Introduction
The question of how and when human beings reached North and South America is an interesting topic of debate (Muckle 2010). Some general understandings and consensuses are that the native populations inherited their genetic pool from Asian groups that initially occupied Siberia before the last glacial period (Jablonski 2002). However, the actual time and process through which these groups reached America remains unknown (Dixon 2003).
A number of theories attempt to address this question, but none of them provides adequate information to show how these groups reached the continents. In the recent times, genetic studies have proved to be effective in determining the relationship between the Native Americans and the Asian groups.
In fact, these studies have shown that the American natives are closely related to a number of Asian groups. Several theories such as the Pacific Rim, Biringia, Solutrean and others have attempted to develop models that explain how the Asian groups reached America. The purpose of this paper is to analyze some of these postulates in order to draw some information that may provide a better understanding of the initial people of North America.
Theoretical explanation of initial peopling in North America
According to scholars in Linguistics, archaeology and evolutional biology, Native Americans moved from some places in Northeastern parts of Asia. During the last Ice Age, geographical conditions could not allow possible migrations of humans from Asia into America (Dickason 2007).
Therefore, the most important task is to explain the route and time that allowed migrations from Asia to America. It is suggested that humans used two routes to reach America- the Bering Land Bridge (Beringia) and along the Northwest coast (watercraft methods). Based on this information, a number of hypotheses have emerged to explain how the ancient people migrated into the New World, despite the large volume of ice.
Two major hypotheses, the ice-free corridor and the coastal migration, tend to agree that the initial people of Americas had ancestral ties with populations that lived in Siberia and that the major route was via Beringia. Beringia, also known as the Bering Land Bridge, was a large ice-free area that connected north-west part of North America with north-eastern edge of Asia (Dickason 2007).
Several Paleoenvironmental research studies have shown that the area on Beringia has a large volume of animals and plants, which acted as resources for the migrating humans. These resources supported the human populations during the entire late ice age, which suggests that the migration was in progress at this time.
The ice-free corridor hypothesis
The ice-free corridor hypothesis is considered one of the most effective models of addressing the migration question. This theory, which is based on the understanding that at various stages during the last Ice age, the northern part of America (Canada) was covered with two large sheets of ice (Burns 2006). The southern region of the ice sheets was approximately along the line that marks the modern boundary between the US and Canada.
One of the sheets was covering most of the areas that lie to west of the Rocky Mountains while the other sheet was on the areas to the east of these mountains. It is believed that the sheets were joined during most of the last ice age, but they must have been separated, which provided a stretch of iceless land known as the ice-free corridor (Burns 2006). According to theorists, the ice-free corridor makes an important landmark during the migration into the new world.
Proponents of this hypothesis believe that people from northeastern parts of Asia first reached Beringia and settled in this region for several years because the two sheets of ice had not separated. However, these populations increasingly moved closer to the areas bordering the ice as it increasingly became warmer.
The theorists believe that the populations simply migrated down the corridor when it developed from warming up of the ice sheets (Dillehay 1994). Noteworthy, several animals were the first organisms to migrate down the corridor, which means that humans were following them.
In fact, there is substantial information supporting this theory of migration, most of which tend to show that the increase in the human populations in Beringia must have forced some groups to move down the corridor in search of animal resources. For instance, Paleoenvironmental evidence suggests that this route was one of the most possible methods through which human and animal populations reached the northern part of the Americas.
However, it is worth noting that the theory is somehow weak because there is no archaeological evidence to support the hypothesis. In fact, there no archaeological sites in the ice-free corridor, especially the ones that older than 13,000 years, yet the theory attempts to explain that the migrations down the corridor must have taken place more than 15,000 years ago (Dickason 2007).
This means that the theory cannot be relied on as the sole method of solving the migration problem. Nevertheless, the hypothesis provides some basic information as well as a platform for additional research to solve the question.
Coastal migration hypothesis
Secondly, the coastal migration hypothesis attempts to use a different approach to the migration problem. Theorists argue that rather than depending on the large number of animals as resources, the early populations in Asia were largely adapted to the maritime and mostly lived on the coastlines, where food security was assured (Dickason 2007). Therefore, populations spread along the coastlines rather than the interior.
This means that the populations migrated along the coastlines. They went round southern margins of the land in Beringia before moving down the west coast of the American continent until they passed the two large sheets of ice (Erlandson 2004). According to some variations of the hypothesis, the earliest populations used boats to move across large water masses before reaching the continent.
However, other theorists suggest that it was possible to move on land along the coastlines because the large glaciers did not cover the entire land in the coast (Fladmark 2000). In fact, it is worth noting that most glaciers in the ice ages did not cover the coastlines, which gave some good environment for the survival of animals and plants. This phenomenon must have given the populations a chance to maintain foot travel to other continents.
In the case of migration into the Americas, a number of evidence supports the coastal migration hypothesis. For instance, locations with a lot of animals and plants needed to maintain the human populations have been found along the coastlines that dates back to 18,000 (Fladmark 2000). This is an important finding because the age falls within the period in which humans populations from Asia migrated into the northern parts of Americas.
However, it is clear that the hypothesis lacks archaeological support because there are no archaeological sites along the coastal region, with the few one dating less than 12,000 years. The implication is that there is a gap in knowledge in this explanation and that the theory can only be used as a platform or basis for further studies. In the 20th century, most scientists disputed this theory based on lack of archaeological evidence.
They thought that the number of locations of animal and plant life on the coastlines, which meant that the human populations could not have used a route devoid of these resources.
Nevertheless, environmental studies are increasingly providing new information to support this hypothesis, especially because the populations are thought to have achieved maritime adaptations few years after glaciations (Erlandson 2001). These studies show that human populations stretched from Alaska to California during the migration period (Erlandson 1994).
These two hypotheses are largely based on the knowledge on the Clovis culture, a big-game hunting culture that archaeologists identify as the main way of life among the Asian groups of people during the last ice age. According to Erlandson (1994), artefacts that had fluted and projectile points mainly characterize this culture. The first evidence of these tools was found at Clovis region in New Mexico, USA, following an excavation in 1932.
Subsequent excavations reveal that the culture was prominent in all parts of North America and later moved to South America with the migrating groups. In particular, the culture was designated by the use of Clovis, a typical set of tools that had flaked flint and a âspearedâ point inserted into a flute-like object. The flute allowed users to insert and remove the point from the shaft when travelling. The flute is one of the most important aspects of the tools in use during human migrations.
Carbon dating for Clovis culture has produced substantial information regarding the migration patterns from Asia to North America. Carbon dating these tools has been done in association with animal bones, which has revealed that the tools were used some 13,000 and 12,000 calendar years ago (Stanford and Bradely 2012).
Despite this, a number of studies have produced controversial evidence that seems to argue that the tools may not be the most important way of explaining the migrations. For instance, it has been shown that at least 11 out of 22 sites excavated have inherent problems. In fact, some studies indicate that even the sites at Clovis, New Mexico, are problematic.
According to such studies, the datable samples in these sites have undergone contaminations due to their integration with earlier materials, rendering them useless in providing evidence to support the migration patterns.
Noteworthy, the Younger Drayas Impact Event made an important and effective influence on the existence of the Clovis culture in North America. About 13,000 calendar years ago, the Younger Drayas event had a major impact on the populations, causing the decline of the culture.
In addition, the Clovis culture is a relatively weak theory in explaining human migrations in North America. A number of problems are associated with this model. For instance, the model fails to explain why there was a short time between the time of human occupation in North America and their arrival at the south most tips of South America (Gruhn 2004). Humans radiated southwards from Asia to America and South America some 12,000 calendar years ago.
This means that the time span used to propagate the populations from the northern end of North America to the southern tip of South America is very short, which shows that it was not possible, considering the geographical and environmental barriers at the time. In addition, evidence collected at the Monte Verde site in Chile has suggested that the Clovis model is relatively weak.
Archaeological evidence from this site produced some radiocarbon evidence that predate Clovis sites found on the Midwest by more than 1,000 years (Erlandson, Graham, Bourque, Corbett, and Estes 2007). The evidence, however, provides support to the coastal migration model as the most possible route by which the human populations of the last ice age used to reach the south.
It suggests that the populations that used the coastlines for migration were able to move fast than their counterparts who used inland migration routes. Noteworthy, a number of studies have shown that the populations had a wide range of food resources, including tubers, shellfish and turtles.
This is an additional indication that humans did not rely on the big game culture that involved hunting mammoths, horses, longhorn bison and camels that were the primary food resources for the populations that followed the inland routes from Asia to North America.
Charcoal evidence and other human artefacts have also led to confusions in explaining the entry and existence of human populations in the New World. For instance, along the banks of River Savannah in Allendale, South Caroline, a site known as the Topper archaeological site shows that charcoal and other human artefacts were already in use some 50,000 years ago.
Radiocarbon dating of these materials has shown that humans were already in existence some 40,000 years before the purported time of entry into the new world. In fact, it implies that humans already inhabited the New World years before the last glacial period. The implication is that the Clovis culture and the migration models based on it may be ineffective in explaining the migration of humans into Americas.
Nevertheless, these new evidences have also been a topic of debate over the last few years. For instance, some studies indicate that charcoal could have resulted from wild fires while geofacts could be mistaken for human artefacts. In fact, it is evident that the region experienced several wildfires caused by the natural processes years before the entry of first humans in the New World (Heaton 2005).
Apart from the Clovis culture model, a number of other theories have been developed with the hope of providing alternative explanations for migration from Eurasia to Americas. The watercraft migrations models are important in explain how humans reached the New World from the populated regions in Asia and Europe. The Pacific coastal model argues that human populations travelled along the coastal regions, which made it possible to reach North America.
According to the proponents of this theory, it is clear that coastlines provided the human populations with a good and friendly environment for humans because they support a wide range of resources, including plants and animals (Heaton 2005). Both terrestrial and aquatic lives were protected and maintained at the coastlines, which means that human populations depended on the coastlines for their food.
The model attempts to show that humans moved along the coast both on land and on using watercrafts to reach various regions between Asia and America. It explains how the human populations colonised distant regions new Bering point, including the Taima-Taime region in Venezuela as well as the controversial Monte Verde region in Chile.
Archaeological excavations have found two layers of cultural components at the Monte Verde site in Chile, which have led to the hypothesis that the Pacific coastal models must have been the most possible routes of migration. The youngest layer is dated about 14,000 years old.
It contains various kinds of seaweeds that were used by the coastal inhabitants. The older layer was found to be more than 30,000 years, but it is highly controversial and not used as strong evidence to support the Pacific coastal migration hypothesis (Dixon 2005).
The Solutrean Hypothesis
A third theory attempts to provide some additional information regarding the migration of the Eurasian populations into the Americas. Known as the Solutrean hypothesis, the explanation suggest that the migration did not involve Asian groups, but rather the groups came from Europe across the Atlantic. In fact, the term Solutrean is derived from a culture that was existed in Europe some 18,000 to 20,000 years ago.
The possible route must have involved boat and raft migration across the Atlantic before moving down beyond the periglacial environment in the eastern parts of the modern day Canada. Although this hypothesis provides an alternative to the Asia-America migration routes, it has a number of weaknesses. For instance, it lacks biological evidence because most of the indigenous people in North America are biologically related to Asian populations rather than European groups.
In addition, the indigenous populations in North America and Asia have a number of general similarities such as cultural attributes. For instance, the stone tool technologies in these two regions are similar especially those developed between 10,000 and 20,000 years ago (Jones 2005). These have been located in various parts of Beringia and north-west parts of North America.
On the other hand, there is little archaeological evidence linking the Indigenous groups in America with those of Europe, which suggests that the Solutrean migration theory is not viable. Most archaeologists argue that there are few similarities in stone tools and technologies between the Europeans and North American populations some 20,000 years ago cannot be used to explain the routes of migration into the new world.
The Paleoindian hypothesis
The Paleoindians of the coast (East Asians) migration model, attempts to show that the earliest humans to reach North America originated from East Asia and were largely boat builders (Stanford and Bradley 2011). Some scholars suggest that boast building communities used crude boats to reach as far south as Chile.
For instance, the theory shows that in the coast of British Columbia, a human population known as the Haida that colonized Queen Charlotte Islands must have been one of the groups that used this migratory route from Asia. It is estimated that the group were descendants of early Asian miners that left Asia between 24,000 and 10,000 years ago.
Like the Clovis migration models, the watercraft migration models have a number of weaknesses that make them less effective in determining the exact routes and processes of human migration from Eurasia to the New World. For instance, this theory cannot explain how humans and animals survived along the coastlines after the glaciations that submerged most coastal regions by more than 100 meters.
For instance, it is clear that sea levels in the world have risen by more than 100 meters after the end of the last glaciations period, which has led to submergence of the old coastlines. These are the coastlines thought to have been used by the migrating groups, which make it difficult to explain how the migrations took place (Dixon 2009). Secondly, it is worth noting that the theories lack archaeological evidence to support their claims.
For instance, there are few sites associated with these migrations and it has become difficult for scientists to discover new sites along the coastlines. In addition, it is worth noting that the former coastlines are now submerged, which means that it is difficult to excavate sites under the water. In addition, genetic studies have shown that some of these theories do not apply at all because there is little evidence to link some European or Asian groups with the indigenous Americans.
With genetic studies, it has been shown that some theories like the Solutrean are unlikely and wrong. In the next section, a review of genetic linkages will be developed to show the relationships between the indigenous Americans and some human populations in Asia (Jablonski 2002).
Genetic evidence and population linkage theory
The development of strong genetic studies, including the polymerised chain reaction and molecular markers improved the process of determining linkages between different organisms. In studying human populations and their relationships, these technologies have proved effective in solving some problems in anthropology and archaeology.
Most genetic studies focussing on indigenous Americans are based on the human Y-Chromosome DNA halogroups as well AS HAPLOGROUPS OF Human mitochondrial DNA (Eshleman, Ripan and Smith 2003). These use these groups to determine the relationship between indigenous Americans and other populations in other parts of the world.
For instance, according to Perego, Angerhofer, Pala, Olivieri et al (2010), a growing number of mitochondrial genomes from Beringia indicate that human populations migrated from Asia to America through the Beringian routes. Haplogroup C1 of human mitochondrial DNA for Asian and indigenous Americans were sequenced and found to have two C1 halogroups as the founder genomes foe the Paleo-Indians.
This study indicates that the American natives are closely related with some Asian populations and not European groups. In addition, other studies have shown that several gene linkages, founding halotypes and a wide range of homozygosity and heterozygosity are evident.
They indicate that human populations spread from Asia to America through Beringia and involved coastline and inland settlements. For instance, the Alaskans, Inuit and Na-Dene exhibit mutations in their haplogroup Q of their Y-chromosomes. This phenomenon is also evident in some Asian groups but missing in European or African populations.
Conclusion
This paper indicates that American natives are closely related to a number of Asian groups. Several theories such as the Pacific Rim, Biringia, Solutrean and others have attempted to develop models that explain how the Asian groups reached America. However, genetic studies appear to show that watercraft theories are unlikely, but Clovis migration patterns are important.
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