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Archaeologist Mark Rose discussed ongoing investigations into the identity of the first Native Americans, a group anthropologists and archaeologists refer to as Paleo-Indians, in an article for the Encarta Yearbook. The article explores what route humans took on their first migration to the Americas, how long ago they arrived, and how they lived.
By Mark Rose
“Great question has arisen, from whence came those aboriginals of America?”
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Thomas Jefferson, Notes on the State of Virginia 1787.
Archaeologists and anthropologists continue to ponder the mysteries of the first Americans just as Thomas Jefferson did in the 18th century. Also known for his amateur archaeological work, Jefferson was one of the first to suggest that Native Americans originated in Asia. While most scholars agree that the first people to reach the New World came across a now submerged land bridge between Siberia and Alaska, two centuries of debate have not settled who they were, when they arrived, or how they went on to colonize the hemisphere. Today, archaeologists have been joined in the search for the first Americans by linguists, physical anthropologists, geneticists, geologists, paleontologists, and others.
Despite the uncertainty, most researchers believe that the first Americans are descended from people who lived in Asia and crossed the Bering land bridge connecting Siberia and Alaska toward the close of the last ice age, possibly following herds of large game animals such as woolly mammoth and bison. These people quickly spread from North to South America, adapting to new environments.
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The first major discovery in the search for the first Americans came when Jesse Figgins of the Colorado Museum of Natural History sent a crew to collect a mountable skeleton of an extinct bison from a fossil bed near Folsom, New Mexico, in 1926. Figgins's crew found a stone point at the site but moved it before an archaeologist could verify its association with the bones. Figgins told his men to contact him immediately if another such find was made and to leave the point undisturbed until he arrived. In August 1927 another point was found near Folsom with the remains of a type of bison that became extinct before the end of the ice age some 10,000 years ago. The carefully crafted point was proof that humans had been in the region at least 10,000 years ago.
In 1937, near Clovis, New Mexico, larger points were found with mammoth bones in a deposit beneath a layer containing Folsom points and bison skeletons. Now called Clovis points, the larger points were recognized as even older than the Folsom points. Characteristic of both points is a flute, a flake struck off the base along the length of the point, presumably to facilitate hafting (attaching a point to a wooden shaft). The site names, Clovis and Folsom, are used to refer to the peoples represented by these specific artifacts, but the general term Paleoindian is used to refer to all of the first Americans.
Until the development of radiocarbon dating methods in the late 1940s, the exact age of these Paleoindian finds was unknown. Radiocarbon dating is based on the fact that in the atmosphere, cosmic radiation changes nitrogen atoms into an unstable form of carbon known as carbon-14 (C-14). Carbon (including C-14) and oxygen atoms combine to produce carbon dioxide gas, which plants and animals absorb as long as they are alive. Once a plant or animal dies and stops replacing carbon, the amount of C-14 relative to normal carbon atoms declines. The decay rate of C-14 is known, so the amount remaining in an archaeological sample can be used to determine how long ago it died. Carbon dates are a statistical best guess of where the true age lies and are usually given in years “before present” (BP).
By the mid-1960s most scientists accepted the view that Clovis Paleoindians—mobile big-game hunters pursuing the ice age megafauna (mammoth, mastodon, and extinct bison)—were the first Americans. In 1964 University of Arizona archaeologist C. Vance Haynes had linked carbon dates obtained for Clovis sites with evidence about glacial conditions in North America. The distinctive Clovis points had been found throughout the continental United States, all in archaeological sites dated to about 11,500 to 11,000 BP, and none before 12,000 BP, the date when geologists believe an ice-free corridor opened up in the north, permitting southward migration from the Bering land bridge.
Haynes proposed a very rapid occupation of the Americas, with Paleoindians virtually sweeping across the continents. The Clovis toolkit—fluted points, bifaces (worked or flaked on both sides), knives, scrapers, and drills—could be used in many different kinds of environments. The Clovis people carried the types of stone used in tool-making long distances from the source of the stone, often more than 320 km (200 mi). More recent evidence, however, indicates people may have reached the New World before the Clovis culture. Artifacts at an archaeological site near Monte Verde, Chile, indicate that it was occupied about 12,500 BP, a thousand years before Clovis points were used.
Paleoindians first reached the Americas by crossing the land bridge connecting Siberia and Alaska that was above sea level by 25,000 BP and remained so until about 11,000 BP. The route south from the land bridge, which was more than 1450 km (900 mi) wide from north to south, has been a matter of considerable debate. Some archaeologists favor an inland route along the eastern edge of the Rocky Mountains, while others propose a coastal route that may have involved the use of boats. Blocking both routes, however, were the massive Laurentide ice sheet, which covered much of northeastern North America, and the Cordilleran glacier, which straddled the Canadian Rockies.
Most scholars believe the coastal route was blocked from at least 20,000 BP and the eastern route from 30,000 BP. Only about 13,000 years ago, after the ice had retreated, did both routes open. Could the first Americans have skirted the ice earlier than 13,000 years ago by following the coast in boats? Although some pockets along the shore may have been ice free, affording landing places, the Cordilleran glacier covered some 1900 km (1200 mi) of coast, making such a journey virtually impossible.
According to anthropologist Alan Bryan of the University of Alberta, the eastern route was closed from 21,300 to 11,600 BP. He based this conclusion on the fact that megafauna bone samples indicate a land corridor began opening about 14,000 BP from the south but did not reach what is now central Alberta until 11,600 BP. If South America was inhabited by 12,500 BP, as the site in Monte Verde, Chile, suggests, and the inland corridor did not open until 11,600 BP, either a coastal route was used or people traveled through the eastern route before 21,300 BP, Bryan argued. However, more research is needed before his conclusions are widely accepted by archaeologists.
Archaeologist Knut Fladmark of Simon Fraser University in Vancouver, Canada, has suggested that some pockets along the Pacific Coast were unglaciated refuges open to plants, animals, and people. Fossilized remains of an extinct dwarf species of caribou on British Columbia's Queen Charlotte Islands off the Pacific Coast indicate that animals were able to move onto the islands during a period of cooler temperatures. Today the islands are separated from the mainland by 70 to 150 km (44 to 93 mi) of open water.
Sometime before 9000 BP the sea level was 33 m (108 ft) lower, which would narrow the distance to the islands to about 5 km (3 mi), making it possible for animals or people to reach them. Recent investigations have found evidence supporting the existence of ice-free refuges in the Alexander Archipelago of southeastern Alaska during the height of the last glaciation. Brown bears, and perhaps other large mammals, have continuously inhabited the archipelago for at least 40,000 years, so habitable refuges were therefore available throughout the last glaciation.
While these studies provide no direct evidence of humans occupying coastal islands that long ago, brown bears and people are both omnivores (feeding on both animal and vegetable matter) and have similar habitat requirements. If bears could survive there, so could humans. The earliest evidence of humans in these islands, a few bones found in July 1996, is dated 9730 BP—considerably later than the conventional date of 11,500 BP for early Clovis sites. The bones confirm human presence along the Alaskan coastline at the end of the last ice age, but researchers have yet to find solid evidence that humans entered North America by a coastal route after crossing the Bering land bridge.
Do Clovis points mark the arrival of the first Americans, or were they developed later? Clovis and other fluted points have been found throughout the Americas, but Alaskan Clovis points are not among the oldest, as one might expect if they arrived with the first Americans. Alaskan fluted points appear to be slightly younger-from 10,500 to 10,000 BP. Were fluted points first made to the south, later spreading back north to Alaska?
Archaeologists Maureen King of the University of Washington in Seattle and Sergei Slobodin of the Department of Education in Magadan, Russia, found the first fluted point outside the Americas on a terrace above the Uptar River 40 km (25 mi) north of Magadan in Siberia—about 1800 km (1100 mi) from the Bering Strait. A volcanic ash layer above the point has been dated to 8300 years ago. The artifacts are weathered and may be much older, but how much older is unknown. Because of the uncertainties about the date, the relationship between the Uptar point and the Clovis points is unclear.
Archaeologists have claimed to find several Paleoindian sites older than the Clovis site, including Meadowcroft in Pennsylvania, Pedra Furada and Pedra Pintada in Brazil, and Monte Verde in Chile. A site in Meadowcroft, excavated by archaeologist James Adovasio of Mercyhurst College in Erie, Pennsylvania, has been dated between 11,300 and 19,600 BP, but some scientists dispute the dates, saying that coal particles in groundwater contaminated the samples, making them appear older than they are. Critics also note that the small sample of plant and animal remains suggests a temperate rather than a cold climate. A cold climate would be expected since the site would have been near the edge of the Laurentide ice sheet, which then covered much of northeastern North America.
Another disputed site is Pedra Furada, a rock shelter in Brazil excavated from 1978 to 1985 by Niède Guidon of the École des Hautes Études en Sciences Sociales in Paris, France, and Fabio Parenti of the Istituto Italiano di Paleontologia Umana in Rome, Italy. The debate centers on whether flaked stones from the site's lowest levels (dated 48,000 to 14,300 BP) are artifacts or whether they were created naturally when quartz and quartzite cobbles eroded and fell from a layer in the cliff above the site. Other scholars accept as valid a later, post-10,400 BP, level at the site with wall paintings and tools of local quartzite and imported chert.
Investigations by archaeologist Anna Roosevelt of the Field Museum of Natural History in Chicago, Illinois, at Caverna da Pedra Pintada (Cave of the Painted Rock) in northern Brazil have revealed an early adaptation to a tropical forest environment. The stone tools from the cave include points that are related to northern Paleoindian types as well as unusual triangular points. Roosevelt believes the site, from which she has obtained radiocarbon dates for 56 artifacts ranging from 11,200 to 10,000 BP, is evidence for the arrival of Paleoindians before Clovis. There would not have been time for Clovis people to travel to the Amazon Basin and become adapted to the tropics if they first arrived in North America in 11,500 BP, Roosevelt argues. Other scientists, including Haynes, are more cautious. Haynes points out that an average of the oldest carbon-14 dates from Pedra Pintada is 10,500 years ago.
There can be little doubt, however, that Monte Verde, Chile, a waterlogged site with excellent preservation, was inhabited before Clovis. The carbon dates from the site's main level indicate it was occupied about 12,500 BP, a millennium before Clovis. The site, meticulously excavated and documented by archaeologist Tom Dillehay of the University of Kentucky from 1977 to 1987, yielded stone tools (but no fluted points), bones, and even remnants of mastodon flesh, abundant plant remains, evidence of rectangular huts, and even a human footprint. Complete results of the excavation, to be published in early 1997, will end any question about the reality of a pre-Clovis occupation of the New World.
A number of archaeological sites have provided a great deal of information about the daily life and diet of Paleoindian people. Monte Verde has given the most complete look into a Paleoindian camp. Located on Chinchihuapi Creek, a tributary of the Rio Maullín in south-central Chile, Monte Verde was inhabited by perhaps 20 to 30 people over the course of one or more years, according to excavator Dillehay.
The ancient camp has 12 rectangular huts, 9 of which are arranged in rows, that originally had wood frames covered, at least in part, by mastodon hide. Small pits inside the huts may have held embers to warm the structures, while larger communal hearths were located outside. Near one of these an imprint of a human foot and two other possible footprints were preserved. The water-logged conditions of the site preserved wooden implements, including spears, mastodon bone and ivory tools, and numerous stone artifacts. Most of the stone tools were simple cobblestones with a few flakes removed to make a usable edge, but there are a few long, narrow points that are unfluted and quite different from Clovis points.
A small wishbone-shaped structure set apart from the rest of the camp produced chewed plant remains (seaweed and tree leaves) used for medicinal purposes in the area today, and a cache of salt crystals. Dillehay is cautious about interpreting this structure but believes that it might have been the residence or work space of a special individual, perhaps a curer.
Some sites afford glimpses of the small hunting camps in which Paleoindians lived. The Page-Ladson site in Florida was a small camp used only for a few generations about 10,000 years ago. Among the artifacts are a variety of flaked stone tools made of locally available flint and chert, and antler flakers used in making them. Early toolmakers would use a rock to strike a piece of flint or chert and cause a sharp flake to separate from the core. They would then use an antler to hone the flake into a finely crafted point. Local limestone was crafted into spherical bola stones that would have been attached to leather cords and hurled at small game animals to entangle them. There are at least three or four hearths—clusters of fire-cracked limestone pieces with charcoal beneath them. Sharpened wooden pegs found at the site may have anchored hide structures.
Spectacular megafauna kill sites, such as those with bison and mammoth, still color our view of Paleoindians as big-game hunters. Many of the 13 mammoths excavated at Clovis were associated with points or other artifacts. Remains of 13 more mammoths were also found with Clovis points and other tools at the Lehner site in Arizona. At Murray Springs, Arizona, remains of 11 bison and 1 mammoth were found with Clovis points. These early hunters specialized in killing large game at ponds and other water sources. As the climate became warmer and drier, bison herds flourished on the expanding grasslands. Later Paleoindians orchestrated mass kills, as at the Olsen-Chubbuck site in Colorado, where 200 bison were driven into a steep-sided arroyo, or at Bonfire Shelter, Texas, where they were driven over a bluff.
There was, however, considerable diversity in the Paleoindian diet. At Lehner, for example, thousands of charred rabbit bones were also recovered. Clovis digs at Kimmswick, Missouri, yielded 23 species of animals, such as deer, snakes, rodents, and turtles as well as mastodon. At Clovis itself several turtles were found stacked up in a roasting pit, and at Little Salt Spring, Florida, remains of an extinct giant land tortoise were found along with a wooden spear used to kill it. Hanson, a Folsom site in Wyoming, had remains of mountain sheep, deer, marmot, and rabbits. Other sites have yielded fish and plant remains including hackberry, blackberry, hawthorn, plum, and grape seeds.
South American sites are yielding evidence for the exploitation of a wide range of environments. Caverna da Pedra Pintada in northern Brazil produced food remains such as Brazil nuts and palm seeds, and fish, birds, reptiles, amphibians, and mollusks. Clearly the people here were adapted to foraging in a tropical rain forest habitat rather than hunting big game.
Farther south, in west-central Argentina, Agua de la Cueva, a rock shelter in the Andes foothills dated to between 10,950 and 9210 BP, has yielded the bones of the guanaco, a wild relative of the llama. Monte Verde deposits produced the remains of several mastodons, both bones and chunks of flesh, and of an extinct llama. But the plant remains recovered at the site were even more extraordinary, with some 72 species of plants represented. Species included seaweed and tortora reeds, which must have been brought from the Pacific Coast some 50 km (30 mi) away. Other plants were brought from higher elevations down to the site. The remains suggest the exploitation of a range of resources by both hunting and foraging.
Other evidence points to a more settled Paleoindian culture. In a Nevada rock shelter known as Spirit Cave, a partially mummified body that was recently carbon-dated to 9415 BP, was found in 1940 with well-preserved leather and textile goods. The textiles show that Paleoindians were accomplished weavers. The body had been placed on a fur blanket dressed in a twisted skin robe and belt and moccasins made of three pieces of leather sewn together with sinew and cordage. A twined mat was sewn around the head and shoulders, and a similar mat was wrapped around the lower part of the body and bound under the feet. Nearly 60 other fiber and fur artifacts were found in the cave. Nevada State Museum anthropologist Amy Dansie believes that the time it took to gather the fibers, the marsh reed tule, hemp, and sage, and weave them into mats indicates a more settled, less nomadic, life than was previously believed.
Examination of Paleoindian skeletal remains also reveals how difficult their lives were. The Spirit Cave man was about 45 years old at death and had a congenitally deformed spine. He had severe abscesses of both upper and lower teeth as well as heavy plaque deposits. One abcessed upper tooth drained through a hole on the side of his face. He had a partially healed skull fracture that was at least several weeks old at the time of his death. Complications associated with the fracture or abscesses may have led to his death, according to Texas A&M University anthropologist Gentry Steele.
Another skeleton of a male Paleoindian, about 50 years old, recently discovered at Kennewick, Washington, has a 5-cm (2-in) long spear point fragment embedded in its pelvis. It is possible the Kennewick man, who apparently survived the wound, was not struck by accident. Anthropologist James Chatters determined the man also had healed broken ribs and his left arm may have been crippled.
If Clovis Paleoindians were not the first to arrive in the Americas, who was? Did more than one group migrate to the New World? Experts in language, dentition (the characteristics of teeth), and genetics are pursuing the answers.
Linguist Joseph Greenberg of Stanford University in Stanford, California, proposed in the 1950s that all Native American languages, which number more than 1000, belong to just three language families, which he called Amerind, NaDene, and Eskimo-Aleut. In his study Greenberg examined 300 words, focusing on pronouns and names of body parts. Linguists believe these words do not change quickly in languages and can be used to track language families.
The number of differences between the three Native American language families convinced Greenberg that Paleoindians arrived in roughly three separate migrations. He also estimated the time at which the individual languages known today split from the parent Amerind, NaDene, and Eskimo-Aleut tongues. This gave dates of more than 11,000 years ago for Amerind, between 5000 and 9000 years ago for NaDene, and about 4000 years ago for Eskimo-Aleut. Assuming the divergence from the three parent languages began shortly after their speakers entered the Americas, these dates would indicate when people speaking each parent language crossed over from Asia in three migrations beginning with the Amerinds.
Many linguists disagree with Greenberg's results and fault his methodology, which permits a fast comparison of many languages but may sacrifice too much accuracy in the process. According to Johana Nichols, a professor of Slavic languages at the University of California at Berkeley, there must have been about ten separate infusions of new language groups into the New World to create so much language diversity in 35,000 years. Researchers are uncertain if these estimates represent the time elapsed since languages diverged after people arrived in the Americas, or if the language divergence took place in Asia before migration. The date the languages split and the date people arrived in the New World may well be different.
In addition to language analysis, researchers can also examine the unique attributes of teeth to track connections between populations. Numerous dental characteristics are transmitted genetically, and because they change very slowly they can be used to trace populations over time. Arizona State University bioarchaeologist Christy Turner analyzed such dental attributes to develop dental profiles of populations. On this evidence he found Asian populations had two distinct dental patterns, which he called Sundadont (found throughout Southeast Asia) and Sinodont (found in northern Asia and in Native Americans). Turner subdivided Native Americans into three groups: Eskimo-Aleut, Northwest Coast (including the Southwest Athapaskan speakers, the Navajo and Apache), and all other American Indians. Eskimo-Aleut and American Indians have the least similar teeth, according to Turner, with Northwest Coast people falling somewhere in between.
Turner has established how much dental microevolution occurs per thousand years, and this can be used to date the divergence of populations from a parent stock. According to the evidence, Turner believes the three Native American groups are descended from a parent population of northern Sinodonts that existed some 20,000 years ago. The Amerinds, he concluded, split about 13,500 BP, the Eskimo-Aleut about 11,500 BP, and the Northwest Coast people sometime later. Critics, however, note problems with the consistency of Turner's dental groups. Furthermore, Turner's study sample includes the teeth of only a few Paleoindians.
Despite the inconsistencies, Turner's three Native American groups roughly correspond to Greenberg's language families. The case for a three-migration model was set forth by Greenberg, Turner, and anthropologist and geneticist Stephen Zegura of the University of Arizona in a 1986 article in Current Anthropology and gained wide acceptance by the mid-1990s. Linguistic, dental, blood-type, and genetic evidence all indicated that three principal groups migrated across the Bering Strait from Asia: Amerinds about 30,000 years ago, NaDene about 10,000 years ago, and Eskimo-Aleuts within the last 7000 to 5000 years.
In the early 1990s genetic support for the three-migration model was found in a series of studies by scientists at Emory University in Atlanta, Georgia. An initial examination of Native American DNA—deoxyribonucleic acid, the basic unit of heredity that is found in every living thing—revealed four common basic lineages. In a 1992 study geneticists Theodore Schurr and Antonio Torroni examined DNA from Amerind and NaDene speakers and found only small genetic differences among their lineages. Such differences represent the degree to which the DNA of modern peoples has changed from a common ancestral sequence. Assuming that DNA changes at a predictable rate, which has been estimated at 2 to 4 percent per million years, Torroni and Schurr concluded that Amerind speakers entered the New World between 42,000 and 21,000 years ago and the NaDene between 10,500 and 5250 years ago. In a later study they concluded that aboriginal Siberian populations had three of the basic lineages found in Native Americans but that they were slightly different, suggesting that Native Americans separated from Siberian aboriginal people between 41,000 and 20,500 years ago.
Geneticist Andrew Merriwether of the University of Michigan in Ann Arbor, in studies published in 1996, disagreed with the Emory team's findings. His analysis of more than 1800 contemporary Native American DNA sequences from North, Central, and South America, as well as 300 sequences from archaeological sources led him to conclude that there are actually nine basic lineages. All of these occur on both sides of the Bering Strait, according to Merriwether, and in widely distributed populations in the Americas, including among the NaDene, Amerind, and Eskimo-Aleut families. It is not, says Merriwether, realistic to believe that the same lineages ended up in all these populations across two continents by separate migrations. He contends that the first Americans came from a single population in Asia, probably in a single wave, though the wave may well have lasted for some thousands of years.
Unlike Torroni and Schurr, Merriwether believes that some of the variation within the lineages occurred before the arrival of Native Americans in the New World. Based on his studies of the genetic makeup of Mongolians, Merriwether concluded that Mongolians and Native Americans are descended from a single ancestral population.
In addition to the many scientific challenges, researchers who study the first Americans face a new obstacle now—the Native American Graves Protection and Repatriation Act (NAGPRA). The 1990 law provides for the repatriation to tribes of Indian skeletons and ceremonial and mortuary artifacts. Despite the good intentions of NAGPRA, the process is not working as it should. Disposition of remains is often determined by negotiation between local tribes and federal agencies without sufficient investigation or allowance for study before reburial. If the situation does not change, scientists may lose much information about the first Americans.
In 1996 the discovery of a nearly complete Paleoindian skeleton near Kennewick in eastern Washington precipitated the first major legal challenge by scientists to the act. The skeleton was found in July 1996 in the Columbia River on land under the jurisdiction of the United States Army Corps of Engineers. When the skeleton was carbon-dated to about 8410 years ago, the corps determined, based on the age of the skeleton, that it was of Native American ancestry and therefore subject to NAGPRA. All study was halted. Ultimately a joint claim was filed by the Umatilla, Yakama, Nez Perce, Colville, and Wanapum tribes, who have occupied the area. The Umatilla and Nez Perce indicated their intention to immediately rebury the remains with no further study, according to their religious beliefs. In late September the corps announced its intent to turn over the skeleton.
Alarmed by this prospect, physical anthropologists Douglas Owsley of the Smithsonian Institution in Washington, D.C., and Richard Jantz of the University of Tennessee in Knoxville warned, in a letter to the corps, that “the loss to science will be incalculable and we will never have the data required to understand the earliest populations in America.”
In October 1996 Owsley, Jantz, and six other prominent anthropologists filed suit against the Army Corps of Engineers in federal district court in Portland, Oregon, seeking to block repatriation of the skeleton on the grounds that the corps accepted the five tribes' claim based on insufficient evidence. According to NAGPRA regulations, cultural affiliation must be established using “geographical, kinship, biological, archeological, anthropological, linguistic, folklore, oral tradition, historical, or other relevant information or expert opinion.” The case has yet to be resolved.
Some early remains have already been lost, as in the case of a 10,600-year-old skeleton of a woman found in a gravel quarry near the town of Buhl, Idaho. The carbon-dated remains were turned over to the Shoshone-Bannock tribe and reburied in December 1991 without further test. In other cases relations have been more amicable. A skeleton found in Hourglass Cave, Colorado, in 1988 and dated to about 8000 BP, was studied and tested for more than two years before it was repatriated to the Southern Ute.
There is no doubt that Indian demands for greater respect regarding skeletal remains are well founded. Anthropologists concede that some collections should never have been acquired. In one repatriation case, museum officials recently returned the remains of 24 Cheyenne killed at Fort Robinson, Nebraska, in 1878 that had been kept in museums ever since. Many collections of skeletal remains excavated decades ago have simply never been studied.
Despite the flood of new evidence from many different sources, the answers to basic questions about the peopling of the Americas remain elusive. Archaeologists must find links between the evidence and past events and ancient cultures. Can they track the movements of ancient peoples through studies of modern languages, biological characteristics (dental markers or genetic makeup), or the shapes of stone tools? Beyond that is the question of how to integrate evidence from such different sources as genetics and dental patterns.
Efforts must be made in several directions if scientists are to solve the questions about how and when people came to the Americas. The search for early sites will continue, spurred on by the final publication of Dillehay's findings at Monte Verde. The surprising early diversity of South American Paleoindians will be explored and explained, but other regions such as Siberia and Panama need to be investigated intensively.
Even so, there has been substantial progress. Current theories on Paleoindian history are substantially different from the long-held belief that the Clovis people were the first Americans. Most researchers believe that between 25,000 and 11,000 years ago, Paleoindians and perhaps Mongolians split from a single parent population in Asia to cross the Bering land bridge when it was above water. Related groups may have crossed the bridge for several thousand years in a single ongoing migration. The earliest groups spread across North America, through Central America into the Amazon and south along the Andes Mountains, reaching Monte Verde by 12,500 BP, and became the first Americans.
About the author: Mark Rose received a doctorate studying Aegean and eastern Mediterranean prehistory at Indiana University, focusing on the analysis of animal bones from archaeological sites. He joined Archaeology magazine in 1988 where he has followed research on the colonization of the Americas.
Source: Encarta Yearbook, January 1997.
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United States (People); Native Americans of North America; United States (History)
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