Shrunken heads were usually used as trophies, in rituals, and as a means of trade. While headhunting - the practice of searching for the head of a victim and tearing it from its body - has occurred in many regions of the world, head shrinking has only been documented in the northwestern region of the Amazon rainforest. Jivaroan peoples, which includes the Shuar, Achuar and Aguaruna tribes from Ecuador and Peru are known to have carried out the practice with zeal.

       The practice originally had only religious significance: shrinking the head of an enemy was believed to harness their spirit and force him to serve the shrinker.

       But with the arrival of Western colonists and traders, a market opened for those who wanted shrunken heads as keepsakes and collectable items.

       A sharp increase in the rate of killings followed.

       To keep up with the demands, tribespeople also began shrinking animal heads, often selling them on to Western traders who would unknowingly pass them to museums and wealthy sponsors.

       In the mid-19th century, the Amazon's rubber trees and rich minerals brought traders, miners and missionaries to the region.

       Settlements sprung up in or near the territory of the Shuar and Achuar.

       Dr Lindset Fitzharris, a medical historian, told the Smithsonian Channel's documentary, 'Secrets: Shrunken Heads', that a lot of subsequent "collectors were being duped".

       She added: "They were being sold incredible stories that were attached to these objects."

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       The documentary explored one museum that had bought a shrunken head in the mid-20th century.

       Curators were told the head belonged to a male shaman who was trying to cure a child but failed, and so the father of the child killed him.

       In 2016, the museum analysed the head's DNA, revealing that the head was indeed human and not an animal's.

       Yet, something was wrong.

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       The DNA analysis showed it was a female head, not a male.

       As the documentary noted: "It's a shocking revelation - genuine ceremony shrunken heads are always male because the Shuar shrank heads to stop the soul of a slain warrior from taking revenge."

       In Shuar society women were never warriors.

       The only reason to shrink a woman's head would be to satisfy the "Victorian demand for more curios".

       The female was not a victim of tribal conflict, but of "cold blooded murder".

       One of the museum's current workers said: "The killings started to increase in order to supply for the demand.

       "So it was most probably an innocent female."

       The head was, like countless others, essentially a commercially shrunken head.

       According to historical accounts, the Shuar usually acquired guns in return for the heads, the rate being one gun for one head.

       However, money was also used, the equivalent of a British gold sovereign for a head, according to a 1952 report by The Times.

       Seeing how lucrative an industry it was, people all across South America, completely unconnected to the tribes, began making counterfeit shrunken heads in the early 20th century.

       They often used corpses from morgues, or the heads of monkeys or sloths, some even using goatskin.

       In 2001, Kate Duncan, in her book, '1001 Curious Things', wrote that it had been estimated that "about 80 percent of the tsantsas (shrunken heads) in private and museum hands are fraudulent".