J. B. S. Haldane - Species Quotes

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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
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."

J. B. S. Haldane
From the fact that there are 400,000 species of beetles on this planet, but only 8,000 species of mammals, he [Haldane] concluded that the Creator, if He exists, has a special preference for beetles.

J. B. S. Haldane
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
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
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