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Mitochondrial DNA and prehistoric settlements: native migrations on the western edge of North America.

Article Excerpt
Before European contact, the western edge of North America exhibited an exceptionally high level of linguistic diversity (Campbell 1997; Mithun 1999), with 90 separate languages being spoken in California alone (Moratto 1984). This great diversity has been cited as evidence for a greater antiquity of human occupation in these regions than in the rest of the Americas [J. Nichols 1990; but see also Nettle (1998)]. Particular patterns of this diversity have also been used to formulate hypotheses of human migration and expansions in western North America as well as a higher-level subgrouping that is presumed to reflect closer relationships among certain groups of Native American populations.

Dixon and Kroeber (1913) first proposed the existence of the Hokan and Penutian language superstocks in California. California Penutian includes four language families--Wintuan, Maiduan, Yokutsan, and Utian (which itself includes the Miwok and Costanoan subfamilies)--which are further subdivided into approximately 30 distinct languages. Hokan languages include a number of language families in California, the Yuman languages in Baja and the southwestern United States, and Washo on the western edge of the Great Basin (Campbell 1997; Campbell and Mithun 1979; Mithun 1999). The notable nonrandom distribution of various Penutian and Hokan languages has long suggested to prehistorians a wave or waves of Penutian migrations into California. Penutian speakers eventually occupied the interior valley extending to the coast around the San Francisco Bay Area, whereas a number of Hokan-speaking populations occupied the periphery of the Central Valley (Moratto 1984). This ring of Hokan-speaking groups surrounding a contiguous body of Penutian-speaking tribes suggests to some that at one time the whole of California was occupied by Hokan speakers who were later displaced to the valley periphery by an expansion of Penutian speakers from a central California homeland (Kroeber 1935).

The "Hokan-Penutian" hypothesis has had considerable influence on interpretations of California prehistory (Breschini 1983; Moratto 1984). Glottochronological estimates for the age of the Utian branch of the Penutian stock (the Miwok and Costanoan language families) in California fall between 4500 and 5200 years B.P. (Callaghan 1997; Moratto 1984). This date coincides closely with the appearance of the Windmiller pattern in the Central Valley, suggesting that the Windmiller pattern represents the earliest presence of Penutian peoples in the area (Fredrickson 1973; Ragir 1972). Archeological characteristics of Windmiller mortuary practices include extended burials, the presence of Haliotis and Olivella beads, characteristic charm stones, red ochre, and large projectile points (Ragir 1972). Similar archeological elements at the Kramer Cave site in western Nevada further suggest cultural contact between Great Basin peoples and the coeval Windmiller cultures, whereas red ochre, charm stones, and large, contracting stem-and-leaf-shaped projectile points suggest links between Windmiller and the Dalles sites in Oregon (9800-6000 years B.P.) on the Columbia Plateau (Hattori 1982), where other languages that are sometimes assigned to the Penutian superstock of languages are spoken (Sapir 1929). Foster (1996) associated Windmiller with Proto-Utian and placed their homeland in the northwestern Great Basin or on the Columbia Plateau, as suggested by similarities in the Altithermal cultures in these regions. Mitochondrial DNA of ancient burials at Pyramid Lake and Stillwater Marsh in western Nevada closely resembles that of modern California Penutians but not that of the neighboring Washo population (a Hokan-speaking group) in the Sierra Nevada (Kaestle and Smith 2001). The argument then suggests that all these areas--the western Great Basin, the Columbia Plateau, and the California Central Valley--were once occupied by closely related people who spoke languages of the Penutian stock.

The vast majority of unadmixed modern Native Americans are members of one of five maternal founding lineages or haplogroups, designated as haplogroups A, B, C, D, and X (Brown et al. 1998; Forster et al. 1996; Schurr et al. 1990; Torroni et al. 1993). These haplogroups are readily distinguished by the gain or loss of one or more restriction sites or, in the case of haplogroup B, by the presence or absence of a 9 base pair deletion in the COII-tRN[A.sup.lys] intergenic region (Schurr et al. 1990) and are associated with corresponding point mutations in the control region (CR) of the mtDNA (Torroni et al. 1993). Each haplogroup can be further divided into multiple discrete haplotypes, or groups of closely related haplotypes, on the basis of additional CR mutations (Torroni et al. 1993).

In North America the distribution of the five haplogroups is decidedly nonrandom, and significant regional patterning exists (Lorenz and Smith 1996; Smith et al. 1999). Studies of ancient mtDNA diversity in North America reveal that Native American haplogroup frequency distributions in some regions exhibit marked temporal and regional continuity (Carlyle et al. 2000; O'Rourke et al. 2000). Carlyle et al. (2000) demonstrated that the haplogroup frequency distribution of ancient human remains associated with the Anasazi cultural tradition in the American Southwest is not significantly different from that of modern Pueblo populations, such as the Zuni. This study provides biological and cultural evidence for unbroken ancestor or descendant relationships in the American Southwest, spanning at least the last 2000 years. In contrast, Kaestle and Smith (2001) demonstrated that ancient western Great Basin populations are genetically dissimilar to modern populations in the same region, probably because of a population spread of Numic speakers into the Great Basin from Southern California approximately 1000 years B.P. (Bettinger and Baumhoff 1982).

Although on a general worldwide level there is a relatively high correspondence between genes and language (Cavalli-Sforza et al. 1992), this relationship might not hold on more local levels (Shields et al. 1993; Ward et al. 1993). Some Native American populations that lack close linguistic ties in the Pacific Northwest share similar haplogroup frequency distributions and several distinct mtDNA haplotypes (Ward et al. 1993), but most Native American populations in western North America have not been studied. Similarly, Uto-Aztecan-speaking and Yuman-speaking populations in the Southwest share similarities in their mtDNA without any apparent close linguistic ties (Lorenz and Smith 1996; Malhi et al. 2003).

The present study uses mtDNA to investigate the genetic relationships among a broader range of populations in western North America, an area that exhibited considerable linguistic diversity at the time of European contact. Because the patterning of this linguistic diversity has been used to generate hypotheses of prehistoric population movements and expansions, we examine the distribution of mtDNA haplogroups and haplotypes in the context of this linguistic diversity and the archeological record.

Subjects and Methods

Haplogroup identities of 584 Native Americans, representing 11 populations, and sequences from a segment of the first hypervariable region (HVS1) of the control region (np 16,090-16365) of 265 of these individuals were gathered from previously published sources, cited in Table 1 (Kaestle and Smith 2001; Johnson and Lorenz 2003; Malhi 2001; Malhi et al. 2003; Shields et al. 1993; Ward et al. 1991, 1993). Sequences that could not be assigned to one of the five known Native American founding haplogroups were not included in these analyses. Although some unassigned...

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