A problem in genetics

Helen wrote:

Of course. That's the way modern contamination works. If the ancient DNA appears too similar to modern human DNA, then we suspect (but cannot prove) contamination with modern human DNA. If the ancient DNA differs significantly from modern human DNA, then we may infer that there has not been significant contamination by modern human DNA. It is just a fact that for this experiment, had the result shown great differences between ancient and modern DNA, then we would be more confident of the results than if (as apparently is the case) the two DNAs are very similar.

There's nothing remarkable about this. A similar problem occurs if the pregnant caucasian wife of a caucasian husband is suspected of adultery. Suppose that her child turns to have pronounced mixed racial characteristics. We can, without more, fairly reliably say that she has been unfaithful to her husband, and that her correspondent is a member of a non-caucasian group. Had the child turned out to be caucasian, on the other hand, we could draw no conclusions without more as to whether she was an adulteress.

Yes, finding different DNA is significant. Finding similar DNA is not necessarily so.

Also remember that if different DNA is found it is possible to tell not only the fact of the differences, but also their nature.

 

Helen,

Instead of bringing up new areas of argument, how about responding to my criticism of the material posted on your web site about the assumptions of C-14 dating. Either you should accept my criticism as being correct or you should point out the flaw in my critique. Perhaps you think that the best way out of a bad situation is to say nothing?

 

The point is that these gentlemen are the latest victims of the quotemining game. Here's what they said, in context:

"You report views that the DNA of Cro-Magnons can be studied only if they were different from us. If they had the bad luck to be like us, their sequences must remain unknown forever.

That is an unusual way to conceive science, and one that leads to paradox. If we are to apply this criterion of certainty to other areas, we should have abandoned anaesthesia (it may have side effects), air transportation (planes can fall down), cooked food (it may burn your fingers) and sexual reproduction (you might get AIDS)."

In other words, they are pointing out the opposite of what your quotes suggests. They are saying that the assertions of some of their critics make no sense, including the one you cited here.

 

The part you showed us here was quite sufficient and not misleading at all. It was only your second, more restrictive cut that made it appear that they believed something they didn't.

Barbujani and Bertorelle were very emphatic about it:

(writing of their critics' argument)

"That is an unusual way to conceive science, and one that leads to paradox. If we are to apply this criterion of certainty to other areas, we should have abandoned anaesthesia (it may have side effects), air transportation (planes can fall down), cooked food (it may burn your fingers) and sexual reproduction (you might get AIDS).

If it can be shown that there is an error in our paper, we shall be happy to reconsider our conclusions. Should our results be confirmed, we will be even happier. But if we did all the right things, as seems to be the case so far, it seems irrational to question our study just because one never knows."

I don't think there's much doubt about their opinion. And it's precisely the opposite of what that snippet seems to suggest.

 

I trust that you included enough of the context to give us a good idea of what they meant. Obviously, from their words to their critics, they thought the criticism was indefensible. Do you agree?

If not, what do you think they meant?

 

Helen, quoting the study authors:

Yeah, it's the kind of argument that goes on about contamination of all sorts all the time in science. Of course the authors did what they could (nine tests) to see if there was contamination with modern DNA. Are they enough? Are the tests reliable? How would one tell? The present study's results might suggest that the Cro Magnon DNA was in fact closer to modern human DNA than previously thought, or that the nine methods used to detect modern DNA contaminationation are insufficient. Which hypothesis is right? I do not knowThat will be the subject of future research I'm sure! And that's what's supposed to happen in science.

Put simply, we have hypothesis A that Cro Magnon man is "old" (for our purposes that will suffice). Hypothesis B is that the nine tests employed are sufficient to eliminate with high confidence the possibility of contamination by modern human DNA. Both A and B were thought to be likely prior to the experiment. But then the authors examined some DNA from Cro Magnon samples and found that it resembled modern human DNA. This is incompatible with the combined hypothesis (A and B). So either A or B must be false. Which one? We do not know. The authors prefer to maintain A and reject B Some critics prefer the reverse. Who is right? We don't know, but future research is indicated to try to test hypotheses A and B separately.

 

One thing is for sure. I bet that any additional research that is published will not be published by creationists, since they have virtually no research going on.