Why on Earth? Shrunken heads
How do Amazon Indian tribes shrink heads?

The instructions for this unusual form of native craftwork are actually pretty simple. First kill your enemy. Remove the head as close to the base of the neck as possible, then slit the scalp from the crown down to the back of the neck. Peel the skin away, turn it inside out and scrape off all the fat, then drop the skin into a pan of boiling water and chinchipi plant juice. Simmer for two hours - this removes the skin’s natural oils and shrinks it to about two-thirds normal size.
Next, sew the back of the neck and the eyelids closed, then place some hot pebbles inside the head and whirl it around, replacing the stones as they cool. This will shrink the skin further. When the opening becomes really narrow, after about 20 hours, use hot sand instead. Throughout the shrinking process, be careful to iron any lose skin that appears on the face with flat, hot stones to prevent distortion of the features. Hang your head in the smoke of a fire to cure. Finally, wash the head - it will now be about 1/4 the original size - and display.