The ability to shapeshift is part of many cultures that depended upon hunting to survive. This primal ability is still seen among Bushmen of South Africa, who not only follow in the tracks of animal prey but run like the animal and making crises similar to them. Around the fire at night before and after a hunt the hunters would take the form of animal imitating and embodying them. This behaviour has been part of the human tradition from the earliest times when the sympathy between hunter and hunted was crucial to survival. Many traditions of disguising and making derive from such pursuits.
In Irish lore the hunter ability to blend into their landscape as an animal to become invisibility. Special shapeshifting spell of invocation called Fith-Fath was employed by Gaelic hunters in order to enable the hunt. Such pagan spells were used by St Patrick who, when he was being pursued by enemies, invoked a Fith-Fath to change himself and his followers into to shape of a deer in order to put scouts off the scent of their human prey. The remnants of that spell are left in the fairy tale giant’s cry of Fee, Fi, Fo, Fum.
In world myth, the ability to shapeshift between animal and humans usually found in talented individuals. One of these heroes is in the Irish myth in Tuan Mac Carill.
Tuan Mac Moville was called upon by Finnen of Moville, the teacher of the great saint Columbia, to relate his lineage. Tuan came with the first colonist the Partholonians, survivors of the Great Flood. When the Partholonians died out, Tuan passed from old age into the form of a stag and saw the coming of the Nemediains. When they died out Tuan passed into the shape of a boar. In this form he saw the coming of the Fir Bolg until the coming of the Tuatha de Danaan who overcame them and took the form of an eagle. He took the form of a salmon and in this form he was caught and served up as a meal to the queen of Ulster. When he was later reborn of her womb, he retained the memories of he had lived through in his past forms.
There is similar tradition is found in the case of the Hindu god Vishnu who is seen to be a shape shifter through the many ages of the world. Each of his appearance is called an avatar or vehicle of manifestation and he passes into these shapes whenever the world is threatened, for he is the preserving god of Hinduism who appeared in the shapes of Rama, Krishna and Gautama Buddha. His earlier avatar include Matsya the fish, Kurma the tortoise, Varaha the boar, Ni-Simla the man-lion as well as Vamana the dwarf. This ability to shapeshift could be said to be in the nature of reincarnation. Although some of Vishru’s forms are purposeful acts of rescue, taken as a whole they are means by which the history of the world is preserved and extended. The final avatar Kalki will govern the age of Strife that is still to come, punish the evildoers, reward the virtuous, destroy the world and so create a completely new cycle of life.
Some shapeshifters do not wish to be caught and will use their skill to avoid entering into contracts or relationship. We see this in the myth of Proteus, the first man of Greek myth or, he is also known as Nereus, the old man of the sea who when challenged takes the successive form of a fish-tailed being, a lion, stag and snake. He was challenged by Aristaeus, the son Apollo, who successfully out-wrestled him. Even without this myth, the whole memory of the world is seen to be embodied in one being whose very cells have come down via the ladder of DNA to their present pattern. In this way, the ability to take animal shape remains magically within each of us.
John and Caitlin Matthews, The Element Encyclopaedia of Magical Creatures, 2013, Shapeshifters, p 418-19