Shramanas and shamans have nothing in common. They are two totally independent and historically separate traditions.(The following is taken from wikipedia, as I am lazy.)
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shramana (Sanskrit ?rama?a
??, P?li sama?a) is a wandering monk in certain ascetic traditions of ancient India, including Jainism, Buddhism, and ?j?vika religion (now extinct) [ZP adds, that Ajivikas were the other branch of Jainism. See Bronkhorst
The riddle of the Jainas and Ajivikas in early Buddhist literature.PDF ] Famous ?rama?a include religious leaders Mahavira and Gautama Buddha.
Traditionally, a ?rama?a is one who renounces the world and leads an ascetic life of austerity for the purpose of spiritual development and liberation. Typically ?rama?as assert that human beings are responsible for their own deeds and reap the fruits of those deeds, for good or ill. Liberation, therefore, may be achieved by anybody irrespective of caste, creed, color or culture, in contrast to certain historical caste-based traditions, providing the necessary effort is made. The cycle of rebirth, sa?s?ra, to which every individual is subject, is viewed as the cause and substratum of misery. The goal of every person is to evolve a way to escape from the cycle of rebirth.
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Shamanism is an anthropological term referencing a range of beliefs and practices regarding communication with the spiritual world. [2] A practitioner of shamanism is known as a shaman, pronounced /????m?n/, /??e?m?n/, (us dict: shâ?·m?n, sh??·m?n, (|?shäm?n; ?sh?-|) noun (pl. -man(s)).[3]
Shamanism encompasses the belief that shamans are intermediaries or messengers between the human world and the spirit worlds. Shamans are said to treat ailments/illness by mending the soul. Alleviating traumas affecting the soul/spirit restores the physical body of the individual to balance and wholeness. The shaman also enters supernatural realms or dimensions to obtain solutions to problems afflicting the community. Shamans may visit other worlds/dimensions to bring guidance to misguided souls and to ameliorate illnesses of the human soul caused by foreign elements. The shaman operates primarily within the spiritual world, which in turn affects the human world. The restoration of balance results in the elimination of the ailment.[4].
The term shaman is a loan from the Turkic word šamán [ZP thinks that the word comes from Tungusic language, not Turkic, as the so called Altaic language-group in not a reality, but a fantasy of earlier linguists, but who cares], the term for such a practitioner, which also gained currency in the wider Turko-Mongol and Tungusic cultures in ancient Siberia. Shamanism played an important role in Altaic mythology. Tengriism which was the major belief of Xiongnu, Turkic, Hungarian and Bulgar [and many many more] peoples in ancient times incorporates elements of shamanism.
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It is of course possible, and even probable, that in Tibet, being a Central Asian region, some shamanic practices gave an outer form to some Buddhist practices, but this must be understood as being just on the level of the surface. For example, the tormas that are offered in many Tantric rites, were in India flat cakes, whereas in Tibet they took the shape of conical cakes because of the then-current Bon practices, and now in the West, the tormas are very often heaps of factory-produced bisquit-packets and assorted candies. The surrounding culture may give the outer form, but the core idea remains Buddhist.
The White Sangha of Tibet is no more Shamanic, than we Westerners are Industrialists, in our practice.