Quote (Spruce @ May 3 2013 10:56am)
"Crossbreeding" is simply another way of saying natural selection. By keeping the bloodlines of dogs "pure" you're bottle-necking undesirable traits. Nature seeks out the best adaptations... This is why "mutts" typically live longer, and with fewer ailments.
Crossbreeding also introduces undesirable traits between each breed. When breeding purebreds, there is obviously some poor quality dogs, however, the number of high quality purebred dogs, bred to achieve highly desirable traits within that breed, greatly outnumbers the number of "high quality crossbreds"