Print

Print


Mapping Human History: Genes, Race and Our Common Origins
Message-Id: <[log in to unmask]>
Mime-Version: 1.0
Content-Type: text/plain
content-length: 5924


[This week the completed draft of the human genome was
published. To mark this occasion, we present a review
of a recent book which uses human genetic information
to unravel the story of our common ancestry, and to
confront myth and reality of human differences. --
moderator.]

Mapping Human History: Genes, Race and Our Common
Origins By Steve Olson

Reviewed by Merete Rietveld

September 27, 2002 Genome News Netword <
http://gnn.tigr.org/articles/09_02/small_world.shtml>


Steve Olson has written a book that promises one of the
best stories we have ever heard: The story written in
our DNA. "It has adventure, conflict, triumph, and
sexlots of sex. It ranges from jungles to deserts to
icy plains, across generations and thousands of years."

Mapping Human History follows humans from Africa to
Europe, Asia, the Middle East, and the Americas,
tracking their movement across continents, exploring
regional genetic histories, and interviewing local
geneticists at every stop. Reconstructing the history
of various peoples, the book points out how the
historical trajectories of humans constantly overlap.

Olson, a science journalist who has also worked for the
US National Academy of Sciences, tells us that everyone
in the world can most likely claim Confucius and Julius
Caesar among our ancestors once we trace our lineage
back a couple of millennia. Population statistics
proves such claims to be true, he writes. The
exponential growth of our ancestorsfrom two parents to
four grandparents, eight greatgrandparents, and going
back forty generations to more than a trillion direct
ancestorsleads us to a time in history when, in theory,
the number of ancestors would exceed the total world
population.

Genetics confirms that human groups are all closely
related and possess only the most superficial genetic
differences. Due to the "natural human tendency to
interbreed" and our species' history of migrating from
continent to continent, everyone is connected to a
common pool of ancestors. The author denies that human
groups have significant biological differences, yet
stops short of saying that race has no genetic basis.
We have not 'evolved' since the emergence of Homo
sapiens from Africa 150,000 years ago.'

Olson contends that race and ethnicity are social
constructions that people have justified by assuming
that biological differences exist. "Many people...cite
genetics as the source of group differences...believing
that outward variations in skin color, facial features
or body shape reflect much more consequential
differences of character, temperament, or
intelligence."

While the genetic differences between ethnic groups
create different physical features and propensities to
certain diseases, Olson claims that these variations
are "meaningless" in comparison to the natural genetic
variation in humans. Still, geneticists will continue
to study the slight variations between ethnic groups
because they have crucial implications for biomedical
and historical research.

Such studies not only look into the genetic causes of
disease, but also reveal information on the merging and
separation of human groups over time. Mutationscreated
when cells reproduce their DNAare the "key to
reconstructing our genetic history," writes Olson.
Parents bequeath mutations to their children, creating
a unique genetic pattern that spreads throughout
certain populations. By counting the mutations that
differ between two distinct DNA sequences, geneticists
can find out who is related to whom and estimate the
number of generations that have passed since a common
ancestor existed.

Despite the genetic variations among humans, Olson
claims that we have not "evolved" since the emergence
of Homo sapiens from Africa 150,000 years ago. "Our
basic body plan was set more than 100,000 years ago.
Since then, we have been in a period of evolutionary
stasis."

Throughout Mapping Human History, Olson says that human
beings have never been able to resist the "urge to
merge." Consequently, our species has interbred too
enthusiastically to develop substantial genetic
differences. The author's enthusiasm for this idea
overreaches in a passage that addresses a period of
cohabitation between Neanderthals and modern humans in
Europe. He rationalizes that humans must have interbred
with local Neanderthals because modern statistical data
show that up to 50 percent of men on farms have had
"sexual experiences with animals." Speculations abound
in the anthropological parts of the book, but there is
no provision of a convincing backup.

In the chapter entitled "The End of Evolution," Olson
contends "no one group is more closely related to our
ancestors than any other." However, a few paragraphs
later he writes that perhaps the Bushmen of eastern
Africa "retain some of the characteristics of our early
modern ancestors" because they live in a place where
the original Homo sapiens are thought to have lived.

In the final chapters of the book, Olson questions the
practice of studying the genetics of ethnic groups. He
worries that although "the only way to understand how
similar we are is to learn how we differ-studies of
human differences can seem to play into the hands of
those who would accentuate those differences." Some may
benefit from tracing their lineage back to royalty, but
others could be stigmatized by possessing genes
associated with disease, for example.

Olson admits that pursuing genetic knowledge implies
both risks and opportunities. His lasting vision is "a
world in which people are free to choose their
ethnicity regardless of their ancestry."

See related GNN book review Clan Mothers and Ancient
Travelers: A review of Bryan Sykes' The Seven Daughters
of Eve

Merete Rietveld is a freelance writer who lives in Palo
Alto, California.