I agree totally with you Bill but have a couple of additions.
Not only does primitive organism mean earlier the earlier organism may infact be more complex. It is a myth that primitive organisms are infact simplier than later decendants (
http://www.newscientist.com/article/dn13...complexity.html)
People assume natural selection is a linear process and Human's are even somehow outside it. Events occur outside the sphere of biology can and do abruptly change the enviroment and hence as per Bill's comment there is no possible concept of progressing. If a massive metorite plowed into Earth tomorrow the most likely survivor would be (
http://www.newscientist.com/article/dn20534-goldmine-worm-shows-animals-could-be-living-on-mars.html). It requires no light, its temperature is very well protected it has a very good survival prospect in such an event we and most other animals and organisms do not.
