Humans are nearly universally the most common of races in a sundry of fantasy settings. Here however the world of the Enclave is different. Humans in the Enclave are matched in numbers by halflings and dwarves. Gnomes are also well represented but in a minority compared to the others.
To the other races, individual humans can look wildly different. Humans vary more in size, body type, coloration, and personality than other races do; black/white skin, straight/curly/nonexistent hair, slight/burly build. This fact is a focus of interest at the University.
'Human' or 'humanity' is sometimes used generically for all 5 Enclave races (humans, dwarves, halflings, gnomes, and half-orcs). It's not clear why this is. Perhaps it was a powerful human who organized the Enclave in the first place.