Polish scientists are launching what they say will be the world's largest scientific study of Egyptian mummies. The Warsaw-based project will examine 42 mummies, looking for clues to ancient diseases, the mummies' former occupations, and even whether the corpses were left-handed.

Though Egypt's mummies are perhaps the most famous, cultures around the world have found creative ways to preserve their dead.

Here are a few of world's mummies, including some you may not have heard of, and their strange path to pseudo-immortality.

Bog Bodies

Ireland is known for its fairy tales of leprechauns and sprites, but it turns out there's something even stranger hiding out in the mists—bog bodies.

Bodies thrown into the bogs of Ireland hundreds of years ago are preserved by this hostile environment. Bogs have very little oxygen, keeping the bacteria that eat dead bodies at bay and allowing bog bodies to be preserved for centuries. (See National Geographic's pictures of bog bodies.)

One of the most recent of Ireland's bog bodies was discovered in 2011 and the oldest bog body on record at 4,000 years old, which is 500 years older than King Tutankhamen of Egypt.

Though the bog can tell us about the lifestyle, diet and living conditions of a person, it also destroys DNA, so no one knows the bodies' exact lineages. Some scientists think that the Irish bog bodies were former kings, violently murdered and then tossed into the bog because they failed to protect their people from disease or famine. (For more theories on ancient bog bodies, check out "Who Were the Ancient Bog Mummies? Surprising New Clues.")

Little did they know that their bodies would be preserved for millennia.

World's Oldest Mummies

Chile's Chinchorro mummies are the oldest known intentionally created mummies in the world. The Chinchorro were a fishing people living on the coast of what is now southern Peru and northern Chile about 9,000 years ago.

The most famous Chinchorro cemetery is in Chile, nestled between the cities of Arica and Cobija, where the remains of what are known as the "Black Mummies" were hidden for millennia. Black Mummies were named for the layer of black manganese, a metal resembling iron, that coated their bodies.

To create a Black Mummy, Chinchorro morticians cut off the body's head, arms and legs, scooped out the organs and flesh, and often emptied the brain through a hole in the skull. The skin was peeled away from the body and reattached later, like taking off and putting on a sock, according to a 1995 study published in the journal Latin American Antiquity. Morticians completed the process by shoving hot coals into the trunk cavity to dry the cadaver.

Afterward, morticians rebuilt the body with sticks and animal hair, and covered it in white ash. As a final touch, morticians attached a crop of short black hair to the scalp, and painted the corpse black with manganese.

View Images The Chinchorro mummies are the oldest known artificially preserved dead, dating to thousands of years before Egyptian mummies. Photograph by Ivan Alvardo, Reuters

No one knows why the Chinchorro mummified their dead. It's possible they believed in an afterlife, or perhaps natural disasters such as earthquakes and El Niños pushed their people toward mortuary rituals and ancestor worship.

21st-Century Mummies

Some villagers in Papua New Guinea still mummify their ancestors today.

After death, bodies are placed in a hut and smoked until the skin and internal organs are desiccated. Then they're covered in red clay, which helps maintain their structural integrity, and placed in a jungle shrine.

(Watch how it's done in "Lost Mummies of Papua New Guinea" on the National Geographic Channel.)

Bodies are brought down from the shrine for celebrations, and loved ones visit the mummies to consult with their ancestors.

View Images A family carries an ancestor back to the cave above their village. In Papua New Guinea, mummified family members are often today a part of the community and are included in village celebrations. Photograph by Ulla Lohmann, Nat Geo Image Collection

The first documentation on Papua New Guinea's mummies was by British explorer Charles Higgins in 1907. In the 1950s, traveling missionaries have discouraged the practice, but there are still villages where revered ancestors are smoked after their deaths.

How to Become a Mummy

Some of our ancestors didn't want to rely on a mortician—they took matters into their own hands through self-mummification.

The grueling and fatal practice was undertaken by Buddhist monks in Japan, China, and India. Some believed that the end result would give them special powers; others thought they'd one day awaken as if from a sleep. Monks hoping to attain self-mummification restricted themselves to a diet of nuts and seeds for about three years and then spent another three years eating only bark and roots. The goal was to deplete their bodies of all fat so, once they'd died, the bacteria that eat corpses would have less food.

This diet was pioneered by the Great Master Buddhist Kûkai, who was said to have forsworn all cereal grains before self-mummifying himself in a stone cave, according to a 1962 article published in the journal History of Religions.

Afterward, monks drank a poisonous tea, causing them to vomit repeatedly so they'd lose their remaining bodily fluids. The lack of water in their bodies and poison flowing through their veins would, again, make it more difficult for bacteria to decompose the body after death.

When the end was near, the monks moved to a tomb, equipped with only an air tube and a bell. These devout men meditated, ringing the bell each day to tell those on the outside they were still alive. When the bell stopped ringing, the air supply was cut off, and the tomb was sealed.

Despite all that work, not all attempts at self-mummification were successful. In fact, it appears that most monks failed, and their bodies decomposed.

Today, self-mummification is discouraged by Buddhist religious leaders, but it's a practice that has existed since at least the 12th century, and scientists are still finding more of these mummies mummies; there are at least 24 known. In 2015, a self-mummified Buddhist monk was discovered entombed in a Buddha statue in China.

Classic Egyptian Mummies

The Egyptian mummies, snug in their pyramids, protected by "curses" are infamous in the worlds of both fact and fiction.

View Images The Egyptian embalming process was so successful that we’re still learning from the ancient, mummified corpses. Photograph by Kennth Garrett, Nat Geo Image Collection

Celebrated by researchers for offering a window into the past and sensationalized by Hollywood, embalmed Egyptian corpses are the créme de la créme of mummies.

Egyptians were embalmed during a process that often lasted 70 days. Priests liquified the corpse's brain and drained it through their nose. All internal organs were removed and placed in separate jars, except the heart, which was left intact because ancient Egyptians believed the heart was integral to a person's being and intelligence.

Afterward, the body was dried with natron, a type of salt, and wrapped in hundreds of yards of linen. Now completely mummified, the body was placed inside its tomb along with paintings or models of food and amulets—all things the person would need in the afterlife.

"The Egyptians believed that the mummified body was the home for this soul or spirit. If the body was destroyed, the spirit might be lost," according to the Smithsonian website.

This type of mummification was so successful that now, thousands of years later, we're still learning from the bodies of long-dead Egyptians.