Neandertal Gene Study Reveals Early Split With Humans

[Orstio]

http://news.nationalgeographic.com/news/2006/10/061026-neanderthals.html

A new genetic study bolsters theories of an early human-Neandertal split and is helping scientists pinpoint what makes humans unique.

Controversy has long swirled in the scientific community over how closely the hairy Eurasian hunters resembled modern humans, with some researchers even claiming Neandertals (often spelled Neanderthals) were actually members of our own species, Homo sapiens.

A new study by geneticist James Noonan at Lawrence Berkeley National Laboratory, however, reveals that modern humans and Neandertals' most recent common ancestor probably perished about 400,000 years ago.

The research was presented earlier this month at the American Society of Human Genetics conference in New Orleans, Louisiana

[Retrospector]

Here's a piece of research espousing a different view - that Neanderthals did interbreed with modern humans. An article from healthday.com:

http://www.healthday.com/view.cfm?id=535790

MONDAY, Oct. 30 (HealthDay News) -- There may be a little Neanderthal in all of us.

That's the conclusion of anthropologists who have re-examined 30,000-year-old fossilized bones from a Romanian cave -- bones that languished in a drawer since the 1950s.

According to the researchers, these early Homo sapien bones show anatomical features that could only have arisen if the adult female in question had Neanderthal ancestors as part of her lineage.

The findings may answer nagging questions: Did modern humans and Neanderthals interbreed on a significant scale? And were the Neanderthals exterminated about 28,000 years ago -- as some anthropologists contend -- or did they gradually assimilate into the gene pool of people living today?

"From my perspective, the replacement vs. continuity debate that raged through the 1990s is now dead," said the study's American co-author, Erik Trinkaus, a professor of anthropology at Washington University in St. Louis.

Trinkaus comes down firmly on the side of the assimilation theory.

"To me, what happened is that the Neanderthals were [genetically] absorbed into and overwhelmed by modern humans coming into Europe from Africa, and they disappeared through this absorption," Trinkaus said.

I don't know. I prefer to believe the evidence of molecules, particularly the mDNA, rather than that of comparative anatomy. Anyway the debate is far from over.

[Orstio]

One must be careful about statements regarding European homo sapiens and Neandertals mixing.  That particular argument has been used, in the past, to try to bring scientific merit to racial supremacy.

I guess we'll know for sure once the Neandertal DNA is sequenced.

http://www.sciencedaily.com/releases/2006/07/060720105836.htm

EDIT -- Just so you know, Retrospector, I was in no way insinuating that you were thinking down those lines; I just wanted to make it clear that there are those with motives behind this particular research.

[Retrospector]

Yes Orstio, I understand completely. That article caught my eye yesterday and, reading it, I realized that not everyone in the field is sold on the idea of tracing the descent of humankind by molecular biology. I thought of this thread and decided it was an appropriate place to post the link.

At first glance to someone outside the field (like me), the principle of doing DNA analysis seems an objective approach as opposed to the subjective one of trying to interpret fossils. However I've learned that DNA analysis is not entirely devoid of interpretation, as there are generally multiple ways to construct genetic histories from the data. Still, while there are many possibilities, a good fraction of them can lead to basically similar conclusions. Some judgment appears necessary as to relative likelihoods.

But while DNA analysis has such issues, the idea of using the fossil record alone with all of its gaps and incomplete specimens is notoriously vulnerable to the personal biases of the researchers. The history of paleontological anthropology is fraught with examples of such biases affecting researchers' thinking - like everyone who fell for the Piltdown Man hoax. When it comes to the history of our own species, all of the emotional and political overtones can make true objectivity difficult. We are fortunate that DNA analysis offers another path for testing theories about our own evolution. Particularly now that analysis of DNA, both present and ancient from the cells' nuclei now appears possible.

And regarding the links you posted, I'm very impressed that DNA analysis has indeed advanced to the point where the people in the field are attempting to construct histories from nuclear, as opposed to mitochondrial DNA. That task is, needless to say, vastly more complex.

[remcook]

two papers came out today about the subject:

http://news.bbc.co.uk/1/hi/sci/tech/6146908.stm

[Orstio]

There are two things that bother me about this latest study:

http://www.sciam.com/article.cfm?chanID=sa003&articleID=ECC43BE1-E7F2-99DF-39AD691683DE05AD&ref=rss

The first step breaks the DNA apart. The pieces are then sequenced directly, and researchers reassemble them by mapping them to similar sections in the human genome.

The methodology in that will undoubtedly reveal that Neandertals are (not) surprisingly similar to humans.  I wonder what happens if you use the same method with baboon DNA?

And, my second problem:

http://www.geotimes.org/current/WebExtra111506_2.html

The bone itself is "rather small and uninteresting," says Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology, and part of the team publishing in Nature. But the bone's insignificance was "fortunate," he says, as it had been "thrown in a big box and not handled much by humans."

So, out of a big box full of uninteresting bones found in a cave in Croatia, we assume that this one came from a Neandertal, and not a homo sapiens?  Or, possibly another animal?

[remcook]

more neanderthal news...

http://news.bbc.co.uk/1/hi/sci/tech/6209554.stm

[Retrospector]

I don't have a link at the moment but I recall scientific speculation associating prion diseases of the nervous system such a Mad Cow disease with the occurrence of cannibalism within a species.

[remcook]

yes, I remember seeing that on TV. Apparantly cannibals in Papua New Guinea (I think) had a huge amount of BSE cases. They thought that the recent mad cow decease outbreak was caused by mixing grounded cow-bones into their food. Something along those lines anyway.

[Orstio]

Apparantly cannibals in Papua New Guinea (I think) had a huge amount of BSE cases.

I think you mean C-J disease, not BSE, Rem. 

[remcook]

that one

[Retrospector]

It's a confusing situation, actually, with the probable transmission of this class of diseases between species and all of the mixing of terminology that occurs in the popular press reports.

But anyway, it's my impression from those press reports that the susceptibility of a species such as ours to prion mediated diseases may be linked not just to cannibalism in the present, but possible long term cannibalism practiced by its ancestors. If Neandertals did it, perhaps the contemporary Cro-Magnons did it too?

I really need to find a link...