I like race. I know it sounds odd, even politically
incorrect. But I really enjoy the differences among people around
the world. One aspect of this is all our different
cultures. But another is all our different physical types.
I get a kick out of reading and thinking about how we got to look the
way we look, where our characteristics came from, why they are there at
all. And, I must admit, it does seem to me that there are some
groupings when it comes to our physical differences, which we have been
calling races for some time.
The races are definitely not "subspecies." All modern human
beings are members of Homo sapiens sapiens - a single genus, species,
and subspecies. To this extent, we are remarkably similar,
sharing perhaps 99% of our genes. But that doesn't mean we are
therefore all alike: We share 98% with the chimps, and even 90% with
mice - and the differences there are quite striking!
Because the concept of race has been confused so thoroughly with our
terrible history of racism, many avoid the term altogether. There
is some justification. For example, there is no such thing as a
"pure" race, and the races clearly blend into each other, unless
dramatically transported to new regions. This is what has made
race such a significant (and problematic) concept in the Americas,
where the original native populations were confronted with European
colonists
and African slaves!
Skin
Speaking of the "red" man, the "white" man, and the "black"
man, skin color is perhaps the first characteristic we think of when we
think of race.
Skin, hair, and eye color are due to relative amounts of melanin.
There are two kinds of melanin: Eumelanin is dark, with two
types, black and brown. Pheomelanin is a light reddish
brown. It is responsible for the color of lips, nipples, and
naughty
bits, as well as freckles, red hair and green eyes.
The experts are pretty much in agreement about how the varieties of
skin color came about. They suggest that prehumans were likely
white with fur - just like our relatives, the chimpanzees. As our
hair became thinner, melanin came to the rescue to protect us from the
sun's damaging ultraviolet rays. We became a brown people as our
whiter relations died of skin cancer or from a lack of the B vitamin
folate, which is needed for DNA synthesis, and without which we see
more birth defects. Some people in Africa even evolved dark black
skin.
Once people were out of Africa, there was a lot more variation in
levels of sunlight. People in northern latitudes did not need as
dark a skin for protection, and so the natural variations returned and
some people became lighter again. Others, staying in southern
latitudes such as India, Southeast Asia, and Australia, retained one
level or another of darkness for protection. So, in Asia, we see
a smooth range of skin tones from very light brown in Siberia to dark
brown
in India:1
In Europe, there was an odd mutation, something like albinism. It
seems that in the far north, there isn't enough sun to help us
manufacture vitamin D. So light - even white - skin became better
for survival, because it can absorb more sunlight. This reduction
in melanin was also reflected in blond and red hair and blue and green
eyes.
Meanwhile, people moved into Siberia, a light brown in color.
Some travelled over into the Americas. The ones that settled near
the equator in Central and South America developed, as one might
expect, darker skin. But they never got quite as dark as people
in Africa or India because some of the genes that originally gave us
very dark skin had disappeared from the Siberians before they left, and
they haven't yet re-emerged.
Eskimos are rather dark for people who live further north than even the
Scandinavians. How did they manage to keep their tans? The
theory is that live on a diet very rich in fish, which, of course, has
a high level of vitamin D. The need for vitamin D may also
account for why some people - especially northern Europeans - became
able to easily digest milk (lactose tolerance), a very recent mutation.
In a very similar way, we can see some of the differences in our builds
as tied to latitudes and climate. There is something called
Bergmann's rule, which says that mammals will tend to be larger (or
taller, in our case), but
with shorter arms and legs, in cold climates, and smaller, but with
longer arms and legs, in warm climates. In cold climates, we need
to conserve heat, so it helps to be large with as little skin surface
as possible. In warm climates, we need to dissipate heat, so
being small with lots of skin surface works best.
Hair
Genetically, Africans have more variety than other races. Every
time a
group advanced out of Africa, or from one isolated area to another even
more isolated, another batch of genetic variations was left
behind.
But on the surface, it's caucasians that have the most variety, for the
simple reason that they have a lot less melanin, which takes the
darkness out of their skin, hair, and eyes to reveal other
possibilities.
Hair color is determined by 4 to 6 genes, each with several alleles,
some with incomplete dominance (i.e. not a matter of one thing or the
other, but perhaps a mix of both - like pink carnations). The
basic genes involved are for black hair (with a recessive allele for
not-black), one for brown hair (with a recessive for blond), and one
for red hair (with a dominant allele for not-red). Some of these
genes are close to eye color genes on chromosomes 15 and 19, and tend
to go along with those genes, which is why we tend to see certain
combinations of hair and eye color more frequently than others.
Black is the most common hair color in the world, and is due to a large
amount of eumelanin. Brown is also common, and is due to
eumelanin mixed with a bit of pheomelanin. Blond is only found in
about 2% of the world's population. It is due to very small
amounts of melanin. Slight amounts of black, brown, and red make
for all the variations we see in blonds - such as ash, flaxen, and
strawberry blond. And red hair is the rarest of all, about 1% of
the world. It is due to high levels of pheomelanin plus low
levels of eumelanin.
If you are curious, gray hair is due to nothing but a little black
melanin, and white hair is a matter of no melanin at all.
As you can see on this map, light colored hair is found primarily in
scandinavia and the baltic sea area. Blond and red hair was
probably more common in Europe centuries ago (as witnessed by Greek and
Roman accounts), but being recessive, it has slowly receded
northward. But you can still find blonds and redheads in places
like Afghanistan and northern Pakistan, where the descendents of
Indo-European
invaders live.
Yellow: 80% or more with
light hair2
Orange: 50 - 79%
Light brown: 20 - 49%
Dark brown: 1 - 19%
Black: 0%
Eyes
Eye color is determined by the amount of melanin (mostly eumelanin) in
stroma of iris, plus density of the stroma cells. The stroma are
those fine bundles of fibers that make the interesting little lines in
your
Iris.
You will have brown or black eyes if there is a great deal of eumelanin
in the stroma. High pheomelanin will give you green eyes.
And if there is very little melanin of any sort, your eyes will be
blue, which is the color of the precursor to melanin, as well as the
reflected color of the sky. If the melanin is extremely low, the
blood vessels (red and blue) will make the eye appear a light purplish
color.
Eye color seems to be mostly a matter of three genes: On
chromosome 15, there is a gene labelled bey 1, which is called the
central brown eye color gene, and bey 2. Bey 2 has a dominant
allele for brown eyes, and a recessive one for blue eyes. There
is also a gene on chromosome 19 called gey. It has a dominant
allele for green eyes, and a recessive for blue. If you have two
blue alleles at bey 2 and a green at gey, you will have green
eyes. Blue alleles at bey 2 and blue at gey, and you will have
blue eyes. If you have any brown alleles on bey 2, you will have
brown eyes, no matter what you have at gey.
But, of course, things are more complicated than this. There are
different degrees of darkness, for example, that allow some green to
peek through light brown eyes to form hazel. And there are all
sorts of variations on blue and brown as well. Nothing is ever
simple.
Blood
But perhaps we should look at some of our inner differences to get at
race. For example, we can look at blood types.
Unfortunately, this approach doesn't get us too far. A is found
most in Europe, Australia, and among north Canadian Indians, and least
from Mexico down through South America. B type blood is found
most in Asia, less in Africa, the Near East, and eastern Europe, and
hardly at all in western Europe, among Australian Aborigines, and among
American Indians. O is found at its highest levels among the
American Indians and least among central Asians.
Rh factors are more
interesting: Rh negative is found most among
the Basques in Spain and France, with 35% showing Rh negative, and 60
carrying it. Europeans generally have a higher percentage of Rh
negative (16%, with 40% carriers). But the rest of the world has
very little indeed - 1% or less.
Genes
Of course, the most profoundly "inner" differences would be at the
genetic level. And there it gets really interesting.
Some researchers prefer the term population
to race. It is
defined as a group of people that have significant genetic similarity
because they have tended to breed within their group rather than
outside of it. Another term some prefer is cline. A
cline is a description of how a trait changes as you move over a
territory. In the social sciences, many prefer terms like ethnicity, usually understood as
having a lot more to do with learned
culture than inherited traits.
Another approach
uses the term lineages.
Rosenberg et al (2002)3 divided 52
populations (using 1056 people) into 6 lineages by comparing and
contrasting 377 genetic markers ("autosomal microsatellite loci").
The analysis is fairly clear: There are five lineages that are
very geographic in nature: African (Sub-Saharan, in orange),
Eurasian
(Europe and West Asia, blue), East Asian (pink), Oceanic (here covering
Melanesia
and
Papua-New Guinea, green), and Amerindian (purple). There is also
a small Central
Asian cluster (yellow) pretty much defined by the Kalash of North
Pakistan.
There is also a lot of admixture, as would be expected: Kenyans
have a bit of Eurasian. North Africans have a bit of African. As one
moves east through Eurasia, we see more and more East Asian, until we
reach the Uygurs, who are roughly half of each. Even as far east
as the Yakuts in the north and the Cambodians in the south have a
little Eurasian. The Kalash genes are found in most South and
Central Asian populations. Oceanic peoples have a little East
Asian. And the many Amerindians (except the Brazilian tribes)
have some East Asian. The Mayans stand out as having a remarkable
amount of East Asian and Eurasian, for a people so remote from either
area!
Mitochondrial DNA
Every cell has mitochondria
in it, which produce energy. But the mitochondria derive entirely
from the mother's egg cell, with no input from the father's
sperm. So the DNA in the mitochondria have been passed down from
mother to daughter since, well, Eve! By looking at the mutations
that have occured in the mitochondrial DNA, and where those mutations
are commonly found, we have a way of tracing our ancestors. The
groups are called haplogroups.
Here
is
a simplified list:
L1 - "Eve," Khoisan and elsewhere in Africa
L2 - Africa
L3 - East Africa
M
M1 - East Africa
C - NE Asia, Siberia, the
Americas
Z - Russia, the Saami
(from Lappland)
D - NE Asia, Siberia,
Columbia
E - Malay, Borneo, Taiwan,
Philipines, coastal Papua-New Guinea
G - NE Asia, Siberia
Q - Papua-New Guinea,
Melanesia
N
A - North Central Asia,
the Americas
I - Europe, Arabia, Egypt
W - Urals, Baltic, India
X - Europe and the Americas
R
B - East
Asia, Polynesia, Micronesia, the Americas (but not Siberia!)
F - China,
Japan
J - Europe
and West Asia
T - Baltic,
Urals (Russia)
P - Papua-New
Guinea, Australia
U
K - Europe, esp. Azhkenazi Jews
H - Europe, Middle East, North Africa
V - the Basques, the Saami
There is a certain nice patterning here, that allows us to map the
connections in a way that shows how our maternal ancestors migrated
throughout the world (prior to the colonial era):
MtDNA migrations, with approximate dates before present (k = 1000)
Y chromosome DNA
The 23rd chromosome pair is the one that defines us as male or
female. Women have two X-shaped chromosomes. Men have one X
and one Y (a scrawny little thing that makes me ashamed of being
male). But that means that men transmit their Y's to their sons,
and they to their sons, in a male lineage that goes all the way back
to, well, call him Adam.
By looking at the mutations that have occured, and finding the
populations that have those mutations, we have another way of looking
at our genetic inheritance. Here's a simplified version of the
results:
A - "Adam," the Khoisans, Ethiopia
B - the Pygmies
C
C1 - some Japanese
C2 - Polynesia
C3 - Mongols, Kazakhs, eastern Siberia, some
Japanese, the Na-Dene of North America
C4 - Australian Aborigines
C5 - some South Asians
D - East and Central Asia, Andaman Islands
E - the Bantus, Middle East, Mediterranean
F - South India, Korea
G - Caucasus, Alps, Pyrenees, Sardinia
H - India, the Romany
I - Europe, especial North Europe
J - Middle East
K - Eurasia, East Asia, the Americas
L - Eurasia, esp. Pakistan, India, Sri
Lanka
M - Papua-New Guinea
N - Urals, the Yakuts
O - East Asia
P
Q - Siberia, the Americas
R - Eurasia, the Americas
Much messier, as you can see. A has the least mutations, and so
is closest to our original ancestors. B defines that magnificent
people, the Pygmies. G is interesting in that it may relate to an
early "alpine" people ranging from the Caucasus to the Pyrenees.
H is characteristic of the people of India, including the Romany, who
came from India perhaps 1000 years ago. I is very European, J
very Middle Eastern. M is specific to Papua-New Guinea. N
practically defines the speakers of the Uralic languages. O is
very East Asian. P, Q, and R are the Siberians and American
Indians, except for the Na-Dene and their relatives in Siberia, who are
C3. The other haplogroups are spread very widely.
Would you like a good guess as to what our early human ancestors looked
like? Well, "Adam and Eve" probably looked most like the Khoisan
people of southern Africa, like this young fellow:
Do you see why I like race? It is so interesting! Human
variation is something to embrace, not to avoid. Let's glory in
our differences, safe in the knowledge that we are also all profoundly
one people.
1 Map from Wikipedia, based on
Jablonski, N.G. and Chaplin, G. 2000. The evolution of skin coloration.
J. Hum. Evol. 39: 57–106.
2 Map from Wikipedia, based on Frost, P.
2006. European hair and eye color - A
case of frequency-dependent sexual selection? Evolution
and Human Behavior 27: 85-103
3 Chart from Wikipedia, based on Rosenberg, N.A.,
Pritchard, J.K., Weber, J.L., Cann, H.M., Kidd, K.K., et al. (2002)
Genetic structure of human populations. Science 298: 2381–2385.
