The Chinese Crested is a perfect example of one of the weird and wonderful dogs that have been created through selective breeding.   The purpose of a hairless dog must be purely an aesthetic one.   For in terms of nature all hairless breeds  (of which there are several)  are at a distinct disadvantage,  furthermore they are subject to certain genetic defects, such as missing teeth,   or in some extreme cases, missing claws too. Often enough there are dogs in a litter which are born with a full compliment of hair.   These dogs are frequently used by breeders to maintain a reasonably healthy gene pool.

Most breeds of hairless dogs are found in tropical or sub-tropical countries.  The actual origins of the Chinese Crested or indeed other hairless dogs  are lost in antiquity,  and it is unclear whether the hairless dogs that are found in South America are indigenous or whether they were taken there by the Chinese.

They were already there at the time of the Spanish conquest in the early 1500s,   and the Aztecs had what appears to be a hairless dog,   indeed the Mexican hairless is also refered to as Xoloizcuintli or Tepeizeuintli,  but both the Chinese Crested and the Mexican Hairless could have originated from Asia,   or Africa.   To confuse matters further hairless dogs in Cuba are often called El Chino.    

Whereever they originate from one thing is certain,  that human beings like to manipulate those peculiar evolutionary quirks of nature to their own ends,  and dogs have proven to be a rich subject with which to explore the boundaries of genetic engineering.