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Ancient DNA Analysis Indicates Paleo-Inuit Peoples Relied on Whale, Other Mammals

Bowhead whale tail

NEW YORK (GenomeWeb) – Whale, seal, caribou, and other animals contributed to the survival of Paleo-Inuit cultures of Greenland, according to a metagenomic analysis of ancient DNA.

Researchers from the University of Copenhagen sequenced sedimentary ancient DNA isolated from four known midden deposits from different sites in Greenland — Fladstrand, Sandnes, Qajaa, and Qeqertasussuk — and spanning different time frames. As they reported in Nature Communications yesterday, the researchers uncovered caribou, walrus, and whale DNA, suggesting these animals played a greater role in ancient Greenlanders' diets than had been thought. The researchers also noticed an increased amount of DNA from the bowhead whale, Balaena mysticetus, at two of the refuse sites, which suggested that the Saqqaq people exploited them some 4,000 years ago.

"These findings expand our current knowledge of the Paleo-Inuit and illustrates that the Saqqaq people had a wider diet-breadth than was previously thought and were able to exploit most of the mammals available to them," University of Copenhagen's Anders Johannes Hansen and his colleagues wrote in their paper.

He and his colleagues collected 34 sediment samples from various stratigraphic sections of the Qajaa, Qeqertasussuk, Sandnes, and Fladstrand midden deposits. The oldest layer analyzed dated back to around 2,000 BC. From these samples, the researchers made 31 shotgun libraries based on total DNA and 27 shotgun libraries based on DNA isolated from helminth parasite eggs. They generated some 2 billion DNA reads.

To determine what animals these reads originated from, the researchers aligned them against Metazoan mitochondrial genomes within the NCBI database. They identified 42 vertebrate taxa. The researchers likewise uncovered 12 different helminth taxa.

The various cultures represented in these middens had distinct vertebrate and helminth taxonomic profiles, Hansen and his colleagues reported. For instance, dog or wolf reads dominated Fladstrand samples, representing the Neo-Inuit Thule culture. Other common reads could be traced to seals, narwhal, caribou, and hare. The samples also contained canine tapeworms that used caribou as an intermediate host. This, they researchers noted, suggests that in addition to its use as a garbage heap, the site was also a spot for tethering dogs.

Meanwhile, samples from Sandnes, a Norse settlement, contained reads from cows, sheep, goats, and, to a lesser extent, wild fauna like seals, caribou, and walrus. These samples also contained canine tapeworms, but included ones linked to sheep and goat intermediary hosts.

Additionally, samples from Paleo-Inuit Saqqaq culture at the Qajaa and Qeqertasussuk sites contained bowhead whale and harp seal reads, while samples from Paleo-Inuit Dorset culture at the Qajaa site contained mostly ringed seal and dog DNA reads.

Some of these findings are at odds with previous morphological studies of bone fragments from these sites, the researchers noted. While bowhead whale DNA made up nearly half of the DNA uncovered at Qeqertasussuk, there were only about 102 whale bone, teeth, and baleen fragments out of a total of some 100,000 excavated bones. However, the researchers noted that whale bones are known to be underrepresented at archaeological sites, owing to the difficulties in moving whale carcasses from the shore and the higher value of blubber or meat as compared to bones.

Hansen and his colleagues re-sequenced two libraries from the Saqqaq layers at Qeqertasussuk and Qajaa that contained high concentrations of vertebrate DNA to better estimate species abundance. They compared these estimates to the expected biomass and the raw bone count, finding a strong correlation between expected biomass and DNA read counts, but a weaker one between raw bone counts and DNA read counts.

This link between ancient DNA reads and expected biomass suggests that bowhead whale was more prevalent than expected among the Qajaa and Qeqertasussuk midden deposits. To confirm its presence, the researchers re-aligned bowhead whale reads from the two re-sequenced libraries against the B. mysticetus mitochondrial genome, which yielded two consensus mitochondrial genomes.

This finding raises questions about the Saqqaq people's whale-hunting and whale-scavenging capabilities, the researchers said. "The presented evidence of Saqqaq whale exploitation requires re-evaluating maritime history," they added in their paper.