During embryogenesis, the three germ layers (endoderm, ectoderm, mesoderm) differentiate into epithelial and non-epithelial cells, which eventually form differentiated tissues and organs. Abundant data now indicates that we humans are very closely related to other hominids including chimpanzees, bonobos, gorillas, and orangutans, the so-called "great apes". UC San Diego School of Medicine professor Nissi Varki discusses the incidence of carcinomas, including the rarity of occurrence of common human carcinomas in captive chimpanzees. (#37382)