My best lecturer at UP was a young privatdozent named fu-Jaardansky for Bio 402: Comparative Astrobiology. The name was an anachronism, or course. Long ago all the sciences that deal with extraterrestrial subject matter dropped the "astro" or "exo" prefixes. There's no more astrophysics or astrobiology -- there's just physics and biology. Even geology, the long holdout, is finally a space-born enterprise. If you study rock formations on Mars you're not a "planetologist" or an "areologist" as some used to insist, you're a geologist. The skills are the same whether you're on Earth or in space, and the things we learn studying other planets applies to Earth as well.
Genetic chemistry was one of his favorite callbacks. There are three naturally-occurring genetic molecules -- RNA, DNA and LNA -- and some common variations like kRNA and As-enriched DNA. Any time there was an odd adaptation or physiology -- which there always is in biology, "astro" or non -- he would always try to tie it back in some way to the fundamental genetic chemistry. It was a quirky affectation that made for thought-provoking lectures, but it wasn't why I loved the class.
It was the Crabs. They made up fully 35% of the syllabus. Crabs are based on kRNA, and they have a chemistry very unlike ours. Early ancestors of Crabs were radially-symmetric aquatic creatures a bit like Echinoderms. At some point their six-fold symmetry became bilateral resulting in hexapods with a front and a back, but with many replicated organs. The different organs specialized over time and the modern Crab looks like a native Bilaterian.
It still has traces of its origins, however, such as an esophagus that passes through its brain. As a radially-symmetric creature the digestive tract used to pass through the center of the body, feeding at the bottom of the organism and excreting out the top. The nervous system, used for sensing and movement, was a ring around the circumference of the body near the eyes and legs. As the lineage evolved the mouth moved to the front, the anus to the rear and the central nervous system got more complex, but the one still had to pass through the other. Everything a Crab eats takes a path directly through its no-longer symmetric but still donut-shaped brain.
This arrangement would turn out to be a haven for parasites, to the Crabs' good fortunes.
Despite fu-Jaardansky's fascinating approach, however, it's not chemistry or even anatomy that make Crabs what they are. It's behavior. And Crabs had a lot of behavior that needed explaining. Whatever the genetic molecule is made from, the organism must pass it along, preferably it's own more than those of others. Behaviors tell us more about biology than any of those other things. Naturally I think so -- it's my field.
Comments