Is It an Issue of Chemical Complexity?

It's a question of chemical complexity, but it's also a much more basic question of taxonomy. We don't have to do that when we're thinking about the larger issues of the natural world. How those chemical, complex systems emerge is not at all obvious. If something is alive, it's going to put its energy into making a few molecules that work really well and ignoring vast number of molecules that don't do much of anything.