From my reading, I think shamanism certainly has its place in the development of martial arts. Codified MA may have worked its way from India eastward and developed into Chinese MA either before or at the same time as Buddhism. Martial arts themselves were developing well before this.
China's lion and dragon dances as well as the names of many styles obviously stem from the ancient, animalistic cultures (in which gods took the forms of animals or vice versa). Just as some American Indian tribes did (or do), the Chinese looked to the animal world for answers to problems, inspiration, etc. The story of how praying mantis was developed is a good example.
So, if you were a member of an animalistic or shamanistic culture, your tribe/village would adopt an animal -- or its spirit -- and worship it, give it gifts, take its image into battle or hang it on the village gate to drive away both evil spirits and physical attackers. The shaman would probably invent a dance based on the movements of the tribe's patron animal, and since shamans were often the tribal leaders (especially in Asia) they would create "signature" battle moves that mimicked the animal's movements. Maybe only one or two moves, along with a really cool-looking dance they would do right before the battle started, just on the off-chance that it would frighten the attackers away.
So yeah, it probably started from shamanistic tradition. (whew) Later on, Buddhist and Taoist philosophies moved in and many adherents shed animalistic beliefs. However, outside the monasteries people intermingled these philosophies with their existing religion. The animalistic tradition continued in a different vein; people didn't worship animals but still considered them powerful creatures worthy of imitation. Which leads back to ... the development of codified martial systems, forms, etc. based around the movements of animals. (double whew)
As far as fighting off physical demons -- whirlwind, I think you need to drink more water during your workout, sounds like you got REAL dehydrated there!
Sam
(who reads way too much National Geographic)
There is a great streak of violence in every human being. If it is not channeled and understood, it will break out in war or in madness. ~Sam Peckinpah