Quotes from book
The Causes of Evolution

Name: The Causes of Evolution
Author: J. B. S. Haldane

The Causes of Evolution is a 1932 book on evolution by J.B.S. Haldane , based on a series of January 1931 lectures entitled "A Re-examination of Darwinism". It was influential in the founding of population genetics and the modern synthesis.

“The change from one stable equilibrium to the other may take place as the result of the isolation of a small unrepresentative group of the population, a temporary change in the environment which alters the relative viability of different types, or in several other ways…”

J. B. S. Haldane book The Causes of Evolution

Source: The Causes of Evolution (1932), Ch. IV Natural Selection, p. 102.

“While the geneticists were disproving many of Darwin's ideas, the palaeontologists were determining the actual historical facts of evolution. …they were able to verify the law of succession, first explicitly given by Darwin's colleague Wallace. "Every species has come into existence coincident, both in time and space, with a pre-existing closely allied species."”

J. B. S. Haldane book The Causes of Evolution

Introduction, pp.20-21.
The Causes of Evolution (1932)

“If the only available genes produce rather large changes, disadvantageous one at a time, then it seems to me probable that evolution will not occur in a random mating population. In a self-fertilised or highly inbred species it may do so if several mutations useful in conjunction, but separately harmful, occur simultaneously. Such an event is rare, but must happen reasonably often in wheat…”

J. B. S. Haldane book The Causes of Evolution

Source: The Causes of Evolution (1932), Ch. IV Natural Selection, p. 104.

“Darwin believed that the crossing of two types generally led to a blend, and that consequently bisexual reproduction tended to make a species uniform. He therefore had to postulate some cause constantly at work to keep up the inheritable variation within a species. He very naturally looked to the effects of differences of environment. …It was shown that Darwin had been wrong in supposing that variations due to environment were inheritable. Selection merely picked out the best available line from a given population, and would not, as Darwin had believed, give rise to an unlimited amount of change.”

J. B. S. Haldane book The Causes of Evolution

Introduction, pp.14-20.
The Causes of Evolution (1932)

“I do not propose to argue the case for evolution, which I regard as being quite as well proven as most other historical facts, but to discuss its possible causes, which are certainly debatable.”

J. B. S. Haldane book The Causes of Evolution

Introduction, pp. 3-4.
The Causes of Evolution (1932)

“Evolution in… cases has clearly been a very slow and almost (if not quite) continuous process, exactly as Darwin had predicted.
We must remember, however, that the organisms studied in this way are far from representative. They are in general the most successful members of animal associations living in very constant marine or lacustrine environments. We have not got similar data for land species… Nor do we possess them for the rarer forms. We shall see… that perhaps dominant species in a uniform environment are the least likely to undergo sudden change to a new type.”

J. B. S. Haldane book The Causes of Evolution

Introduction, p. 22.
The Causes of Evolution (1932)

“We must… carefully distinguish between two quite different doctrines which Darwin popularised, the doctrine of evolution, and that of natural selection. It is quite possible to hold the first and not the second. Similarly with regard to the doctrines of Darwin's great contemporary Marx, it is possible to adopt socialism but not historical materialism.”

J. B. S. Haldane book The Causes of Evolution

Introduction, p. 2.
The Causes of Evolution (1932)

“Evolution must have involved the simultaneous change in many genes, which doubtless accounts for its slowness. Here matters would have been easier if heritable variations really formed a continuum, as Darwin apparently thought, i. e. if there were no limit to the possible smallness of a variation. But this is clearly not the case when we are considering meristic characters. …the atomic nature of Mendelian inheritance suggests very strongly that even where variation is apparently continuous this appearance is deceptive.”

J. B. S. Haldane book The Causes of Evolution

Source: The Causes of Evolution (1932), Ch. IV Natural Selection, pp. 103-104.

“Our ancestors were mostly rather rare creatures.”

J. B. S. Haldane book The Causes of Evolution

Appendix, pp. 213-214.
The Causes of Evolution (1932)
Context: Wright's theory certainly supports the view taken in this book that the evolution in large random-mating populations, which is recorded by palaeontology, is not representative of evolution in general, and perhaps gives a false impression of the events occurring in less numerous species. It is a striking fact that none of the extinct species, which, from the abundance of their fossil remains, are well known to us, appear to have been in our own ancestral line. Our ancestors were mostly rather rare creatures. " Blessed are the meek : for they shall inherit the earth."

“If much of the investigation here summarised has only proved the obvious, the obvious is worth proving when this can be done. And if the relative importance of selection and mutation is obvious, it has certainly not always been recognised as such.”

J. B. S. Haldane book The Causes of Evolution

Appendix
The Causes of Evolution (1932)
Context: Unaided common sense may indicate an equilibrium, but rarely, if ever, tells us whether it is stable. If much of the investigation here summarised has only proved the obvious, the obvious is worth proving when this can be done. And if the relative importance of selection and mutation is obvious, it has certainly not always been recognised as such.

“If human evolution is to continue along the same lines as in the past, it will probably involve a still greater prolongation of childhood and retardation of maturity. Some of the characters distinguishing adult man will be lost. It was not an embryologist or palaeontologist who said, "Except ye... become as little children, ye shall not enter into the kingdom of heaven."”

J. B. S. Haldane book The Causes of Evolution

Source: The Causes of Evolution (1932), Ch. V What is Fitness?, p. 150.

“Another possible mode of making rapid evolutionary jumps is by hybridisation.”

J. B. S. Haldane book The Causes of Evolution

Source: The Causes of Evolution (1932), Ch. IV Natural Selection, pp. 104-106.
Context: Where natural selection slackens, new forms may arise which would not survive under more rigid competition, and many ultimately hardy combinations will thus have a chance of arising.... Thus the distinction between the principal mammalian orders seems to have arisen during an orgy of variation in the early Eocene which followed the doom of the great reptiles... Since that date mammalian evolution has been a slower affair, largely a progressive improvement of the types originally laid down in the Eocene.
Another possible mode of making rapid evolutionary jumps is by hybridisation.... hybridisation (where the hybrids are fertile) usually causes an epidemic of variation in the second generation which may include new and valuable types which could not have arisen within a species by slower evolution.

“Where natural selection slackens, new forms may arise which would not survive under more rigid competition”

J. B. S. Haldane book The Causes of Evolution

“We have now to ask whether God made the tapeworm. And it is questionable whether an affirmative answer fits in either with what we know about the process of evolution or what many of us believe about the moral perfection of God.”

J. B. S. Haldane book The Causes of Evolution

Source: The Causes of Evolution (1932), Ch. V What is Fitness?, pp. 158-159.
Context: I have given my reasons for thinking that we can probably explain evolution in terms of the capacity for variation of individual organisms, and the selection exercised on them by their environment....
The most obvious alternative to this view is to hold that evolution has throughout been guided by divine power. There are two objections to this hypothesis. Most lines of descent end in extinction, and commonly the end is reached by a number of different lines evolving in parallel. This does not suggest the work of an intelligent designer, still less of an all mighty one. But the moral objection is perhaps more serious. A very large number of originally free-living Crustacea, worms, and so on, have evolved into parasites. In doing so they have lost, to a greater or less extent, their legs, eyes, and brains, and have become in many cases the course of considerable and prolonged pain to other animals and to man. If we are going to take an ethical point of view at all (and we must do so when discussing theological questions), we are, I think, bound to place this loss of faculties coupled with increased infliction of suffering in the same class as moral breakdown in a human being, which can often be traced to genetical causes. To put the matter in a more concrete way, Blake expressed some doubt as to whether God had made the tiger. But the tiger is in many ways an admirable animal. We have now to ask whether God made the tapeworm. And it is questionable whether an affirmative answer fits in either with what we know about the process of evolution or what many of us believe about the moral perfection of God.

“If two animals have a common ancestor, their parasites are likely to be descended from those of the ancestor.”

J. B. S. Haldane book The Causes of Evolution

Introduction, p. 9.
The Causes of Evolution (1932)
Context: Comparative parasitology supports the evolutionary hypothesis. If two animals have a common ancestor, their parasites are likely to be descended from those of the ancestor. This principle has been applied with considerable effect to the classification of frogs and other groups.