Mitochondrial DNA from post-Neolithic Santimamiñe (Basque Country)

Four human remains dated to the Bronze Age were sequenced for mitochondrial DNA in Santimamiñe cave (Kortezubi, Biscay, Basque Country), along with single instances from the Neolithic, Chalcolithic and Roman period.

J.C. López Quintana et al., NUEVOS DATOS SOBRE LA SECUENCIA DE USO SEPULCRAL DE LA CUEVA DE SANTIMAMIÑE (KORTEZUBI, BIZKAIA). Arqueología y Prehistoria del Interior Peninsular (ARPI), 2016. Freely accessible (PDF) → LINK [no DOI]

The mtDNA study is not "brand new" but a synthesis of a previous doctoral thesis and advance publications:

Un primer avance de este estudio fue publicado en la monografía de las campañas de 2004 a 2006 de Santimamiñe (Cardoso et al. 2011), incluyendo el conjunto completo en la Tesis Doctoral de L. Palencia Madrid (Palencia 2015).

So we are talking of relatively old data, that has partly remained within the (sometimes absurdly greedy and anti-social) academic circles until now. The relative antiquity of the DNA study is important when assessing it, because genetic analysis is evolving very fast and, in most cases in the rather closed and under-budgeted Spanish universitary circles, they tend to do things "the old way", so we are almost certainly dealing here with HVS-I sequencing, something that is not explicit in the paper (I'm searching for Leire Palencia's thesis to make sure but no luck until now). 

If I am correct in this (and I should be), then we must understand that it is impossible in many cases to determine the exact haplogroup in the crucial R0 upper tier haplogroup, which includes HV and the extremely common H. Lacking the original HVS-I sequences by the moment, I can't but take the authors labels at face value but I must warn here that where it reads "R0" it is almost certainly H (HV0 or V are easy to recognize with this method, as is R0a) and where it reads "H1" it is probably H1 but not 100% certain. 

For more details see the relevant PhyloTree page, where the HVS-I markers are the last bloc in blue, beginning always with the sequence "16" (the other markers in blue of lower numerical value are HVS-II, more rarely used, and the ones in black are the coding region markers, which are in this case fundamental for proper assignment).

The mtDNA haplogroups (as reported) are:

• Neolithic:
• U5a2a (S2011-M2, c. 5100 BCE)
• Chalcolithic:
•  T2b (S-1, c. 2000 BCE)
• Bronze Age:
• U5b (S2011-M1 c. 1700 BCE) 
• H1 (S2011-M4, c. 1700 BCE)
• R0 (S2011-M6, c. 1500 BCE)
• U3a (S2011-M3 c. 1300 BCE)
• Roman period: 
• R0 (S2011-M5, c. 300 CE)

Interpretation attempts

It's difficult to extract conclusions from them but they should be compared with other sequences from the area, for which I recommend my 2013 synthesis. In general, treat "R0" as meaning "H", even if I chose to use a different color (magenta instead of red) for exactitude. 

In order to aid that analysis, I reproduce here my 2013 graphic:

We cannot compare the single Neolithic and Roman Era individuals but we can compare the Satimamiñe Chalcolithic+Bronze group of five sequences with the peripheral Chalcolithic large dataset of De La Rúa:

1. R*+H (very similar):
1. Peripheral "Basque" Chalcolithic: ~40%
2. Santimamiñe Chalcolithic+Bronze: 40% 
3. Santimamiñe Bronze only: 50%
2. U(xK) (very different):
1. Peripheral "Basque" Chalcolithic: ~15%
2. Santimamiñe Chalcolithic+Bronze: 40%
3. Santimamiñe Bronze only: 50%
3. Other lineages (all them of certain Neolithic immigrant origin, very different too):
1. Peripheral "Basque" Chalcolithic: ~45%
2. Santimamiñe Chalcolithic+Bronze: 20%
3. Santimamiñe Bronze only: 0%

However one of the U(xK) lineages in Santimamiñe is U3, which is also quite certain to be of Neolithic immigrant origin, and one is an important figure when n=5 so we can also see it this way:

1. Paleolithic lineages:
1. Peripheral "Basque" Chalcolithic: ~55%
2. Santimamiñe Chalcolithic+Bronze: 60%
3. Santimamiñe Bronze only: 75%
2. Neolithic lineages:
1. Peripheral "Basque" Chalcolithic:  ~45%
2. Santimamiñe Chalcolithic+Bronze: 40%
3. Santimamiñe Bronze only: 25%

The comparison of #1 with #2 is much more similar. This could be important, because Santimamiñe is not anymore a "peripheral" site, as are those from De La Rúa's dataset, but a rather central one with a extremely long and uninterrupted Paleolithic sequence, dating to Neanderthal-made Chatelperronian culture. It is still a single site with a small number of samples but it does provide a counterpoint that, in one approach could produce similar results. 

But, surprisingly, when we consider a distinct Bronze Age category, comparing not anymore with #2 but with #3 everything changes, suggesting a totally different interpretation of the available dataset, in which, the "Chalcolithic interlude" (if real at all, more data is needed) would be reversed quickly with the onset of the Bronze Age. 

I am sorry but I cannot lean for either interpretation: the data is just not extensive enough to allow for conclusions. I am tempted to support the continuity hypothesis, allowing only for lesser changes to happen, and keep the Chalcolithic dataset under a big question mark, but the question mark is admittedly a bit smaller now: something in terms demographic may have happened in the Chalcolithic period and may have been reversed in the Bronze Age. But "may" is not "for sure", we need more data points.

Feel free to discuss in good mood, as always.

Thanks for the heads up to Jean Lohizun (again).