The New York Times, August 22, 2000, Tuesday, Page F1, Science Desk

NATALIE ANGIER

Do Races Differ? Not Really, Genes Show

    In these glossy, lightweight days of an election year, it seems, they
can't build metaphorical tents big or fast enough for every politician who
wants to pitch one up and invite the multicultural folds to "Come on
under!" The feel-good message that both parties seek to convey is:
regardless of race or creed, we really ARE all kin beneath the skin.

    Yet whatever the calculated quality of this new politics of inclusion,
its sentiment accords firmly with scientists' growing knowledge of the
profound genetic fraternity that binds together human beings of the most
seemingly disparate origins.

       Scientists have long suspected that the racial categories recognized
by society are not reflected on the genetic level. But the more closely
that researchers examine the human genome -- the complement of genetic
material encased in the heart of almost every cell of the body -- the more
most of them are convinced that the standard labels used to distinguish
people by "race" have little or no biological meaning.

    They say that while it may seem easy to tell at a glance whether a
person is Caucasian, African or Asian, the ease dissolves when one probes
beneath surface characteristics and scans the genome for DNA hallmarks of
"race."

    As it turns out, scientists say, the human species is so evolutionarily
young, and its migratory patterns so wide, restless and rococo, that it has
simply not had a chance to divide itself into separate biological groups or
"races" in any but the most superficial ways.

    "Race is a social concept, not a scientific one," said Dr. J. Craig
Venter, head of the Celera Genomics Corporation in Rockville, Md. "We all
evolved in the last 100,000 years from the same small number of tribes that
migrated out of Africa and colonized the world."

    Dr. Venter and scientists at the National Institutes of Health recently
announced that they had put together a draft of the entire sequence of the
human genome, and the researchers had unanimously declared, there is only
one race -- the human race.

    Dr. Venter and other researchers say that those traits most commonly
used to distinguish one race from another, like skin and eye color, or the
width of the nose, are traits controlled by a relatively few number of
genes, and thus have been able to change rapidly in response to extreme
environmental pressures during the short course of Homo sapiens history.

    And so equatorial populations evolved dark skin, presumably to protect
against ultraviolet radiation, while people in northern latitudes evolved
pale skin, the better to produce vitamin D from pale sunlight.

    "If you ask what percentage of your genes is reflected in your external
appearance, the basis by which we talk about race, the answer seems to be
in the range of .01 percent," said Dr. Harold P. Freeman, the chief
executive, president and director of surgery at North General Hospital in
Manhattan, who has studied the issue of biology and race. "This is a very,
very minimal reflection of your genetic makeup."

    Unfortunately for social harmony, the human brain is exquisitely
attuned to differences in packaging details, prompting people to exaggerate
the significance of what has come to be called race, said Dr. Douglas C.
Wallace, a professor of molecular genetics at Emory University School of
Medicine in Atlanta.

    "The criteria that people use for race are based entirely on external
features that we are programmed to recognize," he said. "And the reason
we're programmed to recognize them is that it's vitally important to our
species that each of us be able to distinguish one individual from the
next. Our whole social structure is based on visual cues, and we've been
programmed to recognize them, and to recognize individuals."

    By contrast with the tiny number of genes that make some people
dark-skinned and doe-eyed, and others as pale as napkins, scientists say
that traits like intelligence, artistic talent and social skills are likely
to be shaped by thousands, if not tens of thousands, of the 80,000 or so
genes in the human genome, all working in complex combinatorial fashion.

    The possibility of such gene networks shifting their interrelationships
wholesale in the course of humanity's brief foray across the globe, and
being skewed in significant ways according to "race" is "a bogus idea,"
said Dr. Aravinda Chakravarti, a geneticist at Case Western University in
Cleveland. "The differences that we see in skin color do not translate into
widespread biological differences that are unique to groups."

    Dr. Jurgen K. Naggert, a geneticist at the Jackson Laboratory in Bar
Harbor, Me., said: "These big groups that we characterize as races are too
heterogeneous to lump together in a scientific way. If you're doing a DNA
study to look for markers for a particular disease, you can't use
'Caucasians' as a group. They're too diverse. No journal would accept it."

    Yet not every researcher sees race as a meaningless or antediluvian
notion. "I think racial classifications have been useful to us," said Dr.
Alan Rogers, a population geneticist and professor of anthropology at the
University of Utah in Salt Lake City.  "We may believe that most
differences between races are superficial, but the differences are there,
and they are informative about the origins and migrations of our
species.  To do my work, I have to get genetic data from different parts of
the world, and look at differences within groups and between groups, so it
helps to have labels for groups."

    And there are a handful of researchers who continue to insist that
there are fundamental differences among the three major races that extend
to the brain. Dr. J. Philippe Rushton, a psychologist at University of
Western Ontario in Canada and author of "Race, Evolution and Behavior," is
perhaps the most tireless proponent of the belief that the three major
races differ genetically in ways that affect average group I.Q. and a
propensity toward criminal behavior.

    He asserts that his work reveals east Asians to have the largest
average brain size and intelligence scores, those of African descent to
have the smallest average brains and I.Q.'s, and those of European ancestry
to fall in the middle.

    Yet many scientists have objected to his methods and interpretations,
arguing, among other things, that the link between total brain size and
intelligence is far from clear. Women, for example, have smaller brains
than men do, even when adjusted for their comparatively smaller body mass,
yet average male and female I.Q. scores are the same. For that matter,
fossil evidence suggests that Neanderthals had very sizable brains, and
they did not even last long enough to invent standardized tests.

    Dr. Eric S. Lander, a genome expert at the Whitehead Institute in
Cambridge, Mass., admits that, because research on the human genome has
just begun, he cannot deliver a definitive, knockout punch to those who
would argue that significant racial differences must be reflected somewhere
in human DNA and will be found once researchers get serious about looking
for them. But as Dr. Lander sees it, the proponents of such racial divides
are the ones with the tough case to defend.

    "There's no scientific evidence to support substantial differences
between groups," he said, "and the tremendous burden of proof goes to
anyone who wants to assert those differences."

    Although research into the structure and sequence of the human genome
is in its infancy, geneticists have pieced together a rough outline of
human genomic history, variously called the "Out of Africa" or
"Evolutionary Eve" hypothesis.

    By this theory, modern Homo sapiens originated in Africa 200,000 to
100,000 years ago, at which point a relatively small number of them, maybe
10,000 or so, began migrating into the Middle East, Europe, Asia and across
the Bering land mass into the Americas. As they traveled, they seem to have
completely or largely displaced archaic humans already living in the
various continents, either through calculated acts of genocide, or simply
outreproducing them into extinction.

    Since the African emigrations began, a mere 7,000 generations have
passed. And because the founding population of emigres was small, it could
only take so much genetic variation with it. As a result of that
combination -- a limited founder population and a short time since
dispersal -- humans are strikingly homogeneous, differing from one another
only once in a thousand subunits of the genome.

    "We are a small population grown large in the blink of an eye," Dr.
Lander said. "We are a little village that's grown all over the world, and
we retain the genetic variation seen in that little village."

    The human genome is large, though, composed of three billion-odd
subunits, or bases, which means that even a tiny percentage of variation
from one individual to the next amounts to a sizable number of genetic
discrepancies. The question is, where in the genome is that variation
found, and how is it distributed among different populations?

    Through transglobal sampling of neutral genetic markers -- stretches of
genetic material that do not help create the body's functioning proteins
but instead are composed of so-called junk DNA -- researchers have found
that, on average, 88 percent to 90 percent of the differences between
people occur within their local populations, while only about 10 percent to
12 percent of the differences distinguish one population, or race, from
another.

    To put it another way, the citizens of any given village in the world,
whether in Scotland or Tanzania, hold 90 percent of the genetic variability
that humanity has to offer.

    But that 90/10 ratio is just an average, and refers only to junk-DNA
markers. For the genetic material that encodes proteins, the picture is
somewhat more complex. Many workhorse genes responsible for basic organ
functions show virtually no variability from individual to individual,
which means they are even less "race specific" than are neutral genetic
markers.

    Some genes, notably those of the immune system, show enormous
variability, but the variability does not track with racial groupings. Then
there are the genes that control pigmentation and other physical features.
These also come in a wide assortment of "flavors," but unlike
immune-related genes, are often distributed in population-specific
clusters, resulting in Swedes who look far more like other Swedes than they
do like Australian Aborigines.

    A few group differences are more than skin deep. Among the most famous
examples are the elevated rates of sickle-cell anemia among
African-Americans and of beta-thalassemia, another hemoglobin disorder,
among those of Mediterranean heritage.

    Both traits evolved to help the ancestors of these groups resist
malaria infection, but both prove lethal when inherited in a double dose.
As with differences in skin pigmentation, the pressure of the environment
to develop a group-wide trait was powerful, and the means to do so simple
and straightforward, through the alteration of a single gene.

    Another cause of group differences is the so-called founder effect. In
such cases, the high prevalence of an unusual condition in a population can
be traced to a founding ancestor who happened to carry a novel mutation
into the region. Over many generations of comparative isolation and
inbreeding, the community, like it or not, became "enriched" with the
founder's disorder. The founder effect explains the high incidence of
Huntington's neurodegenerative disease in the Lake Maracaibo region of
Venezuela, and of Tay-Sachs disease among Ashkenazi Jews.

    But Dr. Naggert emphasized that medical geneticists had a much better
chance of unearthing these founder effects by scrutinizing small, isolated
and well-defined populations, like the northern Finns, the Basques of
Spain, or the Amish of Pennsylvania, than they did by going after "races."

    Dr. Sonia S. Anand, an assistant professor of medicine at McMaster
University in Ontario, proposed that clinicians think about ethnicity
rather than race when seeking clues to how disease patterns differ from one
group to the next.

    "Ethnicity is a broad concept that encompasses both genetics and
culture," Dr. Anand said. "Thinking about ethnicity is a way to bring
together questions of a person's biology, lifestyle, diet, rather than just
focusing on race. Ethnicity is about phenotype and genotype, and, if you
define the terms of your study, it allows you to look at differences
between groups in a valid way."

    In investigating the reasons behind the high incidence of
cardiovascular disease among people from the Indian subcontinent, for
example, Dr. Anand discovered that Indians had comparatively elevated
amounts of clotting factors in their blood. Beyond tallying up innate
traits, she also takes into account how Indian culture and life habits may
pose added risks for heart disease -- noting, for example, that a woman's
status in India is directly proportional to her number of belly rolls.

    In Dr. Freeman's view, the science of human origins can help to heal
any number of wounds, and that, he says is sweet justice.

    "Science got us into this problem in the first place, with its
measurements of skulls and its emphasis on racial differences and racial
classifications," Dr. Freeman said. "Scientists should now get us out of
it. They need to be leaders in promoting an evolutionary understanding of
the human race."
     http://www.nytimes.com

GRAPHIC: Photos: Scientists say that while it may be easy to tell at a
glance whether a person is Asian, African or Caucasian, the differences
dissolve when one looks beyond surface features and scans the human genome
for DNA hallmarks of "race." (Tony Cenicola/The New York Times)(pg. F1);
Dr. Harold Freeman (The University of Utah); Dr. Eric S. Lander (Chester
Higgins Jr./The New York Times); Dr. Alan Rogers; Dr. Sonia Anand (pg. F6)

Chart: "DNA and the Concept of Race"
DNA studies show that people around the world are far more alike than they
may seem. Over all, scientists estimate that 99.9 percent of the human
genome is the same in everyone.

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