Biological Affinity
Determinations of biological affinity were made using both objective and subjective approaches. In the former case, multivariate analyses were used to generate probabilities of group membership, while in the latter case comparisons were made to known patterns of discrete morphological variation among extant forensic samples in the U.S. Two caveats should be emphasized in the interpretation of the bioaffinity results. First, the Kennewick research team was charged with determining whether the remains were those of a Native American individual; although the federal statute is somewhat ambiguous as to how the term "Native American" is defined, we took this as indicating a modern or recent human population indigenous to the Americas. Based on this goal, we derived the following hypotheses:
H0: Kennewick represents an individual drawn from a population of recent (late Holocene) Native Americans
HA: Kennewick does not represent an individual drawn from a population of recent Native Americans.
The method for examining these hypotheses is drawn from logical empiricism, so that any null hypothesis can only be rejected, but can never be proven to be true. It may be possible to exclude Kennewick from membership in the Native American comparative samples used in the following analyses, but it is not possible to prove that Kennewick is, in fact Native American (i.e., prove the null hypothesis to be true). Secondly, the ability to properly allocate prehistoric remains to a particular population or race depends, in large part, on whether the comparative samples are representative of the population from which the unknown person is drawn, and on the assumption that the such reference groups existed in the distant past. The use of typicality probabilities provides a statistical measure of association and group membership that does not assume that the individual examined is drawn from one of the comparative samples. Finally, it is important to recognize that the Kennewick remains may be thousands of years older than any of the reference samples used in these comparisons. Unless morphological "types" extend far into the past, it may be difficult to place the Kennewick remains into any late Holocene sample used for comparison.
Powell has already noted (Powell 1995; Powell and Neves n.d.; Steele and Powell 1992, 1994) that the geographic groupings or races seen among modern peoples are at best fuzzy and at worst non-existent when examining late Pleistocene and early Holocene populations world-wide. This point has also been noted by Kamminga and Wright (1988) in their analysis of the late Pleistocene skeleton from Upper Cave, Zhoukoudien, China. Thus it is possible that the term "Native American," when used in a biological context, is irrelevant when applied to ancient human remains because founder populations did not exhibit the pattern of morphological and metric variation seen among late Holocene populations in the Americas. However, such a situation does not completely rule out the possibility that these ancient remains might be biologically ancestral to modern American Indian populations (see Powell 1997; Powell in press, and Powell and Neves for data supporting this view). Much of the interpretation of the biological affinity of Kennewick results depends on subjective opinions and assumptions about the rate of morphological change possible during the past 10,000 years, the underlying genetics of the traits examined, and the demographic history of early and late Holocene humans in the New World.
Because the bulk of the skeletal reference samples are of late Holocene (modern) age, the comparisons using these reference groups do not allow us to evaluate the biological similarity of the Kennewick remains to ancient populations in the Americas, particularly to other skeletons of early and middle Holocene age. Because of the small number of Paleoindian and Archaic period skeletal series available for comparison, these results are not as definitive. However, they do provide an assessment of overall morphological similarity and dissimilarity between contemporaneous human groups present in the Americas from 9,000 to 5,000 years before present.
If the Kennewick remains represent a member of a founding population whose descendants evolved in situ over the past 9,000 years, North and South American populations who appear later in time may be dissimilar to the founder population due to the cumulative effects of genetic drift, mutation, and natural selection over time. An alternative explanation is that the Kennewick remains represent an individual with no living descendants among modern American Indians. Human skeletons from the middle and late Archaic periods (8,000 1,900 yr B.P.) represent the temporally adjacent sample for comparison with Kennewick, for testing the following hypotheses:
H0: Kennewick represents an individual drawn from a population of Archaic (middle Holocene) Native Americans
HA: Kennewick does not represent an individual drawn from a population of Archaic Native Americans.
This set of hypotheses allowed us to examine the possibility that the remains are unlike modern American Indians, yet similar to temporally adjacent Archaic populations in the New World. To test the null hypothesis, we collected craniometric data for 13 skeletal series dating to the Archaic period (8,000 - 1,900 yr B.P.) in North America. One caveat should be noted: even if there is a strong similarity of between Archaic groups and the Kennewick remains, this does not necessarily provide evidence to support or refute a connection to later American Indian populations. Only a time series analysis of populations from the Plateau region, extending from earliest occupation to the historic period, can provide a statistically valid means of assessing morphometric continuity of populations through time. Data for performing such an analysis are currently unavailable.
