Taking the "re" out of repatriation

Writer Rachel D'Oro of the Associated Press reports on the repatriation of human remains from On Your Knees Cave, Prince of Wales Island, Alaska:

ANCHORAGE, Alaska - Human remains estimated to be more than 10,000 years old will be returned to southeast Alaska Tlingit tribes 11 years after they were found in a cave in the Tongass National Forest.
It's the first time a federal agency has conveyed custody of such ancient remains to indigenous groups under the Native American Graves Protection and Repatriation Act, U.S. Forest Service officials said Friday.
...
Vertebrae, ribs, teeth, a mandible and a pelvic bone were among the remains discovered in 1996 during a Forest Service archaeological survey for a proposed timber sale on northern Prince of Wales Island. The area is the aboriginal homeland for Tlingit tribes.

Prince of Wales Island is in the Alaska Panhandle, near the British Columbia border.

Some archaeologists, noting the island's placement on the coastal fringe of Beringia, have suggested that it may document some descendants of the earliest settlers of lower North and South America. In this model, people were able to bypass the Cordilleran ice sheet by skirting southward along the coast of the Pacific Northwest. The first Americans lived significantly earlier than this site, which dates at the earliest to around 10,300 radiocarbon years. But the location makes the remains possibly the best skeletal representation of the original inhabitants of the Americas.

Rex Dalton described the site briefly in a Nature news article from 2003:

In the north of Prince of Wales Island, he ventured into the 'On Your Knees' Cave -- so named because it can only be entered by crawling through a narrow tunnel -- which turned out to contain a host of specimens. Subsequent years of summer digs by Heaton and his archaeologist colleagues have unearthed the oldest signs of human habitation in the Pacific Coast region, from sediments in the cave's floor.
The specimens include a bone tool that has been radiocarbon dated to 10,300 years ago, a human bone dated at 9,200 years old, and blades made from obsidian -- a volcanic glass found in lava beds -- of the same vintage. The latter have shown the ancient inhabitants of Prince William Island to be relatively well-travelled coastal seafarers. Craig Lee, an anthropology doctoral student now at INSTAAR, has used X-ray fluorescence spectroscopy to examine trace elements in the obsidian, and so determine its source. His studies show that the material in On Your Knees Cave came from Suemez Island, about 150 km to the south, and Mount Edziza, nearly 400 km to the northwest in mainland British Columbia.

Long-distance contacts along the coast, and between coastal and inland locations, among the early descendants of the New World invaders show the potential for rapid movement down the western coast of the Americas.

That archaeology expresses how important the site is for understanding early New World populations. But what about the skeleton -- how have the human remains contributed to our knowledge?

These remains are relatively fragmentary and therefore don't provide a lot of anatomical information that could be compared to recent people. But they contain a wealth of genetic information, of the kind that has been retrieved more and more routinely during the last 10 years.

Kemp and colleagues (2007) examined the DNA from the human remains, successfully extracting both mtDNA and Y chromosome markers that permitted analysis of the specimen's place relative to New World diversity. The conclusions help to emphasize the importance of such early skeletal remains:

Mitochondrial and Y-chromosome DNA were analyzed from 10,300-year-old human remains excavated from On Your Knees Cave on Prince of Wales Island, Alaska (Site 49-PET-408). This individual's mitochondrial DNA (mtDNA) represents the founder haplotype of an additional subhaplogroup of haplogroup D that was brought to the Americas, demonstrating that widely held assumptions about the genetic composition of the earliest Americans are incorrect. The amount of diversity that has accumulated in the subhaplogroup over the past 10,300 years suggests that previous calibrations of the mtDNA clock may have underestimated the rate of molecular evolution. If substantiated, the dates of events based on these previous estimates are too old, which may explain the discordance between inferences based on genetic and archaeological evidence regarding the timing of the settlement of the Americas. In addition, this individual's Y-chromosome belongs to haplogroup Q-M3*, placing a minimum date of 10,300 years ago for the emergence of this haplogroup.

Possibly the most significant aspect of ancient specimens is their ability to inform directly about the rate of sequence changes over time. Phylogenetic rates of change in mtDNA (e.g., between humans and chimpanzees) appear to have been relatively slow compared to the observed number of mutations between parents and offspring. There are two reasons for this: Some mutations are lost because of purifying selection, and some recur again and again at the same site, and therefore saturate over long time scales. But it is difficult to estimate the relative importance of these factors, and therefore it is hard to assign rates across different time scales (e.g., the founding of New World populations, modern human origins, etc.). Kemp et al. (2007) used the ancient mtDNA sequence from On Your Knees Cave to arrive at an estimate of the rate of change across the 10,000-year span, which ought to allow a more precise chronology for the New World founding:

Applying our most conservative rate of 34%/site per myr (95% CI 15-53%/site per myr) to the nucleotide diversity estimate (pi = 0.86) for mtDNA haplogroups A, B, C, and D in Native Americas (Bonatto and Salzano, 1997b), indicates that human entered the Americas ca. 13,438 YBP (95% CI 8,113-28,667
YBP). While this estimate does not preclude the possibility of an early entry, the estimate is also compatible with an entry more recent than 15,000 YBP (Kemp et al. 2007:617).

That is in contrast to some earlier genetic estimates, which had suggested founding times as early as 40,000 years ago -- often suggested as compatible with a very long-term occupation of Beringia.

Soon, we will surely see more testing of early specimens to try to assess the genotypes for other loci. For example, the idea of an early population bottleneck during the founding of New World populations has become an important hypothesis for explaining the limited variation of many genes in the Americas. But later events may also have been important in limiting variation. For example, Native American populations have substantially less allelic variation at HLA loci than do Asian populations. This reduction in diversity probably began with the initial founding and subsequent dispersal, but may also have involved natural selection during the last 10,000 years. The importance of the initial bottleneck may be tested by finding HLA types for early American skeletons -- if the founding event was almost solely responsible for the current HLA diversity, then the early skeletal samples should be comparable in diversity to recent samples. If they show much more diversity (for example, HLA haplotypes absent in recent Americans) then we can conclude that selection in later populations played more of a role -- implying a different scenario for pathogen-host evolution over time in the Americas.

In that light, repatriating a 10,000-year-old skeleton must subtract from our future inquiries into the origins of New World peoples. Or I should say, patriating, since it isn't being sent back to its people, it is being given to entirely new people who have no demonstrated relationship to the skeleton at all.

I do perceive the real benefits from cordial and cooperative relationships with indigenous peoples, particularly where tribes have well-defined and recognized historic territories. The vast majority of skeletal remains of ancient Americans are quite recent, and might in most cases (given sufficient evidence and analysis) be attributable to particular historic cultural groups.

But for remains over a few thousand years old -- and certainly for the earliest New World populations -- every living person of Native American descent may count these early skeletons among their ancestors.

References:

Dalton R. 2003. Archaeology: The coast road. Nature 422:10-12. doi:10.1038/422010a

Kemp BM and 13 others. 2007. Genetic analysis of early holocene skeletal remains from Alaska and its implications for the settlement of the Americas. Am J Phys Anthropol 132:605-621. doi:10.1002/ajpa.20543