Прије неколико дана објављен је још један ради који методолошки настоји да актуелизује коришћење IBD блокова.
Mapping co-ancestry connections between the genome of a Medieval individual and modern Europeanshttps://www.nature.com/articles/s41598-020-64007-2У раду је извршена IBD анализа великог броја савремених европских популација (нажалост Срби нису били обухваћени) кроз резултате 429 тестираних појединаца. Тестирана је и древна днк једне особе ( ради се о дјевојци 16-17 година) која је преминула од куге 1340-тих у Каталонији (Medieval village of L’Esquerda near Roda de Ter (North of Barcelona, Catalonia)). Извучени су IBD блокови већи од 6cM и извршено је поређење IBD блокова између савремених европских популација међусобно,а затим је извршено и поређење средњовјековног узорка са савременим популацијама. То је открило неке сасвим нове релације које није могла да покаже PCA или Admixture анализа.
Да не бих препричавао, пренијећу неке кључне реченице из рада:
"Identity by descent (IBD) analyses find genomic blocks that represent direct genealogical relationships among individuals."
"Individuals in the plot differ markedly in their connectivity, with some connected by IBD blocks to many individuals while others, in the peripheral branches of the network, being connected only to a single individual."
"Individuals belonging to small and historically isolated populations such as Basque-speakers, Orcadians, Sardinians and Icelanders tend to constitute such densely internally connected modules."
"Remarkably, all Sardinian individuals appear genetically isolated from the rest of the continent, an observation that is in agreement with ancient genomic studies where Sardinians are shown to largely preserve the genetic legacy of early Neolithic farmers"
"By contrast, Southeastern Europe shows a higher degree of mixed connectivity with a number of interpopulation connections to different countries. This suggests a higher level of population heterogeneity, possibly resulting from more recent population movements"
"We then identified IBD blocks based on 369.859 SNPs that were shared between modern Europeans and the Medieval genome. We found a total of only 31 IBD tracks longer than 2 cM (Table S3); 19 of them (61,3%) were shared with individuals from the Iberian Peninsula. As expected, a decreasing number of IBD blocks were found by increasing the length threshold: seven IBD blocks >3 cM
and only one >5 cM (Table S3).
This single relatively long IBD was shared with a Catalan individual, thus coming from the same geographical region as T-145-2."
"Generally, European IBD blocks longer than 4 cM derive from common ancestors living 500–1500 years ago or even more recently, which is a period roughly contemporaneous to our Medieval individual. "
"The network based on >6 cM genomic blocks in modern Europeans uncovers
some interesting genealogical features that are not evident in the commonly applied population genetic methods such as PCAs or ADMIXTURE analyses."
"For instance, in the European network (Fig. 2) we found a cluster of seven Maltese individuals also connected to one Sicilian. This could reflect the XIth century CE invasion of the island by Normands from Sicily. This direct link between individuals is not observed in population genetic analyses such as PCA and Admixture where Maltese and Sicilians cluster with their own respective populations, with whom they share most of their overall ancestry"
"We also observed an Icelander sharing one IBD segment with a Basque individual (Fig. 4). Basque whaling ships were common in the Icelandic Westfjords during the XVIIth century CE and they even developed a Basque-Icelandic pidgin language for trading purposes. It is not implausible that this signal derives from a child conceived by an Icelandic woman and a Basque sailor dating back to that period. Again, modern Icelanders, including this individual, cluster together and far away from Basques in traditional analyses based on overall ancestry"
