Placentals (e.g. humans) are mammals whose young develop internally, in their mother’s womb, nourished through a placenta. Marsupials (e.g. kangaroos) are mammals that carry and suckle their young externally in a pouch. According to the theory of evolution, placentals and marsupials evolved from a common ancestor that looked a bit like a modern shrew. These early placentals and marsupials allegedly then evolved into many different animals. What is so difficult for evolutionists to explain, however, is why, in so many cases, placentals evolved almost identical forms to marsupials (see fig. 6).