Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum More on a human-Neandertal link

A skull found in a cave in Romania includes features of both modern humans and Neanderthals, possibly suggesting that the two may have interbred thousands of years ago. Neanderthals were replaced by early modern humans. Researchers have long debated whether the two groups mixed together, though most doubt it. The last evidence for Neanderthals dates from at least 24,000 years ago. The skull bearing both older and modern characteristics is discussed in a paper by Erik Trinkaus of Washington University in St. Louis. The report appears in Tuesday's issue of Proceedings of the National Academy of Sciences. The article includes a picture of the skull. For the full article: Click Here

Thanks DA. It is Trinkaus though and many people would say he's biased. What makes his interpretation particularly interesting is that it's from near the time and place the Gravettian developed. I have felt for a long time this culture owed a lot to Neanderthals.

Has any actual Neanderthal DNA been discovered or, as in the cases here, are such cases as this one made by observation of various physical features of the bones? In which case the decision can include a measure of personal (although well informed) opinion and inference.

Ellis asks:
"Has any actual Neanderthal DNA been discovered"

Yes.
http://www.archaeology.org/online/news/dna.html

That's interesting. It would seem to me to be unlikely that there would not have been interbreeding between the two groups--but maybe they were incompatible because they really were different species and/or were therefore infertile together.

I find it disagreeable to state this but it is the truth ... human try to mate with anything not fast enough to get away. We had some moron killed here in Western Washington a few years ago because the horse wasn't as interested in him as he was in the horse.

To believe we wouldn't have tried to mate with Neandertals is not credible. Whether we would have succeeded and whether the offspring would have been accepted is quite another matter.

Ellis asked:

"Has any actual Neanderthal DNA been discovered"

I agree with all the points made so far. But the reason it is difficult to correlate the mtDNA, Y-chromosome and fossil evidence is that they're not necessarily that closely related. Their origin quite possibly happened at different times. Obviously many individual human genes have a single origin (well, the same mutation may have occurred twice but a whole gene would be remarkable), most from before we separated from apes and some go back to when we separated from fungi. The fact that each of us now has a version of a particular gene that traces back to just a single origin simply means that other similar genes around at the same time have been eliminated. Through just genetic drift as often as by selection.

Unfortunately for some reason this idea of a single origin for each individual gene has been extended to a single origin for each individual species. Most of us grow up with the idea that each separate species descends from just one pair on Noah's ark. As I've pointed out on SAGG several times it's hard for us to grow out of this idea. Even so it amazes me that many people who should know better still believe some small group of near-modern humans woke up one morning and suddenly found they were modern humans (whatever that means).

Neanderthal genes may well have died out but it's unlikely to be because they were a separate species and incoming humans were genetically superior. How hard will it be to find genes from the indigenous inhabitants of North America in 10,000 years time, or even in a random sample from today?

I certainly don't believe that everything came from Noah's Ark. I don't believe in Noah's Ark. Neither did I grow up believing in it. I merely want to know (as a non-scientist), if it is possible to state without doubt whether the genes of Neanderthals are different or similar to ours- or is the conclusion that hybrids exist deduced by inferring the facts from bones? Both have validity but both are fallible it seems. Common sense would seem to indicate inter-breeding probably took place (maybe it happened on that Ark !!!!) However the fertility of offspring may be compromised and it would probably take a freakish stroke of luck to discover the bones/skull of one such rarity in that case.

TNZ wrote:
"well, the same mutation may have occurred twice but a whole gene would be remarkable"

You will find we share a substantial percentage of our genes with a large percentage of mammalian life forms. I find this statement a bit puzzling.

Ellis asks:
"if it is possible to state without doubt whether the genes of Neanderthals are different or similar to ours"

It is possible to state without a doubt that 95%+ of our genetic material was identical with that of Neandertals. But then I can say just about the same thing about a the common brown rat. Consider this:
"The rat data shows about 40 percent of the modern mammalian genome derives from the last common mammalian ancestor."

source:
http://news-info.wustl.edu/news/page/normal/819.html

Which means that the difference between species, genetically, is actually rather small. Like other aspects of life ... it may be more about expression than content.

DA Morgan wrote:

"I find this statement a bit puzzling."

My point was that genes are actually much more complicated than just a single mutation on a DNA molecule. Most of what we call genes are the result of a whole series of interactions, not just a single mutation. Selection doesn't operate on genes anyway. It can only operate when a gene is expressed, usually this means on individuals with double recessive versions of a gene.

I did actually point out that we even share genes with fungi. I'm fully aware that we share something like 98% of our genes with chimpanzees so we are even more similar to Neanderthals.

Ellis. I have said elsewhere on SAGG (can't remeber where just now) that it probably takes at least three or four million years for two mammal species to develop incompatible genes. Modern human and Neanderthal mtDNA separated about half a million years ago. Therefore I'd be very surprised if hybrids were at any genetic disadvantage. Cultural perhaps.

Understood.

Thank you for being patient with me. I find this very interesting. It seems from recent research ( can't remember where I saw it---I told you I am not a scientist) that we share a considerable part of our genetic heritage with the higher primates and yet ( I assume) we cannot successfully interbreed with them can we? Therefore would it be expected that the Neanderthals would be not closer to us in genetic material than the higher primates? As otherwise would we not be finding considerably more of these apparent hybrids? We haven't, so is it reasonable to assume that either the offspring is sterile (horse and donkey model) or inter breeding is impossible under normal conditions ( mytholoogical chimera)?

Ellis wrote:

"I find this very interesting."

So do I. Of course we share a considerable part of our genetic heritage with the higher primates. However we separated from chimpanzees somewhere between 7.5 and 4 million years ago. I've mentioned elsewhere that research indicates the separation may have taken up all this time with periods of hybridization. We separated from other primates even longer ago. Evidence from mtDNA shows we separated from Neanderthals a mere half million years ago. therefore they are closer to us genetically than are other primates. The evidence from the chimp/human split (3.5 million years) along with information I've given elsewhere shows that half a million years is normally insufficient for two species to develop inter-species infertility.

As for lack of evidence for hybrids between modern humans and Neanderthals. Fossil evidence has certainly often been interpreted as showing formation of hybrids but I maintain there is a huge emotional pressure for most scientists to deny any possibility of hybrids. It fits their ideas of how species, especially the human species, form. I have also mentioned many times I believe these ideas spring from our ancient cultural beliefs.

No genetic evidence for hybrids has yet been found but there may be reasons for this other than that the two species were genetically unable to form hybrids. Perhaps hybrids were selected against but through cultural reasons rather than genetic.

Not surprisingly there is also fossil evidence for hybrids between Pekin man and modern humans as well as between Southeast Asian Homo erectus and modern humans. I am confident scientists will eventually find genes in the modern human population that developed in Europe more than 30,000 years ago. There is already evidence of genes in human populations in other parts of the world dating to more than 200,000 years ago, before mtEve. I've mentioned that elsewhere too, I think in a thread "out of Asia, not Africa" You may like to go back and check it out.

I hope you find all this as interesting as I do.