Why Do Bigger Populations (High Ne) Have Lower Ld Values?

Question

[GabrielMontenegro]

Hi everyone:

For example I am talking about LD decay plots that show the level of LD between SNPs at different physical distances.

http://s17.postimg.org/5bsk9j4jz/Screen_Shot_2014_02_02_at_8_47_55_PM.png

Why do Africans for instance have lower levels of LD... if they have always have had a bigger effective population size, isn't there less genetic drift acting on their genomes and therefore haplotypes are NOT being lost? Wouldn't there be more LD?

Thanks in advance.

[GabrielMontenegro]

Or is it just that because there are more haplotypes, there are more chances of recombination events to occur and therefore less LD???

[Adrian Pelin]

Bigger population = more sex. More sex = more recombination. More recombination is by definition low LD.

Answer 1

[Michael]

LD is inverse proportional to genetic variation. The higher the average LD and the larger the LD blocks, the lower the genetic variation or the general number of different haplotypes. African populations where found to have higher genetic variation than eurasians, and mostly eurasian variation is a subset of african variation. This is consistent with the "Out of Africa" theory of the origin of modern humans.