I once read an article that suggested that centuries of rigid enforcement of the caste system led to an increased incidence of deformities through inbreeding. Not sure if true, but seems like a reasonable hypothesis, or at least a contributing factor.
That has happened in the Amish world. A number of cases of dwarfs, some with 6 fingers and toes and some with 5. Also, normal size people with the 6 fingers and toes. I know of one dwarf man who married a normal size woman. He was a farmer, and they apparently had a nice, enjoyable life. He was a hard worker and well respected.
” suggested that centuries of rigid enforcement of the caste system led to an increased incidence of deformities through inbreeding”
That makes a lot of sense.