The conservative has but little to fear from the man whose reason is the servant of his passions, but let him beware of him in whom reason has become… - J.B.S. Haldane

The conservative has little to fear from the man whose reason is the servant of his passions, but let him beware of him in whom reason has become the greatest and most terrible of passions. These are the wreckers of outworn empires.

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.

Man’s habits change more rapidly than his instincts.

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...