Have you ever seen a hairless dog? They have been domesticated in Peru since the time of pre-Incan cultures. Ancient Peruvians left behind statues and carvings of these dogs, and they were also used during the reign of the Incas. Sometimes a tuft of hair grows on their heads, almost resembling a mohawk hairstyle. Other dogs are completely hairless. They are known for being clean pets that are not prone to fleas. Scientists say that the hairlessness may be the result of a recessive gene, since the average birth rate is one coated puppy for every two puppies that are born hairless.