Even mixed dogs are better fitted to survive than pure breeds. Pure breeds are bred to do one thing in one situation well. They do not function well over a wide range of environment, or circumstance.

Cur (alloyed) dogs have the ability to adapt and change over a wide range. Look up the study that was done on garbage dump dogs around the world. They have adapted and modified by cross breeding to fit the environment. Pure breeds, like Hitler's Aryans, can not adapt and therefore survive.