Original sentence: 0nce a planet has an ecosystem with all habitats filled, the rate of evolutionary change drops considerably.A small number of mass-extinction events may be required to give evolution the chance to explore radical new approaches to the challenges of the environment rather than becoming stuck in a suboptimal local maxima (suboptimal to maximum likelihood of evolving human-like intelligence).So apparently just the right values for hundreds of variables are required to be able to support 'advanced' life on an Earth-like planet.The Evolutionary theory of Punctuated equilibrium argues that:.The fossil record is thought to show that a stable ecology has been reached on Earth several times, first just after the Cambrian Explosion.The period within which evolution fills all niches (reaching equilibrum) is relatively short on Earth, in relation to geological time
Edited sentence: A small number of mass-extinction events may be required to give evolution the chance to explore radical new approaches to the challenges of the environment rather than becoming stuck in a suboptimal local maxima.Evolution, though, is a two edged sword.It stagnates if given the chance.Once a planet has an ecosystem and all habitats are filled, evolution may slow down considerably.So apparently just the right values for hundreds of variables are required to be able to support advanced life on an Earth-like planet.This is thought to have happened on Earth several times, first just after the Cambrian Explosion