Perhaps you should read Darwins works on this matter. He made it absolutely clear that he considered all human beings to be of the same species, and that the advantages that Europeans enjoyed over "savages" were cultural, not genetic. Let us hear him talk for himself:
" On the 19th of August we finally left the shores of Brazil. I thank God, I shall never again visit a slave country. To this day, if I hear a distant scream, it recalls with painful vividness my feelings, when passing a house near Pernambuco, I heard the most pitiable moans, and could not but suspect that some poor slave was being tortured, yet knew that I was as powerless as a child even to remonstrate. I suspected that these moans were from a tortured slave, for I was told that this was the case in another instance. Near Rio de Janeiro I lived opposite to an old lady, who kept screws to crush the fingers of her female slaves. I have staid in a house where a young household mulatto, daily and hourly, was reviled, beaten, and persecuted enough to break the spirit of the lowest animal. I have seen a little boy, six or seven years old, struck thrice with a horsewhip (before I could interfere) on his naked head, for having handed me a glass of water not quite clean; I saw his father tremble at a mere glance from his master’s eye. These latter cruelties were witnessed by me in a Spanish colony, in which it has always been said, that slaves are better treated than by the Portuguese, English, or other European nations. I have seen at Rio de Janeiro a powerful negro afraid to ward off a blow directed, as he thought, at his face. I was present when a kind-hearted man was on the point of separating for ever the men, women and little children of a large number of families who had long lived together. I will not even allude to the many heart-sickening atrocities which I authentically heard of; - nor would I have mentioned the above revolting details, had I not met with several people, so blinded by the constitutional gaiety of the negro, as to speak of slavery as a tolerable evil. Such people have generally visited the houses of the upper classes, where the domestic slaves are usually well treated; and they have not, like myself, lived amongst the lower classes. Such enquirers will ask slaves about their condition; they forget that the slave must indeed be dull, who does not calculate on the chance of his answer reaching his master’s ears.
It is argued that self-interest will prevent excessive cruelty; as if self-interest protected our domestic animals, which are far less likely than degraded slaves, to stir up the rage of their savage masters. It is an argument long since protested against with noble feelings, and strikingly exemplified, by the ever illustrious Humboldt. It is often attempted to palliate slavery by comparing the state of slaves with our poorer countrymen: if the misery of our poor be caused not by the laws of nature, but by our institutions, great is our sin; but how this bears on slavery, I cannot see; as well might the use of the thumbscrew be defended in one land, by showing that men in another land suffer from some dreadful disease. Those who look tenderly at the slave-owner and with cold heart at the slave, never seem to put themselves into the position of the latter; - what a cheerless prospect, with not even a hope of change! Picture to yourself the chance, ever hanging over you, of your wife and your little children - those objects which nature urges even the slave to call his own - being torn from you and sold like beast to the first bidder! And these deeds are done and palliated by men, who profess to love their neighbors as themselves, who believe in God, and pray that his Will be done on earth! It makes one’s blood boil, yet heart tremble, to think that we Englishmen and our American descendants, with their boastful cry of liberty, have been and are so guilty: but it is consolation to reflect, that we at least have made a greater sacrifice, than ever made by any nation, to expiate our sin. "
Darwin had frenzied arguments on the subject with Captain Fitzroy of the Beagle. Fitzroy was a Christian Fundamentalist who justified slavery on Biblical Authority and believed that Biblical Authority trumped all considerations of reason, morality, or logic. Now who does that remind you of?
Something wrong with that? If you think that the Bible outlaws slavery, I would like to know where it says so.
And it was another english christian - William Wilberforce - whose efforts resulted in the abolishment of slavery in the english empire in 1835. Thenceforth, the Royal Navy also interdicted slave ships to the United States and so began the beginning othe end of slavery in the United States as well (where Christians were also responsible for its abolition).