Well, we know that many animals were born with tails. Theyy play an important and necessary part for the animal. A dog's tail, curled around its body and over its nose can provide warmth in cold weather. Dogs tails also communicate their feelings. Animals such as horses and cows use their tail to keep flies away. Monkeys and most tailed animals use their tails for balance. When a predator tries to catch a lizard by its tail, it breaks off and the lizard can escape. Some animals such as flying squirrels use their tails as rudders. So for many of our 4-legged friends, a tail is a handy part to have. As for how they got there, they were just made that way.