The study comes as the field of xenotransplantation — or the act of transferring organs from one species to another — is under increased scrutiny. The first person to receive a pig heart transplant died earlier this year in what scientists believe was an adverse reaction to a drug to prevent rejection. The heart also contained DNA associated with a pig virus. After the incident, the medical community called for more substantial research into the matter, as well as better safety protocols. Meanwhile, the FDA is considering approving clinical trials of pig heart transplants into humans, the Wall Street Journal reported last month. Both human subjects—a 72-year-old Navy veteran and a 64-year-old retired New York teacher—were monitored for three days before being taken off life support. Neither heart needed external support and was functioning normally, which the researchers see as a promising sign for future research. Despite the positive outcome of the NYU experiment, surgeons cautioned that much more research is needed before pig heart transplants can be a viable alternative for people with heart disease. “This is not an isolated situation. Those are going to be years of learning what’s important and what’s not to make this work,” NYU’s Dr. Robert Montgomery told The Associated Press. All products recommended by Engadget are selected by our editorial team, independent of our parent company. Some of our stories contain affiliate links. If you purchase something through one of these links, we may earn an affiliate commission.