Interesting article! I'm a little skeptic to the final paragraph, though, specifically the notion that this research prompted the birth of stereotypes.

Stereotypes might not have existed in their modern form previously, but they're akin to the notion that people have an essence, assigned to them by nature. Platon's ideas about comparing an individual's essence to a metal is a good example (bronze people are good at this, iron people good at that). And I definitely think we'd fool ourselves thinking that the individual held a stronger position in society prior to the early 19th century...