This hierarchical notion of race was widely shared at the time and helped to justify the subjugation of darker skinned races to the European cause. This thinking was legitimized by pseudo-scientific publications like Arthur de Gobineau's An Essay on the Inequality of the Human Races, which postulated the idea that each race had sprung from a separate gene pool. This kind of scientific racism gave rise to human zoos or People Shows in which members of various races were showcased for the general scrutiny of a paying public.
Also known as ottava rima, the Byronic stanza pre-exists Byron by a few hundred years. It is described in the Penguin Dictionary of Literary Terms as 'An eight-line iambic stanza ryhming abababcc'. As used by Byron, the rhyming couplet at the end of the stanza would often be comic in tone.
There are a surprising number of academic books and articles which explore the history of sodomy and homosexuality in the navy, which (at an official level at least) was heavily proscribed and potentially punishable my death. Generally heterosexual licentiousness in port was de rigueur, although to what extent homoerotic activity was tolerated onboard is a matter of some debate. Eighteenth-century British military naval records indicate that allegations made against high-ranking officers by cabin boys were usually dismissed. In Cloud Atlas the two cases of the rape of a minor occur within the context of a work that explores the theme of predation in its many forms.
His choice of insult 'garter snakes' is especially apt. The garter snake feeds on weaker animals, and is in some cases capable of giving out female pheromones, thus luring other males into attempting to mate with them.