“You’re saying there are no categories of relatedness among humans?” “Nope. I’m clueing you that the term ‘Caucasian’ was invented in the seventeen hundreds by German philosophers who said God put the colored folks on all their subpar continents and the beautiful whiteys in the mountains of eastern Europe.”
Kingsolver may be referring to the German philosopher Christoph Meiners (1747-1810) who expressed views that align with this quote by Tig in her novel, Unsheltered. Another, Johann Friedrich Blumenbach, a German anthropologist, had similar views.
Meiners argued that the different human "races" were created by God and placed on separate continents, with Europeans being the superior "race". He believed that the climate and geography of Africa were responsible for the supposedly inferior physical and moral characteristics of the people who lived there.
Interested readers can review Meiners' "Outline of History of Humanity (1785) if a copy can be found; or more readily available, "The Rise and Fall of the Caucasian Race: A Political History of Racial Identity" (2008) by Bruce Baum. (pages 84-85).
Furthermore, in Wilkerson's Caste: The Origins of Our Discontents, she supports this discussion when she writes that the word Caucasian is an arbitrary label and relatively new idea descended from Europe. It came from a German professor of medicine, Johann Friedrich Blumenbach in 1795. He coined the term based on a skull he found in the Caucasus Mountains that he believed supported his conception of hierarchy. (See page 65-66 in chapter 6).