by Nicholas Wade
(NYT) SCIENCE DESK
May 2, 2000, Tuesday
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The book of Genesis mentions three of
Adam and Eve’s children: Cain, Abel and Seth. But geneticists, by
tracing the DNA patterns found in people throughout the world, have
now identified lineages descended from 10 sons of a genetic Adam and
18 daughters of Eve.
The human genome is turning out to be a rich new archive for
historians and prehistorians, one whose range extends from recent
times to the dawn of human existence.
Delvers in the DNA archive have recently found evidence for a
prehistoric human migration from Western Asia to North America;
identified the people who seem closest to the ancestral human
population; and given substantial weight to the whispers, long
dismissed by historians, that Thomas Jefferson fathered a family
with his slave Sally Hemings.
A new history of Britain and Ireland by Norman Davies, ’’The
Isles,’’ (Oxford University Press) begins with an account of
man, an 8,980-year-old skeleton from which mitochondrial DNA was
The DNA turned out to match that of Adrian Targett, a teacher in a Cheddar Village school, proving a genetic
continuity that, despite numerous invasions, had endured through
Unlike the DNA test used in forensic cases, which is designed to
identify individuals, DNA analysis that seeks to reach back in time
usually focuses on lineages, not individuals. From patterns in the
DNA data, biologists can often estimate the sizes of ancient
populations and even the approximate dates when one group of people
split from another.
Though DNA can bear on historical questions, often by acting as a
long-range paternity test, its most spectacular use has been in
prehistory, where it has added a new dimension to the bare framework
provided by archaeology.
The most detailed human family tree so far available is one
constructed over many years by Dr. Douglas C. Wallace and his
colleagues at the Emory University School of Medicine in Atlanta.
Dr. Wallace’s tree is based on mitochondrial DNA, tiny rings of
genetic material that are bequeathed only by the egg cell and thus
through the maternal line. A counterpart tree for men, based on
analysis of the Y chromosome, has been prepared by Dr. Peter A.
Underhill and Dr. Peter J. Oefner of Stanford University.
Population geneticists believe that the ancestral human population
was very small -- a mere 2,000 breeding individuals, according to a
calculation published last December. But the family tree based on
human mitochondrial DNA does not trace back to the thousand women in
this ancestral population. The tree is rooted in a single
individual, the mitochondrial Eve, because all the other lineages
The same is true of the Y chromosome tree, a consequence of the fact
that in each generation some men will have no children, or only
daughters, so the number of different Y chromosomes may steadily
diminish, even if the population stays the same size.
This ancestral human population lived somewhere in Africa,
geneticists believe, and started to split up some time after 144,000
years ago, give or take 10,000 years, the inferred time at which
both the mitochondrial and Y chromosome trees make their first
Mitochondria, which live inside human cells but outside the nucleus,
escape the shuffling of genes that occurs between generations and
are passed unchanged from mother to children. In principle, all
people should have the same string of DNA letters in their
mitochondria. In practice, mitochondrial DNA has steadily
accumulated changes over the centuries because of copying errors and
Because women were steadily spreading across the globe when many of
these changes occurred, some changes are found only in particular
regions and continents.
Dr. Wallace discovered that almost all
American Indians have mitochondria that belong to lineages he named
A, B, C and D.
Europeans belong to a different set of lineages,
which he designated H through K and T through X. The split between
the two main branches in the European tree suggests that modern
humans reached Europe 39,000 to 51,000 years ago, Dr. Wallace
calculates, a time that corresponds with the archaeological date of
at least 35,000 years ago.
In Asia there is an ancestral lineage known as
M, with descendant
branches E, F and G as well as the A through D lineages also found
in the Americas.
In Africa there is a single main lineage, known as
L, which is
divided into three branches. L3, the youngest branch, is common in
East Africa and is believed to be the source of both the Asian and
Dr. Wallace’s mitochondrial DNA lineages are known technically as
but more colloquially as ’’daughters of Eve,’’ because all are
branches of the trunk that stems from the mitochondrial Eve.
The Y chromosome tree has not yet been published by the Stanford
researchers, but in a book that came out in March, ’’Genes, People
and Languages,’’ a colleague at the university, Dr.
Luca Cavalli-Sforza, sketched a preview of the findings.
The tree is rooted in a single Y chromosomal Adam, and has 10
principal branches, Dr. Cavalli-Sforza reports. Of these sons of
Adam, the first three (designated I, II and III) are found almost
exclusively in Africa. Son III’s lineage migrated to Asia and begat
sons IV-X, who spread through the rest of the world -- to the Sea of
Japan (son IV), northern India (son V) and the South Caspian (sons
VI and IX).
Dr. Cavalli-Sforza believes these Y chromosome lineages may be
associated with the major language groups of the world. The South
Caspian population, for example, may have spoken Eurasian, the
ancestral tongue of Indo-European (to which English belongs) and
most of the continent’s other major language families. But Dr.
Wallace, asked if his mitochondrial DNA lineages also corresponded
to the world’s major language groups, said he ’’tended to be more
cautious than Luca.’’
Dr. Wallace has recently been exploring the root of the
mitochondrial tree. In an article published in March in The American
Journal of Human Genetics, he and colleagues identify the Vasikela
Kung of the northwestern Kalahari desert in southern Africa as the
population that lies nearest to the root of the human mitochondrial
DNA tree. Another population that seems almost equally old is that
of the Biaka pygmies of Central Africa. Both peoples live in
isolated regions, which may be why their mitochondrial DNA seems
little changed from that of the ancestral population.
looking at the beginning of what we would call Homo sapiens,’’ Dr.
One of the most vexed issues in human prehistory is the timing and
number of migrations into the Americas. Dr. Joseph Greenberg, a
linguist at Stanford University, has proposed three migrations,
corresponding to the three language groups of the Americas, known as
Amerind, Na-Dene and Eskimo-Aleut. Dr. Wallace’s mitochondrial DNA
data broadly support this general thesis, though the arrival of the Amerind-speakers seems more complex than a single migration.
Of the A through D lineages found in American Indians, A, C and D
also occur in Siberian peoples, suggesting that their ancestors were
the principal source of the Amerind-speakers’ migration. But the B
lineage, though it is found elsewhere in Asia, has not turned up in
Siberia, a hint that the B people may have taken a sea route to the
Americas and then merged there with their A- , C- and D-carrying
In 1998, Dr. Wallace and his colleagues discovered the X pattern, a
rare European lineage, among the northern Native Americans such as
the Ojibwa and Sioux. At first they assumed it came from
intermarriage with modern Europeans. But the American X lineage
turned out to be pre-Columbian and its owners would have arrived in
America either 15,000 or 30,000 years ago, depending on certain
The European X lineage seems to have originated in Western Asia
around 40,000 years ago. Dr. Wallace suggests a part of this group
may have made their way to America via Siberia, even though no
traces of the X-lineage have yet turned up in eastern Asia. A
trans-Atlantic route is a possible alternative.
When modern humans first started to leave Africa, about 50,000 years
ago by present reckoning, they probably consisted of small groups of
hunter-gatherers a few hundred strong. In their determined
exploration of the world before them, they must have overcome, with
the primitive means at their disposal, the extreme rigors of
climate, terrain and perhaps the archaic human populations like the
fearsome Neanderthals who had preceded them out of Africa.
The biologist Edward O. Wilson, in a recent interview with The Wall
Street Journal, mused that a new basis for spiritual values might be
found - not in the usual religious sources but in what he sees as
the inspiring story of human origins and history.
’’We need to
create a new epic based on the origins of humanity,’’ he said,
adding: ’’Homo sapiens have had one hell of a history! And I am
speaking both of deep history - evolutionary, genetic history -
and then, added on to that and interacting with it, the cultural
history recorded for the past 10,000 years or so.’’
Many of the biologists who are reconstructing the human past
certainly believe their work has a value that transcends genetics.
Although their lineage trees are based on genetic differences, most
of these differences lie in the regions of DNA that do not code for
genes and have no effect on the body.
’’We are all Africans at the Y
chromosome level and we are really all brothers,’’ Dr. Underhill
Dr. Wallace remarked that since he started working on mitochondrial
DNA in the late 1970’s:
’’What I have found astounding is that it
clearly shows we are all one human family. The phylogeny in Africa
goes back to the origins of our species, but the fingers of L3 are
touching Europe and Asia, saying that we are all closely related.’’
Whether or not genetic prehistory is suitable material for a modern
origin myth, it is about to be made available to a wider public.
Last month a company called Oxford Ancestors set up business with
the offer to tell customers which of the seven daughters of Eve they
are descended from. (Almost all Europeans belong to only seven of
the nine mitochondrial lineages found in Europe). The test (see
www.oxfordancestors.com) requires sending in a sample of cells
brushed from the inside of the cheek. For a mere $180, anyone of
European ancestry can establish the start of a genealogy far senior
The company’s founder is Dr. Bryan Sykes, a human geneticist at the
University of Oxford in England. On the reasonable basis that the
founders of Dr. Wallace’s mitochondrial DNA lineages were real
women, Dr. Sykes gave them names and sketched in details of their
likely dates and origin.
Thus people found to belong to haplogroup U
will be told they are descended from Ursula, who lived about 45,000
years ago in Northern Greece. Ancestor of the X’s is Xenia, who
lived 25,000 years ago in the Caucasus mountains.
As if fulfilling Dr. Wilson’s suggestion, Dr. Sykes said he had,
’’worked out a mythological framework for these seven women,’’ in
respect of the arduous times in which they must have lived and the
triumph of spreading their mitochondrial DNA to almost all the
inhabitants of Europe.
He is now working on tests to identify other lineages around the
world, including 14 in Africa, and 16 in Eurasia and the Americas.
’’I don’t think this stuff should be confined to academics,’’ he