J. B. S. HALDANE 
be about the time needed for the appearance of a new mam- 
malian species. Even so our descendants would look pretty 
queer chaps to us, and behave even more queerly. Their 
activities will be particularly hard to classify. The same activity 
of a group in contemporary cultures may have analogies with 
ballet, religion, sport, experimental physiology, mathematics, 
and even magic. Some of this syncretism would be more easily 
understood in India than in Europe or America today; and 
perhaps if most of the bricks of the unified science of the future 
are of European origin, India and China will have provided the 
mortar which holds them together into a coherent system. 
My prediction that our descendants will be more interested 
in their own biology than we are, and have far more knowledge 
and control of it, will be criticized. If more visceral sensations 
will prolong our lives, some will ask, why has not natural selec- 
tion favoured their increase? As long as the main causes of 
early death were famine and violence, survival was best secured 
by attending to the external world. With agriculture and 
urbanization, infection became an important killer. But again 
the danger was from outside. Further, without a fair knowledge 
of anatomy and physiology introspection is rather dangerous 
unless, as in yoga, it is elaborately controlled. Such intro- 
spection can have very satisfactory by-products. Thus it is 
possible to cease to find moderate pain unpleasant. On two 
occasions I have walked about for a week or more with a 
fractured malleolus and a fractured metatarsus, which were 
not diagnosed because I kept on walking. I suspect that pain 
is a word which we apply to all sorts of sensations which we 
cannot adequately classify. Ifthey become interesting they may 
cease to be unpleasant. Having undergone really intense thirst 
experimentally, I feel thirst far less than most Indians in hot 
weather. I have good evidence that others can achieve this 
state in the same way, as of course they can through religious 
or magical practices. It will be vastly easier when we achieve a 
nomenclature for our bodily sensations, which we shall only do 
by provoking them under carefully controlled conditions. 
Similarly by understanding and intellectualizing their sensual 
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