are analyzing DNA from ancient individuals found in southeast
Alaska, coastal British Columbia, Washington state and Montana.
A new genetic analysis of some of these human remains finds
that many of today's indigenous peoples living in the same
regions are descendants of ancient individuals dating to at
least 10,300 years ago. Graphic by Julie McMahon
CHAMPAIGN, Ill. A study of the DNA in ancient skeletal
remains adds to the evidence that indigenous groups living today
in southern Alaska and the western coast of British Columbia are
descendants of the first humans to make their home in northwest
North America more than 10,000 years ago.
"Our analysis suggests that this is the same population living
in this part of the world over time, so we have genetic continuity
from 10,000 years ago to the present," said University of Illinois
anthropology professor Ripan
Malhi, who led the study with University of Chicago postdoctoral
researcher John Lindo; Penn State University biology professor Michael
DeGiorgio; Rosita Worl, the director of the Sealaska Heritage
Institute in Juneau, Alaska; and University of Oklahoma anthropology
professor Brian M. Kemp.
The findings, reported in the Proceedings of the National Academy
of Sciences, also suggest that these early American peoples had
a complex population history, the researchers report.
The new work comes on the heels of earlier studies of ancient
Americans that focused on mitochondrial DNA, which occurs outside
the nucleus of cells and is passed only from mothers to their offspring.
"Mitochondrial DNA just traces the maternal line your
mother's mother's lineage so, you're missing information
about all of these other ancestors," said Lindo, the first author
on the paper. "We wanted to analyze the nuclear genome so we could
get a better assessment of the population history of this region."
The team looked at genomic data from Shuká Káa
(Tlingit for "Man Before Us"), an ancient individual whose remains
found in a cave in southeastern Alaska date to about
10,300 years ago. They also analyzed the genomes of three more individuals
from the nearby coast of British Columbia whose remains date to
between 6,075 and 1,750 years ago.
"Interestingly, the mitochondrial type that Shuká Káa
belonged to was also observed from another ancient skeleton dated
to about 6,000 years ago," Kemp said. "It seems to disappear after
that. The nuclear DNA suggests that this is probably not about population
replacement, but rather chance occurrence through time. If a female
has no children or only sons, the mitochondrial DNA is not passed
to the next generation. As a male, Shuká Káa could
not have passed on his own mitochondrial DNA; he must have had some
maternal relatives that did so."
The researchers turned their attention to nuclear DNA, which
offers a more comprehensive record of a person's ancestry.
"DNA from the mitochondria and Y chromosome provide unique yet
sometimes conflicting stories, but the nuclear genome provides a
more comprehensive view of past events," DeGiorgio said.
"The data suggest that there were multiple genetic lineages
in the Americas from at least 10,300 years ago," Malhi said.
The descendants of some of those lineages are still living in
the same region today, and a few are co-authors on the new study.
Their participation is the result of a long-term collaboration between
the scientists and several native groups who are embracing genomic
studies as a way to learn from their ancestors, said Worl, who is
Tlingit, Ch'áak' (Eagle) moiety of the Shangukeidí
(Thunderbird) Clan from the Kawdliyaayi Hít (House Lowered
From the Sun) in Klukwan, Alaska.
"We supported DNA testing of Shuká Káa because
we believed science ultimately would agree with what our oral traditions
have always said that we have lived in southeast Alaska since
time immemorial. The initial analysis showed the young man was native,
and now further studies are showing that our ancestral lineage stems
from the first initial peopling of the region," said Worl, who also
is an anthropologist. "Science is corroborating our oral histories."
The National Science Foundation supported this research.
Malhi is an affiliate of the Carl
R. Woese Institute for Genomic Biology at the U. of I.
of Illinois Urbana-Champaign