Voltaire was a firm believer in racial differences in intelligence. Specifically, he believed that negroes were less intelligent than other races:
[Negroes’] round eyes, their flat nose, their large lips, their differently shaped ears, the wool of their heads, the measure of their intelligence, put between them and other species of men prodigious differences.
He also singled our their inability to concentrate:
The negro race is a species of men different from ours as the breed of spaniels is the greyhounds… one could say that if their intelligence is not of another species than our understanding, it is far inferior. They are not capable of much attention, they mingle little, and do not seem made for either benefits or for abuse of our philosophy.
In his Seventh Letter to Amabed, Voltaire goes further:
It is a serious question among them whether they [Negroes] are descended from monkeys or whether the monkeys come from them. Our wise men have said that man was created in the image of God. Now here is a lovely image of the Divine Maker: a flat and black nose with little or hardly any intelligence. A time will doubtless come when these animals will know how to cultivate the land well, beautify their houses and gardens, and know the paths of the stars: one needs time for everything.
Note Voltaire’s anti-biblical purpose: he uses the example of the negro to mock the idea that man is created in the image of god. However, Voltaire is probably not serious about Monkeys descending from negroes, as he notes that the offspring of any coupling of monkey and man would likely be sterile.
It is not unlikely that in hot countries monkeys have subjugated the girls. Herodotus, in Book II, said that during his trip to Egypt, there was a woman who publicly copulated with a goat in the province of Mendes, and he called all of Egypt in testimony. It is forbidden in Leviticus, Chapter XVII, to unite with the goats and the goats. Thus it must be that these couplings were common, and until things are cleared up, it is presumed that monstrous species could have arisen from these abominable loves. But if they existed, they could not influence the human race and, like the mules, which are sterile, they could not denature other races.
Again, Voltaire gets in a dig against Leviticus. It’s not clear how much he believes in human-monkey sex, and how much he just wanted to take a whack at the bible.
We should note that Voltaire was a big admirer of India and China. In fact, as he learned of Indian civilization, he suggested that European civilization came out of India. Later his tastes changed, and he decided that perhaps it came out of China instead. He also wrote favorably of Japan. Given these facts, any accusation of Eurocentrism or “white supremacy” is simply laughable.