Over at Carl Zimmer’s excellent Corante blog, The Loom, he has posted a graphic of the Tree of Life, a phylogeny of genomic diversity. It is an amazing graphic, and it really drives home the point that most of life on this planet is comprised of things we cannot see with the naked eye. Only the slim red segment represents all eukaryotic life; plants, animals, fungi and protozoans. The rest of the tree is comprised of bacteria. And this chart doesn’t even include the even larger genetic diversity of the viral world, which are technically not alive.
Speaking about life, I recently read a fascinating piece on the origins of life. While scientists might never discover the actual origins of life, they are getting closer and closer, and making ever more educated guesses about what happened. Especially intriguing is the realization that certain kinds of RNA can function as both genetic material and synthesize protein; a ‘ribozyme’ that could have both stored information and produced reactions in the first living organisms.
The article lays out several competing hypotheses for the early environment on earth, and what conditions provided the impetus for organic molecules to self organize into coherent, reproducing structures. Many experiments have shown that amino acids, purines and other building blocks of life form readily in atmospheric conditions considered likely for the early atmosphere of our planet. It is even possible some organic molecules arrived from space on board comets or meteorites, adding to the prebiotic stew bubbling away on the planet. It is a fascinating subject, and the article mentioned above is very well done.