[quote:cbab6]Yes, but do the species inhabiting the planet not also affect the environment around them?[/quote:cbab6]
If it changes at the rate of 250 million years due to our mingling with the environment I'd be hard pressed to say that's simply a human manipulation factor. Huge climate changes have taken place when humans had no more affect on the environment than the cheetah. I don't doubt humans greatly impact the environment, but to me it is still unclear how exactly. They said in the '70s that the greenhouse effect would be very recognizable by the year 2000--further that all the rainforest would be gone.