On what evidence, Michael?
Puddles has posted a couple of C.M. links - I'll assume you're familiar with C.M. and how he describes dog behaviour in terms of the Wolfpack with the Alpha wolf being the dominant leader who asserts his dominance through rolling his subordinates (what he describes as the Alpha roll)...
In the first half of the 20th century, Schenkel studied wolves and published his findings (full report available
here. He observed that wolves live in a hierarchical society with the Alpha being the dominant wolf. David Mech later popularised this idea in one of his early books.
And so the idea spread... dogs are descended from wolves. Wolves live in a hierarchical society, and so "we" must dominate our dogs to let them know who's boss.
Neither Schenkel or Mech suggested that dominance "theory" applied to domestic dogs, but the idea spread and it somehow became "common knowledge".
The wolves that Schenkel studied were not a wild wolf pack living in their natural environment, but captive, made up of individuals captured from different locations. Modern studies have shown that wolves live in family groups with the parents being at the head of the family.
David Mech later withdrew his support of the idea that wolves live a hierarchical society and discusses this here:
View: http://www.youtube.com/watch?feature=player_embedded&v=tNtFgdwTsbU
The idea of a dog vying for dominance as that's what they do in wild is based on a false premise, it has no basis in reality.
Also, Schenkel misinterpreted the behaviour of the wolves he studied with regards to "pinning" others to the ground - one animal will roll onto its back as a gesture of appeasement, it hasn't been rolled (see John Fisher "Think Dog")
Dogs are not wolves, they are by now a separate species. Even the most "wolf like" (or wolf shaped dogs if you like) e.g. GSD, Husky etc have diverged significantly from the wolf - smaller skulls, smaller brains, a male dog once mature may remain fertile all its life whereas a male wolf will only be fertile during the mating season (Kreeger 2003 cited in Barry Eaton's "Dominance in Dogs"), a wolf bitch will only have one oestrous cycle a year so that the pups are born in the spring (Kreeger 2003, Packard 2003, again cited by Eaton).
John Bradshaw founded and is the director of the Anthrzoology Institute at Bristol University. He is the author of "In Defence Of Dogs" which brings all these ideas together.