History

Humans May Have Been Stuck on Bering Strait for 10,000 Years

The ancestors of Native Americans may have lived on and around the Bering Strait for about 10,000 years before streaming into the Americas.

The ancestors of Native Americans may have lived on and around the Bering Strait for about 10,000 years before streaming into the Americas, researchers argue.

In the new Perspectives article, published today (Feb. 27) in the journal Science, the researchers compile existing data to support the idea, known as the Beringia standstill hypothesis.

Among that evidence is genetic data showing that founding populations of Native Americans diverged from their Asian ancestors more than 25,000 years ago. In addition, land in the region of the Bering Strait teemed with grasses to support big game (for food) and woody shrubs to burn in the cold climate, supporting a hard-scrabble existence for ancient people. [In Images: Ancient Beasts of the Arctic]

Given the hypothesis, archaeologists should look in regions of Alaska and the Russian Far East for traces of these ancient people's settlements, the authors argue.

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Genetic differences A dominant theory suggests the ancestors of Native Americans crossed the Bering Strait about 15,000 years ago and quickly colonized North America, and then South America.

But in 2007, genetics researchers found that almost all Native Americans in North and South America shared genetic mutations in their mitochondrial DNA, which is the genetic information that's carried in the cytoplasm of the egg and passed on through the maternal line. None of the mutations show up in Asian populations from which the Native American ancestors diverged, said study co-author John Hoffecker, an archaeologist and paleoecologist at the University of Colorado, Boulder. (Genetic evidence also suggests that some northern populations, such as the Inuit, likely came over in a second wave separate from the ancestors of Native Americans.)

Given the rate at which such mutations occur, the findings suggested a single Native American founding population must have been isolated from its Asian ancestors for thousands of years before dispersing throughout the Americas.

Shrubby landscape Other evidence fits the genetic data. Between 28,000 and 18,000 years ago, glaciers covered much of the Americas and northern Asia, blocking human migration into North America.

But in the 1930s, Swedish botanist Eric Hultén proposed that the region known as Beringia, which includes the land bridge now submerged under the Bering Strait, was a refuge for shrubby tundra plants. Pollen, insects and other plant remains taken from sediments beneath the Bering Sea confirmed this picture. [Photos: Amazing Creatures of the Bering Sea]

The outer portions of Beringia, in what is now Alaska and the Russian Far East, were likely drier grassland steppes where woolly mammoths, saber-toothed tigers and other big game grazed, Hoffecker said.

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This region would have had two crucial resources that other Arctic areas didn't: woody plants to start fires and animals to hunt, Hoffecker said.

"The central part of Beringia was probably the mildest, most comfortable place to live at high latitudes during the last glacial maximum," Hoffecker told Live Science. "It's the most logical place for a group of people to hunker down."

Once the glaciers melted, only then did the Beringian inhabitants stream into North America, traveling along the coastline and into the interior through ice-free passageways, Hoffecker said.

No archaeological sites While it's possible that the ancestors of Native Americans were isolated in Beringia for 10,000 years, the standstill hypothesis is hobbled by one detail: a lack of archaeological evidence prior to 15,000 years ago, said David Meltzer, an anthropologist at Southern Methodist University in Dallas, who was not an author on the new paper.

Some of the archaeological sites would have been washed away as the Bering Strait flooded, but "at least half of Beringia is still above water, so where are the sites?" Meltzer told Live Science. "If people were there for 10,000 years, you'd surely see evidence for them by now."

But the hypothesis is still compelling, said G. Richard Scott, an anthropologist at the University of Nevada, Reno, who was not involved in the work.

"The best explanation for why American Indians are so radically different from northeast Asians is that they just didn't stream over in the late Pleistocene ; they were stuck up there in the Arctic for maybe 10,000 or 15,000 years," Scott said.

The paper gives archaeologists an impetus to look for the potential lost sites of this occupation in Russia and Alaska, he added.

Original article on Live Science.

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A view of the Bering Strait land bridge, as it would have appeared about 21,000 years ago. Humans probably migrated across the temporary link to the New World, recent genetic evidence suggests.

Back in the Beginning

To put a human face on our ancestors, scientists from the Senckenberg Research Institute used sophisticated methods to form 27 model heads based on tiny bone fragments, teeth and skulls collected from across the globe. The heads are on display for the first time together at the Senckenberg Natural History Museum in Frankfurt, Germany. This model is Sahelanthropus tchadensis, also nicknamed "Toumai," who lived 6.8 million years ago. Parts of its jaw bone and teeth were found nine years ago in the Djurab desert in Chad. It's one of the oldest hominid specimens ever found.

Australopithecus afarensis

With each new discovery, paleoanthropologists have to rewrite the origins of man's ancestors, adding on new branches and tracking when species split. This model was fashioned from pieces of a skull and jaw found among the remains of 17 pre-humans (nine adults, three adolescents and five children) which were discovered in the Afar Region of Ethiopia in 1975. The ape-man species, Australopithecus afarensis, is believed to have lived 3.2 million years ago. Several more bones from this species have been found in Ethiopia, including the famed "Lucy," a nearly complete A. afarensis skeleton found in Hadar.

Australopithecus africanus

Meet "Mrs. Ples," the popular nickname for the most complete skull of an Australopithecus africanus, unearthed in Sterkfontein, South Africa in 1947. It is believed she lived 2.5 million years ago (although the sex of the fossil is not entirely certain). Crystals found on her skull suggest that she died after falling into a chalk pit, which was later filled with sediment. A. africanus has long puzzled scientists because of its massive jaws and teeth, but they now believe the species' skull design was optimal for cracking nuts and seeds.

Paranthropus aethiopicus

The skull of this male adult was found on the western shore of Lake Turkana in Kenya in 1985. The shape of the mouth indicates that he had a strong bite and could chew plants. He is believed to have lived in 2.5 million years ago and is classified as Paranthropus aethiopicus. Much is still unknown about this species because so few reamins of P. aethiopicus have been found.

Paranthropus boisei

Researchers shaped this skull of "Zinj," found in 1959. The adult male lived 1.8 million years ago in the Olduvai Gorge of Tanzania. His scientific name is Paranthropus boisei, though he was originally called Zinjanthropus boisei -- hence the nickname. First discovered by anthropologist Mary Leakey, the well-preserved cranium has a small brain cavity. He would have eaten seeds, plants and roots which he probably dug with sticks or bones.

Homo rudolfensis

This model of a sub-human species -- Homo rudolfensis -- was made from bone fragments found in Koobi Fora, Kenya, in 1972. The adult male is believed to have lived about 1.8 million years ago. He used stone tools and ate meat and plants. H. Rudolfensis' distinctive features include a flatter, broader face and broader postcanine teeth, with more complex crowns and roots. He is also recognized as having a larger cranium than his contemporaries.

Homo ergaster

The almost perfectly preserved skeleton of the "Turkana Boy" is one of the most spectacular discoveries in paleoanthropology. Judging from his anatomy, scientists believe this Homo ergaster was a tall youth about 13 to 15 years old. According to research, the boy died beside a shallow river delta, where he was covered by alluvial sediments. Comparing the shape of the skull and teeth, H. ergaster had a similiar head structure to the Asian Homo erectus.

Homo heidelbergensis

This adult male, Homo heidelbergensis, was discovered in in Sima de los Huesos, Spain in 1993. Judging by the skull and cranium, scientists believe he probably died from a massive infection that caused a facial deformation. The model, shown here, does not include the deformity. This species is believed to be an ancestor of Neanderthals, as seen in the shape of his face. "Miquelon," the nickname of "Atapuerca 5", lived about 500,000 to 350,000 years ago and fossils of this species have been found in Italy, France and Greece.

Homo neanderthalensis

The "Old Man of La Chapelle" was recreated from the skull and jaw of a Homo neanderthalensis male found near La Chapelle-aux-Saints, in France in 1908. He lived 56,000 years ago. His relatively old age, thought to be between 40 to 50 years old, indicates he was well looked after by a clan. The old man's skeleton indicates he suffered from a number of afflictions, including arthritis, and had numerous broken bones. Scientists at first did not realize the age and afflicted state of this specimen when he was first discovered. This led them to incorrectly theorize that male Neanderthals were hunched over when they walked.

Homo floresiensis

The skull and jaw of this female "hobbit" was found in Liang Bua, Flores, Indonesia, in 2003. She was about 1 meter tall (about 3'3") and lived about 18,000 years ago. The discovery of her species, Homo floresiensis, brought into question the belief that Homo sapiens was the only form of mankind for the past 30,000 years. Scientists are still debating whether Homo floresiensis was its own species, or merely a group of diseased modern humans. Evidence is mounting that these small beings were, in fact, a distinct human species.

Homo sapiens

Bones can only tell us so much. Experts often assume or make educated guesses to fill in the gaps in mankind's family tree, and to develop a sense what our ancestors may have looked like. Judging from skull and mandible fragments found in a cave in Israel in 1969, this young female Homo sapien lived between 100,000 and 90,000 years ago. Her bones indicate she was about 20 years old. Her shattered skull was found among the remains of 20 others in a shallow grave.