A female boa constrictor has produced not just one baby born by immaculate conception, but rather two litters totaling 22 little miracles. Stranger still, the baby snakes have some very unusual traits. Instead of having the X and Y chromosomes like humans, snakes have Z and W chromosomes—ZZ produces males, and ZW produces females. However, all the snakes in these litters are females with WW chromosomes, which was previously unheard of, reports the BBC.
"Essentially they are half clones of their mother," says the lead researcher. "Our finding up-ends decades of scientific theory on reptile reproduction." Though snakes have been known to reproduce asexually before, the babies have always been ZZ. This is the first known time that a female boa constrictor has produced offspring without a male.