The alternative to thinking in evolutionary terms is not to think at all.

For a scientist must indeed be freely imaginative and yet skeptical, creative and yet a critic. There is a sense in which he must be free, but another in which his thought must be very preceisely regimented; there is poetry in science, but also a lot of bookkeeping.

If a scientist were to cut his ear off, no one would take it as evidence of a heightened sensibility.

Scientists who think science consists of unprejudiced data-gathering without speculation are merely cows grazing on the pasture of knowledge.

I reckon that for all the use it has been to science about four-fifths of my time has been wasted, and I believe this to be the common lot of people who are not merely playing follow-my-leader in research.

In no sense other than an utterly trivial one is reproduction the inverse of chemical disintegration. It is a misunderstanding of genetics to suppose that reproduction is only 'intended' to make facsimiles, for parasexual processes of genetical exchange are to be found in the simplest living things.

Today the world changes so quickly that in growing up we take leave not just of youth but of the world we were young in.