Eugenics and Genetics 
want to stress is that if we can find the right method of exerting 
selective pressure, we could make for human genetic improve- 
ment. We must do it by way of experiment. 
Dr. Trowell talked about breeding for efficiency. This is very 
important because, as psychosocial organizations get more and 
more complicated, we need more and more good brains at 
the top to run them. If you assume as a first approximation 
that intellectual efficiency or intelligence has a strong genetic 
component, and that it is distributed according to the ordinary 
type of symmetrical frequency curve, you can calculate that a 
very small increase in the mean will produce a large percentage 
increase in the upper values; so far as I remember, if you could 
raise mean I.Q. from 100 to 101-5 you would raise the per- 
centage of people with an I.Q. of 160 and over by nearly 50 
per cent. The increased social and cultural efficiency resulting 
from a small difference in the number of outstandingly gifted 
people is also very important in considering the problem of 
possible racial differences. 
Lederberg: The converse of Huxley’s calculation is that in 
order to shift the mean I.Q. by 1-5/100 you must increase the 
production of geniuses by 50 per cent. It is perhaps better to 
aim at just increasing the variance. The question is not whether 
we should think about doing eugenics; we certainly should, and 
should collect just as much information as possible. The point 
is whether we should embark on a concrete programme that is 
very costly in social and political stresses for an aim which 
isn’t very well crystallized yet. 
Huxley: I think most people would agree that even if we 
cannot yet carry out a eugenic programme, we can begin doing 
something about controlling the quantity of population. The 
experience we gain in this field will help us to deal with eugenic 
problems later. 
MacKay: I agree with Crick about the “weakness” of 
saying that the system is probably working as well as it can now; 
but is it any less logically ‘‘weak”’ to say “‘maybe this and that 
remedy will be better’? A good example is this question of 
increasing I.Q. Is it obvious that the psychosocial structure, 
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