So we have analyses of mDNA from one (1) Neanderthal, and one (1) Cro-Magnon. The CM’s is like our own, and the N’s isn’t.

Remeber, though, this is mDNA. It doesn’t get mixed the way normal DNS does. Absent mutations, your mDNA is exactly the same as your mother’, and in any case it’s completely unrelated to your father’s except insofar as his was already related to your mother’s, that is, via common female ancestors.

45,000 years sound like a lot, but one wouldn’t expect many mDNA mutations in that time, so the fact that the CM’s is very similar to that known from modern humans is entirely unsurprising.

As for the rest - if two people have dissimilar mDNA, that doesn’t prove they’re unrelated: just that they do not have any (close) female ancestors.

So, given that we’re fairly (though by no means absolutely) certain that no modern human has mDNA similar to that Neanderthal, neither it nor any of it’s female ancestors, or descendants of those female ancestors, seem to have made it into modern humans. And none of it’s female ancestors were Cro-Magnons.

However, that’s still only one (1) Neanderthal. We currently have no way to know how similar Neanderthal mDNA usually was. (For that matter, we don’t know that about Cro-Magnons either, but the similarity to ours certainly suggests that the spread might have been similar, too.)

So … how about if M/CM hybrids were usually infertile, like mules? You’d still find first-generation exemplars, but no others.

I’m sure there are still more possibilities … among them, of course, the possibility that interbreeding really didn’t occur.

But it’s much too early to claim we know!

These two forms of humans occupied the same territories over a wide area of the Middle East and Europe–is it not possible that a sample taken elsewhere might indicate interbreeding?

Full disclosure: I have never studied DNA testing or methods, and don’t know how it is done. I would appreciate a ref. to a good introductory or intermediate text on the subject, esp. how to compare DNA samples.

The fundamental analytical problem is that we are trying to say, “there is nothing there.” This is a lot harder to prove than “there is something (Neanderthal DNA) there (in Cro-Magnon DNA).” If we must have a negative statement, then we should try to say, “there is no more than X there.” If you think only in terms of yes/no dichotomies, you will have trouble with the above. Sorry ’bout that.

IN the selected section of DNA that the researchers felt was clearly different between the groups:

What is the range (spread) of mitocondrial DNA measurements in Neanderthals, what number and over what geographic range do we have these samples?

How many Cro-Magnon samples did they get, and from what geographic range?

Now I can make a tentative hypothesis, that the selected DNA range is equal in both, and a statistical test will conclude that no, they are not ‘nearly identical’ but radically different. I would conclude from this that, _on average_ the two groups did not mix DNA.

Our question then becomes, “did a number of individuals come from intermixed prior generations?” To answer this, we must look at the ‘outliers’ in the samples - those who were closest to matching the other group. In other words, we need to know the number & spread, and even the distribution, of the Cro-Magnon group (and the Neanderthal group). If we have enough samples, can we see a skewing in the distribution, toward Neanderthal characteristics?

Now, if the measurement is that a characteristic (DNA sequence) is either ‘there’ or ‘not there,’ we have a dichotomy - yes or no. The statistical analysis must be different, and more complex. The fundamental logic will remain the same and the questions will be adjusted only slightly.

George, a commenter 7/31, says they need more DNA testing. Maybe, maybe not. Maybe they only need to explain the analysis in more depth. Perhaps more depth than George, or most other people, would put up with The Discover piece has not enough depth to say. It can’t.

Jay

George.