
The American Colonization Society (ACS)
Used craniometry to promote racial hierarchies.
Craniometry is the scientific measurement of the size, shape, and proportion of the human skull, historically used to study human variation but often misused to support pseudoscientific racial theories.

Who: Samuel George Morton (1799–1851)
What: Used craniometry to promote racial hierarchies.
When: Published “Crania Americana” in 1839 (Note: While Morton’s work is slightly outside the 1700s timeframe, his influence began in the late 18th century, and he is considered a foundational figure in scientific racism).
Details: Morton collected and measured human skulls, claiming that the size of the skull correlated with intellectual capacity. In his works "Crania Americana" (1839) and "Crania Aegyptiaca" (1844), he argued that Caucasians had the largest skulls and, therefore, the highest intelligence, while Africans had the smallest and were the least intelligent.
Why and How It Was Racist: Morton's work was used to justify slavery, segregation, and racial discrimination by providing a scientific rationale for the belief in white superiority.
Sources:
Websites:
Benjamin Rush. University Archives and Records Center. (2018a, September 6). https://archives.upenn.edu/exhibits/penn-people/biography/benjamin-rush/
Brown, B. (2013, February 26). Skull & Bones: It’s not just for White Dudes anymore. The Atlantic. https://www.theatlantic.com/national/archive/2013/02/skull-and-bones-its-not-just-for-white-dudes-anymore/273463
How Samuel Morton got it wrong. Learning for Justice. (2015, May 13). https://www.learningforjustice.org/magazine/how-samuel-morton-got-it-wrong