Everyone can tell a Nubian from a Norwegian, so why not divide people into different races? That's the question explored in "The Difference Between Us," the first hour of the series. This episode shows that despite what we've always believed, the world's peoples simply don't come bundled into distinct biological groups. We begin by following a dozen students, including Black athletes and Asian string players, who sequence and compare their own DNA to see who is more genetically similar. The results surprise the students and the viewer, when they discover their closest genetic matches are as likely to be with people from other "races" as their own.

Much of the program is devoted to understanding why. We look at several scientific discoveries that illustrate why humans cannot be subdivided into races and how there isn't a single characteristic, trait - or even one gene - that can be used to distinguish all members of one race from all members of another. 

HUMAN VARIATION

Modern humans - all of us - emerged in Africa about 150,000 to 200,000 years ago. Bands of humans began migrating out of Africa only about 70,000 years ago. As we spread across the globe, populations continually bumped into one another and mixed their mates and genes. As a species, we're simply too young and too intermixed to have evolved into separate races or subspecies.

So what about the obvious physical differences we see between people? A closer look helps us understand patterns of human variation:
In a virtual "walk" from the equator to northern Europe, we see that visual characteristics vary gradually and continuously from one population to the next. There are no boundaries, so how can we draw a line between where one race ends and another begins?
We also learn that most traits - whether skin color, hair texture or blood group - are influenced by separate genes and thus inherited independently one from the other. Having one trait does not necessarily imply the existence of others. Racial profiling is as inaccurate on the genetic level as it is on the New Jersey Turnpike.
We also learn that many of our visual characteristics, like different skin colors, appear to have evolved recently, after we left Africa, but the traits we care about - intelligence, musical ability, physical aptitude - are much older, and thus common to all populations. Geneticists have discovered that 85% of all genetic variants can be found within any local population, regardless of whether they're Poles, Hmong or Fulani. Skin color really is only skin deep. Beneath the skin, we are one of the most similar of all species.
Certainly a few gene forms are more common in some populations than others, such as those controlling skin color and inherited diseases like Tay Sachs and sickle cell. But are these markers of "race?" They reflect ancestry, but as our DNA experiment shows us, that's not the same thing as race. The mutation that causes sickle cell, we learn, was passed on because it conferred resistance to malaria. It is found among people whose ancestors came from parts of the world where malaria was common: central and western Africa, Turkey, India, Greece, Sicily and even Portugal - but not southern Africa.

CONFRONTING OUR MYTHS ABOUT RACE

We have a long history of searching for innate differences to explain disparities in group outcomes - not just for inherited diseases, but also SAT scores and athletic performance. In contrast to today's myth of innate Black athletic superiority, a hundred years ago many whites felt that Black people were inherently sickly and destined to die out. That's because disease and mortality rates were high among African Americans - the cause was poverty, poor sanitation, and Jim Crow segregation, but it was easier for most people to believe it was a result of "natural" infirmity, a view popularized by influential statistician Frederick Hoffman in his 1896 study, Race Traits and Tendencies of the American Negro.

Racial beliefs have always been tied to social ideas and policy. After all, if differences between groups are natural, then nothing can or should be done to correct for unequal outcomes. Scientific literature of the late 19th and early 20th century explicitly championed such a view, and many prominent scientists devoted countless hours to documenting racial differences and promoting man's natural hierarchy.

Although today such ideas are outmoded, it is still popular to believe in innate racial traits rather than look elsewhere to explain group differences. We all know the myths and stereotypes - natural Black athletic superiority, musical ability among Asians - but are they really true on a biological level? If not, why do we continue to believe them? Race may not be biological, but it is still a powerful social idea with real consequences for people's lives.