Monday, November 4, 2019

Study reveals 10,000 years of genetic continuity in northwest North America

Researchers 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, University of Illinois

10,000 years of genetic continuity in northwest North America
HeritageDailyApril 5, 2017

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.”

Sunday, November 3, 2019

Oldest Evidence of North American Settlement May Have Been Found

The Cooper's Ferry archeological site is in western Idaho.

Oldest Evidence of North American Settlement May Have Been Found in Idaho

The first settlers of North America might have been seafarers

Humans might have first settled North America around 16,000 years ago, setting off on boats from northeast Asia and traveling along the Pacific Coast, new findings suggest. That's the earliest evidence yet of settlement in this region.

The mystery of how the first settlers arrived in North America remains hotly debated. For years, the dominant theory has been that the first people to arrive in North America walked across the Bering Land Bridge, which connected Asia and North America, when sea levels dropped at the end of the last ice age. From there, the theory holds, they followed an ice-free corridor which opened around 14,800 years ago, down to North America.

But growing evidence suggests that the first settlers didn't trudge through a flat, grassy plain following large prey, but rather set off along the Pacific Coast in ancient boats.

This ancient migration was one of the last major movements of people across the planet, said lead author Loren Davis, a professor of anthropology at Oregon State University. So, "people have a sense of wonder" about this journey, Davis said.

To re-create the picture of this vast, ancient migration, Davis and his team analyzed ancient remains found at the Cooper's Ferry archaeological site, which sits at the junction of the Rock Creek and the lower Salmon River in western Idaho.

The Cooper's Ferry site was first excavated back in the 1960s. Prior to that, it was once an ancient village called Nipéhe, according to oral histories recounted to Davis by the Niimíipuu tribe. Between 2009 and 2018, Davis and his team opened up and excavated two large holes in the ground — one of which is the focus of this study. In that pit, spanning just 23 feet by 43 feet (7 meters by 13 meters), they discovered a trove of early remains and artifacts.

The team uncovered 189 artifacts, including 27 stone tools and 161 pieces of debitage, or flakes of rock created in the process of making stone tools. The tools included stemmed point fragments, which have previously been found all around the western U.S.

They also found bone fragments from an extinct horse, Davis said. Around the animal bone fragments the team discovered numerous stone tools. A little ways away, they found something resembling a hearth or fire pit. "We think that represents someone butchering a horse," and then possibly cooking and eating it, Davis told Live Science.

This might be "the earliest radiocarbon-dated evidence of people interacting with extinct animals in North America," Davis said. Through radiocarbon dating, a method that analyzes radioactive carbon in biological samples to figure out their ages, they found that biological samples in the hearth were similar in age to the bones.

The radiocarbon dating of these charcoal and bone samples revealed that people occupied the area for a long period of time, but the oldest biological samples were between 16,560 and 15,280 years old. Since they were found in the same layers as human artifacts, such as tools, they are likely of similar age, Davis said.

For a long time, it was thought that the first settlers of the Americas were the "Clovis" people who arrived around 13,000 years ago. But later excavations at various sites in North and South America revealed evidence of settlements that predated the Clovis culture, such as Monte Verde in Chile, which has some artifacts of human settlement that date to between 14,000 and 19,000 years ago.

These new results suggest that humans already lived in Idaho around 16,000 years ago — over a thousand years earlier than the time during which an ice-free corridor opened up across the western U.S. "So you might say that we refuted the hypothesis of the ice-free corridor," Davis said. The findings lend "great support to the idea that people came down the Pacific Coast instead."

This study "provides further support for the Pacific coast as the route by which Native Americans arrived in mid-latitude North America," said John Hoffecker, a fellow at the Institute of Arctic and Alpine Research at the University of Colorado, Boulder, who was not a part of the study. But "the authors have exaggerated the results of the dating." The dating suggests that the "earliest occupation of Cooper's Ferry is likely to be somewhat younger," closer to 15,000 years ago, Hoffecker told Live Science.

The authors suggest that some of the tools they found at Cooper's Ferry, such as the spear or dart points, are very similar to those found in northern Japan from a similar time. "So one hypothesis is simply that you're looking at the extension culturally of people that are bringing these ideas with them from northern Japan," Davis said.

But "both genetics and dental anthropology indicate unequivocally that Native Americans are not derived from northern Japan," Hoffecker said referring to the ancient people who lived in Japan.

The comparison of these Western stemmed points with Japanese counterparts is "superficial and unconvincing, based on five specimens selected for suggested morphological similarity," said Ben Potter, the department chair and a professor of archeology at the University of Alaska Fairbanks, who was also not a part of the study.

What's more, the findings don't refute the idea that the first people arrived via the ice-free corridor, he said. The feature with the "oldest consistent dates," does not preclude the passage through the ice-free corridor, he said.

In any case, "there appears to be an interesting and dynamic geoarchaeological story here," Potter told Live Science. "My perspective is that Cooper’s Ferry is intriguing, but not paradigm shifting."

Next, Davis and his team hope to further explore if there really is a connection between these ancient inhabitants and the people of ancient Japan and spend more time analyzing the artifacts that they spent a decade excavating.

Friday, November 1, 2019

Earliest Evidence of Humans Living in South America


Monte Verde: Our Earliest Evidence of Humans Living in South America
By Bridget Alex November 1, 2019 2:00 AM

As the Ice Age began to wane, people from northeastern Asia spread to the Americas, some of the last uninhabited continents on Earth. The pioneers traveled south of mile-high ice sheets covering Canada and found vast lands, abounding with mammoth, giant sloth and other now-extinct megafauna.

This much has been known for decades. But when it comes to the details, debates have raged over precisely when and how humans populated the New World. Today, the story is beginning to take shape, thanks to well-dated archaeological sites, DNA analysis and geological work to understand when ice and sea levels permitted entry to the Americas. It’s clear that people occupied the continents by about 15,000 years ago, probably taking a route along the Pacific coast.

And one site, perhaps more than any other, helped scholars reach this conclusion: Chile’s Monte Verde. During excavations begun in the 1970s, archaeologists unearthed numerous artifacts, including remnants of 14,000-year-old huts, food scraps from megafauna and wads of masticated seaweed, likely chewed for medicinal purposes. The preservation was so exceptional, it cleared any doubt that humans had reached the New World by this time, and earned Monte Verde a place in every archaeology textbook to come.

Meanwhile, recent research on the site’s surroundings and deeper layers suggests humans inhabited this patch of South America as early as 19,000 years ago. While the claim remains controversial, it’s clear there’s still more to discover at Monte Verde.

Creekside Campsite
Buried under a peat bog, Monte Verde is near South America’s tip and about 30 miles from the Pacific in present-day Chile. Excavations began in 1976, led by archaeologist Tom Dillehay. Although no human skeletons were found, an excavated layer — radiocarbon dated to about 14,000 years ago — held clear evidence of human inhabitants, including a child-sized footprint.

At Monte Verde, the researchers discovered the ruins of a forager campsite, about as large as a football field, on the bank of a meandering creek. Still surviving were the wooden foundations of a long, rectangular building, which was subdivided into a dozen rooms, each containing food remains and clay-lined fire pits. It seems to have been a communal residence divided into personal dwellings. About 100 feet from these living quarters stood a wishbone-shaped structure accompanied by tools and butchered animal parts — likely a work area.

The archaeologists also recovered spun grass rope, wooden lances, animal hides and human feces from the site. Perishable items like these are rarely preserved at archaeological sites. But because Monte Verde is below peat deposits, organic materials were protected from decomposition. Food scraps also survived, revealing the people gathered at least 60 species of edible and medicinal plants, including a variety of seaweed species brought from the coast. And they hunted now-extinct creatures such as paleocamelids (an ancestor of llama and alpaca) and elephant-like gomphotheres.

Breaking the Clovis Barrier
Just as significant, though, is what the excavators did not find: Monte Verde lacked Clovis points — distinctive stone tools found at North American sites dating to roughly 13,000 years ago. Through much of the 20th century, many archaeologists supported “Clovis First” — the hypothesis that the people who made these artifacts were the first inhabitants of the Americas. Reports of older pre-Clovis sites were dismissed on the grounds that they were incorrectly excavated or dated.

But Monte Verde was remarkably well-preserved, meticulously excavated and analyzed with state-of-the-art methods. It convinced the archaeological community that non-Clovis peoples reached South America by at least 14,000 years ago. Clovis was not first.

Since then, numerous pre-Clovis sites have been reported between 13,300 and 15,000 years old. North America holds about 10 of them. But in South America, besides Monte Verde and its surrounding area, there are only two others: Huaca Prieta in Peru and Arroyo Seco in Argentina. With so few comparative sites, it’s difficult to say who and how widespread the Monte Verde people were.

Older Occupations
Dillehay and colleagues also reported potentially older artifacts from Monte Verde in a 1988 Nature paper. From a deeper layer dated to 30,000 years ago, they found three clay-lined burned areas and at least six stones that appear to have been shaped into tools. However, the finds were considered too meager to constitute a strong case for human presence.

Decades later, in 2013, Dillehay returned to the site to lead a team that dug 80 probes and test pits in the land around Monte Verde. The work, published in a 2015 PLOS One paper, identified 12 discrete spots with signs of a campfire (charcoal, ash, burned clay), stone tools and animal bones. Radiocarbon analysis dated the finds between 14,500 and 19,000 years ago.

The results suggest even earlier peopling of the Americas. Future work at Monte Verde may prove it.