April 9, 1970

Mrs. Jula6 Lederrr
10043 Baks Shore Plass
Chicago, fllinols 60611

Dear Eppie:

The question you mention in your letter about the posaibilitiss of having
cblldrsn blacker than either parent has come up agein and again in tsy am
teaching career.  ff there is a rssurpnce of interest in it I hope it is
based on cmstructive curiosity, folloving upou recent relaxations of tabus
about interracial marriage - that may be too optimiuticl

Let me try to fill you in, although I rrllp would prefer uot to have sny         0
diret attributiou siuee that may cumvey en undue muse of authority about
my answer, or any awwur that could be quoted in a feu vords.  It fs one of     =I
those situations vhsre a little knovldgc might do very considerable mischief.     2i
Were I to be asked about the expectations ii&m the kind of mtiug you describe,
I! think I could wry reasonably reassure a couple that their chlldreu would     q
"almost certainly" be IU) darker than the darker psreut. Ou the other hand,     2%
this is 01~ area where oar rigorous scientifbc infomstion is pauch thiuuer than
you probably imagine, and &h&m is plenty of room for new discovery.  ft would
be exceptional for the child to be darker than I have indicated, but I cer-
tainly do not believe it would be real grounds for suspecting his paterulty.
PigPrentaelon is the lust character in the uorld thst me could rely upon for
making any crucial genetic judgmeuts.  There are apay other fsetors, for
example the blood groups, vhich would be much more reliable.

To give a possibly extreme eamtple of aa exception to the usual rule, it
would be predicted that the mating of a Caucasian with a Negro vho happeued
to be carrying the mutant factor for albino would certainly result In darker
offsprlug.  The generally accepted rule is, however, that children will have
a level of pfgmeutatfon roughly fntermediate betweeu that of their parents.

I m enclosing a couple of paw from Curt Stern*& textbook that you cer-
tainly could use as an authority for anything you tish to say about the subject.

Sincerely your8,

Joshua Lederberg
Professor of G6u6tics