DISCUSSION 
Catholics. What frightens me about Muller and to some extent 
Huxley is their extreme self-confidence, their complete convic- 
tion not only that they know what ends are desirable but also 
that they know how to achieve them. I can perhaps imagine 
approving of the kind of scheme Muller has outlined if he put 
it this way: “‘we don’t really know a great deal about human 
inheritance but with the co-operation of a number of volunteers 
let us put my scheme into practice and perhaps we shall learn 
from it”’. 
Huxley: But surely Muller’s point, and certainly mine, is 
not to think in terms of any definite eugenic ideal; the aim that 
I have in mind is the very general one of gradual improvement. 
Medawar: But you don’t know how to do it! May I 
challenge you to explain Evelyn Hutchinson’s paradox about 
homosexuality? The proportion of homosexuals has probably 
not declined over the period of recorded history; yet according 
to all selection theories which we are so confident about, the 
proportion should have declined on the reasonable grounds (a) 
that homosexual tendencies are to some extent genetically 
determined and (b) that homosexuals are on the whole less 
fertile (even if fractionally less fertile) than normal people. It 
follows that the genetic endowments that make for homo- 
sexuality or parasexuality in general should have declined. In 
fact they have done nothing of the kind. This means either 
that so deep-seated a trait as parasexuality or homosexuality is 
not genetically determined or that we don’t really understand 
the mechanism of its inheritance. 
Huxley: I didn’t know about this paradox, and am afraid I 
can’t answer that point. In any case I want to look at the 
problem from another angle. You say we must know more 
about the details of human genetics before we can think about 
improvement. I really don’t see why. Darwin knew nothing 
about the details of reproduction, still less about genetics, and 
yet he was able to deduce a set of principles and a general 
theory of evolutionary transformation which have stood up to 
the test of time. Our new knowledge is merely permitting us to 
fill in the details and add a few minor modifications. What I 
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