American Indian Council
Land Bridge Migration Theory
as far back as our stories and collective memories go back in time, indigenous
people have always believed that we began our journey on Turtle Island tens of
thousands of years ago -- long before most anthropologists theorize. A
majority of scientists assume that migration began in Asia by a small human
population who survived the last glacial movement in Beringia, the "Land Bridge"
between today's Alaska and China. According to the theory, the small group
was isolated from its ancestor populations in Asia as the glaciers melted for at
least 5,000 years, before expanding to populate the North American continent
sometime after 16,500 years ago.
We are happy to report the latest
scientific DNA studies show a much different picture, one that proves American
Indians did not originate from Asian Mongolians, but are a separate and distinct
race who evolved tens of thousands of years ago from islands or a single island
in the Pacific Ocean.
We invite you to read two reports
attached to this article that offer strong evidence that will hopefully, once
and forever, debunk the Land Bridge theory:
Americans Descended From A Single Ancestral Group, DNA Study
ScienceDaily (Apr. 29, 2009)
— For two decades, researchers have been using a growing volume
of genetic data to debate whether ancestors of Native Americans
emigrated to the New World in one wave or successive waves, or
from one ancestral Asian population or a number of different
painstakingly comparing DNA samples from people in dozens of
modern-day Native American and Eurasian groups, an international
team of scientists thinks it can put the matter to rest:
virtually without exception, the new evidence supports the
single ancestral population theory.
“Our work provides
strong evidence that, in general, Native Americans are more
closely related to each other than to any other existing Asian
populations, except those that live at the very edge of the
Bering Strait,” said Kari Britt Schroeder, a lecturer at the
University of California, Davis, and the first author on the
paper describing the study.
“While earlier studies
have already supported this conclusion, what’s different about
our work is that it provides the first solid data that simply
cannot be reconciled with multiple ancestral populations,” said
Schroeder, who was a Ph.D. student in anthropology at the
university when she did the research.
The study is published
in the May issue of the journal Molecular Biology and
The team’s work follows
up on earlier studies by several of its members who found a
unique variant (an allele) of a genetic marker in the DNA of
modern-day Native American people. Dubbed the “9-repeat allele,”
the variant (which does not have a biological function),
occurred in all of the 41 populations that they sampled from
Alaska to the southern tip of Chile, as well as in Inuit from
Greenland and the Chukchi and Koryak people native to the Asian
(western) side of the Bering Strait. Yet this allele was absent
in all 54 of the Eurasian, African and Oceanian groups the team
Overall, among the 908
people who were in the 44 groups in which the allele was found,
more than one out of three had the variant.
In these earlier
studies, the researchers concluded that the most straightforward
explanation for the distribution of the 9-repeat allele was that
all modern Native Americans, Greenlanders and western Beringians
descend from a common founding population. Furthermore, the fact
that the allele was absent in other Asian populations most
likely meant that America’s ancestral founders had been isolated
from the rest of Asia for thousands of years before they moved
into the New World: that is, for a period of time that was long
enough to allow the allele to originate in, and spread
throughout, the isolated population.
As strong as this
evidence was, however, it was not foolproof. There were two
other plausible explanations for the widespread distribution of
the allele in the Americas.
If the 9-repeat allele
had arisen as a mutation multiple times, its presence throughout
the Americas would not indicate shared ancestry. Alternatively,
if there had been two or more different ancestral founding
groups and only one of them had carried the 9-repeat allele,
certain circumstances could have prompted it to cross into the
other groups and become widespread. Say that there was a second
allele — one situated very close to the 9-repeat allele on the
DNA strand — that conferred a strong advantage to humans who
carried it. Natural selection would carry this allele into new
populations and because of the mechanics of inheritance, long
stretches of DNA surrounding it, including the functionless
9-repeat allele, would be carried along with the beneficial
To rule out these
possibilities, the research team, which was headed by Noah
Rosenberg at the University of Michigan, scrutinized DNA samples
of people from 31 modern-day Asian populations, 19 Native
American, one Greenlandic and two western Beringian populations.
They found that in each
sample that contained the 9-repeat allele, short stretches of
DNA on either side of it were characterized by a distinct
pattern of base pairs, a pattern they seldom observed in people
without the allele. “If natural selection had promoted the
spread of a neighboring advantageous allele, we would expect to
see longer stretches of DNA than this with a similarly distinct
pattern,” Schroeder said. “And we would also have expected to
see the pattern in a high frequency even among people who do not
carry the 9-repeat allele. So we can now consider the positive
selection possibility unlikely.”
The results also ruled
out the multiple mutations hypothesis. If that had been the
case, there would have been myriad DNA patterns surrounding the
allele rather than the identical characteristic signature the
“There are a number of
really strong papers based on mitochondrial DNA — which is
passed from mother to daughter — and Y-chromosome DNA — which is
passed from father to son — that have also supported a single
ancestral population,” Schroeder said. “But this is the first
definitive evidence we have that comes from DNA that is carried
by both sexes.”
Other authors of the
study are David G. Smith, a professor of anthropology at UC
Davis; Mattias Jacobsson, University of Michigan and Uppsala
University in Sweden; Michael H. Crawford, University of Kansas;
Theodore Schurr, University of Pennsylvania; Simina Boca, Johns
Hopkins University; Donald F. Conrad and Jonathan Pritchard,
University of Chicago; Raul Tito and Ripan Malhi, University of
Illinois, Urbana-Champaign; Ludmilla Osipova, Russian Academy of
Sciences, Novosibirsk; Larissa Tarskaia, Russian Academy of
Sciences, Moscow; Sergey Zhadanov, University of Pennsylvania
and Russian Academy of Sciences, Novosibirsk; and Jeffrey D.
Wall, UC San Francisco.
The work was supported
by NIH grants to Rosenberg and Smith and an NSF Graduate
Research Fellowship to Schroeder.
Fragments Hint Some American Natives May Hail From Polynesia
by Jerry E. Bishop, staff reporter
St. Louis -- Douglas C. Wallace can
see the future in a tiny strand of DNA. ... But he also can peer deep into the
past. He has looked back more than 100,000 years to the first humans in Africa.
And recently, as a gathering here of science reporters, he painted a picture of
prehistoric migrations emerging from DNA that is exciting anthropologists.
The scene depicts groups of
prehistoric, intrepid mariners moving, not out of Siberia as anthropologists
have long assumed, but out of Southeast Asia across the Pacific into the
Americas 6,000 to 12,000 years ago. If this picture is accurate, it makes many
American Indians distant cousins of the Polynesians.
Dr. Wallace's crystal ball is a
unique fragment of DNA hidden in every human cell. This clairvoyant DNA is
distinct and separate from the long strings of DNA that house almost all human
genes in the cell nucleus. It resides, instead, in an outlying compartment
called a mitochondrion. Hence its name: mitochondrial DNA, or simply mtDNA.
The mtDNA contains a mere 37 genes
compared with the 50,000 to 100,000 genes in nuclear DNA. And these few mtDNA
genes are devoted largely to the mitochondria's principal job of producing
chemical energy for the thousands of second-by-second chemical reactions in a
Yet, astonished medical researchers
are finding that defects in this snippet of DNA can cause human disease. And, to
the surprise of anthropologists, mtDNA is turning into a kind of biological
Rosetta stone for decoding human origins.
Loud Ties, Deep Theories
Few scientists studying mtDNA are
probing deeper--and risking more--than Doug Wallace, a professor of genetics and
molecular medicine at Emory University in Atlanta. Slight and bespectacled, the
47-year-old scientist is famous among his students for loud neckties and, until
recently, his polyester suits. ("When I finally got a raise my wife took all my
leisure jackets and threw them away," he says.)
Clearly, mtDNA has become Dr.
Wallace's consuming, almost obsessive interest. ... Yet this detour into
anthropology via mtDNA isn't without controversy.
Dr. Wallace, for example,
subscribes to the much-publicized "Eve hypothesis," in which a reading of mtDNA
indicates modern humans originated in Africa 100,000 to 200,000 years ago. Some
anthropologists retort that mtDNA is an unreliable clock for timing human
evolution, and that the fossil evidence shows modern humans evolved much earlier
than mtDNA indicates.
But it is another strange property
of mitochondria that unexpectedly thrust the young scientist into the study of
human origins. Humans inherit two copies of the nuclear genes, one from each
parent. But only the mother's mitochondrial genes are passed on to the child for
reasons still not fully understood.
Thus, every person's mtDNA is
descended in a direct line through female ancestors. There isn't any DNA from
the father's side of the family mixed in to confuse the line of descent. This
phenomenon of maternal inheritance had been seen in animals but it was a young
Doug Wallace who showed it occurred in humans in a series of experiments in 1979
at Stanford University in Palo Alto, Calif.
Dr. Wallace ... saw in this
maternal inheritance a way to tell how closely groups of people are related. As
mtDNA is passed down from mother to daughter, innocuous alterations or mutations
are bound to occur. Over a few thousand years, groups of people who live
together and intermarry will accumulate distinctive patterns of these mutations.
In 1981 Dr. Wallace headed a
Stanford research team that found that ethnic groups could be identified and
linked to their continent of origin by the mutation patterns in their mtDNA.
Moreover, by determining how often these telltale mutations occurred, it was
possible to calculate how long ago certain groups stopped intermarrying and
separated, each going off to develop its own unique pattern of mtDNA mutations.
"Each continent had a different
pattern" of mtDNA mutations, Dr. Wallace recalls of his research findings.
Africans had mtDNA variations that distinguished them from Asians who, in turn,
had variations that distinguished them from European-American Caucasians.
"That's when I knew we had an anthropological story," he says. ...
Dr. Wallace began studying the
mtDNA of Native Americans in the mid-1980s in hopes of resolving a long-raging
debate over when prehistoric peoples entered the Americas. The presumption long
has been that the ancestors of Native Americans came from Siberia. But
anthropologists have argued for year over how many, and when, such migrations
The mtDNA analyses are showing that
the ancestors of the Amerinds, who comprise most Native Americans, entered the
Americans in a single migratory wave 20,000 to 40,000 years ago, Dr. Wallace and
his Emory colleagues ... reported last year. This puts humans in the Americas
long before a fluted stone-spear point--the oldest American tool ever found--was
dropped by a prehistoric dweller near Clovis, N.M., 11,000 years ago.
The researchers also found that
ancestors of the Navajo, Apache and other members of a Native American group,
known collectively as the Na-Dene, are latecomers; they entered the continent in
a second migration a mere 5,000 to 10,000 years ago, the research indicates.
To their surprise, however, the
researchers found that native Siberians lack one peculiar mutation that appeared
in the Amerinds 6,000 to 10,000 years ago. This raises the question of where, if
not from Siberia, this mtDNA originated.
It turns out, Dr. Wallace says,
that this particular mutation pattern is also found in aboriginal populations in
Southeast Asia and in the islands of Melanesia and Polynesia. This hints at what
may have been "one of the most astounding migrations in human experience," he
says. A group of ancient peoples moved out of China into Malaysia where they
became sailors and populated the islands of the South Pacific.
Then some 6,000 to 12,000 years ago
these ancient mariners made it to the Americas. "I don't know how they came,"
Dr. Wallace says. "They either came across the Pacific to Central and South
America or they went up the east coast of Asia and across the northern Pacific
to Alaska and Canada," he says. He already is examining mtDNA samples from
natives of the Kamchatka Peninsula north of Japan to see if there is any mtDNA
trace of these ancient sailors.
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