1963: After a lull of nearly 40 years, physicians again try their hand at xenotransplantation. Keith Reemtsma, then at Tulane University, transplants more than a dozen kidneys from chimps to humans. One woman survives for nine months, even returning for a time to her job as a school teacher. Thomas Starzl, then at the University of Colorado, performs an additional six transplants using baboon kidneys. His patients survive from 19 to 98 days. Although many patients now survive for weeks or months, not all the operations are such "success stories."

In one strange case, the kidneys taken from a chimp work—much too well. They produce an astonishing 54 liters of urine in one day, compared with the modest two liters considered normal for humans. The patient suffers a stroke and dies of heart failure three days later. (The surgeons had transplanted both of the chimp’s kidneys, which, they later comment, "maybe we should not have done.")