String theory predicts 10 spacetime dimensions, but our Universe has only 4. (Why 4 spacetime dimensions? Bertrand's theorem: Stable gravitational orbits exist only in 4 spacetime dimensions.)
String theorists postulate that the other 6 dimensions are curled up into a Calabi-Yau complex manifold. The topology of the Calabi-Yau manifold, and the winding numbers of the fields (fluxes) that wind around them, determine the DNA of the universe. What is the point of having DNA if you don't use it?
Suppose that there exist laws of physics that allow a universe to reproduce.
Reproducing universes fill the Multiverse with their progeny.
Finding oneself in a reproducting universe would be common.