I don't see any evidence that we have "the most efficient machine" and that it's a cow. Evolution is incredibly slow, and humans outpacing it (using their brain

I don't see any evidence that we have "the most efficient machine" and that it's a cow. Evolution is incredibly slow, and humans outpacing it (using their brains) is exactly why we're at the top of the food chain. Who are we to think we can't do better in the lab, when almost every worthwhile human invention has been precisely that – beating evolution at its own game? I do agree with your initial premise though, we should be very careful and spend a lot of time considering the environmental impact. It's also very easy to say that as a well-off westerner with abundant access to food, though ;)