Evolution (Evolution)

by David Turell , Thursday, February 05, 2009, 13:49 (5558 days ago) @ dhw

"Nobody is arguing ... yet ... that the tree concept has outlived its usefulness in animals and plants. While vertical descent is no longer the only game in town, it is still the best way of explaining how multicellular organisms are related to one another ... a tree of 51 per cent maybe. In that respect, Darwin's vision has triumphed: he knew nothing of micro-organisms and built his theory on the plants and animals he could see around him." 
> The whole kerfuffle seems to be about the discovery of horizontal gene transfer, and some scientists now prefer the metaphor of the web as opposed to the tree. Well, if the argument is just about horizontal and vertical, with vertical still the best way of explaining animals and plants, maybe Darwin simply drew the wrong tree. How about a cedar? - The whole issue is homologous vs. analagous. Using morphology, in Darwin's time if it looked alike then it was related. That is analogous. Homologous means one can show true descent and relationship as parts are modified and changed. The key to the tree is DNA/RNA studies. Homologous changes, despite gene transfer, will truly outline how much of a real tree there is. The other way is to study biochemistry. Follow the development of myoglobin or hemoglobin, for example, and see how they relates in various species, etc. Cytochrome C, an enzyme in energy production, is another excellent marker to follow. One can look at the pattern of amino acid sequences in this method. - The trees around our house are mainly post oaks. When they lose leaves in the winter, as now, they look like monster trees out of a Tim Burton movie. Perhaps that is the kind of tree it really is? Science will find out.