races are different types of humans is incorrect,” William R. Leonard, PhD, biological anthropologist and professor of anthropology at Northwestern University, told Healthline.

Anthropology and human evolutionary biology prove that not only are all humans of the same type, species, and kind, we are also a species that, in the history of evolution, has recently evolved.

“In reality then, all the variation of traits we see, in some respect, is literally skin deep. What appears to be huge amounts of variation is masking a low level of genetic diversity,” said Leonard.

The fact that there is so little genetic diversity among humans has been known for a while, but not widely understood, noted Leonard. In fact, in 1950, the United Nations Educational, Scientific and Cultural Organization (UNESCO) issued a statement that all humans belong to the same species, and that “race” is not a biological reality, but a myth.

“Races are an artifact of the human mind’s need to put things into boxes. That’s the way we break up and describe the world,” Leonard said. “This is the paradox of the human experience. Relative to other species, we are genetically all very similar. However, in contrast, in terms of our phenotype, meaning how we look externally — height, weight, hair color, eye color — we are a very diverse species.”

Until recently, these external differences were thought to prove that people’s underlying genetics and ancestry are also very different. “Hence, that’s the origin of the race concept,” said Leonard. “A lot of what we see in the early 20th century discussions about human diversity is not only talking about distinct races, but the social implications of those distinct races — claiming these distinctions were justification for hierarchical ranking of different races.”

‘Clines’ over race

Rather than race, anthropologists say a more accurate way to distinguish differences in populations of people are clines. A cline is a gradation in one or more characteristics within a species, especially between different populations. The concept of clines helps to explain that races as biological categories are not valid.

Leonard suggests thinking of clines as the biological equivalent of the temperature (thermal) gradient on a daily weather map. When you look at a weather map, you see temperature variation across a broad geographic landscape. For instance, rather than distinctly different temperatures and different locations, the map shows a continuous gradient over a geographic space.

How does this carry over to human traits? Anthropologists have taken characteristics, such as height, weight, skin color, hair form, eye color, etc., from across the world, and mapped them on a geographic space.

“What we tend to find with most of these features is that the variation is continuous rather than categorical. That becomes a much better, and more productive way, to describe human variation than races,” explained Leonard.

In 1972, evolutionary biologist Richard Lewontin conducted a study that examined worldwide variation in human blood groups that was used as proxies for genetic diversity before DNA analysis came along. Lewontin divided variation into three components: within populations; between populations; and between races. His purpose was to see which levels of explanation were best at describing the variation. He found that racial categories explained only about 6 percent of human variation. These findings have now been replicated using analyses of human DNA variation.

“His work showed that not only is race not the top explanatory area, it was the least explanatory by a long shot. If races are biologically meaningful, then in theory we should be able to list out biological traits that distinguish a person in racial group A, from a person in racial group B,” said Leonard. “Science shows this isn’t the case. There is no listing out of genes or physical features that is with any degree of confidence going to allow you to identify people with a high degree of certainty because variation in humans is not organized into discrete boxes. It’s continuous.”

Still, racism exists

Despite the fact that there are not enough genetic and biological differences among humans to uphold the idea of distinct “races,” the concept of race still exists socially and culturally, Mitch Berbrier, PhD, dean of the College of Arts, Humanities, & Social Sciences and professor of sociology at the University of Alabama in Huntsville, told Healthline.

When races are believed to exist, racism has a place to brew.

“Racism is more likely to happen at those times and in those places where people most strongly believe that there are different races, and assign social importance to those differences,” Berbrier said. “Conversely, racism is less likely to take hold where people assign less significance to differences.”

Racism is often brought to the surface when there is competition over scarce resources among two or more alleged races. The resources can be economic, political, or cultural.

Plus, there are many parts of the world that do not believe in pure races.

“More likely, the belief in what constitutes physiologically distinct races varies widely. To take one example, the racialized distinction of Hutus and Tutsis in Rwanda in the early 1990’s led to a genocide. But to most Americans of any “race,” both Hutus and Tutsis are simply black people,” said Berbrier.

On the other end, many in the United States tend to perceive that anyone with some African roots is black. For instance, President Barack Obama is seen by most people, and identifies himself, as African-American even though his mother was a white. “This is often very weird to outsiders,” said Berbrier. “It is also an opportunity to point out that due to miscegenation, many ‘blacks’ or ‘whites’ do not have purely African nor European genetic roots.”

So is the case for well-known white supremacist Craig Cobb, who appeared on television to have his DNA testing results revealed. His ancestry turned out to be only 86 percent European, and 14 percent sub-Saharan African.

The fact that people have different ancestral backgrounds than they thought is not surprising to Leonard.

“The history of our species is mixing. Even though we often think marriage and lineages are maintained in groupings of populations, that’s not the case at all throughout the history of our country, and it’s certainly not for our species at large,” said Leonard.

He pointed to conclusive evidence that Neanderthal DNA exists in many of the human species.

“Even in our evolutionary past, our earliest modern human ancestors in Europe and parts of Asia were exchanging genes with related human populations that existed at the same time. Mixing of genes and gene flow and spread of genes and population expansion is something that is literally as old as human history itself,” Leonard stated.