E1. Why Are Europeans White?


Uploaded by frankwsweet on 30.10.2010

Transcript:
Karen: Welcome, ladies and gentlemen. This is Karen Sharpe with another session
in our series of discussions on the study of racialism, with Professor Randolph Hemmings.
Good afternoon, professor, I am sure that the viewers are looking forward to today's
topic. Professor Hemmings: Thank you Karen, I'm glad
to be here. Todays topic is, "Why are Europeans White?"
Of course, the colour White is merely a social designation.
The real question is, "Why do Northern Europeans have such little pigmentation?"
Here is a map, of human skin tone. The natives of northern Europe are oddly light-skinned.
They are paler than anyone else on earth. Most people know that this has something to
do with sunlight, U.V., latitude, and vitamin D.
Here is a map of solar U.V. at the surface taken from satellite.
It matches the skin-tone map everywhere but Europe.
The closer you are to the equator, the darker your skin.
This is because humans are extraordinarily sensitive to sunlight on the skin.
Humans do not have fur. U.V. rays produce vitamin D and reduce folate
when they hit naked skin. And embryos are terribly vulnerable to both
substances in the mother. When it comes to sunlight and skin tone, furless
humans, are balanced, on a knife blade. If a pregnant mother is too pale-skinned under
intense sunlight, then too much U.V.?? penetrates her skin.
This increases Vitamin D. but reduces folate. Lack of folate causes neural tube defects
in the fetus, causing such congenital abnormalities as craniorachischisis, anencephalus, and spinabifida,
leading to many miscarriages. On the other hand, if she is too dark-skinned
under dim sunlight, then too little U.V. penetrates her skin.
This increases folate but reduces vitamin D.
Lack of vitamin D. causes skeletal neo-natal abnormalities.
These include skull, chest, and leg malformations. Rickets being the best known.
Again, this causes miscarriages. And so, humans adapt very quickly to solar
U.V. Prehistoric groups that migrated towards the
equator got darker. Prehistoric groups that migrated away from
the equator got lighter. But this explanation fails for northern Europe.
Northern Europeans are lighter than everyone to the south (Mediterraneans),
to the east (Mongols and east-Asians), to the west (Native Americans across the Atlantic),
and to the North (Inuit, Sammi, Chukchi, Aleut). Clearly, there once was a factor at work in
Europe other than dim sunlight. Here is another map of skin tone.
Again, the blob surrounding the Baltic Sea is like nothing else on the planet.
That this pale population surrounds the Baltic gives the first hint.
It must have something to do with the oceans. Baltic depigmentation is not just in the skin.
Here is a map of hair color. The pigment melanin colors hair as well as
skin. Adult blondes are native only to this unique
region. Children around the world are often blonde,
but their hair darkens at puberty. So it is not just northern European adult
skin that lacks pigment. It is also adult European hair.
But the Baltic depigmentation is not just in the skin and hair.
Here is a map of eye color. Melanin colors eyes, as well as skin and hair.
Adults with blue eyes are native only to this unique region.
Babies around the world are often born with blue eyes, but their eyes darken within a
few months. So it is not just northern European skin and
hair that lack pigment. It is also northern European eyes.
Skin, hair, eyes: adult European pigmentation resembles that of children elsewhere.
This gives the second hint -- neoteny. To solve the puzzle, we must figure out when
it happened. When did the inhabitants of the Baltic region
lose their melanin? Well, it must have happened after 16 thousand
years ago. The Baltic region was covered by ice before
then and nobody lived there. In fact, it probably happened after 13 millennia
ago. Cave art from that time always shows normally
pigmented people. Notice that in this painting from 13 thousand
years ago, the hunters are the same color as the deer.
On the other hand, it must have happened before 4.6 thousand years ago because depigmented
people first began to appear in art at that time.
These Egyptian statues were painted in 2613 B.C.
They portray Prince Rahotep and his consort Nefret of the Old Kingdom early Fourth Dynasty.
Notice that he is brown but she is pink. And so, the next step in solving the puzzle
is to ask, "What happened in Europe between 13 thousand years ago and 4.6 thousand years
ago?" What happened was the invention and spread
of agriculture. Before 10 thousand years ago people everywhere
lived by hunting and gathering. Then, almost simultaneously, cereal growing
was invented in four spots around the globe: Iraq (wheat, barley, rye), China (rice), Nigeria
(sorghum), and Mexico (corn or maize). What does skin tone have to do with eating
grains? Even in darkness, humans get vitamin D from
eating meat and fish. Otherwise they could never inhabit the arctic.
This U.S.D.A. chart shows the vitamin D content of various foods.
All meats have some vitamin D. Fish have very high amounts.
But grains have no vitamin D at all. People who eat grains do not get vitamin D
from food; they must get it from sunlight. This usually works out fine because grains
grow only where it is warm. And this means only in latitudes with bright
sunlight, with one exception. People who live in low latitudes, where they
can live off grains, get plenty of sunlight. People who live in dim sunlight cannot grow
grains, and so they get vitamin D from the meat and fish that they eat.
The exception? There is only one spot on the planet where
grains will grow despite sub-arctic sunlight. It is where the warm waters of the Gulf Stream
wash ashore. The Baltic is the only place on earth where
ocean currents keep it warm enough to grow grain despite dim sunlight.
When the inhabitants of this region switched to grain, about 6 thousand years ago, they
suddenly got insufficient vitamin D to survive. They had stopped eating mostly meat and fish,
in a place where sunlight was too dim to produce vitamin D, in normally pigmented skin.
And so they adapted by retaining into adulthood the infantile trait of extreme paleness.
Blonde hair and blue eyes were other infantile traits that were just swept along accidentally.
Well Karen, that is my presentation for today. Thanks for listening.
Do we have any phone-in questions? Karen: We do, professor.
But before we answer listeners questions, I wanted to say that was just fascinating.
Thank you so much. To be honest, I never liked the explanation
that told only about the sun's ultraviolet. After all, native peoples who live on the
shores of the Arctic Ocean, get less sunlight than northern Europeans, and yet they are
visibly darker. Professor Hemmings: Thats right Karen.
Nowadays, all of the hypotheses that explain northern European paleness depend on something
beyond sunlight alone. Perhaps one of our listeners will bring some
up. Our first question comes from Sally Prentice
of St. Paul Minnesota. She says that The cave painting was not very
convincing, since the artist might have had only one pigment.
Professor Hemmings: Yes. I agree. Nevertheless, other paintings of the time
used multiple colours. The main point however is that the Baltic
was covered by glaciers until then. So when the ice melted and the region was
repopulated from the Mediterranean and from Africa,
either the people who moved to the Baltic got paler over the generations, or everyone
else around the globe got darker. The former makes more sense than the latter.
Karen: A question from Suresh Patel of Aberdeen. He read somewhere that the northern European
paleness might have resulted from either sexual selection or drift.
Could you comment on that? Professor Hemmings: Excellent question!
It brings up the other two main hypotheses. Sexual selection says that males carry a gene
to prefer light-skinned females, which they inherit from light-skinned females.
Or vice-versa. It was supported by the great Cavalli-Sforza
and is advocated today by Peter Frost. The problem with a sexual selection hypothesis
is that sexual selection normally produces dimorphism -- differences between the sexes.
Examples of human sexual selection are that females stay cute into adulthood but males
do not, or that differences between male and female
bodies are greater than needed for child-bearing. But there is no sex difference in skin-tone
among northern Europeans. In fact, since sub-Saharan females tend to
be lighter than males, one could better argue that the very dark skin tone of the Bantu-speaking
peoples resulted from sexual selection. Drift, on the other hand is more plausible.
Its flaw is that the constant ebb and flow of migrations and invasions into Europe, would
likely have stifled drift. Karen: A question from Miriam da Silva, of
Rio de Janeiro. Are you saying that Europeans were once black?
Professor Hemmings: Oh no. Not at all.
I am simply saying that they were once the same skin tone as everyone else at the same
latitude. That is, about like Sicilians, Arabs, Mongols,
or Native Americans. Karen: We have time for only one last question.
Antonio Sanchez of Miami Florida asks about our species original skin tone, before we
spread around the globe and adapted to local conditions.
Were we white, black, or in-between? Well, no one knows for sure because skin color
does not fossilize. But my guess is in-between. like the Khoi-San
of the Kalahari, or the Oromo of Ethiopia. I say that because those two populations are
closely related despite their geographical separation.
They pre-date the migrations of the Bantu-speaking peoples.
And they are the oldest living lineages of our species.
Karen: Thank you professor. Thats all the time we have today folks.
Please come back next week, when Professor Hemmings will discuss the heredity of racial
traits. This is Karen Sharp, signing off.