July 30, 2009

mtDNA from pre-Columbian Peru

Yet another case in which differentiation of ancient with modern inhabitants is established. The paper discusses this issue:
The significant differentiation between the ancient Peruvian coastal populations (Shimada et al., 2004; this study) to the ancient highland and modern Peruvian populations cannot be explained satisfyingly in this moment. Although a recent work of Lewis (2009) shows that for genetic differences between the ancient and contemporary Andean populations genetic drift cannot be rejected as a cause, especially when only relying on mitochondrial haplogroup data, this explanation does not fit for the observed coast-highland differentiation. When the Palpa data is compared diachronically, new haplogroups and haplotypes appear and the overall genetic variability in all studied populations is high. Beside the genetic data, the insights in the cultural dynamic processes show that there were relatively large populations, dynamic processes of spatial and intercultural exchange. All those observations definitely are not compatible with the genetic drift scenario. But, the influences of the evolutionary forces on the observed genetic distribution patterns have to be taken into account and can not be utterly rejected. When compared with more mitochondrial datasets from South America, the Palpa populations show a high affinity to the contemporary indigenous populations of the Southern Andes and Tierra del Fuego like the Mapuche, Pehuenche, and Yaghan in Chile (Moraga et al., 2000). All the three populations show high frequencies of haplogroups C (41%–48%) and D (46%–52%) comparable with the prehistoric Palpa and Paracas Peninsula populations (cf. Table 4).
The current paper is a great step forward in the study of South American prehistory, as the large samples allow us to speak quite confidently about gene pool compositions.

A real problem faced by ancient DNA studies is that of inference of population movements based on modern haplogroup frequencies. Is the similarity between prehistoric Palpa and Paracas Peruvians (high C and D, almost non-existent A) with modern Southern Andeans and Tierra del Fuegoans the result of a genetic relationship? It is hard to arrive at any conclusions until we see what prehistoric Southern Andeans and Tierra del Fuegoans looked like.

The same problem was faced in the study of Etruscans, where relationships of modern Tuscans or ancient Etruscans with the modern Near East were discovered, but such relationships have a question mark next to them until we study the ancient Near East directly.

Hopefully, in the coming years, it will become more feasible to fill up the map of ancient mtDNA gene pools in several locations around the world, allowing us both to understand facets of mtDNA evolution, as well as to correct our inferences of population movements based on modern-day haplogroup distributions.

American Journal of Physical Anthropology doi:10.1002/ajpa.21135

Pre-Columbian population dynamics in coastal southern Peru: A diachronic investigation of mtDNA patterns in the Palpa region by ancient DNA analysis

Lars Fehren-Schmitz et al.


Alternative models have been proposed to explain the formation and decline of the south Peruvian Nasca culture, ranging from migration or invasion to autochthonous development and ecological crisis. To reveal to what extent population dynamic processes accounted for cultural development in the Nasca mainland, or were influenced by them, we analyzed ancient mitochondrial DNA of 218 individuals, originating from chronologically successive archaeological sites in the Palpa region, the Paracas Peninsula, and the Andean highlands in southern Peru. The sampling strategy allowed a diachronic analysis in a time frame from approximately 800 BC to 800 AD. Mitochondrial coding region polymorphisms were successfully analyzed and replicated for 130 individuals and control region sequences (np 16021-16408) for 104 individuals to determine Native American mitochondrial DNA haplogroups and haplotypes. The results were compared with ancient and contemporary Peruvian populations to reveal genetic relations of the archaeological samples. Frequency data and statistics show clear proximity of the Nasca populations to the populations of the preceding Paracas culture from Palpa and the Peninsula, and suggest, along with archaeological data, that the Nasca culture developed autochthonously in the Rio Grande drainage. Furthermore, the influence of changes in socioeconomic complexity in the Palpa area on the genetic diversity of the local population could be observed. In all, a strong genetic affinity between pre-Columbian coastal populations from southern Peru could be determined, together with a significant differentiation from ancient highland and all present-day Peruvian reference populations, best shown in the differential distribution of mitochondrial haplogroups.


1 comment:

Thorfinn said...

Any relation between this and the Coastal Migration Theory? The Fuegans are seen by some to be mixed descendants of original coastal populations (dating +30k years) and Clovis people. These results would suggest that original coastal migrants left a genetic contribution--much as the earliest coastal populations in India mixed with new migrants (with Andamanese as a relict population).