Shamanism is the oldest spiritual healing method of mankind. As far as we know from archaeological findings, shamanism has been practiced all over the world for at least 40,000 years. Some anthropologists even assume that this practice is over 100,000 years old. Evidence for shamanic practices has been found in Asia, Europe, Africa, Australia, Greenland, North and South America - basically all over the world.
Shamanism is not a religion. There is no dogma, no organization, no holy book, no recognized spiritual leader and no founder. While people from all religions practice shamanism, by far not all shamans or shamanic practitioners are part of an organized religion. I personally am without religion.
Shamanism is a healing method that has been developed through the close connection to Mother Nature. All that happened at the same time in many places arround the world. Shamanism was not founded or invented, it was developed as a logical consequence of the closeness to nature and innate spirituality of human beings.