The announcement is charmingly odd: Peppa Pig has a baby sister, and the plot turns one arrival into a family-sized event. You can see the storybook logic: one crib, one name, one fresh center of attention. Cute. That is certain. Real pigs, though, rarely follow such neat arithmetic.Reality is messier. Domestic sows commonly produce litters because multiple ova can be released during ovulation, wh...More