Biologists had originally thought zebra and donkey chromosomes to be incompatible.A rare but adorable cross-breed was introduced to the world this week at a zoo in Reynosa, Mexico. Khumba is the lovechild of Rayas, a female zebra, and Ignacio, a blue-eyed albino donkey. That makes Khumba a zonkey, one of only a few in the world. Though there are now living specimens of zonkeys at zoos in the U.S., Japan, China and elsewhere, biologists had originally thought zebra and donkey chromosomes were incompatible. But apparent genetic incongruity didn't stop Rayas and Ignacio from trying. According to WTVY, the two visited...