Terrific Teeth: Dental Evidence for the Peopling of the Americas
The existence of the Americas and the question concerning the origins of the native inhabitants remains a fervently debated subject in American archaeology. Since the discovery of the Americas in 1492 scholars have pondered the origins of the people in the Americas. There was no mention of a landmass between Asia and Europe in the Bible, or any other known written document in the 15th century. This caused early Europeans to create their own ideas about where the people of America came from.
In the sixteenth century scholars began formulating opinions concerning the origins of the people found on what they referred to as the 'New World'. These opinions ranged anywhere from viewing Native Americans as the survivors of Atlantis to one of the lost tribes of Israel (Powell 2005: 17). In 1590, Jesuit Missionary Joseph de Acosta first suggested the idea that somewhere, in either the north or south, there was some sort of land connection or narrow strait connecting the 'Old World' and the 'New World' (Powell 2005: 19). This idea was later agreed upon by a widespread consensus, which states that during the Pleistocene water levels dropped enough to allow a 'land bridge' in the now submerged Beringia area (Zegura 1985: 5). Acosta also disagreed with a widely accepted idea concerning Native Americans and their own Eden and Ark (Powell 2005: 18).
Around the same time as Acosta, Gregario Garcia also proposed a school of thought concerning Native American origins. He was more contentious about the church and developed a less heretical view about the biblical flood. He researched and presented eleven different theories on this subject, some of which investigated the lost-tribes-of-Israel theory, the Atlantis sunken city Model, and Gonzalo Fernandez de Oviedo y Valdez Model. Oviedo's Model explained that Native Americans were originally from Spain or Portugal. They traveled to the Americas with King Rodrigo in AD711 after his defeat by the Moors (Powell 2005: 19).
Both Acosta and Garcia presented the concept that the origins of Native Americans had biological and cultural roots in Asia. This theory was later adopted by eighteenth century naturalists who developed a classification system for modern humans that consisted of three racial groups. These groups were 'Mongoloids', 'Negroids', and 'Caucasiods'. Native Americans were classified as 'Mongoloids' (Powell 2005: 20).
The end of the eighteenth century and beginning of the nineteenth century saw a change in the way Native American origins was studies. Research was no longer based on where Native Americans came from, but when the Asian migration occurred (Powell 2005: 20). Then, in the late nineteenth century, excavations at Brixham cave proved that humans were around during the Pleistocene age. Charles Darwin also published On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life around the same time. This publication was the basis for Darwin's Theory of Evolution, which states that different characteristics that are helpful to a species become dominant while characteristics that hinder a species die out (Powell 2005: 21).
With the discovery of a prehistoric Europe, several scholars set out to find an equivalent in the Americas. It was not until 1926 that Pleistocene evidence in America was found and verified beyond a reasonable doubt (Powell 2005: 21-22). The twentieth century also experienced a revival in the European Model first suggested by Oviedo. However, this model suggested that Native Americans were descendants of the Solutrean people in northern Europe. This concept was based on the similarities between Clovis projectile points and Solutrean points (Powell 2005: 19-20).
In the field today there still remains a lack of certainty and agreement among scholars over several issues regarding the peopling of the Americas. These disagreements, which include the timing of colonization, the route and pattern of migrations, subsistence modes of migration, and where the migrants dispersed to once in the New World, stem from a lack of adequate evidence to support most theories (Powell 2005: 23). The most recent research has taken anthropological and biological data from past and present Native Americans to accurately depict population dispersal and migration patterns. However, there is still debate over data interpretations (Powell 2005: 24).
In the past few decades anthropologists and scholars have developed several theories concerning the peopling of the Americas. Of the theories presented by these anthropologists and scholars, examining dental characteristics appears to be the best method because out of all of the parts of the human body, teeth preserve the longest. Teeth patterns in populations also tend not to change as rapidly as other parts of the human body (Meltzer 2008a). In Christy Turner II's article, The dental search for Native American origins, he explains that teeth are a good source for discovering relationships between pre-historic populations, not only because of their hardness, but because of the large number of distinctive dental traits. These traits include everything from tooth size, crown and root traits, and sex dimorphism (Turner 1985: 33). According to research into the dental variations of different Asian populations, two types of dental patterns developed from the 'Mongoloid Dental Complex'. These two patterns are Sundadont, which occurs mostly in South East Asia, and Sinodont, which occurs in North East Asia. Similarities in the dental characteristics of Native American populations and North East Asian populations illustrate an ancestral link between the two communities. Within the Sinodont pattern in Native American populations, three sub-patterns exist (Turner 1985: 31). Turner believes this variation suggests that three separate migrations occurred, beginning around 12,000 years ago (Mulligan et al. 2004: 296; Greenberg et al. 1986: 477).
'Mongoloid Dental Complex'
The 'Mongoloid Dental Complex' pattern, discovered by K. Hanihara in 1968, was based on four crown traits he observed in the Japanese, American Indian, and Eskimo populations. The pattern was defined by a high frequency of shovel-shaped incisors, cusp 6, the protostylid, and the deflecting wrinkle (Scott and Turner 1997: 270). Through Christy G. Turner II's research, two different types of dental variation, or patterning, existed within Haniharas' 'Mongoloid Dental Complex'. One of the patterns he identified was characterized by a high frequency of incisor and double shoveling. Those who fell into this grouping also tended to have a higher frequency of upper third molars, lower first molar deflecting wrinkles, 1-rooted upper third molars, and 3 rooted lower first molars. They also had a lower frequency of 4-cusped lower second molars (Scott and Turner 1997: 270). Turner called this pattern the Sinodont pattern. This pattern evolved in China between 40,000 and 20,000 years ago. Sinodonty occurs in pre-Cossack Northeast Asians and Native Americans. The groups included in the pre-Cossack Northeast Asian category are the Chinese, Mongols, Buriats, Siberian Eskimos, Yayoi-modern Japanese, and a few others (Turner 2002: 137).
The other pattern he called the Sundadont pattern. Sundadonty differs from Sinodonty because it is a very simplified pattern. There is evidence of dental reduction caused by fewer Sundadonts having lower molar cusps 5 and 6. Fewer individuals have shoveling or double-shoveling and the 3-rooted lower first molar rarely occurs in Sundadonts. Although there is a relationship between the Sundadonts and Sinodonts in Asia, there is no dental evidence that associations Sundadonts with the peopling of America (Turner 1985: 36). These patterns are defined geographically as being either Southeast Asian (Sundadonty) or Northeast Asian (Sinodonty) (Turner 2002: 135).
Within the Sinodont pattern, Turner identified three sub-patterns in the Americas by examining the 3-rooted lower first molar trait in Native American teeth. He identified these three groups as Eskimo-Aleut, Na-Dene, and Amerind (Scott and Turner 1988: 104).
Figure SEQ Figure * ARABIC 1 Greenberg et al. 1986: 484
Dentochronology is a method created by Christy Turner. His method was based on the idea that the time between two groups with the same common ancestry can be measured by the differences in their dental characteristics (Scott and Turner 1988: 104). He based this on the idea that there is a correlation between distance and time (Scott and Turner 1997: 313).
Turner conducted 45 different comparisons using this method and in all the comparisons the dates were all similar to those found using other lines of evidence. He used a 'dental clock' that assumes that people began migrating into America around 12,000 years ago to determine the MMD (Scott and Turner 1997: 314).
To find the estimated divergence between two groups, Turner finds the Mean Measures of Divergence (MMD), which is found by calculating 28 crown and root trait frequencies.
The Eskimo-Aleut cluster consists of the Aleut, Athapaskan, Northeast Siberian Eskimos, Chukchi, and Koryak. The Na-Dene cluster is represented by the Gulf of Alaska and Northwest Canada/US. The Amerind cluster consists of South America, Mesoamerica, Eastern US and Canada, and California. The reason for the representation of a fourth cluster in this dendogram results from containing some sporadically dispersed Na-Dene cranium in the area (Greenberg et al. 1986: 483).
Three Migration Model
Figure SEQ Figure * ARABIC 2 Mulligan et al. 2004: 297
Despite disagreement regarding the Three Migration Model, also referenced as the Tripartite Model in some works (Powell and Neves 1999: 158), it has remained at the center of research for the past few decades (Mulligan et al. 2004: 298). The theory is based on three separate lines of evidence, which consist of linguistic, dental morphology, and classic genetic markers. Of these three lines, genetics represented the weakest link because of the lack of genetic data while linguistics provided the most evidence for the theory (Mulligan et al. 2004: 296).
The concept behind the Three Migration Model explained that the first migration of people to the Americas occurred around 11,000 years ago. The modern descendants of this first migration speak Amerind languages. The second migration occurred around 9,000 years ago and its modern descendants speak Na-Dene languages. The third and most recent wave of migration occurred around 4,000 years ago. The modern descendants of this last wave are the Eskimo and Aleut peoples (Mulligan et al. 2004: 296). However, there was disagreement between the dental evidence and linguistic evidence in relation to the last two migrations. Although Greenberg's linguistic model shows the Na-Dene as the second migration, Turner's dental model shows the Na-Dene migration as the third migration (Meltzer 2008b; Meltzer 2008c).
The Amerind groups are widely dispersed throughout North and South America. The Na-Dene groups are mostly concentrated in Alaska and Northwest Canada, but are sporadically found throughout the Pacific Northwest. Modern descendants of this group include the Navajo and Apache tribes. Finally, the Eskimo-Aleut groups are found in Alaska and Greenland (Mulligan et al. 2004: 296).
Dental morphology provided one of the strongest threads in a broader tapestry of physical evidence (Scott and Turner 1997: 278).
In the article The Settlement of the Americas: a Comparison of the Linguistic, Dental, and Genetic Evidence, dental evidence is studied because of its excellence of preservation, the existence of numerous independent traits, genetic determination, evolutionary conservatism, between-group variation, and ease of observation that all relate information concerning the history and relationships of populations, both past and present (Greenberg et al. 1986: 480).
The beginning of Dental Anthropology is rooted in the early twentieth century. Comparative studies of crown morphology around this time gave rise to the idea that certain traits could be used to identify different races (Scott and Turner 1988: 100).
It was later discovered that crown and root morphology tended to be very discrete. Crown traits include accessory ridges, tubercles, styles, and cusps that appear on the lingual, buccal, or occlusal surfaces. Root traits refer to the number of roots a tooth has and normally only occur in the lower molars (Scott and Turner 1988: 100).
In the twentieth century there was a revival in the notion that Native Americans were descendants of Europeans. This was based on the resemblance of Clovis points and Solutrean points. However, this theory was dismissed because it was discovered that the reason for the similarities between the two points had to do with the functionality and human ingenuity. The idea that Native Americans were descendants of Europeans still remained a theory for a while after this. The most convincing aspect of the dental evidence for the peopling of the Americas was that it proved that Native Americans could not have come from Europe.
By 20,000 BP European dental characteristics had finished evolving and those characteristics did not match those found in the New World. Since dental characteristics change over such a long period of time, it seems impossible that Native Americans could have migrated from Europe (Turner 1985: 57).
Hrdlicka conducted the original research involving dental evidence for the peopling of the Americas. Through his study he discovered that the best known trait linking Asian populations to Native American populations was shovel-shaped incisors. He also discovered that both populations seemed to have high frequencies of incisor winging, enamel extensions on molars, and single rooted upper first premolars. His study of dental morphology could only prove that Native American populations were derived from the Mongoloid races (Scott and Turner 1997: 278).
In the early 1970's Turner began researching dental evidence that could prove the number of migrations from Asia to the Americas. During this research he surveyed the frequency of 3-rooted lower molars (3RMI) in North American Natives. He discovered that the Eskimo-Aleut populations had trait frequencies between 25-40% and that Amerind populations only had about 6% frequencies. He did not actually study the teeth remains of Athapasken groups, but from X-rays taken of Navajo Indians, he found that they had around a 27% trait frequency. This meant that the Amerind group had a low frequency of 3RMI and they represented the first migration. The second migration was by the ancestors of the Eskimo-Aleut groups who had a high frequency of the trait. Ancestors of the Athapasken groups, or Na-Dene, who had an intermediate frequency of the 3RMI trait, made the third migration (Scott and Turner 1997: 278).
Turner concluded that this was evidence of a three migration theory and that it coincide[d] with major New World linguistic divisions recognized by Sapir and later Greenberg (Greenberg et al. 1986: 480). However, Turner also admits that there are uncertainties pertaining to the linguistic category 'Na-Dene' and the dental group 'Greater Northwest Coast' (Turner 2002: 138). Later dental data also suggested that North China was the ancestral homeland for all Native Americans (Greenberg et al. 1986: 480). Turner also stated that despite the different dental variations found in the Americas, all the New World populations were more like each other then they were like any of the Old World populations (Powell 2005: 203).
Turner used evidence he discovered with dentochronology to support the Three Migration Model. Using this method he discovered that the Amerind group diverged from the Northeast Asians sometime between 13,000 and 16,000 years ago. He also found that the ancestors of the Eskimo-Aleut diverged from Northeast Asia around 11,000 years ago, and that the Eskimo and Aleut populations diverged from each other around 3,888 years ago (Scott and Turner 1988: 104). Dental variation was found to be greater in the north then the south, which illustrated the peopling of America first occurred in Alaska and then moved south. Since the occupation of Alaska has the oldest history, the variation is greatest there. This theory is consistent with the well established theory concerning a Bering land bridge migration (Greenberg et al. 1986: 480).
According to Turner's research the three migrations out of Northeast Asia began with the exit of the ancestors of modern Amerind groups. The migrating group probably traveled to the upper Lena River Basin. There they continued traveling north through the Lena River Basin until they reached the coast near the Laptev Sea. This coast was western Beringia and the area was a cold tundra with very few plants or animal life (Turner 1985: 50-51).
The second migration differs from Greenberg's order, who stated the second migration was the Na-Dene. Turner proposed that the Eskimo-Aleut migration was the second migration. They traveled northward through Manchuria and crossed the Bering Land Bridge on the opposite side as the Amerind (Turner 1985: 52).
The final migration came later in time, right before the Bering Land Bridge was submerged in water. This group, the Na-Dene, traveled through the forest areas before reaching Beringia (Turner 1985: 54).
There has been very little microevolution for the past 11,000 years in America when comparing Paleoindian dentitions with modern Amerind populations (Powell 2005: 203). Proof of this lack of evolution is evident in teeth found at the Pali Aike Cave in Chile that dates back to around 10,000 BP. The teeth found at this site have the Sinodont pattern (Powell 2005: 204-205). Turner explained that genetic drift, or founder's affect was the reason Native Americans have a greater dental homogeneity then east Asia was because Native Americans all descended from the small groups of North China hunting bands that wandered into the harsh environs found in Northeast Asia during the late Pleistocene (Powell 2005: 204). Founder's affect and 'probable mutation effect', when applied to this research, assume that random changes over a very long period of time, and not shifts in gene frequencies that characterize natural selection, are the reason dental differences occur. Since Turner assumes that there were only three founding populations, it is reasonable to assume that this is the why there is little dental variation throughout American Native populations (Powell 2005: 203).
Turner also argued that since less dental evolution had occurred in the Americas that meant that the Americas could not have been populated for very long (Dixon 2001: 280). This idea states that if dental evolution is slow and genetic drift is the main cause of dental morphological differences in populations, then dental differences between these groups could not have occurred in the New World. Based on a Clovis-first chronology, there was not enough time for this kind of dental divergence to occur, so it had to take place in the Old World. The climate in the sub-Arctic northeast Asia required groups to remain small. This, in effect, caused genetic drift, which created biologically distinct groups who then migrated to the New World at three separate intervals (Powell 2005: 208).
Turner found a stability in the dental traits of the three sub-patterns that also suggests a Three Migration Model. The study showed that out of the Eskimo-Aleut population sampled, none developed Amerind characteristics. The Amerind sample showed that no Amerind groups developed Eskimo-Aleut characteristics either (Turner 1985: 45).
Earlier in the paper the Pali Aike Cave in Chile served as an example of the Sinodont pattern in the Americas around 12,000 years ago. Although the teeth at this site have some Sinodont characteristics, the actual pattern cannot be determined without some reasonable doubt. The teeth found at this sight belonged to a person who was cremated, so the tooth crowns were badly fractured and the only traits that could be examined were the root traits. These root traits were also only based off of the empty tooth sockets in mandibles (Powell 2005: 205).
Recent archeological discoveries also suggest that the Sinodont pattern was not the only one present in the New World, which suggests that the origin of the first Native Americans might not actually be northeast Asia, but south Asia and the Pacific Rim. Since these people came from this region, they probably share a common ancestry with ancient Australians (Dillehay 2003: 23). This evidence also supports Dahlberg's findings on tooth size. After discovering that Native American populations tended to have larger teeth, he also found the trait was similar in Greenland Eskimo, Amerind, and Australians (Powell 2005: 205).The evidence for a Pacific Rim migration was based on cranial and facial measurements of the oldest skeletons in America. It was not until a second migration that the ancestors of the modern Amerind migrated from northeast Asia (Dillehay 2003: 23). The Sundadonty pattern also occurs in Kennewick man (Dixon 2001: 280), the 9,400-year-old skeleton that was mistaken for a European trapper prior to the discovery of its radiocarbon age, because of its 'Caucasoid morphology' (Powell 2005: 6). Turner later responded to this Kennewick observation stating that it was possible the researchers were not taking into account erosion and wear. He also explained that although he was unable to examine every dentition of pre-Clovis crania, the ones he had examined were all Sinodont (Turner 2002: 139).
There is also a question as about whether Turner tried to force his results into Greenberg's categories. Since he never published his data, no one can repeat his research without having a prejudice for Greenberg's categorize. Turner also failed to recognize that territory can change owners over time, assuming that a region and people are synonymous (Meltzer 2008c). In Lyle Campbell's response to the article The Settlement of the Americas: a Comparison of the Linguistic, Dental, and Genetic Evidence, which outlines the linguistic, dental, and genetic evidence found by Turner, Greenberg, and Zegura, Campbell states he finds it unconvincing. He states that the author is misleading when he refers to the 'Greater Northwest Coast' clusters 'Na-Dene' because the cluster does not match the 'Na-Dene' language geography (Greenberg et al. 1986: 488). W.S. Laughlin's comments on the article agree that the dental correlations with linguistic evidence do not exist. He even states that instead of proving a three migration theory, Turner's research actually gives evidence of a single migration that split into minor subdivisions once the people entered into the Americas (Greenberg et al. 1986: 490).
There were also issues with Turner's research into the frequencies of 3-rooted lower first molars. There was a close relationship between the Aleut and the Eskimo populations, but linking the three subdivisions together proved difficult. There seemed to be a very large dental gulf separating American Indians from Eskimo-Aleuts (Scott and Turner 1997: 279).
The notion behind the dental evidence Turner and others have present has a lot of potential for future research. Turner's development of dentochronology appears to give accurate results and his initial classification of Sinodont patterns and Sundadont patterns are respectable. He was able to prove that Native Americans could not have come from Europe and that they probably came from northeast Asia. He was also able to determine several dental characteristics that distinguish different ancestral groups. However, there are several flaws with his theory about the migration patterns. His use of the terminology used by Greenberg to illustrate his linguistic model does not fit. He does show a bias for Greenberg's model and it seems as though his research was not as through as it should have been because of that. His theory fails to address the existence of Pleistocene people, like Kennewick man, who have the Sundadont pattern. When the notion of Sundadont patterns existing in Pleistocene people in America was researched, Turner pointed out that finding like these could have been affected by observation errors caused by dental wear and erosion (Powell 2005: 205). However, Turner also points out that the study done by Powell and Rose never stated which dental traits they used to conclude the teeth were Sundadont (Turner 2002: 135). The dental evidence of the peopling of the Americas is a very interesting field to examine and will hopefully result in a better understanding of prehistoric people in the years to come.
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