Athena Review, Vol. 4, No. 2
Teeth from an Alaskan Cave Provide Clues to Ancient Migration Patterns
DNA extracted from teeth in a human mandible, recovered from an island cave off southern Alaska, may provide clues to the route taken by the earliest migrants to the Americas. Representing the earliest human DNA ever isolated in the Americas, the sample, according to molecular anthropologist Brian Kemp, includes fragments of both mitochondrial DNA (mtDNA) and Y chromosome DNA. The teeth came from the mandible of an adult male discovered with associated pelvis bones in 1996 in On Your Knees Cave on Prince of Wales Island (fig.1). This ancient stratigraphic level also contained obsidian microblades, other stone bifaces, and a bone tool dated by AMS (accelerator mass spectrometry) to 10,300 +/- 50 BP (AR 3,2). This is currently the oldest artifact from the Northwest Coast whose date is widely accepted.
According to E. James Dixon, principal investigator of archaeology at the cave site (officially known as 49-PET-408), humans were exploiting the maritime resources of the Northwest Coast by at least 9,500 BP (or 10,150 cal BP). Isotopic analysis of these human remains showed he typically ate maritime food, including saltwater fish, sea mammals, and shellfish (Dixon 2002; AR 3,2). Given the cave's location 1 km from the coast, combined with the presence of non-local obsidian and a maritime diet, Dixon concluded that the ancient inhabitants were coastal navigators with established trade networks. Additional evidence for early maritime adaptations and the use of boats or rafts also occurs at other coastal sites from Santa Rosa Island off California to Ecuador and Peru. Dixon and other researchers have suggested that the first human entryway into the Americas may have occurred along the west coast through the use of watercraft.
[Fig.1: Location of 49-PET-408 on Prince of Wales Island and obsidian sources on Sumez island and Mt. Edziza (after Eric Parrish)].
DNA recovered from the 49-PET-408 individual appears to support this coastal migration theory. The DNA was compared with mitochondrial DNA from more than 3,000 Native American sequences taken from public databases. Matches were obtained from samples of modern and ancient individuals, with the coastal Cayapa of Ecuador accounting for more than 50% of the matches. Others included the Chumash (California), the Klunk Mound people (Illinois), the Tarahumara (Chihuahua, Mexico), and the Mapuche and Yaghan tribes (Chile) - thereby tracing a possible migration route.
Current molecular genetic studies of human mtDNA suggests that five founding lineages were responsible for the colonization of the Americas over 10,000 years ago (Schurr 2002). The four principal lineages (also known as haplogroups), designated A-D, account for over 95% of all mtDNAs of modern New World indigenous populations, as well as the majority of mtDNAs of ancient Amerindian populations. The man from On Your Knees Cave belonged to lineage D, found in significant frequencies among Patagonian Amerindians (over 50%); Andean Amerindians (~33%); Amazonian Amerindians (~33%); N. American Amerindians (10%); US SW Amerindians (5%); Aleut (75%); and Eskimos (~23%) (Schurr 2002: fig.5). A fifth lineage, designated X, is present among a very restricted number of populations.
Comparative studies of these genetic lineages are leading to a better understanding of the ancestry of Native Americans and the timing of the first colonization of the New World. Haplogroup A-D mtDNAs occur together in Asian populations from the Altai Mountain region to Japan and Korea. Significant frequencies of Haplogroup C and D mtDNAs, moreover, are found in all eastern Siberian populations, and are also present in many East Asian populations (Schurr 2002). The timetable for the arrival of these lineages in the New World has been the subject of considerable research, with current estimates of arrival based on molecular studies ranging from an "early" entry of 35,000-20,000 cal BP to a "late" entry of 14,000-12,000 cal BP) (Schurr 2002).
Recent studies of Y-chromosome variations (transmitted only from father to son) have been tracking male migrations in time and space. With Y-chromosome DNA successfully extracted from the On Your Knees man, comparisons with the rapidly expanding genetic database should provide additional insights to his molecular makeup and affinities.
As a footnote to the investigations at On Your Knees Cave, archaeologists and the local Tlingit and Haida tribes, in contrast to the conflict surrounding Kennewick Man, have cooperated in the ongoing quest to learn more about the earliest traces of humans in the Americas.
[Dalton, R. "Caveman DNA hints at map of migration." Nature 436:162; Dixon, E.J. 2002. "How and When did People First Come to America?" Athena Review 3,2:23-27; Schurr, T.G. 2002. "A Molecular Perspective on the Peopling of the Americas." Athena Review 3,2:62-75; http://www.usd.edu/esci/alaska/ oykc.html]
This article appears on pages 8-9 in the Recent Finds in Archaeology of Vol.4 No.2 of Athena Review. The complete text may be obtained in the printed version of the magazine.
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