A belief in the soul as something separate to the body had its origins in pre-history before it took a central role in religion and philosophy. Indeed, many cultures have attributed its presence in all living things, and not just human beings, in the form of animism.
Mainstream scientific investigation into the soul has been limited, with a tendency to understand the concept as a product of the mind and therefore inseparable from neuroscience. That's not to say there have not been radical attempts to uncover it. Back in 1907, U.S. physician Dr. Duncan MacDougall aimed to go one step further. In an attempt to prove it held measurable mass, he conducted a series of experiments by positioning a number of terminally ill patients on a bed fitted with finely balanced scales, and then monitoring them through to death. He concluded that there was a notable drop in their weight on each occasion. The popularised figure of 21 grams emerged based on the results taken from his first subject. Although his work was later considered to be flawed, the legacy of MacDougall's experiments lives on in the 2003 film, which takes its name from this measurement.
The popularised figure of 21 grams emerged based on the results taken from his first subject
This raises the question of whether a soul can travel someplace else, before writers of science fiction can take a further leap to ponder whether it can be removed - or even consumed. But for now, the frightening prospect of a soul eating entity pervades a number of cultures as a folklore figure, found among African peoples, including the Hausa from Nigeria and Niger, and the tribes of the Mount Hagen area of Papua New Guinea.