November 11, 2012

A00 at FTDNA2012: history in the making?

I've been following the #FTDNA2012 tag on twitter where Dr. Mike Hammer has been  talking about A00, the new most basal clade of the human Y-chromosome phylogeny. Apparently, 338ky old Y-chromosome ancestor for modern humans, at 98% confidence, with most basal clade found in western Cameroon and in African Americans separated by ~500 years from Cameroonian chromosome.

Root of human Y-chromosome phylogeny is now much older than both mtDNA Eve and first modern human fossils.

Conference attendees feel free to correct/supplement my understanding of what was said.

UPDATE: With respect to the confidence interval, Bonnie Schrack says:
The 338,000 years ago figure was the median (middle) of the confidence interval, which I believe was 95%, and not 98%. The lower limit of the confidence interval was still a bit over 200,000, I think -- that is, still before the time when fossils have been found showing fully anatomically modern features. Mike specifically said that even if the true age of A00 varied by 10 or 20% from the estimate, it would still be before the time when anatomically modern humans are thought to have appeared. I don't remember the upper limit too clearly, but as I recall, it was over 500,000 ybp.
UPDATE II: There is some uncertainty about the level of significance, with different people remembering anything from 90-98%. Some newer information from Tim Janzen:
Michael gave a TMRCA estimate of 338,000 years with a confidence interval range of 246,000 and 563,000 years for the A00/A0 node. He gave a TMRCA estimate of 202,000 years with a confidence interval range of 133,000 to 366,000 years for the A0/R-M269 node.
I guess we will have to wait for the publication to see the exact numbers, but it certainly appears that A00 branched off from the rest of mankind at an age that is much earlier than the next most basal clade (A0).

15 comments:

Vincent said...

I smell an "evolutionary" mutation rate. I hope I'm wrong.

Dienekes said...

I smell an "evolutionary" mutation rate. I hope I'm wrong.

The tweets mentioned # of SNPs from Chimp, Gorilla, and an R1a, so you probably are.

Mike Keesey said...

Forgive my ignorance -- what is an ""evolutionary" mutation rate"? Do you mean one not calibrated on fossil dates?

Vincent said...

They also mentioned ySearch.

Matty K said...

Sounds like one of those "everything you know is wrong" discoveries....

terryt said...

And even if the date is out by some order of magnitude, it still places Y-DNA 'Adam' before any realistic development of 'Modern' humanity.

The '>338ky old Y-chromosome ancestor for modern humans' makes sense. Obviously the 'modern' human Y-DNA must have some sort of ancestor, as must the modern mt-DNA lines. That it is West African is easily as interesting as any date proposed for it.

n/a said...

Slides: http://prezi.com/kz2c-q4b-_m1/a00-on-the-y-haplogroup-tree/

"A00 on the Y Haplogroup Tree
A new view on African origins from a Y chromosome perspective
by Thomas Krahn on 12 November 2012"

eurologist said...

Also, now we are getting towards the time frame when European, SW Asian, and N African lineages decoupled because of increasingly poor climatic conditions, save a few opportunities of exchange every 100,00 or 50,000 years.

This is exactly the time heidelbergensis separated from the African and European continents, and henceforth Neanderthals developed as a mostly isolated subset.

BES said...

It was an R2, not an R1a. I don't know, you may consider it evolutionary, but the mutation rate being used is based on recently published work. Mike Hammer didn't write any of the tweets, many mistakes went out in the details of people's tweets. What several intelligent observers have commented, who did see Hammer's presentation is that it's the _relative_ ages of the clades, based on the SNPs on each branch, that are definitely very interesting, regardless of what mutation rate you care to use.

Debbie Kennett said...

The discovery of the new SNPs at the root of the Y-tree has been made through Family Tree DNA's Walk through the Y programme:

http://www.isogg.org/wiki/Walk_Through_the_Y

The testing was done through the haplogroup A project run by volunteer project administrator Bonnie Schrack.

A paper is apparently going to be submitted to a scientific journal in the next couple of weeks and all will be revealed when this has been published.

Annie Mouse said...

I dont have a problem with this estimate. But it is worth noting that the Cameroon is a uranium rich country and this can distort mutation rates.

terryt said...

"the _relative_ ages of the clades, based on the SNPs on each branch, that are definitely very interesting, regardless of what mutation rate you care to use".

Yes. Too often people dismiss papers such as this as examples of 'molecular-clockology', thus giving them an excuse to ignore the main points.

Ponto said...

According to John Hawks, Neanderthals are not an isolated subset, but a group of hominins that covered a 7000km stretch of territory from Europe to Asia.

Finding the most basal haplogroup for male humankind is all very well, but the process of "walking thru' the Y" is so tediously slow - it has taken years and involved a lot of expense.

eurologist said...

According to John Hawks, Neanderthals are not an isolated subset, but a group of hominins that covered a 7000km stretch of territory from Europe to Asia.

Ponto, regardless of their geographical extent, they were/are still isolated if they had low genetic diversity (which seems to be the case) and little impact on modern human DNA (which seems to be the case).

BES said...

Introgression concept diagram now available.
http://www.haplogroup-a.com/

Bonnie