Dogs whose parentage is unknown, or a combination of several breeds over a matter of generations, are called mixed breeds. A cross or mixed breed may be as good a dog and as true a friend as any, but you know less about the puppy when you get him. He is usually given away because someone wants to get rid of him. You don't know what he will turn into and may not know how he has been cared for. However, the cross and mixed breed's heart is as big as that of a purebred and properly cared for he will return just as much devotion.
All dogs come from a common ancestor millions of years ago.
But through the ages dogs have changed in time becoming individual types and then breeds, suited to the climate and occupation given them by man. These early dogs can be classified, but only roughly, as there is considerable overlapping in the ancestry of the breeds. The herd dogs with long, dense coats are bred for endurance and cleverness. The northern dogs of the cold countries have heavy coats, curled tails into which they bury their noses while sleeping in the cold, and are powerfully built sled and draft animals. The sporting dogs hunt by airborne scent and some also retrieve game for hunters.