Genetic variations within and between populations

[Tosh5457]

This paper asserts these two different conclusions:

Thus the answer to the question “How often is a pair of individuals from one population genetically more dissimilar than two individuals chosen from two different populations?” depends on the number of polymorphisms used to define that dissimilarity and the populations being compared. The answer, can be read from Figure 2. Given 10 loci, three distinct populations, and the full spectrum of polymorphisms (Figure 2E), the answer is 0.3, or nearly one-third of the time. With 100 loci, the answer is ∼20% of the time and even using 1000 loci, 10%. However, if genetic similarity is measured over many thousands of loci, the answer becomes “never” when individuals are sampled from geographically separated populations.

The fact that, given enough genetic data, individuals can be correctly assigned to their populations of origin is compatible with the observation that most human genetic variation is found within populations, not between them.

How don't they contradict each other? What exactly is "variation between populations" and "variation within populations"?

 

[Ygggdrasil]

There are likely a small number of sites that differ between populations that can be reliably used to distinguish those populations. However, there are a larger number of sites that differ within a population.

 

[Tosh5457]

There are likely a small number of sites that differ between populations that can be reliably used to distinguish those populations. However, there are a larger number of sites that differ within a population.

I don't understand, can you explain it in another way?

 

[aroc91]

I don't understand, can you explain it in another way?

Overall variation may be too high to distinguish populations from each other, but that doesn't mean there can't be specific genes that are still unique to their respective populations.