[darkmighty]

Life can be material-constrained instead of energy-constrained (I know there's E=mc^2, but this may not be technologically feasible hence irrelevant). Environmental domination is more fundamental than energy source tapping imo (you can imagine life in systems that don't even have precise energy analogues, like conway's game of life) -- that is, dominating whatever the basic resources are (space, materials, energy, etc).