Exactly. Mutts may often be better than their purebred parents (by various objective and subjective criteria), but in the end it'll take a few generations of mutts and, well, survival of the fittest before you can see a general trend towards improvements in health and longevity.
Genetics are a lottery, starting with unhealthy parents the odds are against the offspring. It'll take generations for the population as a whole to move towards being healthier on average.
Genetics are a lottery, starting with unhealthy parents the odds are against the offspring. It'll take generations for the population as a whole to move towards being healthier on average.