How was DNA used to indicate paternity with the Jefferson-Hemings
A retired professor of pathology at Tufts University and the University of
Virginia, he designed and carried out the DNA testing that confirmed Thomas
Jefferson fathered at least one of Sally Hemings's children.
We had to use Y-chromosomal DNA exclusively, because the Y-chromosomal DNA is
passed unchanged from generation to generation, from father to son only. The
rest of a person's DNA is diluted by at least half with every generation.
So we looked at the Y chromosome of male members of the Jefferson family. The
reason we had to look at members of the Jefferson family was that Thomas
Jefferson himself did not have any male line of descent. So we actually looked
at the descendants of one of his paternal uncles, Field Jefferson. We found
that, of the five people in this line, they all had the same Y-chromosomal
type, which meant that we had identified the Jefferson family chromosome.
That does not say that it belonged to Thomas Jefferson. But it was the only
way that we could get at the Jefferson family; Jefferson lacked a male line of
descent. . . . We were able to establish what the Jefferson family Y
chromosome was. In conjunction with historical evidence, that piece of
evidence could be used to arrive at an opinion as to whether Thomas Jefferson
was the father of the various people in dispute.
Who is the male descendant of Eston Hemings, whom you have
John Weeks Jefferson.
Does that suggest all other descendants from Eston Hemings are
Well, in a biological way, it would suggest that they are, but it certainly
doesn't prove it. For one thing, there's always a question in any large family
over many generations of adoption that has not been reported, and of
illegitimacy. So from a biological standpoint, one couldn't say that all other
descendants from Eston Hemings are placeable.
We're aware of only three male line descendants of Eston Hemings living in the
world at this time. We have been unable to test the other two. We just
haven't had access to them.
But the fact that you tested one . . .
That's highly significant. Now, if he had been negative, it would not have
been as significant. This whole question of illegitimacy would have been
raised. Then we'd have a strong need to look at least one of the other people
to see if he perhaps matched with Jefferson or with the Jefferson family, or
matched with the first person who didn't match with the Jefferson. But since we
did get a positive result, we really don't need another one.
Have you done this same test with his brother Madison Hemings's
We haven't been able to find a male line descendant. Not one. We're hoping
for someone to come forward. There don't seem to be very good prospects of
that, because two of his sons were known to have died without any descendants.
The third son disappeared into the West in the early part of the twentieth
It's conceivable that he might have some male-line descendant. But so far,
nobody has been identified.
What about the other male line which believes it's descended from Jefferson
and Hemings--the Woodson family?
We tested five men who were descended from two of Thomas Woodson's sons. They
were descendants of James Woodson and Lewis Woodson. Four of those five
matched exactly with each other. One didn't even look at all like it. We
interpret that as meaning that, somewhere along the line, there was either
adoption or illegitimacy. So we're confident that we have the Y chromosome of
that male line.
Now we are in the process of looking at one more Woodson, who is a descendant
of William Woodson, a third son, on the outside chance that it might match with
the Jefferson or might not match with these other two. We do think it's
How did you first get involved in tracking Jefferson's bloodline?
It really was an accident. Several years ago, a friend wondered if DNA might
be used to solve the Jefferson/Hemings controversy. Was Thomas Jefferson the
father of any, or all, of his slave children by slave Sally Hemings? This is
stuff that has not been resolved by historical research for years and years,
and it's a great controversy. So my friend got the idea that maybe DNA could
be used for this purpose. Other people have had the idea, but nothing had been
done about it, which should have been a clue that it was not possible.
At any rate, I got a little interested in it. After reading about it for a
year, I concluded that it was probably not possible. At that point, the local
press found out our general interest in this, published an article in the local
paper, and interviewed various experts who also said yes, this was close to
impossible or flatly impossible.
But then I got a call from an old acquaintance, a professor of biology,
Professor Ralph Benzinger at the University of Virginia, who said, "The experts
don't know what I know. There has been recent work done with the Y chromosome
that makes the DNA ideal for your project. You ought to look it up."
The experts and I had thought that, after five, six or seven generations, the
DNA of the person who you're interested in. . . would be diluted so much that
you can hardly find any. In other words, in each generation, a parent passes
on only half or less of his or her DNA to the children, so with each
generation, it begins to disappear. So even if we knew what was specifically
characteristic of Thomas Jefferson's DNA, we would have very little chance of
finding it in people who are his descendants or think they're his
And then the whole thing was complicated because of other family relationships,
like the fact that Sally Hemings and Thomas Jefferson's wife probably had the
same father. The Carr brothers, who were also implicated in this affair, had
ancestors common with the Jeffersons, and so forth. So it was just going to be
. . . But the Y chromosome is something that is passed. It's the chromosome
that determines whether you are a man. So a man has the Y chromosome and an X
chromosome and the woman has two X chromosomes. The beauty of that is, since
you only have one Y chromosome and it's gotten only from your father, that
means it isn't diluted. It goes from generation to generation, father to son,
unchanged. No one had thought of using it for these purposes, because it had
not been thought to have enough variation.
What we needed to do was to find the living descendants of paternal relatives
of Thomas Jefferson. What we found were descendants of his father's brother,
his paternal uncle, a man named Field Jefferson.
Field Jefferson's Y chromosome should have been the same as Thomas Jefferson's,
and the Y chromosome of all of his male-line descendants should also have been
the same as Thomas Jefferson's. So if we could find two or more of these
descendants who had the same Y chromosome, we could pretty well be quite sure
that this was the same as Thomas Jefferson's. And then we could compare it
with various other people who thought they were descendants of Thomas
Jefferson, such as the Woodsons and some other people.
What are the odds? What is its reliability?
We don't know exactly how reliable it is. Theoretically, we think that it's
probably that there is not a single marker. It's something like a fingerprint,
but not quite as complex. There are about 19 different markers, each of which
varies. The chances that the Y chromosome in one family is the same as in
another family is probably in the neighborhood between one in a hundred and one
in a thousand. So it's possible.
For instance, if we identify the Y chromosome of the Jefferson family . . . and
then we find it in some other person who thinks he is also a Jefferson, there
is a one-in-a-hundred to one-in-a-thousand chance that he just has it by
chance, and it has nothing to do with Jefferson. But that kind of probability
is the most we can ask for in most scientific endeavors.
. . . But there are still theoretical ways that you can look at it. That's why
we get at this number of one through a hundred or one in a hundred or one in a
thousand. There is not enough variation in the Y chromosome to make it like a
There is no doubt that there will be other families in the world--and we don't
know how many--who will have the same Y chromosome as the Jefferson family. We
just don't know that yet. We may know it eventually. . . . But the number one
in a hundred is the usual standard of scientific validity. . . .
I think it would be possible, but highly, highly, highly, highly improbable
that John Weeks Jefferson is not a descendent of Thomas Jefferson.
Did you have any particular interest in Jefferson?
. . . I had no more than average interest in Thomas Jefferson than most
residents of Charlottesville did. Now, people in Charlottesville have a little
more interest in Thomas Jefferson than people in general. Everything is named
Jefferson, and there's the university and so forth. I was a little interested
in him. As Joe Ellis has pointed out in his book, every American seems to have
a stake in Thomas Jefferson.
I say that Thomas Jefferson and his writings are sort of like the Bible. You
can find whatever you want in it, and that is what makes him such a popular
figure in the American line. . . . I had no particular interest in the
Jefferson/Hemings controversy. I looked at it with the usual skepticism I look
at almost everything with and say, "Yes, it's possible. I have no idea. It's
certainly not impossible. And I don't really care." So I think that's about
where I was.
How did you go about contacting descendants of Hemings, and what was
With the help of a lot of people, I identified which ones I needed to get blood
from. Then I composed a letter, which I put on a nice letterhead. I sent it to
all these people, explaining to them in lay terms what the study was about, and
why I wanted to get some of their blood, and the fact that I wanted to get some
of their blood.
One of the people responded immediately and he was one of the Field Jefferson
descendants, and that he'd be honored to participate in the study, so no
persuasion was required. But then I got no answers at all. So I called
Herbert Barger, who had given me the names of the Field Jefferson descendants.
I started with them because if I didn't have them, I wouldn't have anything.
There'd be no use to try to find anyone else. I told Herbert that I had not
gotten any replies. He said, "I'll call them and see what we can do."
A couple of days later, he said, "If you will telephone them, I think that
you'll get some positive responses." So I began to telephone these people. As
soon as I called them they said, "Oh, sure, you can come and take my blood
anytime you want." And so there was no persuasion involved in almost every
. . . I thought it was remarkable that so many people on all sides of the
controversy just wanted to participate. They really wanted to. I don't think
I talked anybody into it.
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