Rare Earth Debate Part 5: Elusive E
http://www.space.com/scienceastronomy/rare_earth_5_020729.html

I had thought PT critical for technology and stability, but Chris McKay may have a point that a lack of PT could build O2 and therefore advanced life faster. I think life tends to quickly exploit chemical energy opportunities. If life existe in the presence of high O2 I think complex life would evolve provided the right temperature range. At any rate I don't forsee a bronze or iron age for early Mars due to the lack of plate techtonics. I agree with your other PT points.

My belief in rapid evolution under the right circumstances (ie punctuated evolution) is why I think there is no clear driving force for our level of intelligence. I think we use intelligence to exploit niche's that have been filled in many other ways by other creatures with repretitive similarities. The uniqueness of our adaption suggests to me that we are one of nature's many unlikely quirks. Quirks aren't impossible they are just the products of unlikely evolutionary paths.

Regards,
Mark