Phrenology...or Scientific Racism.

Okay, here are some thoroughly unpleasant diagrams that were common during the Victorian Era because of the popularity of phrenology. In case one does not know, phrenology is the study of the human skull, which divides its features into a myriad of segments that are utilized to indicate a person's intelligence, capabilities, and characteristics. This particular branch of pseudoscience rose up during the first half of the 1800's and though it was later discredited, the use of it in conjunction with racism, especially in imperialism, is inseparable.

(Note that some of these may be familiar, especially the first image.)

Above is a diagram that was common in the United States because of the belief that Irish people were as gross and disgusting as African people. The insistence that the brain capacity of European people was significantly larger versus that of, well, anyone else, is emphasized through the examination of human skulls. For those in the United States, phrenology reflected the need to keep Irish immigrants and African slaves in places of servitude, which is why the two examples have similar traits. The enlarged noses, the puffed up lips, and the animalistic qualities in contrast to the attractive anglo face, for example. This is furthered by the diagram below, which is predominantly focused on showcasing that an African individual has a skull more closely related to an animal than that of a European person.  

Note that here, the middle diagram acts like a missing link. Yet, it's not limited to Europeans and Africans:

So why this? Well, throughout both Melville's Benito Cereno and Conrad's Heart of Darkness, animalistic language is utilized to emphasize the racial binary between the white narrator or white people and the other. Yes, it is irritating to read, but it is based upon a branch of pseudoscience that was popular at the time, which maintained the superiority complex of oppressive individuals. Simply stating that a person looks different and leaves themselves open to needing guidance is one thing, but to cite a flurry of British journals that maintain the racist ideologies solidifies the dynamic between the oppressor and the oppressed. Any instance where a simile is applied to a person of color that likens them to an animal, to something primordial, to some creature that's not quite develop stems from phrenology, which tends to be coupled with physiognomy as well.