Did Neanderthal genetics play a role in the evolution of modern humans?

[zoobyshoe]

There are two main theories I've heard: 1.) that we killed them off either directly or by encroachment. 2.) that we interbred with them and distinct Neanderthal characteristics got overwhelmed.

Some argue against the latter since it's possible that Neanderthal was a separate species.

Got any ideas about this?

 

[matthyaouw]

I thought they were a subspecies-
Homo sapiens neandertalis and homo sapiens sapiens.

Subspecies are capable of interbreeding, so both are possible. I remember seeing a TV program that said several skulls had been found showing both characteristics of Homo sapiens sapiens and Homo sapiens neandertalis.

 

[zoobyshoe]

I thought they were a subspecies-
Homo sapiens neandertalis and homo sapiens sapiens.

No one knows for certain, of course. I'm reading a book by Ian Tattersall, who is making a good case for them to be taken seriously as a separate species. His main argument is that there was never a good reason to suppose they were the same species as us. It has always been an unsubstantiated assumption they are. He points out that there are many different species who resemble each other more closely than we resemble the Neanderthal, but who can none-the-less not successfully breed.

Subspecies are capable of interbreeding, so both are possible. I remember seeing a TV program that said several skulls had been found showing both characteristics of Homo sapiens sapiens and Homo sapiens neandertalis.

I've seen skulls that look like this as well. I've also seem cro-magnon skulls that seem to have the sapiens sapiens face, but a very Neanderthal length of skull, front to back. The whole thing is very intriguing.

 

[arildno]

I, for one, haven't seen any particular reason why the appearance of cro magnons should necessarily have had a momentous impact on the destiny of neanderthals.
The two groups might well have been entirely in the others periphery so that the demise of neanderthals is basically unconnected with cro magnons.

 

[zoobyshoe]

I, for one, haven't seen any particular reason why the appearance of cro magnons should necessarily have had a momentous impact on the destiny of neanderthals.

Yes, the speculation that they did seems to be based primarily on the timing.

I hope there are lots more fossils out there to be discovered that will clear this up one way or another.
The Neanderthals survived for so very long, it intrigues me to find out what could have made them disappear altogether.

 

[hypatia]

Some scientists claim that a child skeleton, found in Portugal in 1998, has a mixture of Neanderthal and Modern human features. For them, it's proof of interbreeding. Other scientists dispute the claim and mtDNA tests on 3 other Neanderthal fossils have found no evidence for interbreeding.
Samples from the 3 locations proved to have a high content of amino acids, an amino acid composition similar to that of the contemporary bone and a low level of racemization of aspartic acid, alanine and leucine; all criteria compatible with a chance of ancient DNA retrieval. By contrast, where the childs body was found, bones contained almost no detectable amino acids making the retrieval of DNA sequences unlikely. Research on the child continues though no DNA has been extracted from it. The debate is far from over.

 

[zoobyshoe]

all criteria compatible with a chance of ancient DNA retrieval.

I'm not sure what this all means. Do they actually have any Neanderthal DNA, or is there just the chance they might have it?

 

[hypatia]

Yes they do have it, just a tiny bit from 3 locations. Enough to show they were a different species then modern humans. There is some talk that human/neanderthal children failed to thrive, that the genetic mix was not compatible. But maybe a few survived. But without there DNA we wouldn't be able to tell, if and how they might of entered our gene pool.

 

[sssddd]

So what's the verdict today? Was there just not enough DNA samples to construct an accurate phylogenic tree, so we still use the fossils to do it?

 

[Ophiolite]

I may be about to drive this thread off topic, in which case just ignore this post. I have often pondered that behind those supporting option 1.) that we killed them off either directly or by encroachment. was an unconscious (perhaps even conscious) desire to eliminate any possibility that we could be descendants of a species, or sub-species, that is popularily seen as primitive, lacking in culture, language, advanced tool making, etc.. Equally, those favouring a merging of the species were influenced, perhaps, by a desire for political correctness.
But that would mean that scientists, on occasion, allowed emotion and prejudice to influence their findings. Silly me.

 

[zoobyshoe]

But that would mean that scientists, on occasion, allowed emotion and prejudice to influence their findings. Silly me.

Well, there's no end of emotional, predjudiced ideas advanced about the Neanderthals, but the two you point to don't seem to be among them. The first notion, that we wiped them out, is a reasonable conjecture: we showed up, they disappeared. We were presumably similar enough to be in competition for the same things.

The second notion is based on the interesting fact I just read today that the further east Neanderthal remains are found the more sapiens sapiens the remains appear to be. One way to explain this would be to suppose there were "pure" Neanderthals to the west, "pure" cro-magnons to the east, and a smooth blend in between, which would mean we would have to be able to produce offspring with them.

Anyway, you might enjoy the book I'm reading, The Last Neanderthal by Ian Tattersoll, because it is a good history of the notions we have about them, where each generation of notions arose, and how they're constantly being overturned.

 

[Lapin Dormant]

how's about

How's about we arose from a bad and forced mating of the two, (Neo and Cro) the "Ugly genetic deformatey" that we (Homo Sapiens) appeared to be, to them, had always previously been put to immediate death, as tribal law required, but this time, two of them (A Cro- and A Neo- Male and Female) had fled first, and they did not destroy their Mutant Children, actually had many-multiples (male and female) as to enlarge the group for the purpose of the Hunt, time passes, "we" are a large enough group ourselves that we incesteously breed, and start to form our own much larger tribe, "Us" with the Moral Consciouness that had been previously Completely Un-known in any species, following that, we are sort of The 'Pigs and the Ducks' as friends that brings to all, the Viruses that are the Flu season, (from otherwise Non-invasive to humans strains) just that, in this case, we can survive the Flu created in our genome, but niether of our predescents can, they ALL die out from what we inadvertantly did.

Almost Biblical inasmuch as it needs "US" (homo Sapiens) to be born of a prohibited mating, Neo and Cro, then Incestually propagated continuance.

And the point of the instillation, within the Species, of Moral Consciousness.

Sound good?

 

[selfAdjoint]

Sounds like a scenario for a movie.

I had a thought/question about a Neandertal woman bearing a sapiens-style baby. We are told that the N's, whose brains had a larger average volume than ours, evolved to solve the problem of narrow-hipped women bearing big-headed babies by making the brain case a long oval, so high volume with smaller cross-section. Whereas hom sap has a brain case more nearly spherical and the women have evolved wide hips to pass it. So if a Ne woman and a Sap man mated and one of their children had a sap style brain case, it would probably kill the mother! This suggests the Ne-Sap crosses found in the Middle East would have been borne by Sap or Sap-like women. Or am I missing something?

 

[matthyaouw]

There seems to be DNA evidence that humans and neandertals did not interbreed: http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0020080

 

[zoobyshoe]

We are told that the N's, whose brains had a larger average volume than ours, evolved to solve the problem of narrow-hipped women bearing big-headed babies by making the brain case a long oval, so high volume with smaller cross-section.

I'm not sure this notion is tenable. If a Neanderthal baby's head was longer than ours, front to back, how would the head be oriented on the body during birth such that it would come out the easy lengthwise way? Tilting the head way back or way forward would still result in a wide thing to pass because of the face and jaw, if the baby's neck could survive such treatment.

Or am I missing something?

 

[zoobyshoe]

There seems to be DNA evidence that humans and neandertals did not interbreed: http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0020080

From that link:

"While the authors explain that it's impossible to definitively conclude that no genetic flow occurred between early humans and Neandertals given the limited number of early human fossils available, they point out that even fossil samples considered as anatomically transitional between modern humans and Neandertals failed to show evidence of mtDNA exchange. Thus, Pääbo and colleagues conclude, while it's possible that Neandertals made a small contribution to the genetic makeup of contemporary humans, the evidence cannot support the possibility of a large contribution."

Thi makes me wonder about an explanation for the "transitional" looking fossils. Maybe there were at least two different Neanderthal types, some accidently more cro-magnon looking than others, who could interbreed and produced these pseudo-transitional looking fossils?

 

[hypatia]

Plus we need to keep in mind that mtDNA is only female.
I don't think they've isolated any Neandertal Y chromosomal DNA. If they had, then it would be extremely informative.
The mitochondrial DNA seems to indicate that there is no Neandertal DNA in us, but this data is inconclusive for a few reasons. First of all, mitochondrial DNA is passed down only through a maternal lineage, so it tells us nothing about the possiblities of a male Neadertal ancestor (Y chromosomes would tell us this). Secondly, there is only a handfull of mitochondrial sequences available. What they tell us is that those Neadertals likely didn't contribute any DNA to modern humans, but there could be an isolated subpopulation that did. Thirdly, even if they didn't contribute any mitochondrial DNA, they could have contributed nuclear DNA without any direct maternal ancestors. In other words, a female Neandertal could mate with a sapiens male, and have a bunch of male offspring who are our direct ancestors. There would be no mitochondrial DNA passed on, but there might be X chromosomal DNA passed on. Anyway, I don't know that the controversy will be settled any time soon.

 

[Lapin Dormant]

Flip it, slightly, and .. .. .. .. ..

There seems to be DNA evidence that humans and neandertals did not interbreed: http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0020080

In what I had suggested, interbreeding of Human (sapiens) and Neos' was not suggested, it is-was suggested that we arrived from the interbreeding of Neo's and Cro's = Mutant Children produced, US, difficult at best I would think-suspect.

As for the head size, it could be exactly why those particular babies had not been destroyed, the only available emotional connection left, to the male, of the female that he had bred with, inasmuch as she died giving birth, probably from passing too large a head.
(Not suggested as humor, even though it appears as such)

Probablility would suggest fraternal twins, therefore only one birthing need transpire, one male and one female, thereafter, in their teen to adult years, they would have been the only available partners to each other.

(wink? Wink? :tongue2: )

 

[matthyaouw]

It's a theory, but where's the evidence? If we had really arisen from one pair of ancestors, there would be a tremendous amount of inbreeding, with incredibly high incidence of genetic disease. Saying that 'mutant children' would be culled according to tribal tradition is pure speculation, as is much of your theory.

 

[Lapin Dormant]

It's a theory, but where's the evidence? If we had really arisen from one pair of ancestors, there would be a tremendous amount of inbreeding, with incredibly high incidence of genetic disease. Saying that 'mutant children' would be culled according to tribal tradition is pure speculation, as is much of your theory.

Never said it was anything more, or less, then a theory=speculation {a story actually} and the maternal {DNA or is it mitachondrial, darn no references available right now} evidence points apparenlty quite succintly to a very-very small number as possible originators for Homos Sapiens

Also I hadn't said that they would be 'culled', any-most tibal societies usually Kill any offspring that do not match up well with the accepted 'Norms' of that society, Neos and-or Cros would have seen Sapiens Babies as weak, useless, as they had not the size, the hair, the strength, or any of the other attributes that would be seen, tribally, as needed.

That is The entire reason why I had SPECULATED that they would only have arisen from pair that had, themselves, been tribally excluded.

Any-All previous birthings of anything that had even resembled a Sapiens would have been slain immediately by any Good Witch-Doctor, tribal Customs.

As for the inbreeding, the sooner you arrive at greater numbers the sooner the possibilties of Abnormalities will diminish

{Note it does NOT say Vanish, it says diminish}