In Greek mythology, the chimera was a fire-breathing monster with the head of a lion, the body of a goat, and the tail of a serpent. The word has since come to mean any monster made up of incongruous parts. Now, most biologists don't consider humans as monsters (with, of course, exceptions), but do consider us to be chimeras. Not only us, but all creatures except the various kinds of bacteria. The bacteria, better called prokaryotes, really consist of two major, quite different groups, but have in common a simplicity lacking in non-prokaryotes, called eukaryotes.
Evidence is becoming stronger and stronger that the complexity that we
eukaryotes share started off as a symbiotic relationship between members of two
different prokaryotic groups. One of these lived within the other, each benefiting, and
eventually growing so close that what started out as separate organisms merged into
one. Even today, we find cells of one kind of organism living happily within another,
both getting a good deal; we just got a jump on these Johnnys-come-lately and got by
far the better deal!
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.