Do Human Races Exist?


Uploaded by C0nc0rdance on 15.09.2011

Transcript:
I have good news and bad news. The good news is that I've just discovered that you (yes,
you, watching this video) are related to Bill Gates. The bad news is that you probably aren't
in the will.
How can I be so sure that you're related to Bill Gates? Because you're related to everyone
alive today. We are all cousins.
I want to explain using clear language and scientific data why the concept of race is
largely irrelevant. I've never been one for political correctness, and I won't gloss over
the ugly truths. I'm going to just address the biology of what some people call race,
and what scientists call lineage or population or haplogroup or ethnicity, depending on the
context. Here are a couple of facts:
Fact 1. You have a lot of ancestors.
I hope I'm not spoiling the surprise for anyone, but it takes a mommy and a daddy to make a
baby. That means that, unless you are a clone, you have two people who donated genetic material
to make you. Each of those people had, likewise, two parents. So you had or have two parents
and four grandparents. Then eight great-grandparents and 16 great-greats in your direct line. We
could keep doubling the number of ancestors in every generation. Assuming that each generation
is about 20 years, if we go back about 500 years, about the time of Columbus's voyage,
you'd have 1 million ancestors. In fact, that's quite a bit inflated, simply because some
of your ancestors were related to each other. I'm not accusing you of being an inbred hillbilly,
although there are some out there with family trees that don't fork much. What I'm saying
is that one of your great times 6 grandfather on your father's side was the brother of one
of your great times 6 on your mother's side, or something similar. I'll refer you to a
great intro to the topic, The Ancestor's Tale, by Richard Dawkins.
Nevertheless, you are related to an awful lot of people in the direct line of ancestry.
When you then add in all the siblings and cousins and so forth, statistically you're
distantly related to any figure in history who left behind any kind of family. This leads
me to
Fact 2:You're related to everyone alive today.
An Inuit in Canada and an Australian Aborigine are distant cousins to each other, and to
you, whoever you are. The evidence suggests that if we go back somewhere between 2,000
and 5,000 years ago, we find a couple to which we all trace ancestry. That's during the time
of the Roman Empire.
Let me let that sink in a bit. Every human on Earth shares an ancestor that lived in
recorded history, probably between 100 and 200 generations ago. That's the blink of an
eye in genetic lineages. Bacteria have that many generations on your dishes in the sink
before you wash them.
Think about what it means to be a white person. You had millions of ancestors. How many of
them were European? How many were Asian? How many were African? Was it 100% in any of those
categories? Probably not, which leads me to...
Fact 3: We are all Africans.
I don't think we know where our most recent universal common ancestor was, but we know
that for thousands of years, all our ancestors lived in Africa, much longer than the time
since they colonized outside of Africa. We can all lay claim to African ancestors, if
we go back far enough. Africa also contains the most genetic diversity, which is consistent
with our long history as a species there. What most of us think of as African people
are mostly people who had ancestors of the Bantu tribe, which developed a very successful
livestock culture and conquered, colonized or displaced other tribes. The Khoi San, the
Pygmy, and some other tribal ancestries are still noticeable in modern Africans.
Which leads me to...
Fact 4: Skin color is a very poor predictor of ancestry.
It is sometimes beneficial for scientists to distinguish populations because their shared
recent ancestry means a shared genetic risk factor. For example, Ashkenazi Jews are much
more likely to possess the genetic variation for Tay-Sachs, cystic fibrosis, and many other
genetic diseases. Certain Native American tribes have rates of Type 2 diabetes that
approach 100% in some areas. We can't ignore these useful genetic identities.
Unfortunately, most people have no idea what their actual recent ancestry is. Someone who
self-identifies as African-American or Black may actually have multiple great-grandparents
who were not Black. There are certain markers, usually called lineage specific markers, that
distinguish European, East African and Asian ancestries. Most people are a mutt-blend of
these markers, regardless of what ethnicity they actually identify with.
People always assume that the color of one's skin is an easy indicator of the color of
all the parents and grandparents, but skin color is just a phenotype, determined by a
few different loci. Which leads me to...
Fact 5: Genes don't necessarily fall on race lines.
When your two genetic parents got together, their chromosomes lined up next to each other,
and a whole lot of swapping between them happened. This is called recombination, and it's why
you aren't a perfect genetic copy of either parent.
What it means for race is that skin color is not necessarily co-inherited with any other
genetically determined character. You can be white and have great rythym. You can be
black and not have any athletic talent. You can be Asian and very bad at math. Stereotypes
exist because of confirmation bias and social environment, not biology. Even things like
the epicanthal fold that most of us associate with Asians is a pretty simple genetic trait,
unrelated to height or athletic ability. Yao Ming, for example, is a very tall Asian. His
being tall or good at basketball is probably at least partly genetic, but those genes aren't
denied to him because he has the genes for Asian eye folds.
Which leads me to...
Fact 6: Your DNA is not your identity
What makes you interesting or unique goes way beyond what genetic variations you have.
I don't need to pre-judge you because your ancestor was of the Bantu tribe. We are not
limited by our genes for most things. That doesn't mean we should ignore the useful information
we can gain about things that ARE determined by genes: disease risks, tolerances or resistances
to sun or alcohol or breast cancer. In these cases race is just a very poor approximation
of your likely genetics based on who your great-great grandfather was related to. If
you go to a doctor and complain of anemia, long-term bone and chest pain and fatigue,
the doctor will assess your risk of sickle cell anemia based on your self-reported ancestry.
If you're black, it's worth checking that first. If not, there are other conditions
that are more likely.
Which leads me to...
Fact 7: Ethnicity or race is a societal construct
Someone like Tiger Woods is often described as black, in spite of a very recent mixture
of ancestries. Examples like him show how arbitrary the divisions are between supposed
races. Tiger's likely genetic makeup would probably put him in intermediate risk categories
for Asians, African and Europeans, but society gets to decide what label to stick him with.
It doesn't tell me anything about his ancestry to call him Black, or Asian, or White.
There are some genetic markers that are close enough together on the chromosome that when
mommy and daddy's chromosomes line up, they usually end up together. That means they travel
together. We call these grouped markers haplotypes, and geneticists sometimes assign people to
haplogroups, which is the closest thing in science to a race identifier. They represent
markers for recent ancestry, so we can distinguish what population a person's ancestors belonged
to, genetically.
This is: much more accurate than skin color, not affected by societal definitions, actually
indicates something about the person's ancestors and genetic complement, and can be useful
in determining risk factors. You can go to one of several low-cost genetic testing services
in the US or Europe and have your haplogroup determined, and it can tell you something
about your ancestry you may not have known.
Which leads me to...
Fact 8: Humans are divere and interesting, and we shouldn't get hung up on skin color.
What's great about lineage or ancestry or race is that it can give us a sense of community
and uniqueness. We belong to an in-group, with which we share many commonalities. We
can have pride in others who are like us, or celebrate in a group accomplishment.
At it's worst, race divides us, emphasizing only the differences, making people outsiders
or outgroups, and creating hostility and resentment.
Can we have the good without the bad? I don't know. It would be nice if we could all bear
in mind that we are all one big species, one very large family living together on a single
planet. We are diverse, we are unique, but we are all cousins.
Thanks for watching.