In the 19th century, theories of race moved from religious-based racism to:

The correct answer is "scientific based racism."

During the 19th century, several scientists were out to prove that African-Americans were biologically inferior to white Americans. This study of facial characteristics, body composition, and other genetic factors was developed in order to give definitive prove of white racial superiority.

Even though this concept has been disproved several times over, groups or organizations with an agenda that is considered racist may use information from this faulty science in order to justify their actions.