Wednesday, November 23, 2011

National Geographic's "Explorer: How to Build an Ancient Man"

Today National Geographic Channel debuted the newest entry in their Explorer series, "How to Build an Ancient Man" or as it was called by my cable company "Reconstructing a Stone-Age Human". Although the subject of ancient DNA is not my area of expertise, I am posting my notes from today's airing in response to numerous requests.

Most of what was revealed in the show, plus supplementary data can be found in the 2010 scientific article detailing the findings here and in National Geographic's news story here.

In this episode, Professor Eske Willerslev from the University of Copenhagen and his colleagues analyze DNA from a tuft of human hair that was preserved in Greenland's permafrost for 4000 years. They claim that their findings overturn a mainstream theory about how humans populated the Earth.

Approximately 4,500 years ago the first pioneers to Greenland appeared on the western shores, vanishing after about 1,500 years. They are called the Saqqaq people. "Various theories have suggested that they were direct ancestors to the Inuit, or that they were actually Native Americans who penetrated into the High Arctic," Willerslev said. The accompanying article states, "The origin of the Saqqaq and other Palaeo-Eskimo cultures, and their relationship to present-day populations, has been debated since they were first discovered in the 1950s."

Dr. Willerslev traveled thousands of miles, spending years unsuccessfully hunting for viable ancient DNA samples before finally discovering that the elusive DNA was less than 2 km from his office in the basement of the National Museum in Copenhagen and had been for 25 years. A one-of-a-kind 4,000 year old genetic sample was found in the permafrost around Disko Bay in 1986 in the form of a matted tuft of human hair. In 1986 this was just a curiosity, but with technological advances it is a genetic goldmine.

To remove any contamination of the ancient DNA from bacteria and the people who handled it, the hair sample was washed in a bath of bleach. Then they added enzymes to break down the cellular structure of the hair, baking it in high heat. This liquefied the hair, resulting in a concentrated sample. The team was thrilled to discover that almost all of the genetic material survived necessary to reconstruct the genome and there was very little contamination. Because of the presence of a Y-Chromosome, they determined that the hair belonged to a male and named him "Inuk".

Using Illumina technology, the team was able to find genetic markers that indicated that the Saqqaq had adapted quickly to the Arctic region and that Inuk had dark hair (consistent with the sample), brown eyes, shovel teeth, brown skin, dry ear wax and Type A+ blood. All of this pointed toward an Asian origin. He also had a genetic predisposition for baldness, which indicated that he died young since he appeared to still have plenty of thick hair. From the supplemental material in the article linked above, I was able to find that his mtDNA Haplogroup was D2a1 and his Y-DNA Haplogroup was Q1a (according to the supplemental material there is some question about the subclade). The authors also felt that Inuk's genome showed signs of inbreeding and estimated that his parents were, most likely, first cousins. The team compared Inuk's genome to the Dorset people, who were the next human inhabitants in the area, and found that there was no direct genetic link between them and that the Saqqaq must have gone extinct.

"Looking at one million places on the genome (SNPs)," the team further concluded that Inuk and his Saqqaq people were not closely related to the Native Americans or the Inuits currently living in Greenland, but instead had the most genetic similarity to the Chukchi, the Koryak and the Nganasans peoples of Northeast Siberia. These findings challenge the commonly-held view of migrations into the New World, telling us that the theory of only two migrations into the New World is not correct. (#1. ~15,000 years ago across the Beringia land bridge. #2. 6,000-8,000 years ago by boat along the coast.) Because the land bridge had disappeared by the time of this third migration into the New World, the Saqqaq must have traveled to Greenland by boat or walked over the ice in the winter.  The scientists called their migration a "marvel of the Stone Age" and theorized that there were probably many other trial and errors that have disappeared from the genetic record, concluding that the history of ancient migrations and populations is "a bit messier than we thought - a much richer story." Professor Willerslev closed by saying that the sequencing of this first ancient genome was a "new beginning for science" and "Inuk opened the door to a completely new level of ancient genetics and understanding of human migration".


  1. Readers might be interested in this list of markers, posted in the Spittoon blog when the technical paper originally came out: