Human Chimeras

http://www.livescience.com/55684-human-chimeras.html

Recently, researchers have come under fire for their ideas of creating human-animal hybrids, or as they can be called, Chimeras. A chimera is any single organism that contains the cells of two or more individuals. While the idea of introducing cells from an animal into a human may seem extreme, there are certain instances where chimeras occur naturally.

While not the human-animal hybrid researchers are trying to create, thees chimeras involve humans containing the cells of other humans. This can occur if a mother absorbs cells from her fetus, a twin absorbs the other in the whom, or even from a bone marrow transplant.