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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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AFP, Stringer, Getty Images
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Stones, Bones, and Wrecks
The Most Complete Fossil of an Early Human Relative Goes on Display
AFP, Stringer, Getty Images
AFP, Stringer, Getty Images

Twenty years after it was discovered in an African cave, one of the most important fossils in the quest to demystify human evolution is finally on display. As Smithsonian reports, Little Foot, an Australopithecus specimen dating back more than 3 million years, was revealed to the public this month at the Hominin Vault at the University of the Witwatersrand’s Evolutionary Studies Institute in Johannesburg, South Africa.

Paleontologist Ron Clarke discovered the first bone fragments from the fossil in 1994. The pieces came from the remains of a young female’s feet, hence the nickname. Clarke and his team spent years excavating Little Foot bit by bit from the Sterkfontein cave system in South Africa until the bones were fully removed in 2012. The shattered remains had been embedded in a concrete-like material called breccia, making them incredibly tricky to recover. But the sum of the parts is monumental: Little Foot is the most complete Austrolopithecus fossil known to science.

The hominid genus Austrolopithecus played an essential early role in the chain of human evolution. Lucy, another famous hominid fossil, is a member of the same genus, but while Lucy is only 40 percent complete, Little Foot retains 90 percent of her skeleton, including her head. It’s also possible that Little Foot surpasses Lucy in age. Most paleontologists agree that Lucy lived about 3.2 million years ago, while one analysis places Little Foot’s age at 3.67 million years.

Austrolopithecus is believed to have spawned Homo, the genus that would eventually contain our species. The discovery of Lucy and other fossils have led scientists to designate East Africa as the cradle of human evolution, but if Little Foot is really as old as tests suggest, then South Africa may deserve a more prominent point in the timeline.

Following Little Foot’s public debut, the team that’s been studying her plans to release a number of papers exploring the many questions her discovery raises.

[h/t Smithsonian]

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Mark Golitko
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Stones, Bones, and Wrecks
6000-Year-Old Skull Might Belong to World's Oldest Tsunami Victim
Scientists speak to residents in Aitape.
Scientists speak to residents in Aitape.
Mark Golitko

Tsunamis and other natural disasters have taken a deadly toll on human populations for millennia, and now we may have the oldest example of that truth yet. An international team of anthropologists and environmental researchers recently analyzed a cracked skull that belonged to a person who likely died in a tsunami some 6000 years ago. They detail their find in a new study published in PLOS One.

The partial skull in question, known as the Aitape skull, was found in Papua New Guinea in 1929 during a geological survey by an Australian scientist named Paul Hossfield. It has since been dated to the mid-Holocene epoch, or around 6000 years ago.

For the current study, the scientists returned to the site of the 1929 discovery to sample and analyze the sediment there to find out more about what might have killed the person millennia ago. They had only Hossfield's basic field descriptions to go on, but University of Notre Dame anthropologist Mark Golitko, one of the study’s authors, says that based on those descriptions, they think they were able to sample within 100 yards or so of the skull's original location.

The top of a brown cracked skull against a pink background
Arthur Durband

Based on the grain size, chemical signature, and marine microalgae found within the sediment samples, they were able to determine that around the time that the skull was buried, the area was inundated with water, probably from a tsunami. At that time, the site, located near the present-day town of Aitape, would have been just along the shoreline. Aitape was also the site of a devastating tsunami in 1998, and the Holocene sediments resembled the ones associated with that disaster.

It's possible that the skull was buried before the tsunami hit, and the grave was ripped apart by the waters and the rest of the bones scattered. However, during the powerful 1998 tsunami that killed more than 2100 people in Papua New Guinea, bodies buried in modern cemeteries were not uprooted even as the sediment above them washed away, making it more likely that the ancient skull belonged to someone killed in the disaster.

The new analysis has "made us realize that human populations in this area have been affected by these massive inundations for thousands of years," study co-author James Goff of the University of New South Wales said in a press statement. "Given the evidence we have in hand, we are more convinced than before that this person was either violently killed by a tsunami, or had their grave ripped open by one."

Field Museum anthropologist John Terrell, another co-author of the study, said, "If we are right about how this person had died thousands of years ago, we have dramatic proof that living by the sea isn't always a life of beautiful golden sunsets and great surfing conditions."

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