Suggested in my hypothesis is that life is an energy moderator (with modification through descent)
"Generally speaking... chemical stress caused by high or low pH does not require as extensive an adaptational response as high pressure or temperature." - Life on the Edge, M. Gross
Too hot or too cold (I call it the Goldilocks syndrome) may well be the main stress on life. (I think life can be defined as that which best adapts to that heat cycle)
If so you would expect there to be HEAT shock proteins (see the lit on that). But we would also expect to see COLD shock proteins for dealing with the other end of the liquid water spectrum.
Gross's book gives examples and looks at cases of both heat and cold shock proteins.
