Here we go (under Voltaire):
Voltaire's position regarding Africans, slaves and the slave-trade has been a source of scholarly controversy. Claudine Hunting thinks that Voltaire was decidedly against slavery. On the other hand, for example, Christopher L. Miller and Michele Duchet point out that the evidence is otherwise. Also, it has been stated by biased authors that Voltaire profited directly from the trade in slaves overseas, himself. Eugene de Mirecourt had published portions of a letter in 1877 as proof for such accusation, but the letter has been judged not authentic by more recent scholarship. Indeed, however, Voltaire had invested funds in the company "Companie des Indes". This company participated in the colonial wars of conquest and at times held the monopoly for the slave trade in France. Voltaire seemed to be more concerned about the welfare of regular servants than the problems with the trade of slaves which he held to be a necessary evil, perhaps. A ship belonging to a slave trader was named after Voltaire, which he considered an honor.
One of the slave traders brought back an albino person to Paris whom he described as "an animal, which is similar to a human being." The albino seemed to him to be a missing link between animal and human being; this is a topic Voltaire also dealt with in other places. Voltaire thought the African to be a different species of man from the White man, which reproduces with the orangutan monkey.
In Voltaires "Essai sur les moeurs et l'esprit des Nations" [Essay on the Blacks and the Spirit of the Nations.?] there is a passage stating: "We purchase our house slaves only from among black men; some condemn this practice. But a people which trades with its children, is much more damming than one who purchases slaves. This trade demonstrates our superiority; the one who gives himself to an owner has been born to have one (an owner). Already the editor, named Condorcet, an opponent of slavery, commented that this passage by Voltaire is not meant to be seen as a defense of slavery. The older secondary sources commenting on this have not fully supported this conclusion (of Condorcet). The same work by Voltaire also contains the thesis that there exist among peoples of the world a natural gradation, which rarely changes, in regards to genius and character. This is the reason which the black man are different kinds of humans. But, still, Voltaire describes also the unfair treatment of slaves, saying "Humans like ourselves" and compared the disparagement of Jews in the ancient Rome with "our" view of the "negro", as a "less developed species of mankind."
With Voltaire one also finds firmly critical thoughts regarding slavery... He also describes the mutilation of slaves by Surinam in "Candide"... In "Commentaire sur l'Esprit des lois" (1777) Voltaire praises Montesquieu for denouncing slavery. Voltaire commented with enthusiasm on the attitudes of the Quakers of Pennsylvania who had a position against slavery and were able to to abolish it. He called the war of Sparta a just war, if not the only ever just war. [?] In the last years of his life, Voltaire worked toward the abolishing of slavery in the Jura together with a lawyer friend Charles-Frederic Gabriel Christin...
Most likely Voltaire developed his thoughts over time standing somewhere in the middle at times or combining points of views.
Nevertheless, it is interesting to hear in the context also, and in that time, place and with this author, the opinion regarding the descent or interbreeding with the orangutan, the idea that there are different kinds of species of man with different levels of genius or intelligence. Once the biblical view went out, the new semi-scientific, or speculative philosophical view was open to rationalization and viewing others as inferior.
Interesting also that he was commenting on "a link" between animal and human.