Immediately following Columbus's voyage that brought him to the Americas in 1492, Europeans began to speculate about the origins of these newly "discovered" peoples. They wondered where they came from and when they got there. Today, biological and archaeological evidence has answered those questions. We now know that the first Americans were migrants dispersing out of Asia about 15,000 years ago. (Relethford, 2003)
This is only a general answer, however, and we still have specific questions about the origins of Native Americans that have not yet been answered. In this paper, I will attempt to answer three of these questions and analyze the role genetic data has had in solving these issues. Many difficult matters are raised with questions of ancestry. The DNA of humans connects everyone to everyone else after a couple thousand years, so it is very challenging to determine who is an ancestor of whom. (Olson, 2002)
The first question to be answered is: Where in Asia did the first Americans come from? The people the Europeans found when they colonized the Americas were very diverse. Some groups were small hunter-gatherer tribes and others were living in large agricultural societies and cities. (Relethford, 2003) Most European scholars at the time explained the origin of Native Americans with biblical interpretations. They believed that the natives were descendants of the lost tribes of Israel. (Relethford, 2003)
The first person to refuse to rely on biblical reasoning was the Jesuit scholar Jose de Acosta, who in 1590, after living and traveling widely in South America, wrote that Native Americans were descended from people who had migrated from Siberia. (Olson, 2002; Relethford, 2003) His approach to the problem was to look at the geographic distribution of different animal species. (Relethford, 2003) Acosta's theory has held up pretty well to this very day. The ancestors of most, if not all, of the people living in the Americas when Columbus arrived have been proven to be people from Asia who made their way across what is today, the Bering Strait. However, during the last ice age, the New and Old Worlds were not separated by water, but connected by the Bering land bridge, referred to as "Beringia". (Relethford, 2003)
Now I'd like to address my initial image of what occurred during this Ice Age and migration. I've been taught of the Bering land bridge several times during my college education, and admittedly, I imagined what Relethford describes as "a group of people rushing single file across a narrow strip of land connecting Asia and North America". He then goes on to describe the actual situation that took place, which completely altered my perception, thankfully. He states that the bridge was not abruptly available, but the geological changes brought about by the ice age took many, many years to occur. And eventually it was covered with forests and herds of animals that expanded on to it. Relethford describes the event as "not a sudden movement of people, but rather an avenue for dispersal that may have been used for generations" across a "bridge" that was almost 1,300 miles wide. He continues to include that the people probably did not even realize they were crossing a land "bridge" at all. (Relethford, 2003) The understanding of these facts is mandatory to fully comprehend this event in history.
Archaeologists also argue for a coastal hypothesis that there is evidence of people crossing the waters by boat. The evidence that supports this theory is found at sites such as Arlington Springs where two femurs were excavated, and a stone tool found at a location 53 meters below sea level. There is no reason that this form of transportation to the New World could not have occurred; humans were traveling to Australia by boat at least 60,000 years ago. Both theories are possibly true. (Relethford, 2003) What is important to know is that these humans came primarily from Asia, a conclusion completely cooperative with the genetic evidence. In an evolutionary context, it is operative to understand that the first Americans were anatomically modern humans (or AMH). All of the skeletal remains recovered in the new world sites are of anatomically modern humans; no Homo erectus and no early hominids. (Relethford, 2003)
Once the people moved across Beringia into North America, they were prevented from moving into the south west and east by two major glacial ice sheets. (Dixon) Then about 16,000 years ago, the glaciers began receding and within a thousand years or so a corridor opened up east of the Rocky Mountains. By 14,000 years ago, the passageway dried and widened and was safe for humans to pass. (Olson, 2002)
Archaeologists rely on the appearance of a specific kind of stone tool, a Clovis point, to confirm the date of initial passage. The Clovis point was a leaf-shaped arrowhead with a concave base and show up in North America a few hundred years after the opening of the corridor. Therefore, archaeologists have hypothesized that people bearing Clovis technology came through the corridor and spread quickly across North America. (Olson, 2002)
This "Clovis First" hypothesis supported the idea that the principle reason for the migration into the Americas is that they were following their prey across the land bridge around 14,000 - 15,000 years ago. Unfortunately, the technology that supported small game hunting and fishing haven't survived as well as the stone artifacts.
An opposing hypothesis, the Solutrean, concludes that the Clovis culture may not be of Asian origin, but may have come from Southern Europe. It states that the Europeans may have skirted the ice sheets of the Atlantic in boats and gone to the southeastern U.S., where the earliest Clovis points are found. An example of fossil evidence that supports this theory is the Kennewick Man found in 1996 along the Columbia River in Washington State. (Olson, 2002) The Kennewick Man was one of the earliest inhabitants of the Americas.
James Chatters, an archaeologist, initially concluded that with his narrow skull, projecting nose, and pronounced chin, the man was of European descent. (Olson, 2002) However, most archaeologists disregard this generalized claim that was based entirely on the physical appearances. Comparing a 9,000 year old skull with skulls of living populations does not take into account the fact that populations change over time. (Relethford, 2003)
There is a genetic link between Asia and North America. The patterns of human biological diversity support de Acosta's theory of an Asian origin of the first Americans. An example is the several average physical similarities between Native Americans and East Asians, to include straight black hair, relative lack of facial hair, broad cheekbones, and a higher incidence of the epicanthic fold. However, more evidence is required for these traits are not confined to these groups, nor are these traits unanimous in these groups. (Relethford, 2003)
Therefore, geneticists went on to study the classic genetic markers in what is referred to as the Diego Blood Group. This blood group provides a strong similarity between East Asian and Native American populations. Two forms, or alleles of the Diego Blood Group exist, DI-A and DI-B. The DI-A allele is absent in Africa and the Pacific Islands and very rare in Europe and the Middle East. On the other hand, the DI-B allele has higher frequencies in both East and Northeast Asians and Native Americans, providing strong evidence for a historical link between the two peoples. (Relethford, 2003)
Still, more evidence is required to prove a definite linkage. So, the average pattern of genetic distance on many different traits was examined by following the maternal line of the first Americans. In general, utilizing information from mitochondria DNA (or mtDNA), a family tree linking the different haplotypes was built and haplogroups were formed from related haplotypes. (Schurr and Sherry, 2004) These haplogroups proved that Native American populations are most similar genetically to Northeast Asian populations, particularly those in the Arctic. (Relethford, 2003)
It was first concluded that the mtDNA that contains a haplogroup more typical of Europeans was simply the result of mating with the Europeans arriving after 1492. However, the appearance of this haplogroup predates European contact! So, it is possible that the haplogroups may have come in with migrants across Beringia that originated from western Eurasia. (Relethford, 2003)
The second question to discuss is: How many migrations took place? The "Clovis First" hypothesis eventually gained support from other scientific disciplines. These researchers began to find evidence that the people who traveled from Asia to the Americas, traveled in three discrete waves. They linked the first of these waves with the Clovis people. (Olson, 2002)
The linguistic evidence was proposed by the Stanford linguist, Joseph Greenberg. He grouped all the languages spoken by Native Americans at the time of European contact into three large families. The most recent of which being the Eskimo-Aleut languages spoken by Arctic hunter-gatherers who spread into northern Canada and Greenland within the last few thousand years. The next grouping is the Na-Dene languages spoken by people in northwestern North America and by their offshoots the Navajo and Apache, who migrated into the Southwest about a thousand years ago. The oldest grouping, including almost a thousand current and extinct languages, is the Amerind family. The group is extremely large and diverse; however, Greenberg still saw enough similarities to imply descent from a common proto-language. Greenberg did not specify when these languages entered America or who was speaking, but it is a popular assumption that the Proto-Amerind was the language of the Clovis people. (Olson, 2002)
The second form of supporting evidence of the "three-wave model" came from dental examinations. Christy Turner of Arizona State University concluded that, based on an analysis of more than 9,000 North American crania, the teeth of past Native Americans fall into roughly three categories. Conveniently, the three categories of skulls fall into the same three language groupings, again, lending support to the hypothesis of three waves of migration. (Olson, 2002) The three wave model fits very well with the Clovis first model, therefore, any cracks in the Clovis hypothesis cast doubts on the three wave model.
The third and final question to answer is: When was the New World first inhabited? For years, the traditional archaeological answer was based on a relatively "recent" first entry, roughly 12,000 to 15,000 years ago. (Relethford, 2003) Numerous sites had been found dating back to about 11,500 years ago, all sharing the Clovis culture. These sites suggested that humans first entered the New World more than 12,000 years ago, followed by a rapid spread of occupation of North, Central, and South America. (Dixon)
However, over the past few decades, there have been several claims for an earlier occupation of the New World, with a number of sites being identified as "pre-Clovis". For example, the Monte Verde site in southern Chili is thought to date back to 12,500 years ago. Because this site is so far away from the Bering Strait, it implies a much earlier entry than the "Clovis First" theory suggests. Some other pre-Clovis sites include the Meadowcroft Rock Shelter in Pennsylvania dated to be older than 12,000 years, and the Cactus Hill Site in Virginia, which my be as old as 15,000 years. (Relethford, 2003)
Depending upon how rapid the expansion was, the initial date of entry may be not much older than 12,500 or it could be a much earlier date than that. Physical barriers must also be taken into consideration. Many areas of possible movement were basically blocked between about 13,000 and 20,000 years ago. Based upon the assumption that the first Americans came through the ice-free corridor, the inhabitation took place more than 20,000 years ago or less than 13,000 years ago. The answer is still not very clear; however a broad estimate of between 15,000 and 20,000 years ago has been suggested. (Relethford, 2003) The true answer may come in time, as more sites are discovered, more evidence is interpreted, more factors are introduced, and all variables are analyzed. Relethford thoughtfully suggests that "the final determination of the age of the first Americans will be settled by archaeology and not by genetics."
In conclusion, three major questions about the initial occupation of the New World have been discussed: Where in Asia did Native Americans come from? How many migrations took place? When did all of this happen? Although there are many unique theories and hypotheses that have been introduced, accepted, and/or denied, we still do not have an absolute, indisputable answer. Hopefully, however, with more time and research being devoted to this subject, we will have some definite answers in the future.
Dixon, James E. "How and When Did People First Come to North America?". In Athena Review. Vol.3, no.2. Peopling of the Americas.
Olson, Steve. Mapping Human History. Genes, Race, and our Common Origins. (2002). Houghton Mifflin Company. New York.
Schurr, Theodore G.; Sherry, Stephen T. "Mitochondrial DNA and Y Chromosome Diversity and the Peopling of the Americas: Evolutionary and Demographic Evidence". In American Journal of Human Biology. (2004). 16:420-439.
Relethford, John H. Reflections of Our Past. (2003). Westview Press. Boulder.