Ancient DNA from the Illinois Hopewell
Deborah A. Bolnicks 2005 dissertation, entitled The Genetic Prehistory of Eastern North America: Evidence from Ancient and Modern DNA, (University of California, Davis) is an important contribution both to our understanding of Native American prehistory (as well as history) and to the development of new techniques for gleaning data from museum collections of human skeletal remains unimagined by the early archaeologists who excavated this material. Chapter 3 is a consideration of mitochondrial DNA diversity within and between prehistoric Hopewell communities in the Midwest and the following summary is restricted to this portion of her dissertation.
Bolnick studied ancient mitochondrial DNA (mtDNA) from 55 individuals from six different mounds in the Pete Klunk Mound Group in Illinois. Mitochondrial DNA refers to DNA derived from mitochondria in human cells, possibly including bone cells if the bone is well preserved. Mitochondrial DNA is passed solely from mother to child, so it tracks only the lines of maternal inheritance. Bolnick successfully recovered ancient mtDNA from 39 of the 55 individuals she sampled, which is a 71% success rate. This indicates that mtDNA is very well preserved in these ancient bones. The Pete Klunk Mound Group is predominantly a Hopewell culture site dating to about AD 180. Bolnick identified individuals from all five of the mtDNA lineages, or haplogroups, documented for North America: 19 from haplogroup C, 9 from A, 5 from B, 5 from D, and 1 from X.
Bolnick subjected these data to a variety of statistical tests and concluded the following:
1. Haplogroup frequencies do not differ significantly between males and females, burial mounds, or members of different social rank (p. 131). One test, however, did show that there was some haplogroup differentiation by social rank. High status individuals did not freely interbreed with others (p. 131). Haplogroups D and X tended to be associated with high status individuals and haplogroups B and C tended to be associated with lower status individuals. These tendencies, however, were not statistically significant and Bolnick concluded there was no clear evidence of hereditary or ascriptive ranking in Illinois Hopewell communities.
2. Males exhibit significantly greater haplogroup diversity (p. 132). Bolnick interprets this as an indication that this Hopewell society was characterized by matrilocal post-marital residence (p. 137). This means that a husband would leave his home to live with his wife in her community. Males joining a group therefore would be drawn from communities with more or less distinctive genetic makeups. And so the mtDNA of a villages husbands would represent all the disparate communities from which they originated, while the wives mtDNA all would be derived from the communitys grandmothers.
3. Individuals were not buried in matrilineal kin groups (p. 134). This means either that kinship did not greatly influence burial practices in the Midwest during prehistoric times or that paternal relationships [undetectable using mtDNA] may have been more important to these societies (pp. 134-5).
Bolnick compared these results with the data obtained by Lisa Mills in her 2003 study of mtDNA from Ohios Hopewell Mound Group (see post from June 22, 2006) revealing some startling conclusions:
1. The two populations were so similar in haplogroup frequencies that it is highly likely they were interbreeding (p. 132). The rate of interbreeding may have been as high as 141 migrants per generation and people were moving predominantly in one direction from Ohio to Illinois (p. 134). This goes against the traditional view that movement was mainly in the opposite direction. The traditional view is based on archaeological data, which indicate that some Hopewell traditions appeared earlier in Illinois than in Ohio (p. 138).
2. The overall level of genetic diversity in these ancient populations exceeds that observed in most extant Native American populations from eastern North America (pp. 138-9). This observation supports the conclusion that diseases introduced by Europeans, along with warfare and other cultural disruptions, precipitated a major population decline in eastern North America. Such a decline would have significantly reduced the genetic diversity in Native American populations, which is exactly what Mills and Bolnicks data show.
Bolnick concludes that Only by combining archaeological, osteological, and ancient DNA research is it possible to decipher the relationship between past patterns of cultural, morphological, and genetic variation and better reconstruct human prehistory (p. 139). The evidence for close ties between Illinois and Ohio Hopewell is particularly interesting in the light of the recent discovery that most of the effigy pipes in the large deposit of pipes from Tremper Mound, in Scioto County, are made from Sterling pipestone found in northern Illinois.
For more information about the pipe study, see the following article: Wisseman, Sarah U., Duane M. Moore, Randall E. Hughes, Mary R. Hynes, and Thomas E. Emerson 2002 Mineralogical approaches to sourcing pipes and figurines from the eastern woodlands, U.S.A. Geoarchaeology Volume 17 No. 7, pp. 689-715.