William of Ockham
Parsimony, parsimonious and Occam’s Razor often appear in books on dinosaurs. What do they mean? Jeff Poling has offered a useful explanation of the principle of parsimony with some interesting illustrations he has devised, on which this item is based.
Parsimony is a principle that states:
when more than one explanation can be devised for certain observations always prefer that which gives the most complete explanation while requiring the minimum of assumptions, revisions or refinements of current knowledge.
This principle does not dictate. It tells the student to prefer. There is no law that states that natural systems must behave parsimoniously. Nature is often not simple but, by sticking to parsimony, hypotheses are tested and rejected in a regular way beginning with the simplest then moving on to increasingly complicated ideas until the simplest one is found that will hold up.
Any cladogram is really a diagram of evolutionary steps, such as the loss of a feature, or the gain of another. When two cladograms for the same organisms are compared, the one with the least number of evolutionary steps should be preferred by parsimony. But the preferred cladogram can depend upon which features are considered and lead to contradictory conclusions. This is often at the heart of disagreement between phylogenetic taxonomists.
Skeletal features such as vertebrae and hips can easily be seen in the physical fossil record of an extinct organism. Soft features such as organs and skin can rarely be seen. When physical features can not be seen in the fossil record, scientists have to hypothesize about them. Parsimony suggests which of the alternatives is to be preferred.
Larry Witmer has shown that the anatomical features of extinct animals should lie between living (extant) phylogenetic groups. An extant ingroup (a group of organisms within the same clade as those organisms being considered) is compared with the closest living outgroup (a group of organisms closest to those organisms being considered but not in the same clade). Any hypotheses must be compatible with what is known about the two groups and the preferred one is indicated by the principle of parsimony.
Related posts:
- Using Parsimony Some practical examples of the use of Occam’s Razor...
Related posts brought to you by Yet Another Related Posts Plugin.
Loading ...