We are aware of the term "Survival Of The Fittest by Natural Selection". An organism evolves so that it can survive in its prevailing environment. We know that some microbes are capable of living in the most extreme conditions. Viruses in act can kind of switch between living and non-living. So, why don't other animals including humans evolve into microbes so that we can survive better? Why does the arrow of evolution always point in the direction of complexity? Is it because humans are not exposed to extreme conditions?