Edgar Rice Burroughs set his Tarzan series (1912) in the African jungle. Because of Tarzan’s wild upbringing, he avoids the debilitating forces of civilization.
Evolutionary biologists often argue that vertebrate embryos develop in highly similar manners, reflecting their common ancestry.
We can assume that this writer would have been a Connecticut Yankee, a strong opponent of the South and slavery.
The ideas of Ernst Haeckel, in his youth a hardline Darwinian materialist, were to evolve to a surprising degree.
The authors considered human evolution especially important, because they believed it supported their vision of racial inequality.