horse mandible from Cave 2 shows a number of cut marks on
the lingual surface. They indicate that the animal's tongue
was cut out with a stone tool. (photo courtesy University
The timing of the
first entry of humans into North America across the Bering Strait
has now been set back 10,000 years.
This has been demonstrated
beyond a shadow of a doubt by Ariane Burke, a professor in Université
de Montréal's Department of Anthropology, and her doctoral
student Lauriane Bourgeon, with the contribution of Dr. Thomas Higham,
Deputy Director of Oxford University's Radiocarbon Accelerator Unit.
Their findings were
published in early January in the open-access journal PLoS One.
The earliest settlement
date of North America, until now estimated at 14,000 years Before
Present (BP) according to the earliest dated archaeological sites,
is now estimated at 24,000 BP, at the height of the last ice age
or Last Glacial Maximum.
The researchers made
their discovery using artifacts from the Bluefish Caves, located
on the banks of the Bluefish River in northern Yukon near the Alaska
border. The site was excavated by archaeologist Jacques Cinq-Mars
between 1977 and 1987. Based on radiocarbon dating of animal bones,
the researcher made the bold hypothesis that human settlement in
the region dated as far back as 30,000 BP.
In the absence of
other sites of similar age, Cinq-Mars' hypothesis remained highly
controversial in the scientific community. Moreover, there was no
evidence that the presence of horse, mammoth, bison and caribou
bones in the Bluefish Caves was due to human activity.
To set the record
straight, Bourgeon examined the approximate 36,000 bone fragments
culled from the site and preserved at the Canadian Museum of History
in Gatineau an enormous undertaking that took her two years
to complete. Comprehensive analysis of certain pieces at UdeM's
Ecomorphology and Paleoanthropology Laboratory revealed undeniable
traces of human activity in 15 bones. Around 20 other fragments
also showed probable traces of the same type of activity.
"Series of straight, V-shaped lines on the surface of the bones
were made by stone tools used to skin animals," said Burke. "These
are indisputable cut-marks created by humans."
Bourgeon submitted the bones to further radiocarbon dating.
The oldest fragment, a horse mandible showing the marks of a stone
tool apparently used to remove the tongue, was radiocarbon-dated
at 19,650 years, which is equivalent to between 23,000 and 24,000
cal BP (calibrated years Before Present).
"Our discovery confirms previous analyses and demonstrates that
this is the earliest known site of human settlement in Canada,"
said Burke. It shows that Eastern Beringia was inhabited during
the last ice age."
Beringia is a vast region stretching from the Mackenzie River
in the Northwest Territories to the Lena River in Russia. According
to Burke, studies in population genetics have shown that a group
of a few thousand individuals lived in isolation from the rest of
the world in Beringia 15,000 to 24,000 years ago.
"Our discovery confirms the Beringian standstill [or genetic
isolation] hypothesis,'" she said, "Genetic isolation would have
corresponded to geographical isolation. During the Last Glacial
Maximum, Beringia was isolated from the rest of North America by
glaciers and steppes too inhospitable for human occupation to the
West. It was potentially a place of refuge."
The Beringians of Bluefish Caves were therefore among the ancestors
of people who, at the end of the last ice age, colonized the entire
continent along the coast to South America.
The results of Lauriane Bourgeon's doctoral research were published
in the January 6 edition of PLoS One under the title "Earliest Human
Presence in North America Dated to the Last Glacial Maximum: New
Radiocarbon Dates from Bluefish Caves, Canada." The article is co-authored
by Professor Burke and by Dr. Thomas Higham of Oxford University's
Radiocarbon Accelerator Unit, in the U.K.