Help re: evolution

[sfs]

the studies I've seen show that the two irish men would have more differences in their dna than when compared to a korean man. Sure its possible they have more genetic similarity, but its even more possible that they have more genetic differences between them than one and a korean.

No, that isn't right. To a good approximation, Europeans and east Asians each have a subset of African genetic diversity, but they are only partly overlapping. You can find some numbers here (p. 30 of the online supplementary materials for the 2nd article listed under 2007). Comparing two western European chromosomes, they find an average of 0.6044 differences per thousand base pairs, but 0.6579 per thousand when comparing European and East Asian chromosomes. The within-Europe comparison is not much smaller, but it is smaller. (Note that within-Africa comparisons are statistically indistinguishable from African/non-African comparisons.)

 

[Gracchus]

I think we actually agree, and you're just picking up on bits that were poorly expressed.

Just to clarify, this is sort-of what we all mean:

View attachment 119670

Populations aren't significantly different from each other. Two people (red) from one population are often more different to each other than they are to someone from another population (blue).

Ah! Now I see what you meant. Truly, one picture is worth ten thousand words.

 

[sfs]

Populations aren't significantly different from each other.

That statement can be true or false, depending on what you mean by "significantly". If you mean it in the usual scientific sense (significant =
statistically significant), it's false. Geographically bounded populations that have been around for a long time differ from each other genetically in ways that can easily be detected. It is easy to distinguish West African from European from East Asian DNA, and only slightly harder to distinguish northern European from southern European. It is also straightforward to identify the source of individual chunks of DNA in an admixed individual, e.g. we can distinguish western European and West African pieces of chromosome in an African American individual.

The statement is true in the sense that the bulk of genetic differences between populations are only statistical. That is, that genetic differences usually represent modest differences in the frequencies of a trait in different groups, rather than something that is present in one and absent in another. Furthermore, most genetic variation is present in African populations, so that non-African variation is largely a subset of African variation.

 

[mpok1519]

I have to disagree with whatever 'evidence' you put there.

I'm going with what the anthropologists at the university are saying moreso than random internet research.

Theres more genetic variation within racial categories than without.

 

[R3quiem]

I think you should go to the office hours of your professor and ask him about it, because I think you misunderstood whatever you were told.

Think about it- why would somewhat isolated populations, that breed mainly with each other, have more genetic diversity within themselves than with another group on the other side of the world?

Something that odd better have incredible evidence to back it up, and from what I've looked up and from what other people have posted, it seems that different populations are indeed genetically dissimilar to each other more so than within the same population.

 

[Nathan45]

the studies I've seen show that the two irish men would have more differences in their dna than when compared to a korean man. Sure its possible they have more genetic similarity, but its even more possible that they have more genetic differences between them than one and a korean.

You're clearly misunderstanding your professors, lol.

what they're probably trying to convey is that there is more genetic variation within a race than without... which is to say that 50% + 1 or more of the variations that make us different from one another are present within every race. that doesn't mean that an average irishman is more similar to a korean than an irishman.

 

[mpok1519]

isolated populations wont have that much genetic variance, no.

but anywhere else, yes.

 

[R3quiem]

isolated populations wont have that much genetic variance, no.

but anywhere else, yes.

Well that's what a race is- a somewhat isolated population.

In our current world where interracial marriage is socially acceptable, we can expect to see the various races become more mixed.

But when you have a given person, say an irish man, who has two irish parents, four irish grandparents, eight irish great grand parents, then 16, 32, 64, and so on stretching back thousands of years- that's an isolated population stretching back for a while. I don't know the migration or genetic history of Ireland in the slightest, I'm just using an example. Even variances, say, one eighth of his ancestors are from another part of Europe- that's still pretty isolated (compared to, say, Asian influences on his genetic material.) And that's why an Irish man would have more genetic similarity with another Irish man than a Korean man, or any other race.

Very few, if any, populations are completely isolated. But a "race" is still a pretty isolated thing for the time being. One day I guess we'll all be orange, but for the time being, there are still relatively isolated races around. I'm no geneticist like sfs there, of course.

 

[sfs]

I have to disagree with whatever 'evidence' you put there.

You don't have to use scare quotes. What I provided was real evidence: data, published in a respected peer-reviewed journal, that directly addressed your claim.

I'm going with what the anthropologists at the university are saying moreso than random internet research.

Theres more genetic variation within racial categories than without.

What you heard from the anthropologists is correct: there is more genetic variation within populations than between populations. The statement just doesn't mean what you think it means. What it does mean is that you only find a little bit more genetic variation when you compare DNA across populations than when you compare DNA within a population. It doesn't mean that there is more diversity when you compare DNA within a population. Indeed, I have difficulty figuring out how that state of affairs would even be possible.

Oh, and what I provided was not random internet research. I cited that paper because I was familiar with it and knew it would have the estimate I was looking for. (I'm a geneticist who works on large-scale studies of human genetic variation, and I almost certainly know more about the subject than your anthropologists.)

 

[mpok1519]

Well, no one really gets what I'm saying, so I'll just leave it at that.

No big deal.

I couldnt really care nearly as much as others do. =)