The earth is four and half billion years old and life in one form or another hes been around about two billion years. Between meteor strikes, supervolcanoes and glaciation you also have the entire planetary population that crashed - several times, nearly all life on earth died out for reason we can't really explain. If the actions of an entire planets population can have an effect on global climates then one could reasonably expect the climate graph to look different before life began and after life began. So does it?

Look at the temperature graph ofthe very long term, all four million years. If life impacts the environment that much why is it you can't tell when life began on earth by looking at a graph of temperature?

Evolution is the survival of the most adaptable, that's what "fittest" means by definition and earth's diversity provides a dynamic equilibrium that let the planet survive robustly a delicate balance in the incredibly hostile environment of space. We admit we cannot yet understand how it works (otherwise we'd be able to predict the weather correctly) and the notion we can alter a behavior that we don't even understand is the height of hubris.

Look at the graph, just look at it. What do you see? At around the halfway mark is where life began, and all I see different in the second half of the graph is a might be taken for a pulse. Maybe from deep space that's what sight overshoots in heat signatures indicates.

Also, when ever did the climate not change? It's really a stupid term.