I brought up the new discovery of a bacterium that can use arsenic instead of phosphorous, when forced to, about 13 hours ago, with several readers thereof, but no comments. The press is filled with this and a bunch of conjectures re' extraterrestrial life, alien life, etc. Here are several takes on this:-http://www.physorg.com/news/2010-12-sara-seager-discovery-life.html-http://www.newscientist.com/article/dn19805-arseniceating-bacteria-point-to-new-life-forms.html-http://www.sciencedaily.com/releases/2010/12/101202140622.htm-The first site is the most definitive in philosophic take. This is an adaptation of a living organism that is forced to use arsenic, the element most closely related to phosphorous. Arsenic is tiny amounts is found in many living organisms. This bacteria prefers phosphorous, but can use arsenic. All this means is life is tough and living forms can make necessary adaptations to continue living.-None of this means there is extraterresterial life, or alien life, or that it uses arsenic. All it means is life can adapt to extreme pressures for survival. The other thought is bacteria are single-celled. They adapt better than multicelluar organisms. That is why they have been around for over 3.6 billion years. We humans are too complex to adapt ourselves to swimming in Mono Lake, a stinking supersaturated cesspool of water. I've been there. Google it and take a look. Extremophiles are everywhere that the environment for life is extreme.-This is the key 'dodo' point I was making. Evolution naturally results in branching as different adaptations are tried out against natural selection. Because life is so tough, those branches can go on seemingly forever, and seemingly with no purpose till they die out usually by accident. That is why evolution is a giant bush, not a tree. View evolution as the 'bush of life'.