Here is the final sentence of the abstract:
**Look, if I told you that I keep a goat in the backyard of my house, and if you happened to have a man nearby, you might ask him to look over my garden fence But what would you do if I said, I keep a unicorn in my backyard? **
Need we say more? :)
More in another few hours…stay tuned. For clues, please check this commentary.
In March 2013, a Houston-based personalized genome company made a major announcement on a surprising discovery by company’s staff scientists and a well-known researcher of human genetics, who is also on the advisory board of the company.
HOUSTON, March 26, 2013 /PRNewswire/ – Gene By Gene, Ltd., the Houston- based genomics and genetics testing company, announced that a unique DNA sample submitted via National Geographic’s Genographic Project to its genetic genealogy subsidiary, Family Tree DNA, led to the discovery that the most recent common ancestor for the Y chromosome lineage tree is potentially as old as 338,000 years. This new information indicates that the last common ancestor of all modern Y chromosomes is 70 percent older than previously thought.
The surprising findings were published in the report “An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree” in The American Journal of Human Genetics earlier this month. The study was conducted by a team of top research scientists, including lead scientist Dr. Michael F. Hammer of the University of Arizona, who currently serves on Gene By Gene’s advisory board, and two of the company’s staff scientists, Drs. Thomas and Astrid-Maria Krahn.
The corresponding scientific paper was published in AJHG, the top journal of Human Genetics (owned by Cell press).
We report the discovery of an African American Y chromosome that carries the ancestral state of all SNPs that defined the basal portion of the Y chromosome phylogenetic tree. We sequenced ?240 kb of this chromosome to identify private, derived mutations on this lineage, which we named A00. We then estimated the time to the most recent common ancestor (TMRCA) for the Y tree as 338 thousand years ago (kya) (95% confidence interval = 237-581 kya). Remarkably, this exceeds current estimates of the mtDNA TMRCA, as well as those of the age of the oldest anatomically modern human fossils. The extremely ancient age combined with the rarity of the A00 lineage, which we also find at very low frequency in central Africa, point to the importance of considering more complex models for the origin of Y chromosome diversity. These models include ancient population structure and the possibility of archaic introgression of Y chromosomes into anatomically modern humans. The A00 lineage was discovered in a large database of consumer samples of African Americans and has not been identified in traditional hunter-gatherer populations from sub-Saharan Africa. This underscores how the stochastic nature of the genealogical process can affect inference from a single locus and warrants caution during the interpretation of the geographic location of divergent branches of the Y chromosome phylogenetic tree for the elucidation of human origins.
Media was very excited, as you can see from these reports.
What are the implications? One possibility is that Perry’s Y chromosome may have been inherited from an archaic human population that has since gone extinct. If that’s the case, then some time within the last 195,000 years, anatomically modern humans interbred with an ancient African human.
There is some supporting evidence for this scenario. In 2011, researchers examined human fossils from a Nigerian site called Iwo Eleru. The fossils showed a strange mix of ancient and modern features, which also suggested interbreeding between modern and archaic humans. “The Cameroon village with an unusual genetic signature is right on the border with Nigeria, and Iwo Eleru is not too far away,” says Hammer.
Scientists say an African-American male’s odd genetic signature suggests that the human Y chromosome’s lineage goes back further in time than they thought perhaps due to interbreeding with other populations such as Neanderthals.
“This really upsets a lot of ideas, but at the same time, it’s understandable if we accept that human populations were structured in the past so that there were little pockets of diversity,” said Michael Hammer, an evolutionary biologist at the University of Arizona who is one of the authors of a study published in the American Journal of Human Genetics.
And now it turns out that media will get another chance to get excited !!