It’s a lifesaver. Algorithms sort huge pools of potential kidney donors with recipients who are unsuccessfully paired with other, noncompatible donors, creating chains of donations between disparate members. Nearly 6,000 people have received transplants this way since nephrologists, computer scientists and economists fine-tuned the first such algorithm in 2000. Those matches took biology into account — but what about morality? Now programmers are training digital minds to factor in recipients’ ages and healthy habits in order to apply human values in deciding who most deserves the gift of life.