Re: Z16357 In-depth Age Analysis
Thanks, Jared. The new age estimates are very helpful. One more question if I may:
the L513 Descendant Tree Chart has Bennett and I at BY11382. Is that an equivalent for
a SNP included on your Z16357 SNP tree?
From: Z16357@groups.io <Z16357@groups.io> on behalf of Jared Smith <jared@...>
Sent: Monday, March 20, 2017 8:53 PM
Subject: Re: [Z16357] Z16357 In-depth Age Analysis
FGC33966 is your terminal SNP shared with Martin, but I only analyzed
Big-Y testers so I could include the novel variants. So FGC33966 is
counted as one of your 6 novel variants.
This methodology is a fairly standard way of doing age estimates, but
I don't think it had been done to this level for our tree before.
On Mon, Mar 20, 2017 at 3:05 PM, Charles Thomas <charles_002@...> wrote:
> Great analysis, Jared, but I think the SNP names are confusing me. Did you
> include an equivalent to FGC33966 for Martin and me?
> From: Z16357@groups.io <Z16357@groups.io> on behalf of Jared Smith
> Sent: Monday, March 20, 2017 9:52 AM
> To: Z16357@groups.io
> Subject: [Z16357] Z16357 In-depth Age Analysis
> Aging our ancestors using Y-DNA data is far from an exact science. I'd
> be happy to have you poke holes in any of this.
> An analysis of the 11 Z16357 people who have taken Big-Y results in
> the following number of 'good', unique/novel variants/mutations:
> C. Hays 4
> R. Hays 3
> Pillsbury 5
> Merrick 11
> Thomas 6
> Phillips 7
> Bennett 9
> M. Hartley 5
> J. Hartley 5
> J. Smith 12
> Smith 27
> These are variants that each person has that are not shared with
> anyone else who has tested. The higher the number of novel variants,
> the further back one would expect to be related to someone else
> listed. I use the same metric for a 'good' variant as Alex does on his
> Big Tree. This is a bit more aggressive than what YFull uses.
> There are, however, some inconsistencies with this. Merrick, for
> example, has nearly twice as many novel variants as Thomas, even
> though Merrick connects lower/later on the tree than Thomas - one
> would thus expect Merrick to have fewer novel variants. This is
> primarily a factor of test coverage, but this is all we have to work
> with, so we partially account for this variability by averaging. This
> is why each new Big-Y test gives us increased accuracy.
> When I add the novel variants above to the number of 'good' SNPs in
> each block or haplogroup of our tree and average the results, I end up
> with the following average number of variants downstream from each
> listed SNP block:
> ZS349 - 3.5
> Z16854 - 9.3
> BY15420 - 8.0
> BY15419 - 9.7
> Y29969 - 9.5
> A11132 - 5
> Z17911 - 10.9
> Z16343 - 13
> Z16357 - 36.1
> This means, for example, that there's an average of 3.5 variants that
> were formed after the most recent ZS349 ancestor that the two Hays men
> share. For Z17911, we average 10.9 variants downstream (more recent
> than) our most recent common Z17911 ancestor. Altogether, we average
> 36.1 SNPs downstream of Z16357.
> To use these variant numbers to help us in aging, we need to calculate
> a "years per SNP" value. YFull has our last Z16357 ancestor at around
> 3300 years ago (though they've acknowledged this is probably too
> high). Other recent estimates put it as young as 2300 years ago. Until
> someone digs up some Z16357 remains or we get enough DNA testers to
> give us better data, we have to use our best informed estimate. I'll
> assume our most recent Z16357 ancestor lived a minimum of 2500 and
> maximum of 3000 years ago.
> If we divide these age estimates by 36.1 SNPs (on average), this is a
> minimum of 69.3 years per SNP and a maximum of 83.1 years per SNP. We
> can then use these values to assign age estimates to notable
> branchings as follows:
> ZS349 - 327-376 years before present
> Z16854 - 732-861
> BY15420 - 639-750
> BY15419 - 755-889
> Y29969 - 743-875
> A11132 - 431-501
> Z17911 - 837-987
> Z16343 - 986-1166
> Z16357 - 2585-3085
> The values are years before present, and include an additional 35
> years (one generation?) to account for the age of the last ancestor
> that had this SNP - and also adds 50 years as a guessed average of how
> old the 11 Z16357 people are.
> So this estimates that the common ZS349 ancestor for Hays was born
> 347-376 years ago. We know this ancestor was George Hays who was born
> in 1655 - 362 years ago, so these numbers align perfectly!
> This places our Z17911 ancestor being born between 837 and 987 years
> ago. It places the Hartley common ancestor between 431 and 501 years
> ago, the Bennett/Phillips ancestor 639-750 years ago, etc.
> Do keep in mind that accuracy is more variable near the end of the
> branches (closer to present day), especially with data from only 2 or
> 3 people. And SNPs are not always formed at a consistent rate. So this
> all a bit rough, but should give us fairly reasonable estimations.