'These changes in the body,' he wrote in the review paper he sent to the American Journal of Physiology late in 1913, 'are, each one of them, directly serviceable in making the organism more efficient in the struggle which fear or rage or pain may involve; for fear and rage are organic preparations for action, and pain is the most powerful known stimulus to supreme exertion. The organism which with the aid of increased adrenal secretion can best muster its energies, can best call forth sugar to supply the labouring muscles, can best lessen fatigue, and can best send blood to the parts essential in the run or the fight for life, is most likely to survive. Such, according to the view here propounded, is the function of the adrenal medulla at times of great emergency.'

Clarke's Law of Evolution: It has yet to be proven that intelligence has any survival value.

Five per cent vision is better than no vision at all. Five per cent hearing is better than no hearing at all. Five per cent flight efficiency is better than no flight at all. It is thoroughly believable that every organ or apparatus that we actually see is the product of a smooth trajectory through animal space, a trajectory in which every intermediate stage assisted survival and reproduction.
[Rebutting the Creationist assertion that fully developed organs could not have arisen 'by chance.']

Intelligence is a valuable thing, but it is not usually the key to survival. Sheer fecundity ... usually counts. The intelligent gorilla doesn't do as well as the less intelligent but more-fecund rat, which doesn't do as well as the still-less-intelligent but still-more-fecund cockroach, which doesn't do as well as the minimally-intelligent but maximally-fecund bacterium.

Man is an animal with primary instincts of survival. Consequently his ingenuity has developed first and his soul afterwards. The progress of science is far ahead of man's ethical behavior.

Might one not say that in the chance combination of nature's production, since only those endowed with certain relations of suitability could survive, it is no cause for wonder that this suitability is found in all species that exist today? Chance, one might say, produced an innumerable multitude of individuals; a small number turned out to be constructed in such fashion that the parts of the animal could satisfy its needs; in another, infinitely greater number, there was neither suitability nor order: all of the later have perished; animals without a mouth could not live, others lacking organs for reproduction could not perpetuate themselves: the only ones to have remained are those in which were found order and suitability; and these species, which we see today, are only the smallest part of what blind fate produced.

No species … possesses a purpose beyond the imperatives created by genetic history … The human mind is a device for survival and reproduction, and reason is just one of its various techniques.

Our survival, the future of our civilization, possibly the existence of mankind, depends on American leadership

Species do not grow more perfect: the weaker dominate the strong, again and again— the reason being that they are the great majority, and they are also cleverer. Darwin forgot the mind (—that is English!): the weak possess more mind. ... To acquire mind, one must need mind—one loses it when one no longer needs it.
[Criticism of Darwin's Origin of Species.]

Species do not evolve towards perfection: the weak always prevail over the strong—simply because they are the majority, and because they are also the more crafty. Darwin forgot the intellect (that is English!), the weak have more intellect. In order to acquire intellect, one must be in need of it. One loses it when one no longer needs it.
[Criticism of Darwin's Origin of Species.]

The admirable perfection of the adaptations of organisms and of their parts to the functions they perform has detracted attention from the fact that adaptedness does not consist of perfect fit, but capacity to fit or to adapt in a variety of ways: only in this sense is adaptedness a guarantee of further survival and evolutionary progress, for too perfect a fit is fatal to the species if not to the individual. This, I think, sets phylogeny and ontogeny in the correct perspective. It is the genotype which bears the marks of past experience of the species and defines the range of possible fits. What fit is actually chosen, what phenotype is actually evolved, is determined by the ever renewed individual history.

The species does not grow in perfection: the weak again and again get the upper hand of the strong,—and their large number and their greater cunning are the cause of it. Darwin forgot the intellect (that was English!); the weak have more intellect. ... One must need intellect in order to acquire it; one loses it when it is no longer necessary.
[Criticism of Darwin's Origin of Species.]

We are survival machines, robot vehicles blindly programmed to preserve the selfish molecules known as genes. This is a truth which still with astonishment.

We are survival machines—robot vehicles blindly programmed to preserve the selfish molecules known as genes. This is a truth which still fills me with astonishment.