system
A chat on 4chan
human
where do skinwalkers come from?
gpt
The most realistic/ historically plausible shape shifter would have to the be the 'skin walker'.
Pretty much any shape shifter that needs a pelt, cloak, or cloth to transform into an animal can be logically explained.

Tribal hunters throughout the world used to believe that wearing the fur pelt or skin of a certain animal would give them a spiritual connection to the animal which was killed. The idea was that through ceremony, sacrifice, meditation, and or dreams they could 'become' chosen animal over time.

From a practical sense, wearing a pelt often acted as a tribal form of hunting camouflage. This combined with staying low to the ground and covering their sent helped their hunts and kept them warm. (wearing the pelt of a male deer might attract does which makes hunting a whole lot easier)

Many basic folk lore skin walkers come from the institution of an worn object. This comes from the logical conclusion many tribal hunters reached for. Mimic the animal you want with pelts and movements so well that an observer cannot tell the difference at a distance or in low light conditions. As humans, our pattern recognition goes into overdrive and the immersion is broken, the 'holy shit that's not a animal moment' kicks in, and the figure is listed as anthropomorphic, lycanthropic, or a shape shifter.

While not as common as say 100 years ago, some modern 'irl shape shifters' do still exist; however the original hunter gatherer aspect has been lost in the modern era.
(ala furries and otherkin)

TLDR: 'Shapeshifting' the oldest form of LARP used by hunters with drip after hitting the pipe a little to hard, its legacy has been shat on by modern day degenerates.