Given the disposability of humans and all other living creatures, the Earth's world fits quite nicely into a hypothesis of a massive simulation for solving odd social problems. As if, you know, someone has thrown a large pile of play dough, which can be moulded into any weird pile, like a cat or a human. And that play dough must try to preserve its shape for as long as possible. I guess we can call it a law of physics, i.e. reducing the energy by keeping itself in a pile.
The interesting thing is: everything tends to a remarkable uniformity of shape. Look at fruits or leaves or animals. I guess the building of shapes starts somewhere on the atomic level and then proceeds with modifications to sustain the weather. The very perplexing thing is that apart of the size, life on other planets may have quite a lot of similarity with the shapes here on Earth. Makes it kinda boring, really. There must be some 4,5,6-dimensional beings to make existence bearable.