Slashdot Mirror
Lack of Molybdenum May Have Delayed Life on Earth
esocid writes "Scientists from around the world have reconstructed changes in Earth's ancient ocean chemistry during a broad sweep of geological time, from about 2.5 to 0.5 billion years ago. They have discovered that a deficiency of oxygen and the heavy metal molybdenum in the ancient deep ocean may have delayed the evolution of animal life on Earth for nearly 2 billion years. Bacteria cannot fix nitrogen efficiently when they are deprived of molybdenum. And if bacteria can't fix nitrogen fast enough, then eukaryotes — a kind of organism that includes plants, pachyderms and people — are in trouble because eukaryotes cannot fix nitrogen themselves at all. Ariel Anbar, a co-author of the research of Arizona State University, stated that "eukaryotes depend on bacteria having an easy enough time fixing nitrogen that there's enough to go around. So if bacteria were struggling to get enough molybdenum, there probably wouldn't have been enough fixed nitrogen for eukaryotes to flourish.""
Well, I'm no biologist but right off the cuff I think there are some problems with this "theory"... it makes an assumption that in an environment without fixed nitrogen that complex life would not have evolved to either not need it or to do it itself. It also assumes that the availability of molybdenum is required to fix nitrogen.
The fact that eukareotes did not evolve it doesn't mean they couldn't have -- it just means that their environment they evolved in didn't need that ability, likely because prokaryotes evolved it already. (Or they didn't actually originally need it -- which may make more sense because if one assumes that that evolution was necessary for eukaryotes, and they evolved from prokaryotes, then how did they *lose* that ability?)
Again, not a biologist but the critical reader in me gets a "I have a hammer, so everything is a nail" vibe from this theory.