I came across this QI tweet: Meet the quagga, an extinct subspecies of zebra with only half the stripes!#QI. There's a video clip and at around ~0:31 seconds the following is said:
I went to school in Kenya and we read early colonial books and they theorized - because they'd never seen any mixed race children. So they imagined that a child would be born with stripes, if a black person and a white person...
Were mixed race kids really theorized to look like zebras?