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Could Humans Hibernate?

Some animals have it made. Their whole day revolves around eating and having sex (and, to be fair, trying not to get eaten themselves). And when winter arrives, they get to curl up somewhere and wait things out until the weather is nice again. Can humans get in on this hibernation thing?

Bear image via Shutterstock

First, a note on the lingo. While people often use the term loosely to refer to any state of dormancy in animals, true hibernation is a pretty specific thing characterized by “profound reductions in metabolism, oxygen consumption and heart rate.”

A hibernating animal’s core body temperature drops to extreme lows, sometimes matching the local outside temperature. As its body cools, its metabolism slows. This reduces the need for oxygen, and its breathing will also slow, sometimes to just one to five breaths per minute. The heart rate will likewise slow to just a few beats per minute. All of this ensures that the animal’s body will conserve as much energy as possible, which is necessary because it’s largely fueling itself with a limited supply of fat. "True hibernators" don’t shut down for the whole winter, though, and occasionally rouse to use the bathroom, eat from stored food, and stretch a little so their muscles don’t atrophy. Some animals may even switch hibernation spots.

Animals go into this energy-saving mode to ride out long stretches of environmental extremes, like lack of food and water, or very cold or very hot seasonal temperatures (dormancy during cold seasons is hibernation, and dormancy in the summer is called aestivation). Humans can deal with these situations while remaining active because we have things like canned food, greenhouse tomatoes, air conditioners, heaters, and turtleneck sweaters. Our bodies aren’t required to hibernate and we’re not perfectly adapted to it, but scientists have turned up a number of ways in which we’re pretty close.

Deep Sleepers

There are plenty of documented cases of humans going into hibernation-like states. In October, 2006, rescuers found Mitsutaka Uchikoshi 24 days after he’d gone missing on western Japan’s Mount Rokko. When they discovered him, he had no detectable pulse or respiration and his body temperature had dropped to 71 degrees Fahrenheit. Doctors would later confirm that his metabolism was almost at a standstill. When he woke up, remarkably showing no signs of brain damage or other ill effects, he explained that the last thing he remembered was falling on the trail and hitting his head. The entire time he’d been missing, he was unconscious, exposed to the elements and without food or water. The doctors who treated him said that the quick onset of hypothermia slowed his body down like hibernation would, and probably saved his life.

Similar survival stories include a Norwegian skier who’d fallen into icy water and woke up unfazed after showing no heartbeat, no respiration, and a core temperature of 57ºF, and the Canadian toddler who got lost outside on a cold night and was later revived after cooling to 61ºF and exhibiting no heartbeat for a full two hours.

In a controlled experiment in the early 1970s, the Yogi Satyamurti confined himself to a small, sealed underground pit in a state of deep meditation for eight straight days while being monitored by an electrocardiogram. At first, the yogi’s heart rate was normal, and then increased to 250 bpm for a while. On the evening to the second day, the ECG flatlined and remained like that until about 30 minutes before the pit was scheduled to be opened on the last day. The astonished researchers who’d been monitoring the yogi - whose core temperature had dropped four degrees in the pit - were sure that something was wrong with their equipment, but couldn’t find any malfunction or explanation besides the yogi’s heart stopping or decreasing in electrical activity below a recordable level.

Sleep image via Shutterstock

It looks like our bodies have some of the abilities needed for hibernation. But like we said already, we’ve never had to, so our bodies aren’t completely adapted to the task. A few of the things holding us back are rather big obstacles. For example, researchers at the Paul Flechsig Institute for Brain Research in Leipzig discovered a few years ago that the brains of hibernating ground squirrels have brain cells containing modified proteins that are similar to those in the brains of Alzheimer's patients. The synapses that connect the brain’s neurons in both groups were also similarly degraded. The catch is that the squirrels’ brains bounce back after hibernation. They repair themselves and the animals show no signs of damage when they wake up in the spring, while human brains in the same state continue to deteriorate.

But hibernation on-demand would be useful to humans for reasons other than avoiding winter. Inducing hibernation in an accident victim on the way to the hospital could stave off extreme blood loss and cell breakdown, plus buy surgeons extra time to repair the injuries. It would also allow for the sort of space exploration that only seems possible in the movies. Placing astronauts in a dormant state, like in the Alien franchise, would allow them to sleep off the multiple years it would take for a spacecraft to travel to the outer reaches of the solar system and beyond.

Put to Bed

Researchers have been toying around with various ways to turn hibernation states “on” in animals over the last few years. Hydrogen sulfide seems to be one possible way to do that. By binding at the same cell sites as oxygen, the gaseous compound reduces the need for oxygen and depresses the metabolism. Mark Roth at the Fred Hutchinson Cancer Research Center in Seattle induced hibernation for the first time in lab mice in 2005 by having them inhale large doses of a hydrogen sulfide gas. Their metabolic processes slowed, their temperatures dropped, and then they snapped right out of it when they got a big breath of oxygen hours later.

Surgeons at Massachusetts General Hospital took a different approach in an experiment on Yorkshire pigs, to see how beneficial induced hibernation was in a trauma setting. After anesthetizing the pigs and giving them serious wounds that led to shock and extreme blood loss, the surgeons quickly chilled the pigs' bodies to 50ºF and pumped their veins full of a solution used for preserving transplant organs. At that point, the pigs were almost dead. They had little to no heartbeat, extremely reduced blood flow and no measurable electrical activity in the brain. The surgeons operated on the pigs and repaired their injuries. The pigs were revived when their temperatures were returned to normal and warm blood was pumped back in. The pigs bounced back with no noticeable physical or cognitive impairments.

While these are incredible breakthroughs and promising starts, we’re still a long way from making human hibernation simple, safe, and reliable. Other experiments failed to induce hibernation in sheep and pigs with hydrogen sulfide, so it might not work on larger animals, including us. Testing the Massachusetts method on humans, meanwhile, would be a bit tricky, ethically speaking. It’s a start, though, and sooner or later we might move beyond mere sleep and hibernate our way through surgery, or a flight to Jupiter.

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Big Questions
Why Is Holly a Symbol of Christmas?
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Santa Claus. A big ol’ red-and-white stocking hung by the fire. Nativity scenes. Most classic Christmas imagery is pretty self-explanatory. Then there’s the holly, genus Ilex, which found its way onto holiday cards through a more circuitous route. 

Christmas is kind of the new kid on the block as far as holly symbolism is concerned. The hardy plant’s ability to stay vibrant through the winter made it a natural choice for pre-Christian winter festivals. The Roman feast of Saturnalia, celebrated at the darkest time of the year, celebrated the god of agriculture, creation, and time, and the transition into sunshine and spring. Roman citizens festooned their houses with garlands of evergreens and tied cheery holly clippings to the gifts they exchanged.

The Celtic peoples of ancient Gaul saw great magic in the holly’s bright "berries" (technically drupes) and shiny leaves. They wore holly wreaths and sprigs to many sacred rites and festivals and viewed it as a form of protection from evil spirits. 

Christianity’s spread through what is now Europe was slow and complicated. It was hardly a one-shot, all-or-nothing takeover; few people are eager to give up their way of life. Instead, missionaries in many areas had more luck blending their messages with existing local traditions and beliefs. Holly and decorated trees were used symbolically by new Christians, just as they’d been used in their pagan days.

Today, some people associate the holly bush not with the story of Jesus’s birth but with his death, comparing the plant’s prickly leaves to a crown of thorns and the berries to drops of blood. 

But most people just enjoy it because it’s cheerful, picturesque, and riotously alive at a time when the rest of the world seems to be still and asleep.

NOTE: Holly is as poisonous as it is pretty. Please keep it away from your kids and pets.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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What Are the 12 Days of Christmas?
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Everyone knows to expect a partridge in a pear tree from your true love on the first day of Christmas ... But when is the first day of Christmas?

You'd think that the 12 days of Christmas would lead up to the big day—that's how countdowns work, as any year-end list would illustrate—but in Western Christianity, "Christmas" actually begins on December 25th and ends on January 5th. According to liturgy, the 12 days signify the time in between the birth of Christ and the night before Epiphany, which is the day the Magi visited bearing gifts. This is also called "Twelfth Night." (Epiphany is marked in most Western Christian traditions as happening on January 6th, and in some countries, the 12 days begin on December 26th.)

As for the ubiquitous song, it is said to be French in origin and was first printed in England in 1780. Rumors spread that it was a coded guide for Catholics who had to study their faith in secret in 16th-century England when Catholicism was against the law. According to the Christian Resource Institute, the legend is that "The 'true love' mentioned in the song is not an earthly suitor, but refers to God Himself. The 'me' who receives the presents refers to every baptized person who is part of the Christian Faith. Each of the 'days' represents some aspect of the Christian Faith that was important for children to learn."

In debunking that story, Snopes excerpted a 1998 email that lists what each object in the song supposedly symbolizes:

2 Turtle Doves = the Old and New Testaments
3 French Hens = Faith, Hope and Charity, the Theological Virtues
4 Calling Birds = the Four Gospels and/or the Four Evangelists
5 Golden Rings = the first Five Books of the Old Testament, the "Pentateuch", which gives the history of man's fall from grace.
6 Geese A-laying = the six days of creation
7 Swans A-swimming = the seven gifts of the Holy Spirit, the seven sacraments
8 Maids A-milking = the eight beatitudes
9 Ladies Dancing = the nine Fruits of the Holy Spirit
10 Lords A-leaping = the ten commandments
11 Pipers Piping = the eleven faithful apostles
12 Drummers Drumming = the twelve points of doctrine in the Apostle's Creed

There is pretty much no historical evidence pointing to the song's secret history, although the arguments for the legend are compelling. In all likelihood, the song's "code" was invented retroactively.

Hidden meaning or not, one thing is definitely certain: You have "The Twelve Days of Christmas" stuck in your head right now.

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