Small, Slimy, and See-Through

Scientists have discovered a snail with a glasslike, translucent shell living half a mile below the surface in Croatia. Just a millimeter across and practically immobile, the snail, Zospeum tholussum, makes its home in a hot, humid cave within the Lukina Jama-Trojama cave system.

Alexander Weigand of Goethe-University in Frankfurt, Germany, described the snail in the journal Subterranean Biology.

J. Bedek

A new species of cave-dwelling snail called Zospeum tholussum.

Global Love of Bananas May be Hurting Costa Rica's Crocodiles

A Costa Rican banana worker carries a stalk of freshly harvested fruit on a plantation in Costa Rica, where many of the bananas that Americans eat are grown. Kent Gilbert/AP

Americans love bananas. Each year, we eat more bananas than any other fruit. But banana growers use a lot of pesticides — and those chemicals could be hurting wildlife. As a new study shows, the pesticides are ending up in the bodies of crocodiles living near banana farms in Costa Rica, where many of the bananas we eat are grown.

Of course, there's a reason why banana plantations rely heavily on pesticides. For one, banana trees are particularly susceptible to infestations, says Chris Wille, the chief of sustainable agriculture at the nonprofit Rainforest Alliance. He works with banana growers to help them reduce the amount of pesticides they use.

Second, most plantations are in the tropics, "where there are a lot more kinds of pests and in abundance," he says.   And insects aren't the only problem there. There are worms and fungi, too.
"When you see pictures of airplanes spraying banana farms, they're spraying for airborne fungal disease called Black Sigatoka, which can devastate a plantation in a matter of a week or so," says Wille.

Many of Costa Rica's banana plantations are in the remote northeastern region, at the headwaters of the Rio Suerte. The area is full of streams and canals, flowing past the banana farms and into protected rain forests that are part of the Tortuguero Conservation Area.

Paul Grant, a wildlife biologist at Stellenbosch University in South Africa, went there to investigate whether pesticides are hurting local wildlife.  "In the past, I have witnessed and a lot of the locals have pointed out that there have been massive fish kills as a result of pesticide exposure in high levels," says Grant.

He wanted to know whether these pesticides are also ending up in animals that eat the fish. In particular, he was interested in a small crocodile called a spectacled caiman (so named because a bony ridge between its eyes makes it look like it's wearing eyeglasses). These caimans live in the Tortuguero Conservation Area, which is just downstream from the banana farms. The animal is considered a threatened species by the International Union for Conservation of Nature.

Grant wanted to test caimans because they are long-lived animals and are top predators in the ecosystem. "A lot of the pesticides will wind up at the top of the food chain," he says. He collected blood samples from 14 adult caimans. Some of the animals lived closer to plantations and others farther downstream, in more remote, pristine areas. He and his colleagues analyzed the blood samples for 70 different pesticides. The results concerned him.

 The samples contained nine pesticides, of which only two are currently in use. The remaining seven are "historic organic pollutants," says Grant. These are pesticides like DDT, dieldrin, and endosulfan — chemicals that have been banned, some of them for nearly a decade. But they persist in the environment and build up in the bodies of animals.

These chemicals are also found in significant levels in all sorts of aquatic animals, including crocodiles in the U.S. and whales and seals in different parts of the world. The overall levels of pesticides in the Costa Rican caimans in comparison were modest, says Peter Ross, an environmental scientist at the University of Victoria in British Columbia, also an author of this study. Still, he says there was some indication that the chemicals may be harming the caiman.

"What was revealing to me was the fact that the caiman that were near the banana plantations had not only higher concentrations of pesticides, but also they were in a poorer state of health relative to the caiman in more pristine, remote areas," says Ross. Ross and his colleagues have published their findings in the latest issue of Environmental Toxicology and Chemistry.

There's an important lesson here, says Wille of the Rainforest Alliance. "You know, we're now reckoning with the problem left by past use of highly toxic, highly persistent pesticides," he says. "So, what plantations must avoid now is leaving similar toxic legacies for the next generation to deal with." Especially as the demand for bananas has been growing worldwide, and farms move toward more intensive methods of cultivation.

For more wonder, rewild the world

Wolves were once native to the US' Yellowstone National Park -- until hunting wiped them out. But when, in 1995, the wolves began to come back (thanks to an aggressive management program), something interesting happened: the rest of the park began to find a new, more healthful balance. In a bold thought experiment, George Monbiot imagines a wilder world in which humans work to restore the complex, lost natural food chains that once surrounded us. In his book "Feral," George Monbiot advocates the large-scale restoration of complex natural ecosystems.

Is Living With Extreme Wildfires The New Normal?

A wildfire in burns Prescott, Ariz., on June 18. The fire would eventually take the lives of 19 firefighters in an area near Yarnell.

It has been a deadly year for the people who fight wildfires. In total, 32 people have lost their lives fighting fires in 2013; the highest number in nearly 20 years, according to the National Interagency Fire Center.

Just one incident accounts for most of those deaths, the Yarnell Hill fire in Arizona. In June, the blaze blasted through a firefighting crew known as the Granite Mountain Hotshots; 19 of the 20 men died.

As people move farther into wildland areas and climate change turns landscapes into tinder, experts say the wildfire danger around the country will likely only grow. But there may be a lesson to learn from how the U.S. stifled an earlier fire crisis in urban settings.

Tragedy In Arizona

The Yarnell Hill fire started from a lightning strike that sparked a brush fire. A fire hadn't hit the area in more than 45 years, and it was "primed to burn," according to a report released Saturday.

Powerful winds spread the flames across thousands of acres in a matter of hours, catching residents unaware. Residents had to leave their homes at a moment's notice.

Deployed between the flames and people's property were the Hotshots.

The crew members moved away from a safe, burned-out area and toward a ranch, another safe zone. But along the way, the winds shifted, and they became trapped by the fire. The crew leader radioed back that they were deploying fire shelters — a last resort.

"That was the last time that I heard my superintendent's voice," says Brendan McDonough, the lookout who was separated from the group and the sole survivor. The 21-year-old recalled the tension of that day in an interview with Arizona's Prescott Daily Courier.

Investigators have tried to piece together exactly what happened in the Yarnell Hill fire. The Arizona State Forestry Division's incident report, released on Saturday, said the fire was moving fast — more than 10 miles per hour. In the end, the Hotshots had just two minutes to prepare shelters.

Investigators also say they cannot explain one central mystery: why the firefighters moved away from a safe area. In a news conference, lead investigator Jim Karels said, "That decision-making process went with those 19 men."

More Forests, More Fires

Environmental journalist Michael Kodas tells NPR's Arun Rath that the Yarnell Hill fire was so deadly because of a number of converging factors that occur in Arizona.

"We've been putting out fires in the western United States for more than a century, and this allowed our forests to grow unnaturally thick," Kodas says. "That's something that's really noticeable in Arizona."

Kodas says the forests there, after years and years of fire suppression, often have 10 or 20 times more trees, scrub and grass than they did naturally.

There is also an expanding wildland-urban interface, he says, a "term firefighters use to refer to the point where homes and communities abut really flammable forest."

A house destroyed by a wildfire in Yarnell, Ariz. Experts say increasing expansion into wildfire-prone areas has created new challenges for firefighters unequipped to protect houses and structures.

This expansion has changed the way wildland firefighters operate, and many are now expected to also protect homes and property in the woods. This is something Kodas says they aren't equipped to do, unlike their urban counterparts.

"They're wearing very lightweight, flame-retardant clothing and just carrying the fire shelters," he says. "When a forest firefighter ends up trying to protect a house, they're really not prepared for the hazards that come with trying to protect a structure."

Kodas, who is writing a book about the wildfire crisis, believes the only explanation for why the Hotshots left the safety zone was that they wanted to get to a place where they could "re-engage the fire and try to prevent it from burning into the town of Yarnell."

Learning From The Past

In tackling the growing problem of wildfires, the nation's handling of its structural fires could serve as an example.

In the early 1970s, the U.S. had reached a crisis point with structural fires. Blazes were killing more than 12,000 Americans every year. The federal government established a commission and released a report called America Burning.

Alexander Maranghides, a fire protection engineer with the National Institute of Standards and Technology, says the America Burning report marked a major turning point in fire safety.

"This was really the catalyst to really put together a research effort that resulted in significant improvements in the building codes and standards and test methods," Maranghides says, "which, over decades, has yielded a fantastic level of success."  Now, the number of deaths from fires every year has decreased to around 3,000.

Assessing Future Risk

But Maranghides says fires in the wildland-urban interface present a new and dangerous threat.

"The wildland-urban interface problem, when compared to interior building fires, is technically, and I'm being conservative here, an order of magnitude more complex," he says.

Maranghides says understanding wildfires will require the kind of focus that the America Burning report once provided. He says with wildland-urban interface fires, the U.S. is currently about where it was 30 years ago with building fires. So Maranghides and his colleagues have proposed a scale to assess potential wildfire risk.

"You can think of our proposed scale as a way to quantify the hazard," he says.

The scale ranges from 1 to 4, and would measure the potential hazard from fires and hot embers in an area. Maranghides says building codes have been developed to deal with earthquakes and even hurricanes, but there's a big blind spot when it comes to understanding wildfires.

He says the scale, however, is not an attempt to restrict where people can build.

"All we're saying is, 'At this point in space, this is the fire and ember exposure you can expect,' " he says. "So if you want to build there and you want your home to survive, the building materials and assemblies have to be able to withstand that exposure."

If the history of structural fires is any guide, changing the approach to wildland threats won't take just years, but decades. In the meantime, the U.S. will almost certainly see more devastating fires.

Auto-Brewery Syndrome: Apparently, You Can Make Beer In Your Gut

This medical case may give a whole new meaning to the phrase "beer gut."

A 61-year-old man — with a history of home-brewing — stumbled into a Texas emergency room complaining of dizziness. Nurses ran a Breathalyzer test. And sure enough, the man's blood alcohol concentration was a whopping 0.37 percent, or almost five times the legal limit for driving in Texas.

There was just one hitch: The man said that he hadn't touched a drop of alcohol that day.

"He would get drunk out of the blue — on a Sunday morning after being at church, or really, just anytime," says Barabara Cordell, the dean of nursing at Panola College in Carthage, Texas. "His wife was so dismayed about it that she even bought a Breathalyzer."

Other medical professionals chalked up the man's problem to "closet drinking." But Cordell and Dr. Justin McCarthy, a gastroenterologist in Lubbock, wanted to figure out what was really going on.

So the team searched the man's belongings for liquor and then isolated him in a hospital room for 24 hours. Throughout the day, he ate carbohydrate-rich foods, and the doctors periodically checked his blood for alcohol. At one point, it rose 0.12 percent.

Eventually, McCarthy and Cordell pinpointed the culprit: an overabundance of brewer's yeast in his gut.

That's right, folks. According to Cordell and McCarthy, the man's intestinal tract was acting like his own internal brewery.

The patient had an infection with Saccharomyces cerevisiae, Cordell says. So when he ate or drank a bunch of starch — a bagel, pasta or even a soda — the yeast fermented the sugars into ethanol, and he would get drunk. Essentially, he was brewing beer in his own gut. Cordell and McCarthy reported the case of "auto-brewery syndrome" a few months ago in the International Journal of Clinical Medicine.

When we first read the case study, we were more than a little skeptical. It sounded crazy, a phenomenon akin to spontaneous combustion. I mean, come on: Could a person's gut really generate that much ethanol?

Brewer's yeast is in a whole host of foods, including breads, wine and, of course, beer (hence, the name). The critters usually don't do any harm. They just flow right through us. Some people even take Saccharomyces as a probiotic supplement.

But it turns out that in rare cases, the yeasty beasts can indeed take up long-term residency in the gut and possibly cause problems, says Dr. Joseph Heitman, a microbiologist at Duke University.

"Researchers have shown unequivocally that Saccharomyces can grow in the intestinal tract," Heitman tells The Salt. "But it's still unclear whether it's associated with any disease" — or whether it could make someone drunk from the gut up.

We dug around the scant literature on auto-brewery syndrome and uncovered a handful of cases similar to the one in Texas. Some reports in Japan date back to the 1970s. In most instances, the infections occurred after a person took antibiotics — which can wipe out the bacteria in the gut, making room for fungi like yeast to flourish — or had another illness that suppresses their immune system.

Still, such case reports remain extremely rare. Heitman says he had never heard of auto-brewery syndrome until we called him up. "It sounds interesting," he says. But he's also cautious.

"The problem with a case report," he notes, "is that it's just one person. It's not a controlled clinical study."

4 Legless Lizard Species Discovered in California

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The Bakersfield legless lizard (Anniella grinnelli), which today ranges from downtown Bakersfield in California.

Four previously unknown species of snakelike creatures have been found in California — but don't call them snakes; they're legless lizards. Prior to the discovery of the new species, there was only one known legless lizard species in the United States: the California legless lizard.

Surprisingly, the newfound legless lizards were discovered at a series of sites that weren't exactly pristine: They include a dune bordering a runway at Los Angeles International Airport; an empty lot in downtown Bakersfield, Calif.; a field littered with oil derricks; and the margins of the Mojave Desert.

"This shows that there is a lot of undocumented biodiversity within California," Theodore Papenfuss, a herpetologist at the University of California Berkeley's Museum of Vertebrate Zoology, said in a statement from the school.

The lizards live their entire lives underground or near the surface, and often don't leave an area the size of a small table, the statement noted. When they are found at the surface, it's usually in moist areas under dead wood or logs — or cardboard.

A map showing where the new legless lizard species are found.

To find the lizards, Papenfuss and James Parham, a researcher at California State University, Fullerton, placed thousands of slips of cardboard at various sites around central and Southern California. They then checked and rechecked the sites before finally finding the four new species. 

Three of the animals were found in the southern San Joaquin Valley. "These are animals that have existed in the San Joaquin Valley, separate from any other species, for millions of years, completely unknown," Parham said in the statement.

The species found near the oil fields has a silver belly and is named Anniella alexanderae. The yellow-belliedAnniella campi lives in three isolated dry canyons on the edge of the Mojave Desert, east of Walker Pass in the Sierra Nevada Mountains. The purple-bellied Anniella grinnelli was found in three vacant lots in Bakersfield, though only one of these lots remains. The fourth species, found outside the valley near the airport, is named Anniella stebbinsi.

Legless lizards live in loose soil on five continents, eating insects and larvae, and this limbless trait has independently evolved several times, the statement noted. It is difficult for the untrained eye to distinguish these creatures from snakes. However, unlike snakes, many legless lizards have external ear openings and movable eyelids. They also typically spend their entire lives underground, unlike snakes.

The species were named after four UC Berkeley scientists: Museum of Vertebrate Zoology founder Joseph Grinnell, paleontologist Charles Camp, philanthropist and amateur scientist Annie Alexander and herpetologist Robert Stebbins.

The animals are described in a study published Sept. 17 in the journal Breviora.

10-Inch-Long Earwax Plug Reveals Blue Whale's Life History

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The male blue whale whose earwax was used in the study was found on the coast of California in 2007.

A blue whale's buildup of earwax archives its history of stress levels and exposure to chemical pollutants, which could allow researchers to piece together new details about the animal's life, a study shows.

The blue whale is the largest animal on Earth, and an endangered species. Like many other baleen whales, these massive creatures tend to accumulate layers of wax in their ear canals, which over time results in long earplugs.

"Scientists in the past have used this waxy matrix as an aging tool, similar to counting tree rings," study researcher Sascha Usenko, an assistant professor of environmental science at Baylor University, explained in a statement. The earplug, however, had never been used to obtain a chemical profile. 

Finding a lifetime chemical pro?le for an animal can be tricky, especially for free-ranging creatures. Scientists previously have used whale blubber to determine the animal's stress hormone levels and chemical exposure, but that method provides a peek at only a limited period of the whale's life history.

In the new study, Usenko and colleagues studied a 10-inch-long (25 centimeters) earplug that was pulled from the carcass of a 70-foot-long (21 meters) male blue whale in 2007 near Santa Barbara, Calif. The whale was around 12 years old and had died after being hit by a ship.

The whale earplug from a blue whale that was used in the study.

In the earwax archive, the researchers found traces of 16 pollutants, including pesticides and flame retardants, which were most prevalent from the whale's birth until it was 6 months old. This suggests that the pollutants were transferred to the whale from its mom while the baby was developing in the womb and nursing after it was born, the researchers say.

The earwax also showed the whale's level of the stress hormone cortisol generally increased over time, which could be explained by a number of possibly stressful experiences, including weaning, migration, changes in social status and environmental noise.

The cortisol level shot up most significantly around the time the whale's testosterone levels peaked and it reached sexual maturity (between 9.5 and 10.5 years old). That timing might indicate the whale was stressed out by competition for a mate or the social bonds it was forming during sexual maturity, the researchers say.

Usenko and colleagues hope they can use this novel earplug method to answer questions about the human impact on whales.

"There is ship traffic, environmental noise, climate change and contaminants," Usenko said. "Now, we are able to provide definitive answers by analyzing whale earwax plugs."

What's more, they say this approach can be used to analyze earwax plugs that are sitting in museums, some of which might date back to the 1950s. With further study samples, researchers might be able to put together a more extensive picture of how increasing pollution, sonar use and the introduction of specific pesticides have affected whales, Usenko said.

The research was detailed in the Proceedings of the National Academy of Sciences. 

Natural Gas May Be Easier On Climate Than Coal, Despite Methane Leaks

A rig drills a hydraulic fracturing well for natural gas outside Rifle, Colo., in March.

From the standpoint of global warming, burning natural gas can be better than burning coal, a study published this week suggests.This is a contentious issue among people who are opposed to the natural gas drilling practice known as fracking. That technique involves injecting water, sand and chemicals into wells to release far more gas than conventional drilling can. Opponents of fracking have been concerned not only about local environmental issues, but also about the potential for methane leaks to make global warming worse.

Even though natural gas burns much cleaner than coal, the main constituent, methane, also leaks into the atmosphere during production. Methane is a potent greenhouse gas, so those leaks could potentially wipe out the climate benefits of natural gas.

And fracking technology took off before anyone really understood how much natural gas leaks out in the process.

"We wanted to go out and collect some of the first data on some of the new types of operations underway in natural gas production and what the methane emissions are," says David Allen, an engineering professor at the University of Texas in Austin.

Allen got funding from the Environmental Defense Fund, as well as support from nine major companies that volunteered to participate in the study. His conclusion: Currently the U.S. Environmental Protection Agency greatly overestimates methane emissions from a new well that is being prepared to produce gas for the first time. But he found that the EPA also greatly underestimates emissions from wells that are already in production. And when you add the whole thing up, it's basically a wash, Allen says.

That's potentially good news for advocates of natural gas, because it supports the argument that, if done right, natural gas production can be much better for the climate than coal.

The study appears in the Proceedings of the National Academy of Sciences, and suggests ways to make the production of natural gas cleaner than it is today.

For example, it turns out there's a lot of methane leakage from fracking operations that separate natural gas from oil and water as they come up the well at the same time.

"That was the biggest surprise for me, as an operator," says Edwin Hance from Pioneer Natural Resources, a natural gas company that operates mostly in Texas and participated in the study.

"I would say that's the primary area we need to focus going forward," Hance says, "as far as practices where we can have the opportunity to reduce emissions further."

It's important to note that the study relied on data from nine companies, all of which volunteered to be studied. Bob Howarth, a professor of ecology and environmental biology at Cornell University, says that means the results from the 190 study sites are not necessarily representative of the industry as a whole.

"I would view this as best-case scenario for what industry can do to reduce methane emissions when they want to," Howarth says.

A different study, published last month by the National Oceanic and Atmospheric Administration, may be more representative of a worst-case scenario. The NOAA study sampled the air in an entire basin in Utah, rather than tracking emissions down to specific pieces of equipment and specific practices.

"They're finding methane emissions that are 10 to 20 times higher than this new study," Howarth says, "and I think [that's] probably more representative of at least those western gas fields, when industry does not realize it's being watched."

Figuring out what practices are responsible for large methane emissions, like those in Utah, will take more work.

Steve Hamburg, chief scientist at the Environmental Defense Fund, says his organization is funding 16 studies to look at the entire natural gas system in the United States. The PNAS study, focusing only on production, is just one part of that.

"Regrettably, we need another year, and then we'll have all of these pieces together and we really can get a much clearer picture of what's going on," Hamburg says.

At stake isn't simply gas production in the United States. Natural gas is taking off globally. So Hamburg says these measurements offer producers and regulators an opportunity to fix what's wrong in the U.S. and to spread those best practices around the world.

Mount McKinley's Gotten Shorter Again

Mount McKinley. There's a bit less of it than we thought.

Could Alaska's Mount McKinley be in danger of developing a Napoleon complex?

Well, it's still said to be the tallest peak in North America, so perhaps it won't need to worry about its height just yet. But for the second time in recent decades, the mountain's been shortened.

This week's announcement by Alaska's lieutenant governor, Mead Treadwell, that the U.S. Geological Survey now thinks McKinley is 20,237 feet tall rather than 20,320 is getting plenty of attention:

— "Say it ain't so!" writes Alaska Dispatch.

— "McKinley's perch as the tallest mountain in North America just got a little less comfortable," says the Anchorage Daily News.

McKinley is also known as Denali. According to Treadwell's office:

"Denali's elevation was originally measured to stand 20,320 feet in 1952, based on photogrammetry. A 1989 field survey recorded an elevation of 20,306 feet — 14 feet shorter than the 1952 recording.

"The 2012 revision of 20,327 feet was recorded with radar technology deployed as a result of Alaska's Statewide Digital Mapping Initiative (SDMI), which also revealed that an entire ridgeline of Mt. Dickey in Denali National Park was missing from previous maps — one of many discrepancies corrected by recent map updates.

"The State of Alaska invested $9.59 million in SDMI since 2010, and the federal government has invested $14 million toward the overall cost of creating a digital elevation model for Alaska. The initiative, nearly 50% complete, is on schedule for statewide completion by 2016."

Which mountain is still North America's No. 2? It's thought to be Canada's Mount Logan, which comes in around 19,550 feet.

Why Szechuan Peppers Make Your Lips Go Numb

New research shows that a molecule in Szechuan peppers activates your cells’ touch receptors, making them feel like they’ve been vibrated rapidly. Photo by Flickr user diwineanddine

If, in the midst of a Szechuan pepper-heavy meal, you have the presence of mind to ignore the searing hot pain that fills your mouth, you might notice a more subtle effect of eating the hot peppers: a tingling, numbing sensation that envelops your lips and tongue.

What’s behind this strange phenomenon, scientifically known as paresthesia? Scientists believe that it has something to do with a molecule called hydroxy-alpha-sanshool, naturally present in the peppers.

Research has shown that the molecule interacts with our cell’s receptors differently than capsaicin, the active ingredient in the world’s hottest chili peppers. Capsaicin produces a pure burning sensation by binding to the same sorts of receptors present in our cells that are activated when we’re burned by excessive heat, but the Szechuan peppers’ active chemical appears to act on separate receptors as well, perhaps accounting for the distinctive tingling that can persist for minutes after the burn has gone away.

Now, in a study that required some uncommonly compliant volunteers—they let their lips get brushed with ground Szechuan pepper—researchers found that the peppers produce the tingle by exciting tactile sensors in our lips and mouth. In other words, it seems that apart from tasting the peppers’ spiciness, we feel it too, as though our lips are being physically touched by the chemicals present in the Szechuans.

Hydroxy-alpha-sanshool, the molecule responsible for Szechuan peppers’ tingle-inducing ability. Image viaWikimedia Commons

As part of the study, published today in the Proceedings of the Royal Society B, a group of neuroscientists from University College London gathered 28 people and subjected them to ground Szechuans and small metal vibrating tools. Initially, they ground up the peppers, mixed them with ethanol and water, and brushed them onto the lips of the participants, who reported the level of tingling they felt.

Then, to try figuring the exact frequency of the tingling—a concept that becomes a bit more intuitive if you think of the tingling, or numbness, as the lips being vibrated quickly—they held a small vibrating tool up to the volunteers’ fingers. They could control how fast or slow the tool vibrated, and were asked to set it so that it matched the same feeling as the tingling on their lips. After the Szechuan tingling had time to die down, the vibrating tools were placed on their lips in the same spot, and again the participants could control the vibrating to make it resemble the pepper numbness as closely as possible.

When they looked at the records of the tool’s frequency, they found that the participants consistently set it to vibrate at 50 hertz (another way of saying 50 cycles per second). This consistency across people was telling—specific classes of tactile receptors in our cells are each activated by different frequencies (when touched, they pass along an electric current through nerve fibers, ultimately signaling to the brain that physical contact has occurred), so it supported the idea that touch receptors were involved.  Which class of receptor, though, is activated by Szechuan peppers?

The scientists say that frequency of the Szechuan’s numbing sensation fell within the range of vibration typically conveyed by a highly-sensitive type of tactile receptor called Meissner receptors, which cover around 10-80 hertz. Previous work has shown that in human nerve cells cultured in petri dishes, the sanshool molecule caused fibers associated with Meissner receptors to fire, passing along a burst of electricity.

This experiment showed that in the real world, the Szechuans’ active ingredient seems to do the same thing, triggering activity in this set of receptors and causing them to pass along tactile stimuli towards the brain, thereby making our lips feel numb, as though they’ve been vibrated quickly. It’s a strange idea, but not unlike the feeling of spiciness: When you eat the pepper, you’re not actually being burned, but your heat-sensitive receptors are being activated, making it seem that way. In the same way, if you’re daring enough to bite into a Szechuan, the touch receptors in your lips and mouth will be stimulated, and as a result, they’ll go numb in a few minutes.