re: #3 Rightwingconspirator

Aliens on earth. Kinda. Paralleled evolution? Panspermia?

I’d bet not. Instead, I expect this will eventually be understood as an evolutionary adaptation from phosphorus-based life to a setting where arsenic is all too plentiful and maybe phosphorus is scarce.

There’s an easy enough pathway, after all. Start with bacteria that tolerate slight concentrations of arsenic. These prosper when their competition is killed. But once they’re established in some sheltered corner of the lake, where the concentrations of arsenic aren’t so high, a whole lake awaits gradual invasion, up the arsenic concentration slope. The selective pressures would be fierce whenever the lake’s freshwater intake dropped, as it has in recent times.

I expect this new species to have all sorts of structural and organizational similarities to existing life, even strings of “DNA” that match what is found in other, somewhat similar bacteria, but with the wrinkle that it can use arsenic in place of phosphorus.