The miracles of modern science not withstanding, it's unlikely that mankind will ever be free of disease. This is not because of failures of science, but because of the simple fact of evolution. Imperfect copies of the genetic material, DNA, are created constantly in all kinds of organisms because of errors in copying as cells reproduce and because of the susceptibility of DNA to damage by various chemicals and radiation. If, by chance, the altered DNA of a disease organism helps its survival, individuals carrying the mutation multiply—natural selection in action.
The very medical techniques used to defend against microorganisms
insure that any variation that helps avoid the defense will be selected for. Thus as
one battle is won, the seeds of the next are sown. Even worse, from our viewpoint, a
disease organism doesn't need to be the precursor. Relatively few genetic changes
may allow an organism to change from harmless to a pathogen, capable of causing
disease. Cheery news—we in the Chihuahuan Desert have a wealth of microorganisms,
candidates for the next spreading plague.
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.