Wednesday, May 11, 2005

Mix and match

Chimeras have replaced clones as the most contentious topic in bioethics.

A chimera is an animal with its own cells and cells of another animal (often a different species) in its body.

Cardiac surgery patients who have received pig valves to repair their hearts are chimeras. Scientists at the University of California at Davis fused sheep and goat embryos to make a "geep." Human brain cells have been implanted in mice.

These mixed up species are called chimeras after a female creature in Greek mythology who possessed the body of a goat, the head of a lion, and the tail of a snake. Think also of the Sphinx (lion and human), Pegasus (horse and bird), centaurs (horse and human), Capricornus (goat and fish), and angels (humans and birds). Ancient cultures were rife with imaginary biological amalgams.

The struggle of humanlike gods against monsters was an important theme in ancient religions. The struggle was that of light against darkness, order against chaos, good against evil. It was out of this struggle that the universe was born.

The mixed-up monsters of yesteryear were vanquished by the gods, but it is always possible, according to those ancient faiths, that if the pressure of order and goodness is relaxed, even for a moment, the universe might slip back into chaos.