Anthropologists for more than a century have been intrigued by the biological similarities between Siberians and North American Indians. Christy Turner II of Arizona State University has studied the changing physical characteristics of Native American teeth, especially in their crowns and roots, and has compared them with those of Old World Asian populations.
The dental features studied by Turner are more stable than most morphological traits. There is a high genetic component that minimizes the effect of environmental differences, sexual dimorphism, and age variations. Turner has studied more than 4000 individuals, ancient and modern. From this, he has developed a series of hypotheses about the first settlement of the Americas based on dental morphology.
Prehistoric Americans display many fewer variations in their dental morphology than do Eastern Asians. Turner calls these features sinodonty. It is a pattern of dental features that includes shovel-shaped incisors, single-rooted upper first premolars, triple rooted lower first molars and other attributes.
(What kind of frequencies are observed? Three-rooted lower first molars are reported in 25-40% of Eskimo-Aleuts and 6% for most North American Indian groups.) The cornerstone of Turner's hypothesis is this: sinodonty only occurs in northern Asia and the Americas. Sinodonty does not occur among the neighboring Mal'ta people of Lake Baikal or in the Stone Age Ukraine.)
Turner's earliest evidence for sinodonty comes from northern China in about 18,000 B.C. He believes, however, that it emerged much earlier, perhaps as early as 40,000 years ago. According to his calculations, the Sinodonts migrated into Mongolia about 20,000 years ago and across the Bering Strait about 14,000 years ago.
European Upper Paleolithic peoples do not display sinodonty. It is Turner's belief that the Sinodont northern Chinese may have evolved from a primeval Southeast Asian Homo sapiens population.
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