The early selective breeding resulting in domestication, described in the above article, was followed by a grand eugenics approach to create individual breeds with definitive characterisitics. This eventually led to the establishment of breed standards:
On September 17, 1884, a group of twelve dedicated sportsmen..., met in the rooms of the Philadelphia Kennel Club in that City. Each member of the group was a representative or "delegate" from a dog club that had, in the recent past, held a benched dog show or had run field trials. This new "Club of Clubs" was, in fact, The American Kennel Club. (http://www.akc.org/about/history.cfm)
Also see: http://en.wikipedia.org/wiki/Dog_breed - esp. the History of Dog Breeds section.
~S~
Don't forget to use plenty of paragraph breaks (and short paragraphs), to make your posts as readable as possible for this ole geezerette. It will keep me calm/submissive, too. :~)