All interpretation or observation of reality is necessarily fiction. In this case, the problem is that man is a moral animal abandoned in an amoral universe and condemned to a finite existence with no other purpose than to perpetuate the natural cycle of the species. It is impossible to survive in a prolonged state of reality, at least for a human being. We spend a good part of our lives dreaming, especially when we're awake. As I said, pure biology.

— Carlos Ruiz Zafón

All life evolves by the differential survival of replicating entities

— Richard Dawkins

All of today's DNA, strung through all the cells of the earth, is simply an extension and elaboration of [the] first molecule.

— Lewis Thomas

All organisms vary. It is in the highest degree improbable that any given variety should have exactly the same relations to surrounding conditions as the parent stock. In that case it is either better fitted (when the variation may be called useful), or worse fitted, to cope with them. If better, it will tend to supplant the parent stock; if worse, it will tend to be extinguished by the parent stock. If (as it is hardly conceivable) the new variety is so perfectly adapted to the conditions that no improvement upon it is possible, —it will persist, because, though it does not cease to vary, the varieties will be inferior to itself. If, as it is more probable, the new variety is by no means perfectly adapted to its conditions, but only fairly well adapted to them, it will persist, so long as none of the varieties which it throws off are better adapted than itself. On the other hand, as soon as it varies in a useful way, i.e. when the variation is such as to adapt it more perfectly to its conditions, the fresh variety will tend to supplant the former.

— Thomas Henry Huxley

All our sentiments - religious, romantic or any other - are born in the neurons.

— Abhijit Naskar

All social animals, including people, live under constant pressure from two competing interests: protecting themselves from others and aligning themselves with others. When these two interests are balanced, the result is dynamic social homeostasis.

— Mystery

All the more recent work on alkaptonuria has... strengthened the belief that the homogentisic acid excreted is derived from tyrosine, but why alkaptonuric individuals pass the benzene ring of their tyrosine unbroken and how and where the peculiar chemical change from tyrosine to homogentisic acid is brought about, remain unsolved problems.

— Archibald E. Garrod

All the so-called philosophical notion of “love without attachment” or “detached love” are biologically non-existent on this planet. We humans are biologically designed through millions of years of evolution to grow attachment. Love cannot survive without attachment.

— Abhijit Naskar

Amidst the vicissitudes of the earth's surface, species cannot be immortal, but must perish, one after another, like the individuals which compose them. There is no possibility of escaping from this conclusion.

— Charles Lyell

Among all the occurrences possible in the universe the a priori probability of any particular one of them verges upon zero. Yet the universe exists; particular events must take place in it, the probability of which (before the event) was infinitesimal. At the present time we have no legitimate grounds for either asserting or denying that life got off to but a single start on earth, and that, as a consequence, before it appeared its chances of occurring were next to nil. ... Destiny is written concurrently with the event, not prior to it... The universe was not pregnant with life nor the biosphere with man. Our number came up in the Monte Carlo game. Is it surprising that, like the person who has just made a million at the casino, we should feel strange and a little unreal?

— Jacques Monod