Over the past couple years, scientists around the world have successfully integrated human cells into animals, resulting in pigs with human blood, mice with human neurons, and lambs with human livers. These chimera are the blending of cells from two species into one creature. The work promises new organ sources for transplants and the observation of and experimentation on human cells in living systems (bypassing the strict regulations and ethical issues against using human subjects).
Like all new technologies, the development of chimeras opens up new possibilities and ethical consequences. How much human tissue in an animal makes it human enough to be protected by our laws and guidelines? Are animals better or worse off with human cells? Could this result in animals with human-level intelligence and how should they be treated? Could chimeras develop human embryos and could these embryos be brought to term in animal wombs? And none of these begin to address the genetic manipulation of humans with animal DNA.
While people are just now beginning to get their heads around the idea of cloning and human stem cell research, the existence of animal/human chimeras reminds us that progress is composed of a multitude of different technologies, most of which seem to pop up out of no where. The fabric of the future is composed of technology threads we know, threads we imagine that eventually come true, and threads that catch everyone by surprise.