One further discussion point is whether evolution is or is not purposeful (teleology). > Evolution certainly looks purposeful in the sense that it continuously changes toward the more complex. - Here is an example where evolution might have paused, but did not move backward. Does this tree have vestigial parts? Our appendix was promoted the same way, but it is now shown it is useful as it has an immunity function. In the article is a picture of a Moa. Gould discusses in 'Full House' the observation that over time species tend to grow larger. - http://sciencenow.sciencemag.org/cgi/content/full/2009/724/1