Misunderstandings about evolution are widespread. A prominent one is that evolution progresses from simple to more and more complex through time. Now to some degree, this is true—but only because we necessarily start from very simple beginnings. Certainly a one-celled organism is less complex than an individual made up of trillions of cells. But let's not get carried away! Were the sharks of the Permian Sea in the eastern portion of what now is our desert any less complex than sharks of today? Or, for that matter, than any number of living organisms? A good case can be made that a high level of complexity among animals was reached several hundred million years ago and, on average, has changed but little since.
On the other hand, some things simplify through time. The distant
ancestors of our desert rodents had 44 teeth, but the most toothy rodents now living in
our area have only 22, and most of our rats and mice are limited to 16. If that's
not convincing, look at parasitic tapeworms—little more than overgrown reproductive
systems.
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class="three"> 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.