Some questions on evolution

[Angrboda]

I get what you are saying about single cells and the only way is up to more cells. But I want to play devil's advocate and keep asking why. We could have just mutated to a different single celled organism instead.

I think it may be more appropriate to say that life forms diversify, rather than that they become more complex. When they diversify, they evolve into all different levels of complexity, but a single celled level of complexity can't get any simpler, and so it forms a wall on one side of which is a range of complexity. Thus, from humans, if we evolve into different life forms, some will be simpler and some more complex. If you arrange all life forms as simple to complex, it will seem that things are getting more complex, but they're really only becoming more diverse.