qT=2&tQ=Baboon hearts have been transplanted into humans.&tC=True|False&cC=1&fB=The first such operation in the U.S. was in 1984 and was performed on a baby known as "Baby Fae." Dr. Leonard Bailey lead a group of surgeons who transplanted a baboon heart into the infant, whose heart was underdeveloped on the left side.<br><br>Unfortunately, the child died in 20 days. Many speculate that it was not the heart but rather differing blood types that caused the tragedy. Some scientists still believe that baboon hearts remain the best possibility in such procedures.