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View Full Version : Neanderthals live on in DNA of humans



WaxRubiks
2010-May-10, 01:54 AM
There is a little Neanderthal in nearly all of us, according to scientists who compared the genetic makeup of humans with that of our closest ancient relatives.Most people living outside Africa can trace up to 4% of their DNA to a Neanderthal origin, a consequence of interbreeding between the two groups after the great migration from the contintent.

Anthropologists have long speculated that early humans may have mated with Neanderthals, but the latest study provides the strongest evidence so far, suggesting that such encounters took place around 60,000 years ago in the Fertile Crescent region of the Middle East.
http://www.guardian.co.uk/science/2010/may/06/neanderthals-dna-humans-genome

So the Neanderthals didn't quite die out completely.

BigDon
2010-May-10, 02:08 AM
Bovine excrement.

LotusExcelle
2010-May-10, 02:41 AM
That sounds incredibly dubious.

Gillianren
2010-May-10, 02:47 AM
How do they figure out whether it's shared or due to crossbreeding?

WaxRubiks
2010-May-10, 02:55 AM
How do they figure out whether it's shared or due to crossbreeding?

I would guess that they tested native Africans and found that DNA missing.

BigDon
2010-May-10, 02:55 AM
While I have no doubt people in the Fertile Cresent regen may have had sex with Neanderthals, you are going to have a difficult time convincing me of viable offspring. This isn't Star Trek. And for another we share more DNA than that with fruit flys! Somebody want to try and make a coherent headline here?

BigDon
2010-May-10, 03:01 AM
A friend just texted me and asked me to explain something.

There are several sites in the Middle East where there is evidence of long co-habitation.

Friend said my first post looked like I was being racist.

Sorry.

WaxRubiks
2010-May-10, 03:12 AM
If Humans and Neanderthals did successfully interbreed, and produce fertile offspring, perhaps you couldn't really say that they were separate species.

nauthiz
2010-May-10, 04:23 AM
Species is a weird thing. On one hand, lions and tigers can interbreed to produce fertile offspring. On the other hand, there are ring species.

BioSci
2010-May-10, 05:10 AM
Species is a weird thing. On one hand, lions and tigers can interbreed to produce fertile offspring. On the other hand, there are ring species.

Yes, it is important to remember that the concept and definition of "species" is an invention by biologists to help classify the variety of living creatures. It is not a absolute characteristic. Many (perhaps even most) species can successfully hybridize with other, close species.

The whole process of specie definition is a gray area - full of subspecies, hybrids, and disagreements as to which box to insert what is often a continuous variation.

It is certainly possible that humans could have formed viable hybrids with Neanderthals - this research indicates that it may have happened. The problem is also that there is a significant possibility of DNA contamination or simple sequencing error. If other labs can repeat this result, then the evidence will be much stronger.

Delvo
2010-May-10, 01:36 PM
I'm still not buying it yet. They say some genes are sapiens genes and some are Neanderthal genes, but there's no basis for calling them that. Previous genetic studies of the modern human population have found a lack of genes showing the right allele age range. And the amount of the genome that Eurasians could have gotten from Neanderthals would have to be equal to or less than the amount of the genome that distinguishes the present human races from each other, but the numbers they give for this story are greater than that.

Strange
2010-May-10, 01:46 PM
Yes, it is important to remember that the concept and definition of "species" is an invention by biologists to help classify the variety of living creatures. It is not a absolute characteristic. Many (perhaps even most) species can successfully hybridize with other, close species.

Quite. There are also subgroups of modern humans who cannot interbreed and produce viable offspring. That (probably) doesn't make them different species.

adapa
2010-May-10, 03:01 PM
Quite. There are also subgroups of modern humans who cannot interbreed and produce viable offspring. That (probably) doesn't make them different species.

What subgroups of humans are these?

Strange
2010-May-10, 03:13 PM
What subgroups of humans are these?

One example I have read of, is related to the variety of mutations that can infer protection from malaria. Perhaps the best known of these is the one that can cause sickle-cell disease as a side effect. There are others which involve changes to the structure of hemoglobin. A given population will normally have just one of these mutations. Having both mutations is, in some cases, fatal. You can find cases where two villages living next to each other have different mutations. Any breeding between these groups would not produce living offspring. I suppose in time, this could lead to what we would consider different species. It may be things like this that drove the earlier speciation of Homo.

Gillianren
2010-May-10, 05:28 PM
One example I have read of, is related to the variety of mutations that can infer protection from malaria. Perhaps the best known of these is the one that can cause sickle-cell disease as a side effect. There are others which involve changes to the structure of hemoglobin. A given population will normally have just one of these mutations. Having both mutations is, in some cases, fatal. You can find cases where two villages living next to each other have different mutations. Any breeding between these groups would not produce living offspring. I suppose in time, this could lead to what we would consider different species. It may be things like this that drove the earlier speciation of Homo.

Can you? First I've heard of it.

BioSci
2010-May-10, 05:44 PM
One example I have read of, is related to the variety of mutations that can infer protection from malaria. Perhaps the best known of these is the one that can cause sickle-cell disease as a side effect. There are others which involve changes to the structure of hemoglobin. A given population will normally have just one of these mutations. Having both mutations is, in some cases, fatal. You can find cases where two villages living next to each other have different mutations. Any breeding between these groups would not produce living offspring. I suppose in time, this could lead to what we would consider different species. It may be things like this that drove the earlier speciation of Homo.

I would be interested in any references you might have. To me this sounds highly unlikely. It could be true on an individual basis - certain individuals may not be cross-fertile for such possible combinations (and even then this would likely require both parents to be homozygous for the defective gene - which often is problematic) - but this would highly unlikely for populations - I think that human populations are simply not that uniform.

Strange
2010-May-10, 06:55 PM
Some mutations are driven (or drive themselves) to become uniform in a population by selection pressures.

This is the first reference I found in a quick search: http://www.scientificamerican.com/podcast/episode.cfm?id=human-evolution-ii-recent-evolution-09-11-03

That is because hemoglobin C and sickle-cell negatively interact with each other, it is a negative epistasis. So, you cannot have both. If one is high, the other one has to be low.

BioSci
2010-May-10, 09:15 PM
Some mutations are driven (or drive themselves) to become uniform in a population by selection pressures.

This is the first reference I found in a quick search: http://www.scientificamerican.com/podcast/episode.cfm?id=human-evolution-ii-recent-evolution-09-11-03

Thanks for the cite. The genetics of malaria and various mutations is complex. Hemoglobin mutants can be protective against malaria but individuals homozygous for the mutant can suffer from sickle cell diseases and this results in a "balanced polymorphism" where the gene is both selected for and against. This seems especially true for the common African allele S. The E and C alleles do not appear to be as negative in the homozygous condition - but they may also be less effective in prevention of malaria.

So in the even more complex situation with S, C, and malaria as referenced in your cite, the genetic conditions with negative selection include: SS(sickle cell disease), SC(incompatible mutants), and AA (non-mutant alleles) the conditions selected for include: SA, CA, & CC. Depending on the relative strengths of disease resistance, disease prevalence, sickle toxicity, and medical intervention, the prevalence of these alleles can reach different equilibrium values in a population- but this would likely not be enough to push human populations to speciate! You could have a transient situation where genetic exchange between the populations may be slowed - but people being people - they would likely trend to a common equilibrium.

A nice discussion of these malarial mutations here: http://sickle.bwh.harvard.edu/malaria_sickle.html

Boratssister
2010-May-10, 10:59 PM
http://www.guardian.co.uk/science/2010/may/06/neanderthals-dna-humans-genome

So the Neanderthals didn't quite die out completely.

Ahh, is this the ginger genes? Only kidding.

JohnD
2010-May-11, 12:20 PM
Ugh? Ugh ugh ughugh, ugh! Ugh ugh ugh ugh, ugh ugh ugh, Ugh ugh-ugh.

Ugh

mugaliens
2010-May-11, 01:11 PM
Bovine excrement.


That sounds incredibly dubious.

Sounds like knee-jerk reactions, guys.


How do they figure out whether it's shared or due to crossbreeding?

Well...


I would guess that they tested native Africans and found that DNA missing.

I don't know if that's the answer, but before putting forth the hypothesis in the first place, the standard approach would be to eliminate such possibilities before putting forth the hypothesis.


While I have no doubt people in the Fertile Cresent regen may have had sex with Neanderthals, you are going to have a difficult time convincing me of viable offspring. This isn't Star Trek. And for another we share more DNA than that with fruit flys!

Than Neanderthals? No we don't. We have far more common DNA with Neanderthalls than we do chimps, and more with them than we do lizards, and more with them than we do fruit flies.


If Humans and Neanderthals did successfully interbreed, and produce fertile offspring, perhaps you couldn't really say that they were separate species.

The definition of "species" has undergone some changes in the last few decades, and if I'm not mistaken, the exact definition remains in flux, depending upon with whom one talks. My personal take is that if they're capable of breeding a viable breeding offspring, they're of the same species. Thus, horses and donkeys producing sterile mules means that horses and donkeys aren't of the same species, though more closely related than separate species. Interspecies?


A friend just texted me and asked me to explain something.

There are several sites in the Middle East where there is evidence of long co-habitation.

Friend said my first post looked like I was being racist.

Sorry.

No worries. Goodness! Look at the "scientific" documentation over the last 100 years - it's replete with such racial bias. Two of my favorite movies are Men of Honor and The Tuskegee Airmen for the simple fact they both highlight and counter the ridiculous "scientific" racial bias at the time.


If Humans and Neanderthals did successfully interbreed, and produce fertile offspring, perhaps you couldn't really say that they were separate species.

Ligers.


Species is a weird thing. On one hand, lions and tigers can interbreed to produce fertile offspring. On the other hand, there are ring species.

Ligers (http://en.wikipedia.org/wiki/Liger). At 904 non-obese pounds, Hercules (http://en.wikipedia.org/wiki/File:Ligertrainer.jpg)is well beyond the typical 550 lb upper limit for male lions and the 674 lb upper limit for male tigers.

Ara Pacis
2010-May-11, 04:44 PM
Fertile Crescent indeed! Anyone suppose this supports the concept of the Nephalim (http://en.wikipedia.org/wiki/Nephalim)?

David Holland
2010-May-11, 11:36 PM
John Hawks at johnhawks.net/weblog has an article about this. First if neandertals had contributed no genes to modern populations they would be equally related to every one living today no matter where they live. It turns out that people living outside of Africa are more closely related to neandertals than people living in Africa. Second they looked at gene trees that had deep roots outside of Africa. In 10 out of 12 cases neandertals had the non-African version of the gene. He goes into a lot of detail about this study, if you're interested it is a good place to start.