Raghavan et al., Science (2015)
Raghavan et al., Science (2015)

The First People Entered the Americas 23,000 Years Ago, Study Finds

Raghavan et al., Science (2015)
Raghavan et al., Science (2015)

People arrived in the Americas relatively later than on other continents. The oldest evidence for anatomically modern humans in Asia comes from bones that are at least 46,000 years old, for instance, while the oldest archaeological evidence for people in the Americas, found in Chile, is only 15,000 years old

Two new scientific papers provide new information about how people migrated to North and South America thousands of years ago, one that indicates that humans migrated in a single wave from Siberia 23,000 years ago, and one that finds evidence for a genetic link between some Amazonian peoples and indigenous Australians and islanders from southeast Asia. 

In a study published in the journal Science, an international team of researchers led by the University of Copenhagen analyzed the DNA of contemporary Native American and Siberian populations and compared their genetics to genetic data taken from ancient Native American DNA dating back 200 to 6000 years ago, including some from the ancient Washington state resident known as Kennewick Man.

They determined that all Native American populations descended from a single migration wave across the Bering Strait and into the Americas as long as 23,000 years ago, though there was a later wave of migration that established Eskimo and Inuit populations in the Arctic. The genetic split between North and South American populations might have occurred around 13,000 years ago. 

"Some of the most important questions people ask are: Who are we? Where did we come from?" study co-author Michael Crawford, an anthropologist at the University of Kansas, says. "Now, thanks to genetic analysis, the picture is clearer for Native Americans: They came from Siberia."

However, the picture may not be quite crystal clear. “At the same time, we see surprises including genetic signals of East Asians and Australo-Melanesians, presumably coming in after the first migration wave,” study author Eske Willerslev of the University of Copenhagen explains in a press release. Those genetic signals are discussed in a separate study published in Nature this week, which claims genetic evidence for a link between some indigenous Amazonian populations and people from southeast Asia and Australia. The analysis, led by Harvard Medical School geneticists, shows that two groups who currently live in the Amazon are more closely related to indigenous populations of modern Australia, New Guinea, and the Andaman Islands than to contemporary Eurasian or Native American populations. 

The two groups have diverging hypotheses about how this Australian DNA got mixed into American populations. The University of Copenhagen-led research points to Australasian ancestors arriving in the Americas less than 9000 years ago, while the Harvard group argues that the Australasian ancestors of the Amazonians came to America along with the first migration, but that this Population Y was later wiped out and replaced by other genetic populations. 

It’ll take a lot more research to sort out the mystery of the strange Australian genes in South America, but at least now we know that humans have been wandering around the Americas for some 20,000 years. 

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Keith Holmes/Hakai Institute
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Stones, Bones, and Wrecks
Ice Age Human Footprints in Canada Reveal a Walk on the Beach Taken 13,000 Years Ago
Calvert Island
Calvert Island
Keith Holmes/Hakai Institute

The prehistoric mariners rowed their canoe into a secluded channel and then onto the island's sandy beach, just above the high-tide mark. One person got out of the boat and stood for a moment, facing northwest. Others, including another barefoot adult and child, followed the leader and walked toward higher, drier land.

Today, roughly 13,000 years later, their footprints have been preserved in a layer of sediment and confirmed to date from the last ice age. The discovery, on Calvert Island on the central coast of British Columbia, Canada, adds to the growing body of evidence that suggests ancient humans crossed from Asia to North America and traveled south along the Pacific shoreline.

"This finding provides evidence of the seafaring people who inhabited this area during the tail end of the last major ice age," said University of Victoria anthropologist Duncan McLaren, lead author of the new study in the journal PLOS One, in a statement.

Archaeologists on Calvert Island, British Columbia, Canada
Researchers Daryl Fedje (left) and Duncan McLaren (right) dig at the Calvert Island site.
Grant Callegari/Hakai Institute

Most anthropologists believe that early peoples migrated from Asia to North America across Beringia, the region where Russia's Chukchi Peninsula and Alaska face each other across the Bering Strait. Then the migrants took two possible routes. One popular theory, proposed in the 1930s, suggests people traveled south along an ice-free corridor that lay on the eastern slope of the Rocky Mountains where two colossal ice sheets split from one other. A more recent theory proposes that they sailed along a coastal route from Alaska to Washington State.

The coastal route lies within the territories of the Heiltsuk First Nation and Wuikinuxv First Nation. Their oral histories describe how the scattered islands between the open ocean and the edge of the ice sheet remained unglaciated. On these refuges, their ancestors subsisted on the abundant fish, shellfish, and marine mammals and likely used watercraft to travel between the islands. "Heiltsuk oral history talks about our people living in our territory before the ice age, and talks about the physical features of the landscape that our people witnessed change over time due to the ice, which influenced things like place names in our territory," William Housty, chair of the Heiltsuk Integrated Resource Management Department board of directors, tells Mental Floss.

Archaeological evidence affirming the histories is scarce, in part because few researchers have focused on the area. In 2014, McLaren and colleagues from the University of Victoria and the Hakai Institute, along with representatives of the First Nations, began combing the beach at a Calvert Island site called EjTa-4 for sediments dating back to the late Pleistocene epoch (also known as the Ice Age, which ended 11,700 years ago). Back then, the sea level around Calvert Island was 6.5 to 10 feet lower than it is today, so the team concentrated on the intertidal zone. After probing several test holes, they found what appeared to be footprints near the base of a huge shell midden.

A 13,000-year-old human footprint on Calvert Island, British Columbia, Canada
A photo of Track #17 beside a digitally enhanced image of the same feature. Note the toe impressions and arch, which indicate that this is a right footprint.
Duncan McLaren

Over the next three field seasons, they continued to excavate a 6.5-foot-by-13-foot pit, removing strata of sand, pebbles, and organic matter before striking the layer of clay. "The site was below the high-tide water line, so we only had one day from the time we opened the last layer. When the high tide came up it would wash everything away," Jennifer Walkus, the research liaison between the Wuikinuxv Nation and Hakai Institute, tells Mental Floss. "We had an idea from the test pit the previous year that there might be footprints, so we knew that day was going to be busy. It was amazing as the last layer was pulled up and the measurements were taken."

In the substrate, the team found 29 individual human tracks, darkened by time, left by at least three different people—two adults and a child—based on the dimensions of the individual prints. "The fact that they were footprints was more and more obvious as the measurements came in and there were three lengths," Wallkus says. The orientation of some of the tracks at the ancient shoreline indicated that a group of people may have disembarked from a watercraft and walked northwest, toward higher ground, with their backs to the prevailing wind.

Researchers also collected samples of clay and fragments of shore pine from the sand underneath the prints. Radiocarbon dating confirmed that the pine bits, and the footprints, were between 13,317 and 12,633 years old.

"I can't speak for the Nation as a whole, but for me, it's a validation of the fact that we have been here for much longer than the previous narrative," Walkus says. "The fact that these footprints put people in the vicinity in the time of glacial recession underlines that our legends are grounded in living in our area over huge spans of time."

When William Housty, who was not present at the dig, heard of the discovery, "I immediately started to think about our first ancestors and the stories of their origin," he says. "I also thought that, once again, science [and] archeology have confirmed what our oral history has been telling us all along."

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University of York
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Stones, Bones, and Wrecks
UK Archaeologists Have Found One of the World’s Oldest 'Crayons'
University of York
University of York

A prehistoric chunk of pigment found near an ancient lake in England may be one of the world's oldest crayons, Colossal reports. The small object made of red ochre was discovered during an archaeological excavation near Lake Flixton, a prehistoric lake that has since become a peat wetland but was once occupied by Mesolithic hunter-gatherers. Though it’s hard to date the crayon itself, it was found in a layer of earth dating back to the 7th millennium BCE, according to a recent study by University of York archaeologists.

Measuring less than an inch long, the piece of pigment is sharpened at one end, and its shape indicates that it was modified by a person and used extensively as a tool, not shaped by nature. The piece "looks exactly like a crayon," study author Andy Needham of the University of York said in a press release.

A pebble of red ochre thought to be a prehistoric crayon
University of York

The fine grooves and striations on the crayon suggest that it was used as a drawing tool, and indicate that it might have been rubbed against a granular surface (like a rock). Other research has found that ochre was collected and used widely by prehistoric hunter-gatherers like the ones who lived near Lake Flixton, bolstering the theory that it was used as a tool.

The researchers also found another, pebble-shaped fragment of red ochre at a nearby site, which was scraped so heavily that it became concave, indicating that it might have been used to extract the pigment as a red powder.

"The pebble and crayon were located in an area already rich in art," Needham said. "It is possible there could have been an artistic use for these objects, perhaps for coloring animal skins or for use in decorative artwork."

[h/t Colossal]

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