However, hard as it may be for many to accept, the lines of influence -- as say History Professor Richard Weikart documented in details (e.g. in his From Darwin to Hitler) -- are real, and remain of concern to this day.
U/D, Jan 10, 2012: Given various attempts to deny or dismiss, let me embed Weikart's Lecture on "From Darwin to Hitler" as a key point of reference:
For, to refuse to learn from history is to set up the conditions to repeat its worst chapters.
So, it is wise for us to now pause and observe that in 1898, famed science fiction novellist H G Wells opened the narrative of his famous War of the Worlds, thusly:
No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own; that as men busied themselves about their various concerns they were scrutinised and studied, perhaps almost as narrowly as a man with a microscope might scrutinise the transient creatures that swarm and multiply in a drop of water . . . No one gave a thought to the older worlds of space as sources of human danger, or thought of them only to dismiss the idea of life upon them as impossible or improbable. It is curious to recall some of the mental habits of those departed days. At most terrestrial men fancied there might be other men upon Mars, perhaps inferior to themselves and ready to welcome a missionary enterprise. Yet across the gulf of space, minds that are to our minds as ours are to those of the beasts that perish, intellects vast and cool and unsympathetic, regarded this earth with envious eyes, and slowly and surely drew their plans against us . . . . looking across space with instruments, and intelligences such as we have scarcely dreamed of, they see, at its nearest distance only 35,000,000 of miles sunward of them, a morning star of hope, our own warmer planet, green with vegetation and grey with water, with a cloudy atmosphere eloquent of fertility, with glimpses through its drifting cloud wisps of broad stretches of populous country and narrow, navy-crowded seas.
And we men, the creatures who inhabit this earth, must be to them at least as alien and lowly as are the monkeys and lemurs to us. The intellectual side of man already admits that life is an incessant struggle for existence, and it would seem that this too is the belief of the minds upon Mars. Their world is far gone in its cooling and this world is still crowded with life, but crowded only with what they regard as inferior animals. To carry warfare sunward is, indeed, their only escape from the destruction that, generation after generation, creeps upon them.
And before we judge of them too harshly we must remember what ruthless and utter destruction our own species has wrought, not only upon animals, such as the vanished bison and the dodo, but upon its inferior races. The Tasmanians, in spite of their human likeness, were entirely swept out of existence in a war of extermination waged by European immigrants, in the space of fifty years. Are we such apostles of mercy as to complain if the Martians warred in the same spirit?
Man is liable to numerous, slight, and diversified variations, which are induced by the same general causes, are governed and transmitted in accordance with the same general laws, as in the lower animals. Man has multiplied so rapidly, that he has necessarily been exposed to struggle for existence, and consequently to natural selection. He has given rise to many races, some of which differ so much from each other, that they have often been ranked by naturalists as distinct species . . . .
At some future period, not very distant as measured by centuries, the civilised races of man will almost certainly exterminate, and replace, the savage races throughout the world. At the same time the anthropomorphous apes, as Professor Schaaffhausen has remarked, will no doubt be exterminated. The break between man and his nearest allies will then be wider, for it will intervene between man in a more civilised state, as we may hope, even than the Caucasian, and some ape as low as a baboon, instead of as now between the negro or Australian and the gorilla.
Any crossing of two beings not at exactly the same level produces a medium between the level of the two parents . . . Consequently, it will later succumb in the struggle against the higher level. Such mating is contrary to the will of Nature for a higher breeding of all life . . . The stronger must dominate and not blend with the weaker, thus sacrificing his own greatness. Only the born weakling can view this as cruel, but he after all is only a weak and limited man; for if this law did not prevail, any conceivable higher development of organic living beings would be unthinkable.
The consequence of this racial purity, universally valid in Nature, is not only the sharp outward delimitation of the various races, but their uniform character in themselves. The fox is always a fox, the goose a goose, the tiger a tiger, etc., and the difference can lie at most in the varying measure of force, strength, intelligence, dexterity, endurance, etc., of the individual specimens. But you will never find a fox who in his inner attitude might, for example, show humanitarian tendencies toward geese, as similarly there is no cat with a friendly inclination toward mice . . . .
In the struggle for daily bread all those who are weak and sickly or less determined succumb, while the struggle of the males for the female grants the right or opportunity to propagate only to the healthiest. [That is, Darwinian sexual selection.] And struggle is always a means for improving a species’ health and power of resistance and, therefore, a cause of its higher development.
If the process were different, all further and higher development would cease and the opposite would occur. For, since the inferior always predominates numerically over the best [NB: this is a theme in Darwin's discussion of the Irish, the Scots and the English in Descent], if both had the same possibility of preserving life and propagating, the inferior would multiply so much more rapidly that in the end the best would inevitably be driven into the background, unless a correction of this state of affairs were undertaken. Nature does just this by subjecting the weaker part to such severe living conditions that by them alone the number is limited, and by not permitting the remainder to increase promiscuously, but making a new and ruthless choice according to strength and health . . .
Practical men, who believe themselves to be quite exempt from any intellectual influences, are usually the slaves of some defunct economist. Madmen in authority, who hear voices in the air, are distilling their frenzy from some academic scribbler of a few years back. I am sure that the power of vested interests is vastly exaggerated compared with the gradual encroachment of ideas. Not, indeed, immediately, but after a certain interval; for in the field of economic and political philosophy there are not many who are influenced by new theories after they are twenty-five or thirty years of age, so that the ideas which civil servants and politicians and even agitators apply to current events are not likely to be the newest. But, soon or late, it is ideas, not vested interests, which are dangerous for good or evil.