Question about 1-4% Neanderthal DNA present in non African humans

[whimsyfree]

Your knee-jerk response leads me to believe that you didn't even open any of the links.

That's wrong.

If you had you would know that what you've said is incorrect.

Nothing you cited from the peer reviewed literature supported the hypothesis. Do you have any cites from the peer reviewed literature that support the claim that autism is due to Neanderthal genes? The rest of what you cited could just as well be said to support autism's being caused by pale skin or vaccines. You cite one 35 year old paper that explicitly disqualifies itself as a prevalence study to support the claim that autism is less frequent amoung Africans. The other paper is equivocal with opposite results for ASD and autistic diagnosis. Did you look at any other papers on the epidemiology of autism? It's a good idea to type relevant terms into google scholar. The first one that I found that had something to say about prevalence by race was Descriptive Epidemiology of Autism in a California Population: Who Is at Risk? ("Increased risks were observed for males, multiple births, and children born to black mothers."). The second I found was the review article The Epidemiology of Autism Spectrum Annual Review of Public Health Vol. 28: 235-258. The find little evidence of racial differences in frequency and cite Schieve LA, Rice C, Boyle C. 2006. Mental health in the United States: parental report of diagnosed autism in children age 4–17 years–united states 2003–2004. MMWR 55:481–86 who found no difference in reported diagnosis rates between black and white Americans. Wikipedia cites another survey, New Developments in Autism Psychiatric Clinics of North America, Volume 32, Issue 1, Pages 1-14, which says

No well-established studies have consistently identified differences in the rates of autism across ethnicities or demographic backgrounds.
Therefore, most professionals maintain a belief that the occurrence of autism is not influenced by economic, social, racial, or ethnic background.

[Ara Pacis]

The concept of "octoroon" seems less relevant here that the one-drop rule.

If some or all of us present-day humans have any genetic component that comes from Neanderthals, it matters. It tells us something about where we have come from and who we are. It tells us something about the prehistoric relation between our species (or subspecies) and the other species (or subspecies) of hominids.

However, it would be scientifically impossible to "draw the line" definitively between present-days humans who do or don't have Neanderthal ancestry.

Another point mentioned in John Hawks' article Neandertal Introgression, 1000 Genomes style is that Sub Saharan Africans too have some Neanderthal-like material in their "derived alleles" (the component of human genome not shared by chimps etc.) The Neander genetic component in the Africans is significantly smaller than the Neander component in Europeans, Chinese, etc, but it is present nonetheless.

Hawks says that, in the case of the Africans, this genetic component can be explained as coming entirely from the epoch before Neanderthal and Early Modern Human populations diverged, rather than from later cross breeding between Neanders and EMHs.

It is a scientifically conservative assumption, but still an assumption. Another possibility is that all present-day humans have Neander-EMH hybrids among their ancestors. Africans just have fewer.

If the "one-drop rule" is applied, we present-day humans may all be Neanderthals.

My point is that you're conflating culture and mathematics.

Why do you say it would be "scientifically impossible to "draw the line" definitively between present-days humans who do or don't have Neanderthal ancestry"?

[Colin Robinson]

My point is that you're conflating culture and mathematics.

What specifically did I write that conflated culture and mathematics?

Why do you say it would be "scientifically impossible to "draw the line" definitively between present-days humans who do or don't have Neanderthal ancestry"?

The nuclear DNA findings show that some present-day human populations are more closely related to Neanderthals than other present-day humans are to Neanderthals. Eurasians have more genes in common with Neanderthals, than Africans have in common with Neanderthals. This implies that Eurasians have more Neanderthal ancestry than Africans have. Or at least, more ancestors closely related to Neanderthals....

The difficult part ("impossible" was probably too strong a word) is working out whether it means that most sub-Saharan Africans have zero Neanderthal ancestry, or whether it means Africans, like Eurasians, have Neanderthal ancestors, but that Africans have fewer than Eurasians have.

[RupertVanstersher]

Do you have any cites from the peer reviewed literature that support the claim that autism is due to Neanderthal genes?

Hominins and the Emergence of the Modern Human Brain (Published Jan 2012):

Autism...is referenced in studies of fossil hominin brain structure and function, either as an analogy for developmental differences between closely related species or as a potentially atavistic indication of actual primitive phenotypes. For example, an autistic child lacking language created naturalistic artwork much like that from the Upper Paleolithic, on the basis of which it was suggested that fAMHS could have also lacked fully modern cognition

[Ara Pacis]

What specifically did I write that conflated culture and mathematics?

The part where I asked about octoroon. I don't think there's a need for nuanced distinction in fractional descent. If it can be scientifically shown or estimated that all living humans have some neanderthal DNA then it is what it is. I'm more interested in how we know that such genes can be identified as neanderthal.

[Colin Robinson]

I don't think there's a need for nuanced distinction in fractional descent.

Well, I agree with you up to a point. Although I think it is important to distinguish here between three different theories:

1. The theory that present-day humans in Eurasia are predominantly descended from earlier Eurasian species/subspecies, such as Neanderthal, Denisova, Homo erectus.
2. The theory that present-day humans in Eurasia are predominantly descended from a population that came out of Africa fairly recently (ca 50 thousand years), but that the new population (the Early Modern Humans) interbred to a limited extent with the Neanderthals etc.
3. The theory that after the Early Modern Humans reached Eurasia from Africa, they did not interbreed with Neanderthals etc at all.

These are three very different "takes" on human evolution...

If it can be scientifically shown or estimated that all living humans have some neanderthal DNA then it is what it is. I'm more interested in how we know that such genes can be identified as neanderthal.

As I understand it, this is how we know (using the word "know" somewhat tentatively)...

1.There are Neanderthal remains which contain DNA that can be extracted and analysed.

2. Once you do that, you can compare the Neanderthal's genes with someone else's genes, for instance, genes from a chimpanzee, genes from a present-day African human, genes from a present-day European etc...

3. You can then see what genes there are in different categories, for instance:

(a) Genes found in Neanderthals, which are also found in present-day humans, and chimps as well.
(b) Genes found in Neanderthals, which are also found in all populations of present-day humans, but not in chimps.
(c) Genes found in Neanderthals, absent in chimps, absent or rare in some present-day human populations, but significantly more frequent in others.

The genes in category (a) are irrelevant to the question of whether present-day humans have Neanderthal ancestors, because they presumably derive from a more ancient ancestor of both chimps and humans.

The genes in category (b) are not all that relevant either. We might have got some of them from the Neanderthal. Or we might have got them all from someone more ancient than the Neanderthal -- a common ancestor of Neanderthals and of Early Modern Humans. (Homo ergaster would be a candidate...) All that the genes in category (b) really tell us, is that we present-day humans are more closely related to the Neanderthal than we are to the chimp. But we knew that already.

The genes in category (c) are the really interesting ones. They are the ones Europeans (and Chinese, and Melanesians) have more of, compared to sub-Saharan Africans. They are the genes that suggest relatively recent interbreeding of Neanderthals and Early Modern Humans...

[whimsyfree]

Hominins and the Emergence of the Modern Human Brain (Published Jan 2012):

That'd be a "no" then.

[RupertVanstersher]

That'd be a "no" then.

Um, did you even read the quote? The theory that neanderthals are behind autism isn't published, but the idea that it's an atavistic phenotype certainly is. Here's another:

Conceptualizing the autism spectrum in terms of natural selection and behavioral ecology: The solitary forager hypothesis (2011)

Perhaps some of the genes for autism evolved not in our direct ancestral line but in a solitary subspecies which later merged genetically with our line of descent through gene flow. Demes, or subpopulations of relatively solitary humans, could have been assimilated into our gene pool after a fair amount of interbreeding following migration.

[whimsyfree]

Um, did you even read the quote?

Yes and it didn't mention Neanderthals once. You are obviously not someone who respects the principles of honest debate so I have nothing further to say to you.

[RupertVanstersher]

Yes and it didn't mention Neanderthals once. You are obviously not someone who respects the principles of honest debate so I have nothing further to say to you.

[Disinfo Agent]

I'm not sure how those two ("don't"/"can't") are distinguished.
For some reason it left me with the various forms of a "farmer and a sheep..." joke coming to mind.

The farmer and the sheep probably can't produce viable offspring. The "don't" should be read as "negligible breeding", whether or not there are attempts.

Are racists a different species because they refuse to take a healthy canon ball splash into the gene pool? Or does it only count if its ingrained as an instinct, not learned behavior?

They would need to practice what they preach, by not producing any significant clandestine offspring with members of the races they publicly disparage, and to convince all their descendants to be just as racist as them... for a very, very long time. I dare say there'll be a cold day in hell...

[Disinfo Agent]

What if one of my great-great-great-grandparents is Portuguese, while the other 31 are Polish? Would you say I am of Portuguese descent?

That question is more challenging than it may seem at first glance. Remember that you inherit some genes from each of your grandparents, but not all of their genes!

Let's suppose (absurdly) that you had a gene that made you either Polish or Portuguese. Suppose you had complete dominance for the sake of the argument:

pp makes you Portuguese
PP makes you Polish
Pp or pP make you Polish

To make the question more interesting suppose you had 2 Portuguese ancestors against 30 that were Polish. No doubt the most likely, if one were to pick one of their descendants at random, would be for that person to be Polish. But there is still a nonzero probability that that person might turn out to be Portuguese! After several generations, you cannot be sure if you ended up with more DNA from a minority of your ancestors than from the majority of them. It happens.

But this is just genetics. One could argue, as Ara Pacis rightly did, that for most people identity has more to do with cultural aspects than with what's in their DNA (notwithstanding the obvious overlap between the two).

[Ara Pacis]

Not to mention that some DNA gets shuffled from one side to the other in Chromosomal Crossover during meiosis, confusing the matter even more.

[ShinAce]

This got me thinking about my mom, who's french canadian. A few hundred years ago, orphaned girls were sent to canada to colonize 'new france'. From quebec city, a group left and went north to Charlevoix. Again, a group left and continued to what is now called the bay, or saguenay. The genetic diversity is poor considering the hundreds of thousands of persons living here. I can easily imagine that a paternity test between myself and a neighbor wouldn't be one in a billion, but rather one in several million. Migration seems to be a huge factor.