AbstractTo gain a better understanding of North American population history, complete mitochondrial genomes (mitogenomes) were generated from four ancient and three living individuals of the northern Northwest Coast of North America, specifically the north coast of British Columbia, Canada, current home to the indigenous Tsimshian, Haida, and Nisga’a. The mitogenomes of all individuals were previously unknown and assigned to new sub-haplogroup designations D4h3a7, A2ag and A2ah. The analysis of mitogenomes allows for more detailed analyses of presumed ancestor–descendant relationships than sequencing only the HVSI region of the mitochondrial genome, a more traditional approach in local population studies. The results of this study provide contrasting examples of the evolution of Native American mitogenomes. Those belonging to sub-haplogroups A2ag and A2ah exhibit temporal continuity in this region for 5000 years up until the present day. Of possible associative significance is that archaeologically identified house structures in this region maintain similar characteristics for this same period of time, demonstrating cultural continuity in residence patterns. The individual dated to 6000 years before present (BP) exhibited a mitogenome belonging to sub-haplogroup D4h3a. This sub-haplogroup was earlier identified in the same general area at 10300 years BP on Prince of Wales Island, Alaska, and may have gone extinct, as it has not been observed in any living individuals of the Northwest Coast. The presented case studies demonstrate the different evolutionary paths of mitogenomes over time on the Northwest Coast.
Category Archives: Paleolithic
|Figure 1. An eight base-pair tract of identity by state (IBS).|
There has been much recent excitement about the use of genetics to elucidate ancestral history and demography. Whole genome data from humans and other species are revealing complex stories of divergence and admixture that were left undiscovered by previous smaller data sets. A central challenge is to estimate the timing of past admixture and divergence events, for example the time at which Neanderthals exchanged genetic material with humans and the time at which modern humans left Africa. Here, we present a method for using sequence data to jointly estimate the timing and magnitude of past admixture events, along with population divergence times and changes in effective population size. We infer demography from a collection of pairwise sequence alignments by summarizing their length distribution of tracts of identity by state (IBS) and maximizing an analytic composite likelihood derived from a Markovian coalescent approximation. Recent gene flow between populations leaves behind long tracts of identity by descent (IBD), and these tracts give our method power by influencing the distribution of shared IBS tracts. In simulated data, we accurately infer the timing and strength of admixture events, population size changes, and divergence times over a variety of ancient and recent time scales. Using the same technique, we analyze deeply sequenced trio parents from the 1000 Genomes project. The data show evidence of extensive gene flow between Africa and Europe after the time of divergence as well as substructure and gene flow among ancestral hominids. In particular, we infer that recent African-European gene flow and ancient ghost admixture into Europe are both necessary to explain the spectrum of IBS sharing in the trios, rejecting simpler models that contain less population structure.
Update: even Dienekes agrees, on his own well documented reasoning, with a x2 mutation rate being necessary for the above graph.
- a large and rather high cliff;
- a cavity, cave, overhang or hole around the foot of the cliff;
- a main coloured (red-yellow to red-brown) wide strip pouring out, or reaching down to the cavity;
- a (facultative) step-bank (coral or karst platform) at the foot.
Update (Feb 24): after being down for days, causing perplexity among some readers and myself, the WAC source site is up again. Exactly as it was four days ago. Just in case this time I’ll upload the images here.
|The boulders at lake Huron were to trap the reindeer (caribou)|
Metal Ages and Historical periods
The majority of mtDNA haplogroups and the greatest proportion of NRY lineages identified in our Iban sample are associated with population movements that occurred prior to this expansion. More NRY haplogroups than mtDNA haplogroups were introduced into this population during the Neolithic expansion, but the proportion of NRY haplogroups attributed to this more recent event is still less than half of the total NRY haplogroups identified. Therefore, it appears that migrations during the Neolithic did not eradicate pre-Neolithic groups.
Another blow against Neolithic replacement nonsense.
Before I forget, just a quick mention of another potentially interesting paper published at PLoS ONE this week:
L.S. Premo and S.L. Kuhn, Modeling Effects of Local Extinctions on Culture Change and Diversity in the Paleolithic. PLoS ONE 2010. Open access.
AbstractThe persistence of early stone tool technologies has puzzled archaeologists for decades. Cognitively based explanations, which presume either lack of ability to innovate or extreme conformism, do not account for the totality of the empirical patterns. Following recent research, this study explores the effects of demographic factors on rates of culture change and diversification. We investigate whether the appearance of stability in early Paleolithic technologies could result from frequent extinctions of local subpopulations within a persistent metapopulation. A spatially explicit agent-based model was constructed to test the influence of local extinction rate on three general cultural patterns that archaeologists might observe in the material record: total diversity, differentiation among spatially defined groups, and the rate of cumulative change. The model shows that diversity, differentiation, and the rate of cumulative cultural change would be strongly affected by local extinction rates, in some cases mimicking the results of conformist cultural transmission. The results have implications for understanding spatial and temporal patterning in ancient material culture.
This mention is not adhesion. I find the modeling potentially interesting in its essentials but I surely have many discrepancies on issues such as assuming tiny “populations” of some 25 individuals in black and white (life or death) states. Such size is ok with operative hunter-gatherer bands but these are not “sovereign” units but just dynamic and fluctuating economic ones, integrated in larger groups. Probably a better size would be something like 100 or 200 people but again integrated into larger units of several hundreds to several thousands (tribes or nations).
Also we have to consider that people change “clans”, for example when marrying. So cultural, as well genetic flow is persistent at least within the borders of the ethnicity, which are anyhow generally open. So I guess that the modeling needs a lot of refinement but still it is a curious speculation – or exploration if you wish.
Something I do agree is in the authors founding their research on previous works that strongly suggest that population size and specially connectivity is critical in driving and maintaining the rhythm of innovation.