Well, you'll call it speciation, and I'll call it randomness. See, scientists and researchers didn't just wake up one morning in a fit of seredipidy and proclaim, 'Pigs and Cows, founts of human tolerant insulin!'. They performed massive trials with lots of errors. Pigs and cows, and to some extent horses, can provide human tolerant insulin. Not so with other members of the swine or equine families, and no success at all regarding felines, canines, sea mammals, and rodentia, which includes to my view squirrels, possums, rats, mice, groundhogs, prairie dogs, bats, and raccoons, to name a few.
Of all the classes of mammals out there, including humans, only domestic pigs and domestic cows (not javelina, warthogs or musk oxen) can provide human tolerant insulin which most can use. Those that can't can sometimes utilize horse insulin. Of all those mammals, including humans, you hold true to 'all from common ancestors', yet only a few can produce insulin type 1 diabetics can use. And that, to me, sound far too random to be natural selection, adaptation, or evolution. Micro or macro.