Biological Big Bang

It is an exciting time in biology. Last year, several articles about origin of life (OOL) and evolution by Eugene Koonin from the National Center for Biotechnology Information, National Institutes of Health, Bethesda, MD, were published. Though I don't agree with his theories, Koonin does the best job in summarizing the state of OOL and evolution that I have seen. One article was called "The Biological Big Bang model for the major transitions in evolution," Biology Direct, 2007; 2: 21, published online August 20, 2007. Koonin discusses the areas in biology that show "the sudden emergence of diverse forms at a new level of complexity." These areas typically co-exist with the old forms rather than replace them as is predicted in Darwin's theory.

Koonin lists six areas of transition that are unexplained: Origin of protein folds; Origin of Viruses; Origin of cells; Origin of the major branches (phyla) of bacteria and archaea; Origin of the major branches (supergroups) of eukaryotes (true cells); Origin of animal phyla.

Several very interesting facts emerge from the text. One is that two of the principle cell types that exits, bacteria and archaea (one-celled organisms) have, among other things, "non-homologous core DNA replication enzymes." This means that the proteins of bacteria are distinctly different from another group of simple cells, the archaea (to see examples, scroll down or hit DNA label below or on right under topics). Some scientists had expected the archaea to be the evolutionary precursors of the bacteria, but they are not. The DNA polymerase molecule of a bacteria, Cyanobacteria, (Uniprot  Q2JWV2 ) which has over 900 amino acids is different than the DNA polymerase in one of the archaea species (Uniprot Q7SIG7 ) which has 773 amino acids.

Now, this does show that different molecules can do the same thing. But, as Koonin says, "This severely complicates the reconstruction of a cellular ancestor of archaea and bacteria..." Two different molecules with the same specific job came from a tremendously large pool of possible combinations. After all, I've shown you molecules that do very different jobs within the cells, so the amino acid sequence is crucial to function.

Hubert Yockey used Information Theory to estimate that with a short protein of 100 amino acids, only about 1 in 10^65 are functional for a specific job. A longer protein would have even less chance to be functional enough to replicate DNA in conjunction with other equally complex molecules.

Koonin proposes alternate solutions, still hoping for that common ancestor. But for Cyanobacteria, just one long protein, the DNA polymerase, has about 10^1200 combinations of 20 specific amino acids. The number of events (including chemical reactions) in the universe, if it is about 14 billion years old, has been less than 10^150. This number of events in the universe leaves very little probability that even one long protein formed by chance.

2019 Update: Koonin's full article can be found online at the link in the title of the article above.