Ancient European DNA

more new info on SPAIN

Northern European gene flow into Spain

While investigating the genetic history of Spain, we discovered
an interesting signal of admixture involving Sardinia and
northern Europe. We made a data set by merging genotypes
from samples from the population reference sample (POPRES)
(Nelson et al. 2008), HGDP (Li et al. 2008), and HapMap
Phase 3 (International Hapmap 3 Consortium 2010). We
ran our three-population test on triples of populations using
Spain as a target (admixed population). We had 137 Spanish
individuals in our sample. With Sardinian fixed as a source,
we find a clear signal using almost any population from northern
Europe. Table 4 gives the top f3-statistics with corresponding
Z-scores. The high score for the Russian and Adygei is
likely to be partially confounded with the effect discussed in
the section on flow from Asia into Europe (below).
A geographical structure is clear, with the largest magnitude
f3-statistics seen for source populations that are northern
European or Slavic. The Z-score is unsurprisingly more
significant for populations with a larger sample size. (Note
that positive Z-scores are not meaningful here.) We were
concerned that the Slavic scores might be confounded by
a central Asian component and therefore decided to concentrate
our attention on Ireland as a surrogate for the ancestral
population as they have a substantial sample size (n = 62).

Spain: rolloff

We applied rolloff to Spain using Ireland and Sardinians as
the reference populations. In Figure 7C we show a rolloff
curve. The rolloff of signed LD out to about 2 cM is clear and
gives an admixture age of 3600 6 400 YBP (the standard
error was computed using a block jackknife with a block size
of 5 cM).

We have detected here a signal of gene flow from
populations related to present-day northern Europeans into
Spain around 2000 B.C. We discuss a likely interpretation.
At this time there was a characteristic pottery termed “bellbeakers”
believed to correspond to a population spread across
Iberia and northern Europe. We hypothesize that we are seeing
here a genetic signal of the “Bell-Beaker culture” (Harrison
1980). Initial cultural flow of the Bell-Beakers appears to have
been from South to North, but the full story may be complex.
Indeed one hypothesis is that after an initial expansion from
Iberia there was a reverse flow back to Iberia (Czebreszuk
2003); this “reflux” model is broadly concordant with our genetic
results, and if this is the correct explanation it suggests
that this reverse flow may have been accompanied by substantial
population movement. (See Figures 8, 9, and 10.)

It is important to point out that we are not detecting gene
flow from Germanic peoples (Suevi, Vandals, Visigoths) into
Spain even though it is known that they migrated into Iberia
around 500 A.D.
We believe such migration must have
occurred, based on the historical record (and perhaps is
biasing our admixture date to be too recent), but any
accompanying gene flow must have occurred at a lower
level than the much earlier flow we discuss.
it confirms some HLA genes surveys about Algerians, Spaniards and Basques, showing among the late two a north component OR RATHER 2 north components, 1 atlantic and 1 N-C european; the Bell Beakers story is linked by some historians to a foggy "celto-ligurian" stage of indo-europeanization of W-Europe - hard to be too affirmative, but the date (3000 BC) is coherent with BB and common sense (linguistic, archeology) -
Thanks for the digest - kouskit c'hweg! (sleep agreably)
I think nevertheless that "my" atlantic component could be older and just a back migration along with ruler newcomers
I am waiting for Varna necropolis,

I think is the key, it is exactly before arsenic bronze entrance,

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