Enlarge / Cloned piglets that are engineered to be useful for organ transplants to humans. (credit: Getty Images / Staff) Last week, when we reported on the first pig-to-human heart transplant, we complained that the commercial company behind the operation wasn't more forthcoming about the genetic engineering that converted the pig into a viable donor. We now know much more about porcine genetic engineering thanks to a new paper covering a different, more cautious test procedure.