Date: Fri, 31 Oct 2003
16:46:14 -0000
From: "Aneb Nua"
Subject: Mesmerized by Melanin: PHYSIOLOGY
I found this article to be very interesting. Being one of the ones
who have studied the effects of melanin I would be included in the
author's assessment as being one who is trying to compensate for white
racism. The problem being that, out in the open, scientists do not
acknowledge the results of the studies on melanin. Carol Barnes and Dr.
Jewel Pookrum are a couple of the very few black scientists who are
actively doing research on the subject. It's also interesting to me
because I heard about the effects of melanin way before I was becoming
conscious of my Afrikan roots, from those in the yogic community. It
is yogic knowledge that activating kundalini and long
periods of meditation will cause melanin to be developed.
While you don't change colors your inner organs will become darker and the
more melanin you develop the more psychic you become. See Anodea
Judith's book on the chakras for more information on this. I guess
the real giveaway for me about the author's motives was that she is
writing for Disney. In all seriousness, I think we have to ask and
get information from our own scholars and weigh it in the balance with
what is 'accepted knowledge'.
The Skin We're In
We humans are
mesmerized by melanin, the pigment that gives color to our skin, but
almost always for quite the wrong reasons.
By Christopher Wills
DISCOVER Vol. 15 No. 11 | November 1994 | Anthropology
Melanin is in the news these days. There's a pseudoscientific idea
floating around that says that if you have lots of melanin--the pigment
that colors your skin and hair and the irises of your eyes-- you will be
smart and exquisitely attuned to life's rhythms and have a warm, outgoing
personality. In short, you will be nicer and more talented than people
with less melanin--that is, white people.
Proponents of this idea, such as Leonard Jeffries, chairman of the
Department of Black Studies at the City College of New York, have based
their conclusions on the single scientific fact that melanin is found not
only in the skin but also in the brain, and they have used the compound's
presence there to imbue it with magical properties. Their "melanist"
approach has gone beyond promulgation in a few pamphlets and backroom
debates; it is now being taught at a number of high schools and colleges
in the United States, usually as part of an effort to correct a
Eurocentric view of the world. Not surprisingly, such programs have
generated a great deal of criticism in the mainstream, white-dominated
press--which the melanists claim is in itself an expression of
racism.
Why,
they counter, hasn't an equal amount of disapproval been directed against
the pronouncements of white biological superiority?
Two wrongs, of course, do
not make a right. As a reaction and antidote to white racism,
melanism is understandable. But from a scientific standpoint it is
just wrong. There's no evidence for melanist claims of black
superiority, just as there's no evidence for the pseudoscientific
claims of white superiority that have been made for centuries.
That's not to say that melanin isn't a fit subject for scientific
inquiry. Indeed, just the opposite: what research has shown us is that the
real story of melanin is much more interesting, and tells us more about
ourselves, than any magical hokum trotted out to support divisions
between the races.
We are visually oriented animals, and the color of a stranger's
skin, if different from our own, is often the characteristic we
notice first. Of all the superficial differences that divide us--the shape
of our nose, the texture of our hair, and so on--none seems to
mesmerize us as much as skin color. Our hyperawareness of it shapes our
perception not only of others but of ourselves as well. As psychologists
have shown, among blacks in this country, at least, the darkest-skinned
children in a group or family are often treated less well than other
children by their teachers, their peers, and even their parents and thus
suffer repeated blows to their self-esteem. Obviously, differences in skin
color matter greatly to society--but is there any physical basis for all
the prejudice and psychological damage that these differences have
generated?
Today geneticists like myself would say no. We have known for decades that
variation in skin color is caused by rather small genetic differences, and
it seems highly unlikely that these differences have anything to do with
intelligence, personality, or ability. Sadly, though, genetics
itself has not always been free of the taint of racism. The models that
early geneticists used to explain the inheritance of skin color actually
had a segregationist bias, reflecting the pervasive prejudice of
their time. The white American eugenicist Charles Benedict Davenport
set the tone (so to speak) in 1913 with an investigation into the genetics
of "Negro-white crosses." Davenport was as racist as most of his
contemporaries, and he assumed that blacks were inferior to whites. He
did, however, correctly deduce that there were distinct genes that control
skin color. But he thought only two genes were involved and that each of
them came in two forms, or alleles: a "white" allele and a
"black" allele. How dark you were was a function of how many of
the four alleles you inherited from your mother and father were
"black." Davenport assumed
that the black and white alleles were clearly different from each
other, as the black and white races themselves, he thought, were clearly
different from each other. We now know that this is not correct and that
the differences between the alleles carried by the different races are
small. But Davenport was right in his conclusion that a rather small
number of genes make substantial contributions to skin color-- more than
two, it turns out, but fewer than half a dozen. And, as he noticed,
skin color is inherited independently of other characteristics used
to differentiate between races. Among the grandchildren of interracial
marriages, he saw, there were often individuals with light skin and
tightly kinked hair, and others with dark skin and straight hair. Skin
color and hair texture were thus not indissolubly wedded.
Davenport knew nothing about how genes work and so had no notion of how
his black alleles caused pigment to form. Only recently have studies at
the molecular level shown how slight the allelic differences between races
really are, and how few the steps that separate all of us from being as
dark as the Bougainville Islanders of the South Pacific or as pale as
Swedes. What we have learned is that
the mechanics of pigment formation are surpassingly subtle. Melanocytes,
the cells that form the pigment melanin (and that occasionally run amok,
giving rise to the malignant tumors known as melanomas), are closely
related to nerve cells. Both types of cell arise in a part of the early
embryo called the dorsal ectoderm, but while nerve cells mostly stay put
to form the core of the nervous system, melanocytes migrate along with
other cells to give rise to the skin. As they mature, melanocytes and
nerve cells continue to share some attributes. Like nerve cells,
melanocytes develop branching processes that attach to nearby cells. But
whereas nerve cells use their branches to send messages, melanocytes use
theirs to send packets of pigment to adjacent skin cells. A single
melanocyte can color quite a large bit of the skin by pumping pigment into
the cells that adjoin it.
We now know that in mice more than 50 different genes influence how
melanin forms and when and where it's deposited. So it's likely that a
similar number of genes will turn up in humans as well, although perhaps
only half a dozen will be shown to have really substantial effects. The
pigments they produce, though they're all lumped together under the
melanin label, can actually be black, brown, yellow, or red. They all have
a common starting point in tyrosine, an amino acid made in large amounts
in the melanocytes and converted by the enzyme tyrosinase into a compound
called dopaquinone. At first, biochemists thought that dopaquinone then
underwent spontaneous chemical changes to form the long polymer molecules
that make up melanin. But the truth was much more complex--it takes a
bewildering mixture of reactions, some spontaneous and some catalyzed by
enzymes, to get from dopaquinone to melanin. To cut a very long
story short, dopaquinone follows two different routes, one leading to
black and brown pigments, and the other to red and yellow pigments.
The master enzyme in all this is tyrosinase. If the gene for this enzyme
is defective, the result is a person with albinism, someone who makes no
melanin at all. But the most remarkable discovery made by molecular
biologists has been that most of us, regardless of skin color, have quite
enough tyrosinase in our melanocytes to make us very black. In those of us
with light skin, something is preventing the enzyme from functioning at
full capacity--and that seems to be a combination of two genetic
mechanisms: a switch that causes the cell to make most of the tyrosinase
in an inactive form, and a tendency to make a lot of inhibitors of the
enzyme. In the body, the effects of either or both of these mechanisms can
be modified by such environmental factors as exposure to ultraviolet
light. People with albinism are highly sensitive to ultraviolet, which can
easily damage skin and eyes, but most of us, regardless of which alleles
we have for skin color, can protect ourselves by darkening our skin
through tanning.
So it turns out that what separates blacks and whites is not different
numbers of clearly different black and white alleles, but rather a
collection of tiny genetic differences in the way the genes possessed by
all of us are regulated--how much tyrosinase is made in an active form,
how much and how many of the various tyrosinase inhibitors are made, and
so on. Mutations with dramatic effect do contribute to color variation in
the human population--for example, people with albinism don't make
functional tyrosinase, and redheads make only small amounts--but these
mutations affect only a relatively small number of people. Other mutations
that lighten or darken skin color occasionally happen. Children with
piebaldism, for instance, are born with a white forelock and colorless
patches on their forehead and trunk. Another, more dramatic example is
melasma, a skin condition that sometimes runs in families. A child with
this condition is born with large patches of darker-than-normal
pigmentation, which spread as the child grows older. In the late 1970s an
even more unusual condition was described, in Mexico: a child was born
with light skin that turned a deep, uniform black by the age of 21 months.
(It is not yet known whether this condition is inherited.)
Such mutations are probably the tip of the iceberg. Richard King, a
molecular geneticist at the University of Minnesota who has examined color
variation in mice, suspects that much milder mutations must also happen in
humans but that they tend to go unnoticed because they fall within the
range of normal pigmentation. He is convinced that we are not exempt from
the mutation-and-selection process that has repeatedly resulted in lighter
and darker strains of animals over the course of evolution. The most
famous example of such evolution is industrial melanism in moths, in which
dark forms that arise by mutation are selected for in polluted areas and
selected against when the pollution goes away.
In animals, melanin comes and goes at the dictates of evolutionary
pressures. It is reasonable to assume, then, that we humans have this
molecule not because it makes us smarter but primarily because it helps us
survive a variety of environmental conditions. Clearly, melanin protects
us from the ravages of ultraviolet light. Some of the most darkly
pigmented people in the world, natives of the North Solomon Islands,
almost never get basal cell carcinoma or melanoma, and if they do have
melanomas, these tumors arise on the light-skinned soles of their feet.
Caucasians living in Hawaii, on the other hand, have the highest
documented skin cancer rate in the United States.
But while the protective effect of having a lot of melanin is clear, it is
rather less clear why many groups of humans living far from the equator
have lost much of their pigment. One popular theory is based on the fact
that exposure of our skin cells to ultraviolet light is necessary for the
formation of a precursor of vitamin D, which in turn is required for
proper bone formation. Thus, the theory goes, people who live at high
latitudes--where the sun hangs low in the sky and where people are forced
to keep their skin covered during much of the year--can still make enough
of this precursor if they have little ultraviolet-blocking pigmentation in
their skin. Conversely, the large quantities of pigment in the skins of
people in the tropics should prevent them from producing too much vitamin
D, which can be as harmful as too little and can cause inappropriate
calcium deposits in tissues.
In evolutionary terms, of course, it makes sense that most of us have all
the machinery in place to make us black or white or anything in between.
Darker and lighter "races" of animals are quite common, and
probably arose as a response to the dangers of predation. Dark and light
Sceloporus lizards from Colorado will even move about in a
laboratory setting to match themselves to the appropriate background, an
instinctive attempt to protect themselves against sharp-eyed predators. My
guess is that over a span of hundreds of millions of years our remote
animal ancestors had to change color repeatedly, for a great variety of
reasons ranging from protective camouflage to sexual attractiveness. Much
of this must have taken place long before they had acquired enough brains
to be prejudiced about it. Even in Homo
sapiens there are many examples of groups that have evolved toward a
lighter or darker skin color than that of their close relatives. The
Negritos of the islands of Luzon and Mindanao in the Philippines, for
instance, superficially resemble other dark-skinned groups in Africa and
Australia. Yet their overall genetic affinities turn out to be far
stronger to the lighter-skinned Asian peoples who surround them. This
suggests that the Negritos' ancestors may once have been lighter and that
they independently evolved features that are somewhat reminiscent of black
Africans, or that the Asian peoples surrounding them were also once much
darker and evolved toward lighter skin--or possibly both. Another example
is the Ainu of northern Japan, who have light skin but overall are very
similar genetically to the darker-skinned groups that surround them. The
evolution of skin color was apparently not a onetime event; it has
occurred repeatedly during the history of our species.
What about neuromelanin, that other melanin, found in our brains, that
Jeffries and his fellow melanists have made so much of? More skin melanin,
they imply, must mean more brain melanin--which is, in some undefined
fashion, good. As we have seen, melanocytes and nerve cells do have a
common origin in the fetus, and indeed it's likely that nerve cells once
evolved from primitive melanocytes. But this evolutionary connection does
not mean that the pigment of the skin is somehow connected with the
function of the brain. People with albinism, who have no melanin in their
skin, hair, or eyes, have normal amounts of melanin in their brain cells.
And even though the ultimate source of both types of melanin is tyrosine,
the processing pathways leading to neuromelanin are quite different from
those leading to skin melanin--in the brain, tyrosine is converted into
dopamine, a neurotransmitter, which in turn gives rise to neuromelanin.
Finally, it should be pointed out that while neuromelanin is by its very
nature highly visible in brain tissues, it is only one of thousands
of compounds unique to the brain and is unlikely to be freighted with
mystic significance.
As for the real significance of brain melanin, the jury is still out-- we
have no idea what it does. We do know that a lot of it is found in the
substantia nigra (the "black substance"), a darkly colored
structure buried deep in the brain that makes dopamine. We also know that
melanin- rich cells in the substantia nigra are the ones most likely to be
destroyed in people who have Parkinson's disease, resulting in tremors and
rigidity. But whether this preferential destruction is due to some
property of the neuromelanin or is the result of some other process that
just happens to destroy neuromelanin-rich cells is not yet clear. What is
clear is that neuromelanin isn't obviously related to skin pigment, much
less to a warm, outgoing personality.
Still, melanin may confer some benefits we have yet to learn about.
Intriguingly, there are hints that people with lots of skin melanin are
less prone to hearing damage than the more lightly pigmented among us. And
as it turns out, melanin of the skin variety is indeed found in certain
cells of the cochlea of the inner ear. But whether it is melanin or
something else in these cells that confers the protection is unknown.
Melanin has also been connected with an odd benefit of smoking. Tobacco
smoke stimulates production of skin melanin, particularly in the cells
lining the mouth and possibly in other tissues as well. One study has
actually suggested that smokers have less noise-induced hearing loss than
nonsmokers (other studies, however, have shown the reverse). The benefit,
if any, is hardly enough to justify taking up the habit, though smokers
will be comforted to know that if increased melanin production does
protect their hearing, they may be able to go on listening to every wheeze
and rattle of their abused lungs.
Clearly melanin is a handy and fascinating compound, with an intriguing
evolutionary history. But because its effects are so visible in our skin,
it has for centuries been made to bear an utterly undeserved burden of
sociological and political significance. As is detailed elsewhere in this
issue, there are far more genetic differences among the people who make up
these arbitrary constructs we call races than there are differences
between races. It is time to move away from simplistic efforts to explain
all our differences in terms of just one molecule and to pay
attention to the tens of thousands of other molecules that make up our
wondrously complex cells--and selves.
© 2003 The Walt Disney Company. All rights reserved.
Reproduction in whole or in part without permission is prohibited.
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