IBD sharing in Europe

[Coolguy1]

I was wondering if someone could help me interpret IBD sharing, as it actually measures common ancestry within ethnic groups. Here is a chart from a study from 2013 that studied most European populations.

http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001555

http://journals.plos.org/plosbiology/article/figure/image?size=large&id=info:doi/10.1371/journal.pbio.1001555.t001

From what I understand the higher the self column, the closer the population. And the higher the other column, the higher amount of ancestry from other groups. Is this correct?

[de Burgh II]

Segments of IBD are broken up over time by recombination, which implies that older shared ancestry tends to result in shorter shared IBD blocks. Sufficiently long segments of IBD can be identified as long, contiguous regions over which the two individuals are identical (or nearly identical) at a set of single nucleotide polymorphisms (SNPs) that segregate in the population. [...]

Since everyone has exactly two biological parents, every individual has exactly 2n paths of length n meioses leading back through their pedigree, each such path ending in a grandn–1parent. However, due to Mendelian segregation and limited recombination, genetic material will only be passed down along a small subset of these paths [8]. [B]As n grows, these paths proliferate rapidly and so the genealogical paths of two individuals soon overlap significantly. (These points are illustrated in Figure 1.) By observing the number of shared genomic blocks, we learn about the degree to which their genealogies overlap, or the number of common ancestors from which both individuals have inherited genetic material.

Mean number of IBD blocks of lengths 1–3 cM (oldest), 3–5 cM, and >5 cM (youngest), respectively, shared by a pair of individuals across all pairs of populations; the area of the point is proportional to sample size (number of distinct pairs), capped at a reasonable value; and lines show an exponential decay fit to each category (using a Poisson GLM weighted by sample size).

Table 1. Populations, abbreviations, sample sizes (n), mean number of IBD blocks shared by a pair of individuals from that population (“self”), and mean IBD rate averaged across all other populations (“other”), sorted by regional groupings described in the text.

Essentially is measuring genetic relatedness among in-group and outgroup populations via centimorgans to determine how historical immigrations played out for each European population via founder effects dispersed throughout Europe. "1–3 cM (oldest), 3–5 cM, and >5 cM (youngest)..." Thus, Kosovo or Albanians for example in the self column express genetic homogeneity among one another denoting their origins comes from a relatively small, isolated population not influenced too much by other immigrations on their genetic makeup. Thus, are less genetically diverse, but are homogeneous overall. Whereas Portugal, Spain and Italy in the self column have more ancient, heterogeneous populations within their countries that may convey historically distinct peoples/tribes that co-existed with one another that hints more complex, historical immigration within these given areas that too has been minimally impacted by other countries due to low centimorgans in other column.

[Coolguy1]

Essentially is measuring genetic relatedness among in-group and outgroup populations via centimorgans to determine how historical immigrations played out for each European population via founder effects dispersed throughout Europe. "1–3 cM (oldest), 3–5 cM, and >5 cM (youngest)..." Thus, Kosovo or Albanians for example in the self column express genetic homogeneity among one another denoting their origins comes from a relatively small, isolated population not influenced too much by other immigrations on their genetic makeup. Thus, are less genetically diverse, but are homogeneous overall. Whereas Portugal, Spain and Italy in the self column have more ancient, heterogeneous populations within their countries that may convey historically distinct peoples/tribes that co-existed with one another that hints more complex, historical immigration within these given areas that too has been minimally impacted by other countries due to low centimorgans in other column.

So basically the first column represents how homogenous the ethnicities are in terms of shared ancestry, and the second column represents foreign ancestry?

[Wrong]

Albania only has 9 samples while Kosovo 15, so it's hard to make a conclusion yet(not to mention other ethnicities).

It also depends on where they tested them, from the highlands, lowlands, villages, cities etc. Though I'm not surprised if Albanians get the highest. I want to see a study done on the Basque aswell.

This would indicate that Albanians originate from a few ancient populations.

[Dick]

Essentially is measuring genetic relatedness among in-group and outgroup populations via centimorgans to determine how historical immigrations played out for each European population via founder effects dispersed throughout Europe. "1–3 cM (oldest), 3–5 cM, and >5 cM (youngest)..." Thus, Kosovo or Albanians for example in the self column express genetic homogeneity among one another denoting their origins comes from a relatively small, isolated population not influenced too much by other immigrations on their genetic makeup. Thus, are less genetically diverse, but are homogeneous overall. Whereas Portugal, Spain and Italy in the self column have more ancient, heterogeneous populations within their countries that may convey historically distinct peoples/tribes that co-existed with one another that hints more complex, historical immigration within these given areas that too has been minimally impacted by other countries due to low centimorgans in other column.

Majority of Europeans descend from people born from survivors of the Black Death anyway(except for Pollocks)


https://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Blackdeath2.gif/300px-Blackdeath2.gif

[Coolguy1]

Albania only has 9 samples while Kosovo 15, so it's hard to make a conclusion yet(not to mention other ethnicities).

It also depends on where they tested them, from the highlands, lowlands, villages, cities etc. Though I'm not surprised if Albanians get the highest. I want to see a study done on the Basque aswell.

This would indicate Albanians originate from few ancient populations.

Id also like to know if Pontic/Anatolian Greeks were used, if so then the results would he skewed considering mainlanders and Anatolians were always seperated.

[Petalpusher]

Apparently they love to sample Swiss people


More telling

https://s22.postimg.org/xbvuvz0a9/journal_pbio_1001555_g003.png

[Wrong]

Apparently they love to sample Swiss peopleYeah, it's a fucking waste. They should have donated everything to the Balkaners.

[Petalpusher]

Majority of Europeans descend from people born from survivors of the Black Death anyway(except for Pollocks)


https://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Blackdeath2.gif/300px-Blackdeath2.gif

Natural selection at its best!

[Dick]

Natural selection at its best!

Too bad it skipped R1etheland.

[Dick]

Apparently they love to sample Swiss people


That's because their women taste like Toblerone

[de Burgh II]

So basically the first column represents how homogenous the ethnicities are in terms of shared ancestry, and the second column represents foreign ancestry?

Yes, quite correct.

Essentially, "self" = genetic relatedness within population/ low=heterogeneous and high=homogeneous////// "other"= genetic relatedness shared among all Europeans ("founder ancestor") low= low relatedness & high= high relatedness.

Understandably low for "other column" like Dick said from examples like Black plague that kill 1/3 of Europe's population probably kicked in bottleneck effects that made a loss of genetic diversity in Europeans so founder effects kick in to preserve what is left of European populations to evolve in much more smaller, fragmented and slightly differentiated populations.

[Petalpusher]

Too bad it skipped R1etheland.

Couldn't risk to get plumbed down in the pipes. Nice dodge, smart plague.

[Peterski]

Too bad it skipped R1etheland.

It skipped Poland because we had been immune to it already before. Superior genetics.