Appendix B: Opinions of Scientists Consulted

Report of the Research Committee
on Thomas Jefferson and Sally Hemings

Thomas Jefferson Foundation
January 2000

Appendix B: Opinions of Scientists Consulted

Dr. Kenneth K. Kidd, Professor of Genetics, Yale University, January 1999

"I have read and thought about the article quite a bit. First, there is nothing wrong with the science. The markers on the Y are well documented and most have been studied in several hundred men. The male to male transmission is about as basic in mammalian biology as you can get. All of the authors that I know personally (less than half of them) are very reputable and I trust them. So, the only 'controversy' that exists is over the interpretation.

"I think Eric Lander and Joseph Ellis in their News and Views commentary over-interpreted the results as proving that Jefferson was the father of Eston; I think the actual authors are more correct when they consider other explanations 'unlikely.' What the data do prove, beyond any reasonable doubt, is that Thomas Jefferson and H21, a descendant of Eston Hemings, had Y chromosomes that were identical by descent. The Y chromosome data do not prove that Thomas Jefferson himself was the ancestor of H21, but that is certainly one of the likely specific scenarios within the 'identical by descent' family of explanations.

"The term 'identical by descent' is standard population genetics terminology and means that the instances being considered, in this case the two Y chromosomes, Thomas Jefferson's and H21's, can be traced to a single common ancestral Y chromosome. That could be Thomas Jefferson's OR it could be an ancestor of Thomas Jefferson who was also an ancestor of H21. Obviously, the evidence favors Eston being the Great-Great Grandfather of H21 since there is no reason to question that lineage. Thus, the question becomes one of who Eston's father was. For example, J5, J12, J6, J13, and J14 look likely to have been alive and old enough to have fathered Eston and they have Y chromosomes identical by descent with Thomas Jefferson's. How many other male-line relatives of Thomas Jefferson were alive at that time? Did Thomas Jefferson II (Peter's and Field's father) have any brothers and/or any paternal uncles? One can go back this way to other male-line ancestors and then forward again among their male-line descendants to the relevant time. In sum, a male-line relative quite remotely related to President Thomas Jefferson would likely have the same Y chromosome as Jefferson. (For example, J41 and J49 are fifth cousins once removed and have the same Y chromosome.)

"The data do prove that Thomas Woodson was not the son of Thomas Jefferson or any close male-line relative of Jefferson. The Carr brothers are also excluded from being fathers of Eston or Thomas Woodson. Thus, as with modern day paternity testing, we can prove a man is/was not the father, but we cannot absolutely prove a man is/was the father.

"So, the proof ultimately rests on demonstrating that Thomas Jefferson was present at the time Eston was conceived and that no other male relative with the same Y chromosome was hiding in the bushes. This is something I have no knowledge of, but some of the people there at Monticello probably do know a lot in this area of history. Obviously, this can all get very sensitive if people get emotionally or personally involved. I personally think the simplest answer is that Jefferson was the father of Eston. He may have been the father of all of Sally Hemings's children except Thomas Woodson, and she may have thought that Jefferson was the father of Thomas Woodson as well.

"A comment about the statistics. There is fair uncertainty in the exact numbers that should be used because it is very difficult to estimate accurately a small number. But, it is clear that the specific Y chromosome pattern is rare--it was not seen elsewhere in a sample of over 600 European men. Thus, the authors are right when they say these results for H21 are at least 100 times more likely if Thomas Jefferson is Eston's father than if someone unrelated [to Jefferson] was the father. As noted above, however, that statement says 'unrelated' and J5, J6, etc. are all related. It is also correct to say 'these results for H21 are at least 100 times more likely if Thomas Jefferson's cousin J5 [or J6 or J12 or ...] is Eston's father than if someone unrelated [to the Jeffersons] was the father.'

"One final comment. I notice that the pattern for the Woodson descendants is very similar to the pattern for the Carrs. It would not take many mutations to convert one into the other. That makes it possible that John Carr and Thomas Woodson had fathers who were male-line relatives within a few generations. That could just mean that their fathers came from the same town or county back in Europe since I do not know how common these particular allelic combinations are in Europe (England?)."

Dr. Mark E. Lovell, Director of the Molecular Biology Laboratory, University of Virginia School of Medicine, January 1999

Dr. Lovell felt that the tests were proper in all aspects. The specimens were collected and stored properly prior to the DNA extraction. They were randomly labeled and Dr. Foster was the only person with the identity code. Dr. Lovell's lab extracted the DNA and refrigerated the specimens in a locked refrigerator until Dr. Foster collected them to take to England. Three separate laboratories performed three separate and distinct marker identifications. When asked if the tests should be repeated by another independent investigator, Dr. Lovell said, "Probably not." He said if anybody were trying to skew the results, he would have a much harder time making a match occur than to make a mismatch occur. The use of three labs and the almost identical results would tend to discourage other testing. When asked if he would do anything differently if he had been conducting the study, he said that he would not change the methodology, but would have had "witnessed" collections.

Dr. David Page, Associate Director, Whitehead Institute, MIT Center for Genome Research, December 1998

Dr. Page expressed no concerns about the basic design of the study and said that the labs that did the work are very reputable in Y-chromosome studies. He has full confidence in their technical competence. He said that if he has any concerns about the study, they would have to do with "bookkeeping" and the interpretation of results.

Basically, "bookkeeping" is worrying about a mistake, such as mixing up the test tubes, that could have led to the significant match. He would feel better if blood was redrawn from the Eston Hemings descendant and retyped.

Dr. Page felt that more thought and attention could be paid to the "competing hypotheses" in interpreting the results. He pointed out that, in these kinds of studies, "non-paternity" is a big problem, that it is observed (at least in the past fifty years or so) 10 percent of the time, that it makes for background "noise," and that, in a case like this involving many generations, the non-paternity problem only increases. He called it "historical degradation." He noted that this is more of a problem in the case of a non-match, as with the Woodsons and Carrs, making the interpretation of these non-matches more ambiguous.

He also wished more was known about "the local population structure around Monticello two hundred years ago," as respects the Y chromosome. He would ask to what degree has the potential that it was somebody else's gene been sampled.

Dr. Page stressed that there is a low probability that any of these possibilities represent true problems, but rather that they are the areas for which he might wish for more data, to shore up the authors' favored conclusions.

Dr. Bruce Stillman, Director, Cold Spring Harbor Laboratory, February 1999

Mr. Stillman said that there was nothing exceptional in the methodology of the study. Scientists at Cold Spring Harbor know and respect the people who undertook the analysis. They feel the DNA study does not merit a scholarly conference since the science involved was so routine.


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