The Real Story Behind Game of Thrones’ Dragonglass

By Gemma Tarlach | April 12, 2019 11:37 am
tormund giantsbane

Tormund Giantsbane Kristofer Hivju) fights an army of the undead with a weapon made of obsidian on Game of Thrones. (Credit: HBO)

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Shiny and sharp, obsidian is enjoying a bit of a pop culture moment. It plays a central role in HBO’s hit fantasy series Game of Thrones, now wrapping its final season. Called dragonglass on the show, obsidian is one of only two substances that can cut down White Walkers, malevolent otherworldly warriors.

In the real world, the volcanic glass reveals the human story in a way no other material can.

Our evolutionary ancestors used obsidian for toolmaking for more than a million years. Thanks to the material’s unique chemical attributes, archaeologists can determine the geographical origin of even small pieces. But that’s only part of the story.

Arizona State University archaeological scientist Andrew Zipkin says knowing where our distant ancestors collected obsidian allows researchers to ask much broader questions, such as where early humans traveled, and why.

“It’s easy to source obsidian and determine where it came from, but that’s only the first step, because that’s chemistry, not archaeology,” says Zipkin. “The ultimate goal is to understand what motivated these people to collect it from that location.”

obsidian point

An obsidian projectile point from central Alaska, backlit by sunlight. (Credit: Andrew Tremayne/National Park Service)

Getting To The Point

Obsidian artifacts turn up at archaeological sites going back at least as far as 1.7 million years ago, when an early member of the genus Homo made tools with it at the Ethiopian site of Melka Kunture.

Around the world, the prehistoric record is littered with obsidian scrapers, choppers and all-purpose hand axes. Early toolmakers likely chose the volcanic glass because it flakes predictably — it can be shaped more easily than other materials — and the result is a razor-sharp edge.

Ellery Frahm

Archaeological scientist Ellery Frahm holds an obsidian hand ax unearthed in Armenia. (Credit: Courtesy of Ellery Frahm)

“The fresh edge of an obsidian flake is just a few dozen atoms thick,” says Ellery Frahm, an archaeological scientist at Yale University. “When viewed under a microscope, a steel surgical scalpel would look like a dull and badly abused ax next to an obsidian flake.”

Obsidian is also brittle, a bonus for hunters.

“An obsidian projectile point creates a lot of damage because it’s sharp and also likely to break inside the animal,” says Albuquerque-based geoarchaeologist M. Steven Shackley, professor emeritus at the University of California, Berkeley. He adds: “If you want to create damage, you want to use obsidian.”

The material’s bold appearance — shiny and usually black, though red and other colors occur — may have made it attractive for symbolic or aesthetic reasons as well. Whatever its appeal, early humans sought it out. Despite its frequent use throughout prehistory, the raw material is not common.

“Obsidian is rare most places in the world, and it takes the right kind of volcanic eruption to create it,” says Frahm. “The lava needs to be highly viscous — or sticky — to form glass. A high amount of silica is required to get that sticky lava.”

While this high-silica lava is still below ground, minerals from surrounding rock leach into it, adding different elements specific to that location. When it finally erupts, if it reaches the surface fast enough, the lava will cool quickly and turn into uniform glass before its unique chemical mix has a chance to organize itself into crystals.

“When that happens, all the elements are frozen inside that glass like a snapshot,” says Shackley. “That’s why we can distinguish all these different sources.”


Read more: The Wall of Westeros Would Be Its Own Worst Enemy


X Marks the Source

Determining the source of a piece of obsidian means analyzing the chemistry of the artifact and then matching it to a database of geochemical signatures unique to individual sources, called flows.

For decades, archaeologists have had few options for that analysis. Most of the equipment is expensive and limited to lab settings. The most precise methods also require destroying the material to be analyzed and, as Shackley notes dryly, “for some reason, people in museums get really upset when you break their artifacts into tiny little pieces.”

That’s why non-destructive X-ray fluorescence (XRF) emerged as the most popular method for sourcing obsidian. Though not the most exacting analysis, it’s particularly good at identifying strontium, rubidium and other elements that are frequently key ingredients in a flow’s signature.

“XRF is a beam technology,” says Zipkin. “It hits the target atom, knocks electrons out of orbit, exciting them, and then, as they drop back down [into normal orbit], they emit characteristic energy that the device measures.”

Andrew Zipkin

Andrew Zipkin collecting obsidian samples in Arizona. (Credit: Courtesy of Ben Walker)

Lab-based XRF devices have gotten smaller over the years: “The first XRF [machine] I used in the ’80s filled a room,” says Shackley, who is director of the Geoarchaeological XRF Laboratory. “Now the equipment sits on a desktop, a little bigger than a breadbox.” Outside the lab, the technology has seen even more impressive downsizing.

The first commercial portable XRF (pXRF) devices arrived in the 1990s, intended for industrial applications such as exploratory mining and quality control in cement manufacturing. They soon found their way into the hands of many an archaeologist. In those early adoption years, enthusiasm for the new tool’s potential sometimes outpaced scientific rigor, and results were not always reliable.

Methods and standards across the field have since improved, as have the portable devices, which continue to get cheaper and more precise. Today’s pXRF devices — which “look like a combination of a ray gun and a hair dryer,” says Zipkin — run less than $40,000.

“One can put it in a carry-on bag and bring it almost anywhere in the world,” says Frahm. “No longer do we have to request permission to export a few artifacts to a distant lab. Instead, we can work where the artifacts are, whether in a museum, in a field lab, or even at an archaeological site itself.”

He adds: “In only 10 or 20 seconds, we can know where a particular obsidian artifact originated, hundreds, thousands, or even hundreds of thousands of years ago.”

Dates That Don’t Hold Water

While the tools to determine the source of obsidian become ever more user-friendly, obsidian hydration, a method used to date the material, remains problematic.

dragongalss dagger

A dragonglass dagger from Game of Thrones. (Credit: HBO)

Developed in the mid-20th century, the method takes advantage of the fact that an obsidian surface starts absorbing atmospheric water as soon as it’s exposed to the air. To date the artifact, researchers take a cross-section and look at the hydration rim, a gauge of how far water has penetrated into the volcanic glass.

“It’s a great idea, but it’s almost impossible to put into action,” says Zipkin, who calls the results “really just an educated guess.”

That’s because the speed of moisture penetration is affected by numerous factors, including temperature and humidity. A difference in temperature of 1 degree Celsius, for example, can change the hydration rate by 10 percent; a single event such as a forest fire roaring past the artifact’s location might reset the hydration rim completely.

Most archaeologists instead date obsidian artifacts by context — what else was found with it at the site — and relative dating methods, such as the age of the layer of sediment in which it was found.

Tracking Ancient Travel

As groups of hunter-gatherers moved across prehistoric landscapes, collecting obsidian and leaving behind flakes of it after making or resharpening tools, they created maps of their movement that archaeologists can follow with ever greater precision.

Tracing the paths obsidian traveled with early humans, says Frahm, can reconstruct how people “made use of their surroundings and met their subsistence needs through mobility across the landscape and connections with other groups.”

In 2018 in Science, for example, Zipkin and colleagues published a trio of papers about finds, including obsidian artifacts, at the Kenyan site of Olorgesailie. The obsidian pieces, more than 300,000 years old, came from multiple flows up to 70 miles away: a distance significantly greater than the average territory of hunter-gatherer groups. This means that the obsidian collectors may have either traveled into another group’s territory or traded with them for the material. Both scenarios suggest that humans were cognitively capable of complex social interactions and planning long-distance expeditions more than 200,000 years earlier than once thought.

Obsidian continues to tell us more about not only ourselves, but our closest evolutionary kin.

obsidian outcrop

An obsidian outcrop in Armenia provided raw materials for tools found nearby. (Credit: Courtesy of Ellery Frahm)

In February, for example, in the Journal of Archaeological Science: Reports, researchers described obsidian artifacts up to 73,000 years old, made of raw material from the Baksan River valley. The location is the only known obsidian source in the Northern Caucasus — part of a rugged stretch of mountainous land straddling southern Russia and the Republic of Georgia.

The artifacts were found at sites up to 150 miles from Baksan and, based on style, were made by different, culturally distinct groups of Neanderthals. It’s the latest blow to the idea that Neanderthals were less mobile and less capable of networking than early modern humans.

Ekaterina Doronicheva, lead author of the paper and an archaeologist at the Laboratory of Prehistory in St. Petersburg, Russia, says the Baksan obsidian source was probably a zone of contact between different populations: “We can assume the existence of cultural contacts between these regions . . . and that local Neanderthal groups were part of developed social networks.”

As technology improves and archaeologists turn up additional sites, obsidian will remain the glass through which we see our deep history.

“It’s a bit like being Sherlock Holmes,” says Frahm. “We are trying to wring every last bit of information out of these objects that were simply tossed aside in the past.”

CATEGORIZED UNDER: Living World, Top Posts
MORE ABOUT: archaeology

What The Event Horizon Telescope Reveals About Galaxy M87

By Jake Parks | April 10, 2019 10:00 am
Here is the first direct image of a supermassive black hole. Captured by the Event Horizon Telescope, a network of eight radio telescopes spread across the world, the image shows the bright, spinning disk of material around the galaxy M87's supermassive black hole. Due the the intense gravity present near black holes, the appearance of the disk is warped. (Credit: EHT Collaboration)

Here is the first direct image of a supermassive black hole. Captured by the Event Horizon Telescope, a network of eight radio telescopes spread across the world, the image shows the bright, spinning disk of material around the galaxy M87’s supermassive black hole. Due the the intense gravity present near black holes, the appearance of the disk is warped. (Credit: EHT Collaboration)

A massive international collaboration of researchers has released the first-ever direct image of the hellish environment surrounding a supermassive black hole. As part of the Event Horizon Telescope (EHT) project, the team used a global array of telescopes to probe the fiery disk of material swirling around the gargantuan black hole at the center of the galaxy M87.

The results confirm that the hot gas swirling around a black hole is traveling at nearly the speed of light, creating a chaotic maelstrom around the black hole itself. And according to research published today in The Astrophysical Journal Letters, the structure of black hole is nearly circular, as predicted by Einstein’s theory of general relativity, meaning the theory has passed yet another stringent test.

“Overall,” the paper states, “the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity.”


Event Horizon Telescope Releases Humanity’s First Ever Black Hole Image


Galaxy M87 Revealed

Messier 87 (M87) is a behemoth elliptical galaxy that sits some 53 million light-years from Earth. This giant holds trillions of stars and helps anchor the roughly 2,000 galaxies — including the Milky Way — that make up our local cosmic city, dubbed the Virgo Cluster. In turn, the Virgo Cluster is a primary component of the much larger Virgo Supercluster.

Without the striking spiral arms that decorate many of its neighbors, M87 comes off as something of a dull, spherical blob. But within it hides one of the most powerful galactic engines in the local universe. M87’s supermassive black hole packs the mass of several billion suns into a surprisingly tiny volume. And a seven-year study with the Hubble Space Telescope caught this invisible beast firing a powerful jet of high-energy particles out at nearly the speed of light, shooting them roughly 5,000 light-years into space.

Previous research on M87’s supermassive black hole indicates the galaxy’s mighty jets are produced when a dense disk of matter – called an accretion disk – whirls around the black hole at up to 2 million miles per hour (3.5 million km/h). The material within the accretion disk grinds together as it circles, with the innermost regions spinning faster than those farther out. This differential rotation causes the magnetic fields to get coiled up, ejecting the material falling into the black hole at nearly the speed of light.


The Event Horizon Telescope: How Does it Work?


“We think the spin of the black hole interacting with the magnetic field is what causes the jets, but we don’t have proof,” Feryal Özel, University of Arizona astrophysicist and EHT team member, told Astronomy in an interview. “If we see jet-like images or anything associated with it, I think it increases our confidence that jets are formed very close to the black hole.”

m87 black hole jet

M87’s powerful jet streams from the galaxy’s black hole like a cosmic searchlight, extending out some 5,000 light-years. The jet is believed to originate from tangled magnetic fields in the accretion disk of M87’s supermassive black hole.
NASA/The Hubble Heritage Team (STScI/AURA)

Though many researchers have explored the inner workings of M87 before, in 2012, the then-new Event Horizon Telescope took its first peek. At the time, it had fewer radio observatories in its array, and it collected much less data, so it couldn’t produce an image yet. But it still managed to uncover evidence that M87’s supermassive black hole rotates in the same direction as its accretion disk.

They also calculated that the innermost edge of the black hole’s accretion disk spans only about the width of five solar systems. Keep in mind, M87’s black hole is between about 3 and 7 billion times the mass of the Sun, or about 1,000 times more massive than the Milky Way’s black hole, Sagittarius A*. That’s a lot of mass crammed into a relatively small space.

EHT Zooms In

With this new EHT image of M87, we now have an unrivaled look at a black hole and its surrounding region, including its jet. And though the image is not quite 8K-quality, the black hole’s discernible shape and shadow go a long way in advancing our understanding of these reality-bending objects.

Anything – be it matter or light – that falls past a black hole’s accretion disk and beyond the point-of-no-return, called the event horizon, is forever lost, so we can’t actually see the black hole itself. But we can see the shadow of the black hole silhouetted against the smoldering material spinning around it.

“The image that we see includes the shadow not because it’s opaque, but because it absorbs light from behind it,” Harvard University astronomer Avi Loeb, who was not involved in the EHT project, told Astronomy. “So it’s a dark region surrounded by a sliver of light, like a moon crescent. One side is approaching; one is receding. So the approaching side is bright.”


Inside The Event Horizon Telescope’s Quixotic Quest to Image a Black Hole


This first image will be studied and analyzed for years to come, but EHT is just getting started. Now that it’s possible to resolve the area around a black hole lurking in the core of a galaxy, we can expect to eventually capture images of other black holes beyond M87.

But by directly imaging M87’s supermassive black hole and accretion disk, researchers are already gaining insight into the complex processes that shape the jets of active galaxies. And since powerful, jet-spewing supermassive black holes tend to be more prevalent in the early universe, these insights may just reveal new discoveries into how our young cosmos evolved.

You can watch the National Science Foundation’s stream of the Event Horizon Telescope announcement below.

CATEGORIZED UNDER: Space & Physics, Top Posts

Event Horizon Telescope Releases Humanity’s First Ever Black Hole Image

By Korey Haynes | April 10, 2019 8:30 am
Event Horizon Telescope

The first ever image of a black hole shows the supermassive black hole at the heart of galaxy M87. (Credit: Event Horizon Telescope)

On Wednesday, astronomers revealed the first image ever taken of a black hole, bringing a dramatic conclusion to a decades-long effort. The iconic image offers humanity its first glimpse at the gas and debris that swirl around its event horizon, the point beyond which material disappears forever. A favorite object of science fiction has finally been made real on screen.

Their target was a nearby galaxy dubbed M87 and its supermassive black hole, which packs the mass of six and half billion suns. Despite its size, the black hole is so far from Earth – 53 million light-years – that capturing the image took a telescope the size of the planet.

This monumental accomplishment was only possible thanks to the Event Horizon Telescope (EHT). The image data was taken back in 2017 but scientists have spent two years piecing it together. That’s because EHT is made of up eight independent observatories that are scattered across the globe, cooperating together to act as one enormous detector. Shep Doeleman, director of the EHT, announced at today’s press event, “We are delighted to report to you today that we have seen what we thought was unseeable.” Researchers made their grand announcement simultaneously in seven different countries this morning, accompanied by a series of scientific papers published at the same time in The Astrophysical Journal Letters. Read More

CATEGORIZED UNDER: Space & Physics, Top Posts
MORE ABOUT: black holes, cosmology

The Event Horizon Telescope: How It Works

By Erika K. Carlson | April 10, 2019 8:20 am
ALMA

The Atacama Large Millimeter/submillimeter Array (ALMA). (Credit: ESO/C. Malin)

A black hole isn’t an easy thing to photograph. The famously inscrutable objects are so dense that even light can’t escape their vicinity. By definition, they are invisible. So when the Event Horizon Telescope team released the first image of a black hole, what they really released is an image of the black hole’s event horizon — the minimum distance from the black hole’s center where gravity is still weak enough for light to escape.

And how they imaged the supermassive black hole in galaxy M87 it is nearly as impressive as the image itself. EHT scientists convinced researchers around the world to point their radio telescopes at a select group of black holes, then combined the observations to create one giant array the size of our planet.

“With this technique, we were able to use essentially the diameter of the Earth as the resolving power,” says John Carlstrom, who heads the EHT partnering South Pole Telescope. That let them glimpse finer details than even the Hubble Space Telescope can.


Read more: Astronomers Get Their Very First Picture of a Black Hole


Imaging a Monster

In 2017, the EHT turned its gaze to supermassive black holes at the centers of two galaxies: our own Milky Way and an elliptical galaxy about 50 million light-years away called M87. Each of these astronomical monsters has a disk of material — gas, dust, plasma, what have you — swirling around the black hole. That material heats up and glows until it eventually falls in. By capturing an image of the glowing disk around M87’s black hole, and the dark inner edge caused by the black hole’s event horizon, scientists not only made history, but also expanded our knowledge of how black holes work.

M87 Jet

Taken by the Hubble Space Telescope, this image shows a jet of matter blasting from galaxy M87. (Credit: NASA and The Hubble Heritage Team (STScI/AURA))

So why haven’t astronomers snapped such a pic before? Because it’s an incredibly difficult feat. One of the biggest challenges is how tiny a target they actually are. Supermassive black holes have a lot of mass, sure, but they’re also super compact. The one in the center of our galaxy, called Sagittarius A* (Sgr A*), has an event horizon smaller across than the distance between the sun and Earth. And it’s roughly 26,000 light-years away, so it takes up a minuscule amount of sky — just a few billionths the width of the full moon. The black hole at the center of M87 is a whopping 1,000 times bigger than our own but it also sits roughly 2,000 times farther away. So it’s more or less the same size in Earth’s sky as Sgr A*. To photograph either black hole, you need a really powerful telescope.

Generally, the resolution of a telescope — how small of a target it can see — comes down to its size. The larger the telescope, the more resolving power it has, and the smaller the details it can make out. But even the largest radio dishes in the world, like the Arecibo Observatory in Puerto Rico and the Five-hundred-meter Aperture Spherical Telescope in China (each more than 1,000 feet across), aren’t big enough to image these black holes.


Read more: The Event Horizon Telescope’s Quixotic Quest to Image a Black Hole


Black Hole Photography 101

Radio astronomers can get around this problem by linking together lots of smaller radio dishes into a single array, where they effectively act as one giant telescope. It’s a technique called astronomical interferometry. Each dish in the array collects light from a target object, like the glowing disk around a black hole, and converts the radio waves it receives into an electronic signal. Then a computer called a correlator combines all the electronic signals from the various dishes into what’s called an interference pattern. Finally, astronomers tapped a special kind of math (Fourier transforms for the curious) to decode that pattern, showing what the target would look like in the sky if our eyes could see in radio wavelengths.

Very Large Array

The Very Large Array in New Mexico, which is part of the larger Event Horizon Telescope. (Credit: Alex Savello/NRAO)

With an array of radio telescopes, it’s the distance between individual dishes, rather than the diameter of a single dish, that determines the array’s resolving power. The farther apart two dishes are, the better the resolving power of that array. That’s why radio observatories like the Very Large Array in New Mexico and the Atacama Large Millimeter Array in Chile can have dishes miles apart. But even these arrays aren’t big enough to resolve the tiny radio speck in the sky that is the supermassive black hole in the Milky Way, or the one in M87.

So, to really crank up the resolution, the EHT used a form of this technique called very-long baseline interferometry. Instead of relying on a single location, astronomers combined data from telescopes in entirely different areas — different continents even — using precise atomic clocks and GPS systems to carefully time the observations and keep everything in sync.

“You can put your antennas anywhere on the Earth that you like. You can put one in California, and put one in West Virginia,” says Jim Braatz, an astronomer at the National Radio Astronomy Observatory who is not part of the EHT collaboration. “With those two antennas, you can kind of simulate or mimic a telescope with the diameter of the whole country.”

The EHT has taken that to a global scale to make a telescope as big as our entire planet. Radio telescopes in Arizona, Hawaii, Mexico, Chile, Spain and even Antarctica all observed their black hole targets in tandem. With dishes spread as far as possible, the EHT aims for nothing less than the maximum resolution a radio array can get without leaving Earth.

“In general, the more pairs of antennas that you have,” Braatz says, “the better the image you’ll get at the end of the day.” That’s why this first black hole image is so impressive — and it’s just the first of many results we’ll soon see from the EHT.

The research is published today in The Astrophysical Journal Letters.

CATEGORIZED UNDER: Space & Physics, Top Posts

Inside The Event Horizon Telescope’s Quixotic Quest to Image a Black Hole

By Steve Nadis | April 10, 2019 8:15 am
The Atacama Large Millimeter/submillimeter Array is part of the globe-spanning Event Horizon Telescope effort to directly image a black hole. (Credit: ESO/C. Malin)

The Atacama Large Millimeter/submillimeter Array is part of the globe-spanning Event Horizon Telescope effort to directly image a black hole. (Credit: ESO/C. Malin)

Trying to take a picture of a black hole — an object that is, by definition, invisible—sounds like an exercise in futility. But for decades, theoreticians suspected it may just be possible to get a detailed view of a black hole’s perimeter, right up to the edge of the event horizon, the fabled point of no return. And a core group of astronomers spent years trying to turn that prediction into reality. Now, they finally have.

Astronomers announced Wednesday that they’d captured a clear view of the supermassive black hole in galaxy M87. It was a truly international unveiling, with press conferences held around the world — a fitting stage to describe the results of an astronomical instrument, the Event Horizon Telescope (EHT), that also spans the globe.

Their results were published in a series of six papers released Wednesday in The Astrophysical Journal Letters.

Here is the first direct image of a supermassive black hole. Captured by the Event Horizon Telescope, a network of eight radio telescopes spread across the world, the image shows the bright, spinning disk of material around the galaxy M87's supermassive black hole. Due the the intense gravity present near black holes, the appearance of the disk is warped. (Credit: EHT Collaboration)

Here is the first direct image of a supermassive black hole. Captured by the Event Horizon Telescope, a network of eight radio telescopes spread across the world, the image shows the bright, spinning disk of material around the galaxy M87’s supermassive black hole. Due the the intense gravity present near black holes, the appearance of the disk is warped. (Credit: EHT Collaboration)

Party like it’s 1999

The idea of black holes dates back to at least 1783, when British scientist John Michell suggested that our universe harbored “dark stars” whose density was so great and gravity so strong that “all light emitted from such a body would be made to return towards it.” But the notion of possibly seeing one is much more recent, and relies on the counterintuitive idea that an invisible object still casts a visible shadow — in this case a darkened region, or silhouette, extending inward from the event horizon, bounded by a ring of hot, luminous gases. Read More

CATEGORIZED UNDER: Space & Physics, Top Posts

The Human Brain Has been Getting Smaller Since the Stone Age

By Bridget Alex | April 8, 2019 5:15 pm
(Credit: Discover magazine; Tory Kallman/Shutterstock and Hein Nouwens/Shutterstock, after Die Frau als Hausarztin (1911))

(Credit: Discover magazine; Tory Kallman/Shutterstock and Hein Nouwens/Shutterstock, after Die Frau als Hausarztin (1911))

I don’t mean to alarm you, but the average human brain size is shrinking. And we can’t blame reality T.V. or twitter. No, this decline began tens of thousands of years ago.

It’s something of a well-known secret among anthropologists: Based on measurements of skulls, the average brain volume of Homo sapiens has reportedly decreased by roughly 10 percent in the past 40,000 years. This reduction is a reversal of the trend of cranial expansion, which had been occurring in human evolution for millions of years prior (see chapter 17).

Let’s review the boney evidence backing this observation, then explore some potential explanations.

And just to ease your anxiety: Although you may have a smaller cranium than our Stone Age predecessors, human brains today are still about three times the size that’s normal for a primate with our body weight. Read More

CATEGORIZED UNDER: Living World, Top Posts

Analysis of 4 Million Pitches Reveals Umps Really Do Suck at Calling Strikes

By Mark T. Williams, Boston University | April 8, 2019 4:40 pm
baseball umpire

(Credit: Richard Paul Kane/Shutterstock)

Baseball is back, and fans can anticipate another season of amazing catches, overpowering pitching, tape-measure home runs – and, yes, controversial calls that lead to blow-ups between umpires and players.

Home plate umpires are at the heart of baseball; every single pitch can require a judgment call. Yet ask any fan or player, and they’ll tell you that many of these calls are incorrect – errors that can affect strategy, statistics and even game outcomes.

Just how many mistakes are made? Read More

CATEGORIZED UNDER: Technology, Top Posts
MORE ABOUT: computers

Craft Beer’s Quest For The Funky Flavors of Wild Yeast

By Anna Groves | April 5, 2019 5:15 pm
A brewer watches beer bottles track down a factory line. (Credit: Jacob Lund/Shutterstock)

A brewer watches beer bottles track down a factory line. (Credit: Jacob Lund/Shutterstock)

Whether your preferred pint is crisp or hoppy, fruity or caramelly, you owe a lot to the single-celled fungus doing the important work of putting the booze in your brews. Hops may get most of the love on the craft beer scene, but yeast is an overlooked heavy-hitter when it comes to giving beer flavor.

“Cool people are obsessed with yeast,” says Simon McConico, co-owner of Milwaukee’s Vennture Brew. “It’s because hops are sexy; yeast is a bit more nuanced.”

He adds, “Yeast is starting to get more sexy among nerds.”

Scientists are buying in, too. Ever since a microbiology expedition to the mountains of Patagonia uncovered a new wild yeast species in 2011, scientists have been hard at work on ingredients that may soon bring totally new flavors to a beer near you.

yeast

Saccharomyces cerevisiae, also known as brewer’s yeast, has long been vital for making ale, wine and bread. (Credit: Illustration by Kateryna Kon/Shutterstock)

Yeast 101

The art of brewing can be broken down into a just a few key steps. First, grains are soaked until they start to germinate; then they’re roasted. Roasting is the first beer flavor checkpoint: lighter roasts might get turned into pale ales or pilsners; darker roasts into porters and stouts. Then this malt gets mashed and boiled, which converts the starches in the grain into sugars. Hops are added to make the wort — hot, sweet food for yeast. That’s when it’s ready-to-ferment.

Yeast arrives and eats up the sugars, turning them into alcohol, carbon dioxide and flavor compounds. However, just two yeast species are currently used to make beer: Brewer’s yeast (Saccharomyces cerevisiae) and lager yeast (Saccharomyces pastorianus.) The former comes in hundreds of strains, which can impart all sorts of different flavors on a beer.


Brewing Better Beer, With Wild Yeast and Genetics


If you’ve tasted banana, butterscotch or clove in a beer — that’s a byproduct from the yeast. You might find flavors that are spicy, sweet, tangy, medicinal or even musky. And just last year, the yeast flavor palate was really rounded out after scientists engineered yeast to produce the bitter yet aromatic flavors of hops.

Sierra Nevada brewing

Sierra Nevada Brewing Company’s North Carolina location. (Credit: digidreamgrafix/Shutterstock)

A lot of major breweries have a main house yeast strain they use for most of their brews. Stone, for example, uses a strain that originated at a now-defunct Canadian microbrewery and is cultured at beer-yeast-powerhouse White Labs. Lagunitas and Sierra Nevada are rumored to have house strains, too. These brewers get clever with different grains, hops, recipes, and techniques to come up with new pints. Some beer fans speculate that reliance on a house strain gives these mega-craft brews a signature flavor, for better or for worse.

A Literal Quest for Lager Yeast

Hundreds of years ago, brewers figured out that if they turned down the temps during the brewing process, they’d end up with the crisper, cleaner beer that still dominates the beer market today: lagers. Now we know that those lower temps are critical because they keep rogue yeasts and bacteria out of the brew. Only lager yeast can tolerate the cold.

Louis Pasteur, the godfather of yeast, discovered fermentation is caused by living things. (Credit: Everett Historical/Shutterstock)

Louis Pasteur, the godfather of yeast. (Credit: Everett Historical/Shutterstock)

For a long time, the lager yeast itself was a bit of a mystery. For the first century or so that we even knew it existed, we thought it was its own species: Saccharomyces pastorianus, named after Louis Pasteur, who discovered that fermentation was caused by living organisms.

But in the 1980s, scientists discovered that lager yeast wasn’t a species of its own at all, but a hybrid: a cross between the common brewer’s yeast used in all the other ales, and something else. Something else, not yet known to science, which passed on the critical characteristic of cold tolerance to the lager yeast.

This wild lager yeast ancestor remained a mystery for decades, until a microbiologist on a sampling expedition in Patagonia found a new Saccharomyces species growing on a beech tree in a remote mountainside in Patagonia. In the cold.

It was the missing yeast. They named it S. eubayanus. And its discovery in 2011 has opened up a new realm of possibilities for scientists — and brewers.


Everything Worth Knowing About … Yeast


New Yeast On The Block

Chris Hittinger is a University of Wisconsin microbiologist who’s researched Saccharomyces for years. He says this wild yeast discovery was a big step forward for the field. Since then, his lab has been setting the groundwork that could set us up for some pretty sweet brews in the future.

First, his research team figured out exactly how the wild yeast crossed with brewer’s yeast to make lager yeast. Through experiments crossing the two yeasts, they learned that the key to cold tolerance in lager yeast was in the mitochondria — organelles that make energy for the cell and hold a little bit of DNA — coming from the wild yeast.

This find allowed them to re-create lager yeast in the lab — which means new lager yeasts could now be developed from new crosses. “There’s just a lot more genetic diversity on the table,” says Hittinger.

Next they studied whether they could coax the wild yeast to evolve into something that could be used to brew. On its own, the wild yeast wouldn’t cut it as a beer fermenter. Maltotriose, the second-most abundant sugar in brewing worts, is too big of a molecule for nature’s version to eat.

In search of a solution, the scientists set out on an experiment that created 1,000 generations of wild yeast grown. It failed. Then they switched gears, instead trying to select for a wild yeast that was extra good at eating a different sugar: maltose, the most common sugar in brewing worts. Within two days, their yeast could grow four times more rapidly when given maltose. And, thanks to some genetic serendipity, it also gained the ability to digest maltotriose. They’d succeeded on accident.

Hittinger’s team had created a version of the wild yeast that could be used in lager production. But it’s a whole different species, meaning it could make a lager with a completely different flavor profile than we’re used to.

What kinds of flavors?

“One thing you get from the wild is what the industry calls phenolic off-flavors. And we’re starting to get to the genetic basis of what those flavors are,” Hittinger says. “We know that for some beer styles, those basically drive consumer preferences: like Weiss beers, Chimay-style, Trappist [beers], those are key flavor components and those come through in the wild lagers.”

Heineken's visitor center

Glistening brew tanks are the centerpiece of Heineken’s visitor center in Amsterdam. (Credit: Anton Ivanov/Shutterstock)

Something About Yeast

Heineken was first to step up to the plate after news broke of the wild yeast discovery. They released their first “wild lager” back in 2017, named H41 for the latitude where the yeast was discovered. It’s not clear how Heineken’s brewers got around the issue of the wild yeast not digesting all the sugars — their brew came out more than two years before Hittinger’s lab developed the new maltotriose-digesting strain.

But harnessing the flavors of wild yeasts isn’t exactly new to brewers. Before they opened, a proto-Vennture brew used yeast collected from peach trees down the road from the brewery. McConico explains that yeast is all around us in the environment. “You can basically culture yeast out of anything,” he says. “Whether or not it will ferment is a different story.”

Farther back in time, wild yeasts gave traditional “Farmhouse Ales” their unique-to-the-barn-it-was-brewed-in flavors. Modern beers, especially sours, are once again embracing some of these natural flavors, looking beyond strains of the traditional brewer’s and lager yeasts to species like Brettanomyces to ferment their wort.

And last year, a group led by biologist Richard Preiss from the University of Guelph sequenced strains of traditional Norwegian Kveik (pronounced something like, K-why-k) yeast, learning that they are a genetically distinct subset of common brewer’s yeaststrains that have been passed down through generations by local Norwegian brewers and have some interesting qualities. Global brewers are interested in Kveik because it can brew faster and at a hotter temperature than other strains of brewer’s yeast.

“Since craft beer has grown so much, people are looking for ways to be new and interesting,” says McConico. “Wild yeast could mean a new flavor, a new aroma.”

But whatever yeast strain is the current favorite for a brewer, scientist, or beer-drinker, it matters less than the great blessing that is yeast. “If you have no yeast then you have no alcohol,” reminds McConico. “If you have no alcohol, then you have no beer.”


 

KNOW YOUR BEER TERMS 

Malt: Short for malted grains, usually barley, but could also be wheat, rye, or anything else. Soaking the barley allows it to germinate, then heating stops the process. This roasting stage has the first impact on flavor: light roasts might get turned into pale ales, golden ales, or pilsners. More and more roasting leads to darker and darker malts and darker and darker beers.

Wort: The brewer’s concoction of everything-but-the-alcohol. The malt has been mashed and heated so the starches in the grains are converted to sugar. Hops and any other ingredients have been added. Wort is hot and sweet and ready to be fermented into beer.

Hops: Famously bitter, hops can also give fruity, floral and other tastes to beer. The part of the hop plant, Humulus lupulus, that’s used in brewing is the flower, traditionally dried and available as pellets or occasionally “whole leaves” (don’t be fooled, these are still petals.) A popular trend is to “wet hop” a beer, which adds fresh instead of dried hops to the wort — Sierra Nevada’s Harvest Ale was the first wet hop IPA in 1996.

Wild or open-air fermentation: The beer tank is literally open to whatever might fall inside. Before Louis Pasteur and sterilization, all beer was made this way. Now, traditional beers are more controlled, while open-air fermentation is making a comeback because of the interesting flavors wild yeasts and bacteria can introduce.

Saccharomyces: The O.G. brewer’s yeast. S. cerevisiae is the most well-known, and is used in beers, wines, and breads worldwide. Hundreds of ale yeast strains are available that can give beers different flavors, with names like American Ale 1056 and Old Sonoma Ale WLP076. Lager yeast, S. pastoralis, is cold tolerant and is actually a hybrid between S. cerevisiae and its wild relative S. eubayanus, which was only found in the wild for the first time in 2011.

Brettanomyces: A yeast that ferments like Saccharomyces but is slightly less predictable, works slower, and is likely to give your beer a funky taste (good or bad — if you’re not making a sour, you might want to make sure to keep Brett out of your brew.)

Lactobacillus and Pediococcus: Not yeasts, but species of bacteria. Lacto and pedio eat the sugars in the wort, just like the yeasts do, but turn the sugars into lactic acid instead of alcohol. Lactic acid tastes sour: You might find it in a gose, lambic, Berliner weiss or Flanders red.

Wine: Technically referring to fermented grapes, the term also sometimes gets thrown around to describe beverages that are closer to beers but have higher alcohol contents. Examples include barley wine (really just a strong beer), honey wine (also known as mead, though it sometimes does have fruit or grains added, blurring the taxonomy) and rice wine (or sake — no grapes here.)

CATEGORIZED UNDER: Living World, Top Posts
MORE ABOUT: Food Science

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If stories about psychopaths fascinate you, you might’ve heard of something called the dark triad. It’s a trio of traits that psychologists developed in the early 2000s to measure the more sinister aspects of human personality. Now, a team from the University of Pennsylvania and the University of Hawai’i-West O’ahu has finally crafted a counterpart test of the so-called light triad traits.

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First let’s establish what’s probably not the story: Conventional wisdom about wisdom teeth assumes evolution was doing away with these unnecessary chompers until modern medicine halted the process. Read More

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