Joshua Lederberg was awarded a Nobel Prize in Medicine in 1958. Prior to winning the prestigious award, he had served as Professor of Genetics at the University of Wisconsin. He was also the Chairman of the Dept. of Medical Genetics, a department which he had organized in 1957. Professor Lederberg has graciously allowed C.U.D.D.L.E. to reprint the following:

Should Cousins Marry?

(c) Joshua Lederberg
from letter to Ann Landers
November 7, 1977
Reprinted with permission

 For the sake of this note, we are not going into questions  like 'Should anyone marry, and worsen the population problem', or 'Is  it better to marry than to burn?' Any couple that is contemplating  marriage needs to confront a whole range of pressing questions, and we  hope that whether cousins or not, a couple will be asking them with  great seriousness, deliberation and hope.

In addition to all of those, cousins inherently do face additional challenges that come out of their prior family relationships, and these special ones are the only ones that will be faced here.

Two things come to mind: the issues that arise from family  tradition, and those from genetic or biological relatedness. I do not know of any factual data on the success or failure of marriages as a
function of the common traditions of the mates. Commonsense would say that large differences in economic, social, religious outlook may be sources of misunderstandings in the later married life of a couple; and as cousins are more likely than the average to share these things they may be relatively free of those burdens. Commonsense also suggests that mates may become bored if there are no differences; but even cousins are likely to have different life experiences and perspectives. There is
some danger that cousin-marriages have been arranged to suit the convenience of others; but even here there is little factual evidence on how this affects the outcome. Obviously such matters will vary enormously with the immediate cultural background that the couple brings into the marriage, and the setting of their future life.

The more obvious questions are "What about the children?", and "Is there a social interest in discouraging such marriages on account of the possible hazards to the genetic quality of the population?" There are so many taboos about close marriages in many cultures and religious faiths,
and in some state laws, that it is obvious many people harbor these questions.

First, it should be stressed that inbreeding does not in any way generate "bad genes", that is genetic factors that may cause disease or impair the functioning of the child. This is a superstition that has
grown over the centuries, from the observation that inbreeding tends to expose the genetic defects already carried by almost every individual of the species. These defects are the legacy of evolution, the mutations without which higher organisms and human beings could never have emerged out of the primeval ooze, millions and billions of years ago.

The exposure of previous mutations is not to be taken lightly: everyone of us is carrying 2 or 3 "bad genes" in a masked condition, in a way that only only be revealed by the bad luck of meeting a partner with a similar defect. In practical terms, first cousins who marry have to face the fact that they will have about twice the risks of bad luck with the genetic dice as do unrelated partners when they have children. It has to be said that women who have children after age 35, or couples who have
children knowing that there are definite hereditary problems in their ancestry are taking similarly increased risks. Whether cousins should marry (and have children) in the face of these concerns is an ethical problem they alone must answer.  However, the risks of disaster are greatly increased for cousins who are also carriers of known genetic diseases: they may be increasing the odds of a bad result from less than 1:100 (the general average) to over 1:4.  For that reason, the least advice
that should be pressed on cousin-mates, before they have children, is to visit a genetic counselor and get informed advice about their own specific situation, rather than try to play the odds that apply to the whole average population.

 Joshua Lederberg