Xenotransplantation failure dissipated. An American infant girl known as "Baby Fae" with hypoplastic left heart syndrome was the first infant recipient of a xenotransplantation, when she received a baboon heart in 1983. The procedure was performed by Leonard L. Bailey at Loma Linda University Medical Center in Loma Linda, California. Fae died 21 days later due to a humoral-based graft rejection thought to be caused mainly by an ABO blood type mismatch, considered unavoidable due to the rarity of type O baboons. The graft was meant to be temporary, but unfortunately a suitable allograft replacement could not be found in time.
Baboon as a full species, but regard all the others as subspecies of "P. cynocephalus" and refer to them collectively as "savanna baboons". This may not be helpful: it is based on the argument that the hamadryas baboon is behaviorally and physically distinct from other baboon species, and that this reflects a separate evolutionary history. However, recent morphological and genetic studies of "Papio" show the hamadryas baboon to be more closely related to the northern baboon species (the Guinea and olive baboons) than to the southern species (the yellow and chacma baboons). In 2015 researchers found the oldest baboon fossil dating