Phylogenetic tree of haplogroup mtDNA K1a1b1. Time scale (ka) based on ML estimations for mitogenome sequences. K1a1b1a (slightly re-defined, due to the improved resolution of the new tree) accounts for 63% of Ashkenazi K lineages (or ~20% of total Ashkenazi lineages) and dates to ~4.4 ka with maximum likelihood (ML); however, all of the samples within it, except for one, nest within a further subclade, K1a1b1a1, dating to ~2.3 ka. K1a1b1a1 is also present in non-Ashkenazi samples, mostly from central/east Europe. As they are nested by Ashkenazi lineages, these are likely due to gene flow from Ashkenazi communities into the wider population. The pattern of gene flow out into the neighbouring communities is seen in the other two major K founders, and also in haplogroups H and J; it is especially clear when the nesting and nested populations are more distinct, for example in the case of haplogroup HV1b, which has a deep ancestry in the Near East. 
The K1a1b1 lineages within which the K1a1b1a sequences nest (including 19 lineages of known ancestry) are solely European, pointing to an ancient European ancestry. The closest nesting lineages are from Italy, Germany and the British Isles, with other subclades of K1a1b1 including lineages from west and Mediterranean Europe and one Hutterite (Hutterites trace their ancestry to sixteenth-century Tyrol). Typing/HVS-I results have also indicated several from Northwest Africa, matching European HVS-I types, likely the result of gene flow from Mediterranean Europe. K1a1b1a is also present at low frequencies in Spanish-exile Sephardic Jews, but absent from non-European Jews, including a database of 289 North African Jews. Notably, it is not seen in Libyan Jews, who are known to have a distinct Near Eastern ancestry, with no known influx from Spanish-exile immigrants (although Djerban Jews, with a similar history, have not been tested to date for mtDNA, they closely resemble Libyan Jews in autosomal analyses27). Thus the Ashkenazi subclade of K1a1b1 most likely had a west European source.
Marta D. Costa,	Joana B. Pereira,	Maria Pala,	Verónica Fernandes,	Anna Olivieri, Alessandro Achilli,	Ugo A. Perego,	Sergei Rychkov,	Oksana Naumova,	Jiři Hatina,	Scott R. Woodward,	Ken Khong Eng,	Vincent Macaulay,	Martin Carr,	Pedro Soares,	Luísa Pereira	&amp; Martin B. Richards
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Marta D. Costa et al. A substantial prehistoric European ancestry amongst Ashkenazi maternal lineages. Nature Communications 4, Article number: 2543 doi:10.1038/ncomms3543 <a rel="nofollow" class="external free" href="http://www.nature.com/ncomms/2013/131008/ncomms3543/full/ncomms3543.html">http://www.nature.com/ncomms/2013/131008/ncomms3543/full/ncomms3543.html</a>