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View Full Version : How long a period between L21 and DF13?



alan
01-14-2016, 06:24 PM
Can someone though some light on this? It always confused me.

I ask because we have a 4000 year old DF21 guy with 5 private SNPs. So he is 6 further SNPs down from DF13. How many SNP down is he from L21?

swid
01-14-2016, 10:25 PM
Alex's tree has 7 phylogenetically-equivalent SNPs in L21 block:
L21/S145/M529
L459
S245/Z245
S461/Z290
Z260
FGC3218/S552/Y2598
Z21145

and 2 phylogenetically-equivalent SNPs in the DF13 block:
CTS241/DF13/S521
CTS8221/Z2542

so 9 in total. I'm not going to offer absolute times, but it's fairly safe to say that a relatively longer period of time occurred between the initial appearance of L21 and the initial appearance of DF13 than occurred between the initial appearance of DF13 and the man who was the most recent common ancestor of all DF13 men today.

miiser
01-14-2016, 10:40 PM
There is some linguistic ambiguity that complicates this discussion. From Alex's tree, there are 7 phylogenetically equivalent SNPs at the L21 node. When people say "L21", they may be referring to either the L21 SNP itself, or the branch that has become labelled as L21, but may just as well have been labelled after one of the other 6 phylogenetically equivalent SNPs.

So we first have to come to a consensus that, when someone speaks of the appearance of L21, they are really speaking of the final SNP in the block of SNPs that are equivalent to L21. They do not usually intend to refer to the time that the actual L21 SNP occurred. We have no idea whether L21 was first in the block or last. It might have been any time along the branch of equivalents.

The question that really needs to be answered is, when did the last SNP within this equivalent block occur? So, for example, if I say that L21 may have formed circa 2500 BC, I don't really mean that the L21 SNP itself occured circa 2500 BC. I really speak of the time when the last phylogenetically equivalant SNP occurred within the branch which has been labelled as L21.

There are 2 equivalent SNPs in the DF13 node, and only 1 in the DF21 node.

If we want to assign a time equivalence, we need it calibrated to some standardized SNP acceptance criterion. Y-Full uses a period of 144 years per SNP, which is valid only for their SNP acceptance criterion. If we use Y-Full's numbers, this gives a total of 3 SNPs from L21 MRCA to DF21 MRCA, which corresponds to 144*3=432 years from L21 MRCA to DF21 MRCA. By Y-Full's reckoning, we maybe have 4 SNPs from DF21 to Rathlin1, although we can't be sure that's Alex's SNP acceptance standard (while excluding INDELs to get 4 instead of 5) gives the same answer as Y-Full's. So Y-Full's reckoning might give a different number. Assuming 4 is the number Y-Full would get, we would have 4*144=576 years from DF21 to Rathlin1.

Alex's reckoning gives a greater number of SNPs. But we don't have a rigorously calibrated time standard associated with his SNP acceptance criterion, as we have with Y-Full. So I don't think we can say with much confidence that each SNP in Alex's tree corresponds to a certain length of time.

The other thing to keep in mind is that there really is a pretty wide variation in the occurrence of SNPs. So when looking at only a single lineage, the actual time per SNP is likely to be considerably more or less than the 144 year average. For example, look at Y-Full's tree, and compare the dating of DF63 and A5846. Both are only 1 SNP below the L21 node, but they put DF63's MRCA estimate at 4500 ybp, concurrent with L21, and A5846's at 4200 ybp. Y-Full's actual calculated age for DF63 based on SNP count is 5211 ybp! But they fudged it to 4500 ybp in order to force consistency with L21's age!

There's a really good chance that the actual time between the L21 and DF21 nodes is either much more or much less than 432 years. Likewise for the time between DF21 and Rathlin1. So, supposing the L21 MRCA appeared on the Isles requires the time to be on the shorter side of the average, but not by a great deal, and is very much within a standard deviation of the variation seen in SNP timing.

alan
01-15-2016, 02:27 AM
3 SNPs from L21 to DF21 and 4 SNPs from DF21 to a 4000 year old guy in Rathlin would (if SNP gathered at an average rate) mean at the 144 year rate that DF21 would datesto 2576BC and L21 to jusy before 3000BC but with with a very wide possibility of error of several centuries.

Personally I think DF13 one up from DF21 must pre-date the beaker arrival in the isles c. 2400BC as continental L21 is also overwhelmingly DF13. If I was a betting man I would place DF21 around 2400BC and DF13 around 2500BC. It would be hard to make archaeological sense of things otherwise and I dont think the real dates are more than a century out from these. We can quibble but 3 SNPs back to L21 from DF13 would surely place L21 back in the early 3rd Millenium BC and P312 to near 3000BC. However we know that the L21 lineage didnt prosper pre-DF13 so we wouldnt expect the big beaker expansion into the isles to coincide with the date estimate of L21 - it should correspond with the expansion of DF13 towards and into the isles which would make sense if DF13 dates to c. 2500-2400BC.

However there is a problem in that U152 clearly is linked to the bell beaker east (central European) group which came into existence c. 2550BC. That suggests to me that U152 is only 150 years maximum older than DF13 while SNP counting would suggest that the difference in age should be greater by a few centuries. This may well be simply down to the fact that SNPs dont actually work like constant clocks and the occasional rapid run of more than one SNPs does happen.It is hard to believe that the archaeological correlate of the U152 expansion is not the beaker east group forming c. 2550BC just as it is hard not to see the archaeological correlation of the DF13 expansion as not linked to the arrival of beakers around the channel coast and Lower Rhine and expansion into the isles.

I think a much quite phase can be seen in the branching running up to P312 and back to L11. Only very modest branch took place in that era - basically the lines leading to P312 and U106. This period L11 to P312/U106 where far more modest branching took place seems likely to be immediately pre-beaker in central European terms. Then there is the huge period L51 to L11 where it was an entirely different world of bare survival of the line for millennia. To me this best matches a pre-expansion phase in an area with little in the way of developed agriculture on the steppes up to 3000BC.

rms2
01-17-2016, 02:26 PM
If we accept YFull as ballpark correct and the best we have for now, then it seems likely that L21 arose fairly early (c. 2500 BC) in east-central European Bell Beaker and was on the crest of the wave that moved northwest up the Rhine to the North Sea coast. By "wave" I do not mean to imply a massive tsunami of humanity; maybe "ripple" would have been a better choice of words. What I meant was that L21 was in the northern and western vanguard of the Bell Beaker movement.

DF13 probably arose on the Continent, as well, and that seems likely to me for at least some of its subclades. The DF13+ branch of L21 was apparently first across the Channel: it has the look of first-in trail blazers who pushed farthest west fastest and became overwhelmingly dominant in Ireland, the westernmost of the two big Isles.

Some of the younger DF13+ subclades may have arisen in the Isles, but I don't think that is true for the older branches, although that is certainly open to debate.

I'm really looking forward to the ancient dna papers that are supposed to be due out this year. I hope they really do a thorough job on Bell Beaker and western Yamnaya and clear up a lot of our questions. I'm sure we'll still have plenty left to argue about in 2017.

alan
01-17-2016, 03:53 PM
If we accept YFull as ballpark correct and the best we have for now, then it seems likely that L21 arose fairly early (c. 2500 BC) in east-central European Bell Beaker and was on the crest of the wave that moved northwest up the Rhine to the North Sea coast. By "wave" I do not mean to imply a massive tsunami of humanity; maybe "ripple" would have been a better choice of words. What I meant was that L21 was in the northern and western vanguard of the Bell Beaker movement.

DF13 probably arose on the Continent, as well, and that seems likely to me for at least some of its subclades. The DF13+ branch of L21 was apparently first across the Channel: it has the look of first-in trail blazers who pushed farthest west fastest and became overwhelmingly dominant in Ireland, the westernmost of the two big Isles.

Some of the younger DF13+ subclades may have arisen in the Isles, but I don't think that is true for the older branches, although that is certainly open to debate.

I'm really looking forward to the ancient dna papers that are supposed to be due out this year. I hope they really do a thorough job on Bell Beaker and western Yamnaya and clear up a lot of our questions. I'm sure we'll still have plenty left to argue about in 2017.

IMO it would be surprising if L21 only dates to 2500BC as someone else indicated 8 or 9 SNPs from Rathlin to L21 at 144 years in the best counting system which is more than twice the SNPs required to get back from 1950BC to 2500BC. I am not saying that there wasnt a run of SNPs faster than the average but even so, it seems likely to me L21 is a bit older than that. I would be more inclined to think DF13 is more likely that sort of date, certainly pre-2400BC and L21 might be 2600BC or older. I think the people like Michal who suggest the official best estimates are a little too young may have some support for that from the Rathlin guy albeit its not open-shut.

My other reason for think this is that its only from DF13 that the branching structure is indicative of the sort of rapid spread of beaker seen in the isles and adjacent part of the continent around 2400BC or a little before. L21 to DF13 seems to be a moribund bare survival period for L21 which doesnt seem to me to match the sudden expansion of beaker across the areas where L21 is found today above trace levels. Some sort of delay of a couple of centuries in the expansion of L21 (until DF13 level) relative to the rapid take off of U152 does broadly echo the delay of arrival of beaker in the isles and northern Europe compared to central Europe.

rms2
01-17-2016, 04:36 PM
IMO it would be surprising if L21 only dates to 2500BC as someone else indicated 8 or 9 SNPs from Rathlin to L21 at 144 years in the best counting system which is more than twice the SNPs required to get back from 1950BC to 2500BC. I am not saying that there wasnt a run of SNPs faster than the average but even so, it seems likely to me L21 is a bit older than that. I would be more inclined to think DF13 is more likely that sort of date, certainly pre-2400BC and L21 might be 2600BC or older. I think the people like Michal who suggest the official best estimates are a little too young may have some support for that from the Rathlin guy albeit its not open-shut.

My other reason for think this is that its only from DF13 that the branching structure is indicative of the sort of rapid spread of beaker seen in the isles and adjacent part of the continent around 2400BC or a little before. L21 to DF13 seems to be a moribund bare survival period for L21 which doesnt seem to me to match the sudden expansion of beaker across the areas where L21 is found today above trace levels. Some sort of delay of a couple of centuries in the expansion of L21 (until DF13 level) relative to the rapid take off of U152 does broadly echo the delay of arrival of beaker in the isles and northern Europe compared to central Europe.

I agree with you completely; I was being conservative in going with YFull's current age estimate for L21. Personally, given the Rathlin 1 result, I don't think even DF21 originated in the Isles.

I know this doesn't prove anything, but Alex's recent discovery of the INDEL Z39589 that links DF41, DF49, L1335, S1051, Z251 and Y14240 is interesting in part because our only Z39589* result thus far is Thomas Krahn. Thomas' y line, if I recall correctly, comes via the German ethnic minority in Transylvania and originated in the Rhineland.