Talshere said:
EDIT: By the time the environment became contaminated beyond repair, it is plausible that life could have evolved to cope. Which would also support the reasoning behind there only being one form of carbon life.
Non-sufficient amounts to kill would not likely have established a driving evolutionary pressure and lethal amounts would have made the organism extinct. You'll notice that despite Arsenic being something like in the top 15 elements composing our bodies, we still don't have an organ specializing for dealing with it - and inorganic forms of it are particularly difficult for our metabolism to deal with.
What I'm questioning is the existance of a specialized organ. That requires significant and constant evolutionary pressure, organisms with it must have survived particularly well in comparison to carbon-based ones without it. But at the same time, I believe such concentrations would have been inherently lethal to the point of inducing extinction. Not to mention arsenic-based life-forms competing for space and resources being far, far more suited to the environment.
And yet supposedly, the carbon based life was the one to reach sapience - meaning it had sufficient energy available for the development of a brain.
I'm not buying that. Everything I know of biology and species development(which admittedly is restricted to basic university courses) just screams at me "this is not right."