On December 4th, 2017 we learned about

From Optimi to As, a short look at educational grading systems in the United States

My third grader brought her report card home today, and I’m happy to say she’s a straight Optimi student. Well, mostly— she did have Class II, but thankfully no As (meaning absences, naturally.) Now, these grades may not seem terribly informative, but grades are still a work-in-progress. The American educational system has been experimenting with them since the 1780s, and with the number of iterations we’ve gone through, progress hasn’t always been clear. Many of us are currently familiar with As, Bs, and Cs, but they certainly aren’t the last word on how to rate student performance. While there wasn’t actually any Latin on my child’s report card today, those famous letter grades weren’t there either, instead being replaced by a numeral system reminiscent of even earlier grading systems.

Experiments in higher education

The aforementioned Optimi grade comes from the first written account of assigning a grade to students’ test scores, from Yale University in 1785. Prior to these one-word descriptions ranging from “best” to “worst,” students were generally evaluated via personal feedback from their instructors. Students’ rankings in a class were more-often based on their family’s status rather than their academic performance, which was made all the easier by the exclusive nature of higher education. Still, Yale launched a number of grading experiments, particularly when it came to exams. One that will feel more familiar today dates to the early 19th century, where exams were rated along a simple four-point scale that set the basis for our current grade-point-averages.

Other colleges tried their hands at designing grading systems as well. Four-point scales were changed to nine-point scales. The University of Michigan tried a simple P for “passing,” C for “conditioned” and A for “absent” in the 1860s. Other schools tried a series of Divisions, Classes and other organizational concepts that usually revolved around a 100-point scale in one way or another. In the case of Harvard, the school tried nearly all of the above, even going back to a basic “Passed with Distinction,” “Passed” or “Failed” system in 1895.

Harvard also had the first letter-based grade, according to a reference in 1883. A student earned a B grade, although that grading system didn’t really take hold until Mount Holyoke adopted it in 1897. As with today’s grades, the letters were basically shorthand for positions on a 100-point scale, although many were more narrowly defined than many schools currently use, being limited to a five-point range. Another difference that this scale went from A to E, with the latter signifying a failing grade for any score lower than 75 percent. Mount Holyoke adjusted their scale the following year, promoting E to passing and adding the now infamous F to signify failure. Obviously, E didn’t last as long as the other letters, possibly for the slightly silly reason that it could be read as “excellent” right next to F‘s “failure,” although why that bit of branding needed addressing while A through D had no real meaning isn’t clear. Still, a scale that can’t even follow proper alphabetization seems somehow appropriate, highlighting how arbitrary these grades can be.

Transferable grades that take less time

So if grades are abstract shortcuts without real meaning, how did they catch on? While early students of Harvard could expect fairly exclusive, intimate academic communities, changes in primary education in the 20th century drastically altered how much time a teacher could spend on each student’s work. For the first time, laws required children to attend school, which when coupled with waves of immigration, meant that the number of students needing evaluation skyrocketed. Starting in 1870, the number of public high schools alone grew by 2,000 percent, reaching 10,000 schools in 1910. Teachers needed a consistent way to rate students’ performance, both for efficiency and to make grades a useful metric between schools. They haven’t always lived up to those promises, and many teachers today would like to be able to provide more personal feedback to their students. In the mean time, I’m morbidly hoping someone will start using loading bars, experience points and maybe unlockable achievements from video game interfaces, just to build a sense of progression in students’ work. At the very least, they seem as helpful and motivating as being called “worst” in Latin.

Source: An A Is Not An A: A History Of Grading by Mark W. Durm, The Educational Forum, vol. 57, Spring 1993

On December 3rd, 2017 we learned about

Like humans, baby bats pick up more speech patterns from their peers than from their mothers

For all the time and energy spent raising offspring, at some point every parent has to come to terms with the fact that they’re not only influence on their children. Whatever manners and language gets used at home, it’s nearly impossible for kids to avoid picking up the sound, style and charming phrasing of their peers’ voices. Apparently this is common not only among human families, but other social mammals as well, as researchers were able to induce the development of a non-native dialect, or group-specific accent, in baby bats.

Bats roost in groups, and spend a lot of that time chatting and bickering with each other. Like humans, baby bats develop their language skills by listening and imitating the sounds they hear in their local environment, which allowed researcher from Tel Aviv University to manipulate some bat pups’ emerging dialects. To do this, they placed some newborn baby bats with their mothers in a lab-controlled colony. When the animals were roosting, researchers played recordings of bats with dialects that contrasted from the pups’ mothers. They then observed and listed to the babies as their voices developed to see if they would sound more like their mother, or more like the artificial group they heard every day.

Gabbing like the larger group

The pups grew up vocalizing in a dialect that sounded more like the recorded chatter than their own mother’s voice. This may sound intuitive to anyone who has heard the children of immigrants speak with the accent of their adopted country, but it’s significant to see it in another species. Songbirds, for instance, are known to learn songs from their elders but seem to be instructed by a single tutor, like their father. This seemingly left humans as the only animal that picked up language instruction from everyone in their local population, aggregating the pronunciation and grammar rules into what we think of as accents.

These bat pups shake those assumptions up, since they’re picking up a dialect from their community like we do. This means that this structure for language acquisition may have been put into a common mammalian ancestor’s brain long ago, or that it has evolved more than once thanks to how useful it may be. To test the utility of sounding like your neighbors, researchers are now planning to see just how much of a difference a dialect can make, studying how bat colonies interact with animals that don’t sound like they grew up in the same group.

Source: Young bats learn bat 'dialects' from their nestmates, Phys.org

On December 3rd, 2017 we learned about

Using languages invented in a lab to reveal the brain’s linguistic biases

From a scientific perspective, the problem with languages is the cultures that help create them. There are over 7,000 languages spoken on Earth today, but they’re all so closely tied to cultural learning that it’s hard for researchers to be sure which aspects of language come from history, and which come our brains. To study how human brain structure influences language, researchers needed a language that was somehow free of the baggage that comes from being spoken, read and shared for thousands of years. Since such a language obviously wasn’t in use anywhere around the world, the only solution was to make up some new ones for the lab.

The hypothesis was that while human languages have been shaped and steered by events in the outside world, they were probably also shaped by the structure and functionality of our brains as well. These traits, called linguistic universals, would then be the foundation for all human language, even if they were modified or dressed up later on. If people could be tested using new languages that were designed to be free of these modifications, the underlying mental mechanisms that come straight from our gray matter would hopefully be revealed.

Keeping associated words close together

To test how brains handle a culture-free language, English speakers without other linguistic experience were taught two synthetic languages over the course of three days. The languages were different from both English and each other, making it easier to compare how people worked with these mental frameworks. Once proficient at these new ways of speaking, test participants were asked to explain a task in the synthetic languages, forcing their brains to make use of the new words and rules. The first pattern to emerge was related to word order, or more specifically, word dependencies.

Word dependency is when one word is partnered with another to complete an idea. For example, a sentence with the “29” doesn’t tell you nearly as much as “November 29.” All languages, including the two synthetic languages in this study, use this concept, but this experiment showed that our brains show a bias towards shorter dependencies. When speaking in either synthetic language, test participants regularly tried to pair dependent terms as closely in a sentence as possible, rather than allow them to drift apart through the sentence.

Aiming for cognitive efficiency

This may seem intuitive because we’re so used to it, but that’s probably the result of how much our brains prefer that grammatical construction. Researchers suspect that by pairing dependent words together as much as possible, our brains may be reducing the cognitive load to parse the sentence’s meaning. When the dependent terms are joined together, they can share the same space in our memory, vs. taking up multiple “slots” in what’s a fairly limited mental resource. This word order isn’t universal among the 7,000+ languages humans speak today, but it’s more common than it should be if it were strictly coincidental, indicating that the basis for many linguistic rules may stem from our brains’ cognitive abilities.

Source: Why do we see similarities across languages? Human brain may be responsible, Medical Xpress

On November 30th, 2017 we learned about

Destroyed Hamipterus colony yields unique views of pterosaur embryos, growth and development

120 million years ago, disaster struck a pterosaur nursery in what is now northwest China. What was likely a huge, sudden storm washed hundreds of nesting pterosaurs out of their nests, burying them in a jumble of fine sand and silt. While it was certainly a terrible way to die, the water and silt did an amazing job of preserving huge swaths of the nesting colony’s population, from young animals to old. Most remarkably, some of the soft-shelled eggs of Hamipterus tianshanensis tore open, allowing silt to enter and envelop developing embryos, saving them from being crushed and flattened in the fossilization process.

Delicate structures preserved in sandstone

Paleontologists have found and studied prehistoric eggs before, but finding developing pterosaurs is especially rare. Even adult pterosaurs have thin, hollow bones that make flying easier, but aren’t especially durable when buried in rock for millions of years. Embryos developing in soft, lizard-like eggs are understandably rarer, making this particular cache of fossils a unique opportunity to learn about pterosaur life cycles. A nine-cubic-foot block of sandstone is still being studied, but researchers believe it contains bones from H. tianshanensis of all ages, as well as up to 300 eggs.

Not every egg survived the rough process that swept them out of what was probably a nesting colony, similar to what some bird species use today. Out of the 215 eggs extracted, 42 retained their original dimensionality enough to scan, and 16 had developing embryos to study. To examine these delicate structures without damaging them, researchers employed computerized tomography, essentially letting them build a 3D model of the shapes still encased in sandstone.

New details on pterosaur development

These fossils have also sparked a somewhat controversial conclusion about these pterosaurs’ growth patterns. A particularly mature embryo was judged to be close to full term, but surprisingly didn’t have fully developed deltopectoral crest bones on its wings. In contrast, it did have some full-strength femurs, raising the possibility that these pterosaurs could only walk when they first hatched, waiting to fly until they’d had a chance to grow up a bit. This is in contrast to other studies from other species, and probably can’t be resolved until more embryos can be found. Otherwise, it’s hard to say if this single specimen represents the development of all pterosaurs, all members of its species, or even if it was as close to term as the study’s authors speculate.

With so many individuals crammed into a single block of limestone, we should have more details to how pterosaurs grow up. Many researchers agree that the diversity of ages seen in this collection is strong evidence of communal nesting. The variety of ages also suggest that nesting season was at least long enough for some babies to hatch before their neighbors were still incubating in their eggs. As much of a calamity as the original storm was for these pterosaurs long ago, their well-preserved deaths will soon give us an incredibly clear picture of a H. tianshanensis‘ life cycle.

Source: Huge haul of rare pterosaur eggs excites palaeontologists by John Pickrell, Nature News

On November 30th, 2017 we learned about

Overactive olfactory abilities provide clues about people who can’t understand their own emotions

Many nursery rhymes are meant to teach simple lessons, but “If you’re happy and you know it” may also be a step towards diagnosing a neurological disorder. While most toddlers are probably more concerned with learning the order of hand-clapping and foot-stomping, the simple song’s question about knowing when you’re happy is actually a significant challenge for people with alexithymia. There’s a range of symptoms in alexithymic people, but they mostly revolve around difficulty identifying one’s own emotional state, from understanding what is being felt to figuring out how to express those feelings to others. Weirdly, the other major symptom associated with alexithymia was recently discovered to be an altered sense of smell, which may prove to be useful in understanding the neurology behind the condition.

Connecting odor and emotion

The nexus of smell and emotional awareness seems to be tied to where some of this mental processing takes place in the brain. Previous studies found that there was overlap in some of the brain areas that handle emotion and olfactory perception, prompting researchers to look at how alexithymic people might experience smell differently than the general population. If a pattern could be detected, it would hopefully shed light on the relationship between emotional and olfactory understanding, and why that overlap might exist in the first place.

The experiments divided alexithymic participants into various sub-groups. For instance, some people were found to struggle with identifying emotions to themselves, while others only had problems describing those emotions to others, and everyone operated on a spectrum of how severe the symptoms were. Once sorted, volunteers were asked to sniff and rate various smells from Sniffin’ Sticks, which are standardized odor samples for these kinds of experiments. Since reactions to many odors are specific to a person’s cultural background, researchers tried to avoid getting people’s opinions on smells. Instead, they asked them about how strong smells were while measuring physiological responses, such as heart rate and breathing, to each scent.

Doing less with more

The pattern that emerged was about as intuitive as the overlap between odor and emotional perception as a whole. People who had more severe alexithymia symptoms also had more acute senses of smell, detecting smaller traces of scents than people who had an easier time parsing their emotions. Instead of facing confusion because of muted odor and emotional response, researchers now believe that these people may have a hard time making sense of emotions because of an overwhelming amount of activity. If the olfactory and emotional centers in the brain are activated constantly, getting the signal from all that noise likely becomes difficult, leaving people with fewer cues about when exactly to clap their hands or stomp their feet, even if they can smell them across a room.

Source: The nose reveals our relationship with our emotions, EurekAlert!

On November 29th, 2017 we learned about

Dinosaur’s unusual feathers maximized fluffiness over all other functions

A penguins’ feathers help insulate its body. An eagles’ primaries can form a surface to create lift. An Anchiornis‘ feathers…well, that’s difficult, because nobody has ever seen this Jurassic period dinosaur make use of its plumage. Complicating things further, Anchiornis‘ feathers were a very odd shape, deviating from the fluffy down or stiff primaries you see on modern birds. According to paleontologists from the University of Bristol, one of the most striking effects of Anchiornis‘ odd feathers was simply how floofy they must have made this dinosaur look.

Your average flight feather on a bird today is stiff, with the vanes coming together to form a single plane that can contribute to creating lift, or at least help streamline a bird’s silhouette. Some feathers, like the decorative plumage found in peacock’s tail, are looser, fanning out while still retaining a unified shape. Anchiornis seems to have been an evolutionary experiment, with a feather shape that doesn’t seem to have withstood the test of time. Instead of a tapered tip, the vanes in this dinosaur’s feathers split in two distinct directions, forming a “V” shape. En masse, it would have made for a fluffy, uneven profile, with the tufts of thick fluff covering the paravian dinosaur’s whole body.

Purpose of poofy plumage

These feathers wouldn’t have been great at creating lift like the flight feathers on a modern bird’s wing, but that doesn’t mean that Anchiornis was stuck on the ground. It actually had wings on it’s arms and legs, each with multiple layers of feathers to help catch the air. It wouldn’t have been capable of powered flight, but probably could glide between trees on these thick, fluffy wings. The fluff would have also created a lot of drag in the air, so Anchiornis was also adept at grasping at tree branches, looking more like a shaggy monkey than the robins, crows and parrots we can see perched in trees today.

One thing Anchiornis‘ feathers could do as well as their modern counterparts is to provide coloration. Sure, crisp lines and detailed markings may have been a bit of a stretch, but previous studies have found evidence of the pigments that once colored this creatures’ floof. Wings were likely light, with dark spots along feathers’ “tips,” while the majority of the body was a dark gray or black. These colors may have served to impress peers, but likely also resembled the dappled light and shadows that would have been found in Anchiornis forest home. Obviously, modern birds prove that the “V” shape feathers weren’t strictly necessary to remain camouflaged or soar through the air, but evolution doesn’t always iterate along a single design path.

Source: Feathered dinosaurs were even fluffier than we thought, Phys.org

On November 29th, 2017 we learned about

Urban traffic has been terrible for at least two thousand years

Even though they’re too young to drive, my kids have already learned to dread traffic. They know how car-clogged roads make us tense, late, and are generally unpleasant, even before you start worrying about noise, air pollution and increased risks for accidents. As much as this may seem like an unavoidable part of driving a car, humans have been struggling with congested roads for thousands of years, going back at least as far as ancient Rome. In some respects, citizens of ancient cities like Pompeii may have had it worse than we do, starting with fact that their roads had to double as sewage lines.

There were a lot of complications in getting your ox cart down the road in a city like Pompeii, but one of the most ubiquitous issues would have been the water, sewage and other garbage running down the stone streets. While Romans famously designed aqueducts, public toilets and more, not every form of waste management seems so innovative from a modern perspective. There was management involved though, as streets had intentionally deep curbs to keep water off the sidewalks. They also had raised stepping stones across streets, acting as a simple crosswalk to let pedestrians cross the road without stepping in the muck. Wagon wheels were expected to thread their way between the stones, but that’s probably ok since it would have been hard to move quickly in the first place.

No easy navigation

Moving carts and wagons through these sullied streets was a slow process, partially thanks to the tight fit these vehicles dealt with to get through town. Most streets weren’t more than three feet across, leaving just enough room for a single cart at a time. Since advanced maneuvers like turning were out of the question, as many as 77 percent of the streets were essentially one-way. This likely created bottlenecks when a cart or wagon needed to park, or maybe try to get around a corner with very little room to work with.

Beyond the mechanical issues that made moving through Pompeii difficult, the city layout was a mixed bag. Some streets were winding and less predictable, having been built according to old paths or trails. Much of the city was planned though, with most streets being laid out along a grid that may have been hard to squeeze through, but was at least comprehensible. To balance that out, only a portion of the streets had clearly marked names, ensuring that people new to the city had more reason to slow down traffic while figuring out where they were.

Understandably, all of the above could come together for a difficult, frustrating trip through town. Like today, there were complaints about noise and safety, with Roman writers making a point to comment on the clatter of wagons and swearing from their drivers. If the familiarity of these traffic woes feels somewhat disheartening, there are some silver linings to take solace in. After all, it’s much safer for a distracted pedestrian to stare at their phone now that they’re less likely to fall into a sewage covering the street. If they do manage to pull that off, at least we know there will still be plenty of other people around to swear at them.

Source: Pompeii Had Some Intense Rush Hour Traffic Too by Sarah Bond, Forbes

On November 28th, 2017 we learned about

Flying beetles found to swing their legs to tighten their turns

When a bird flies, it tucks its feet close to its body to avoid creating turbulence in the air around it. So do dragon flies. So do large aircraft, even if they’re tucking in wheels instead of feet. Flying beetles, on the other hand, seem to have missed the memo on aerodynamics, because they do the exact opposite, flying with their legs outstretched in all directions. This certainly creates drag, which is why scientists suspected that this akimbo posture must offer some other benefit to beetle flight, like maneuverability.

Turning while tethered

It seemed quite plausible that outstretched legs could play a role in beetle steering, but scientists couldn’t just ask them why they flew that way to get an explanation. To get around this, they simulated flight for a beetle, then watched as it responded to turning either left or right in the air. Insects don’t have the inner ear we do to detect motion, relying almost exclusively on visual stimuli to tell them how they’re moving through space. So a beetle could be glued to a fixed point, and as long as stripe patterns in front of it looked like they were panning to the right or left, the beetle thought it was actually zooming around enough to demonstrate how it uses its legs in a turn.

When “turning” left, the beetle would pull in its right leg, doing the opposite when the visuals were reversed. So instead of simply pretending to not have drag-inducing legs, the beetles apparently put their legs to work, creating a rotational force to change their trajectory. At least, that’s what it looked like the beetles wanted to do, because in this first test they weren’t actually moving. To see if they were actually affecting their rotational inertia with these leg twitches, the insects were untethered and allowed to actually fly.

Controlling cornering

To isolate the role of the beetle’s swinging legs, researchers implanted electrodes to actually take control of their legs’ muscle movement. That way they could trigger the previously seen leg motion on its own, without waiting for the beetle to initiate a turn that might involve other motion. As expected, the swinging legs made a difference in the insects’ flight path, with small turning motions initiated in less than a fifth of a second. They don’t turn with their legs alone, but swinging their legs lets them begin a maneuver faster than they could if using only their wings.


My four-year-old asked: What kind of beetles were they?

In this case, researchers were working with one of the biggest flower beetles in the world, Mecynorhina torquata, which can grow up to 3.3 inches long. The green-shelled natives of Africa are robust aviators, and have been used in a number of different studies, including one that allowed researchers to completely control their movement, effectively turning them into a remote controlled bug.

Source: Why Beetles Fly Like Superman by Jeremy Rehm, Scientific American

On November 28th, 2017 we learned about

Origami-inspired robots promise significant strength in a soft, squishy shell

I’ve made a few origami frogs in the past, and while they did successfully hop, I never appreciated how close I was to making a robot. The amount of potential and kinetic energy in the frog’s flexing legs seemed negligible, but apparently carefully controlled folding can not only trigger movement, but it can offer some considerable strength as well. While my little paper frogs weren’t about to do any heavy lifting, researchers from Harvard and MIT have found that lightweight, foldable materials can do a lot of work, even moving objects 1,000 times their own weight.

Air-powered contraction and expansion

The key to these folded robots is how they turn folded materials into veritable motors. A simple example uses a strip of stiff paper or plastic, folded in a basic accordion shape. That zig-zagging strip functions as a sort of “skeleton” for the machine, but it needs an outer covering to be activated. A simple plastic bag sealed around the folded strip is sufficient to act as the machine’s “muscles,” as long as that bag has a valve that can manipulate air flow. Sucking the air out of the valve with an air pump naturally causes the bag to contract, constricting around the folded paper. As the whole machine contracts, it’s strong enough to lift a weight many times its own mass. Letting air back into the bag allows the folded strip to expand again, lowering the weight in a controlled manner. In short, it’s a simple crane, powered by lightweight materials and a vacuum pump.

A folded strip is only the beginning though, as well-placed creases and joints in the inner skeleton can make for much more complicated articulation. One prototype was a four-pronged claw that can contract with enough strength to lift a tire. Another was a multi-jointed arm, ending in a flower-shaped gripper that can open and close as air is added or removed from the system. While they promise outsized strength, each design works with very simple, zig-zagged folds in the internal plastic structures, keeping them lightweight and very importantly, squishy.

Softer and safer

We have many machines that can lift a lot of weight, but the strength exhibited by these machines is quite noteworthy for something that’s soft and relatively safe. With no hard motors, actuators, joints or power sources, these machines can be used in places that harder robots wouldn’t be appropriate, like close to the human body. Since less than an ounce of foldable machine can lift over six pounds of weight, researchers think these gentle robots could be fit to human bodies, supporting or augmenting people who need help with certain tasks. They’d need to have a way to inflate and deflate the machine, but it would still be safer and more comfortable than carrying a huge set of gears, servos or hydraulic pistons.

At this point, researchers still haven’t made a jumping frog, unfortunately. The snap you get when releasing an origami frog is actually a bit speedy for these machines, as they can only move as fast as they’re inflated. An upcoming goal instead focuses on maximizing strength and articulation, as researchers aim to build a robotic elephant trunk. Since a trunk contains no hard bones but is incredibly mobile thanks to its 150,000 muscle fascicles, or muscle sections. It will likely require some carefully coordinated folding, but it would also prove that these inflation-based “muscles” will allow for very versatile machines in the near future.

Source: Artificial muscles give soft robots superpower, Phys.org

On November 27th, 2017 we learned about

Most of the mammoths found trapped in hazardous terrain turn out to be male

One of the most important features of the La Brea Tar Pits in Los Angeles are the traffic cones. The museum’s collection of Pleistocene animals is great, as are the continuing excavations taking place at the site, like Project 23. However, having just returned from my kids’ first visit to the Tar Pits, I think the entire experience was greatly enhanced natural liquid asphalt bubbling out of the ground in the surrounding Hancock park. Some bigger pools are fenced off, but it’s clear that the asphalt is slightly unpredictable, sometimes oozing outside a barrier, or simply popping up in the middle of the lawn, with only an oil-splattered traffic cone to warn you of its sticky presence. It all helps drive home just how animals living in the Los Angeles basin 60,000 years ago might have gotten into trouble without the bright green cones in place to warn them.

The La Brea Tar Pits weren’t the only natural hazards Ice Age animals had to worry about, and a recent study of mammoth (Mammuthus primigenius) remains from Siberia looked for patterns in which creatures most often got themselves into these sticky situations. Excavations of geological dangers like asphalt pools and icy lakes had already established that one trapped herbivore was likely to attract huge numbers of carnivores (that would also end up trapped), but this study looked to see which particular mammoths couldn’t stay out of the asphalt, ice or other pitfall. Since these animals were well preserved from only 60,000 years ago, DNA from hair and bones could be used to determine that 69 percent of the trapped mammoths were male, despite having originated from a balanced population.

Males in the muck

Researchers suspect that, if mammoths follow some of the behaviors seen in their modern elephant relatives, the unusual sex-ratio was due to male mammoths’ inexperience. Elephants today generally rely on the leadership of an older female, and that matriarch retains and transmits information about everything from when to migrate to how to avoid hazards in their environment. Young male elephants have to figure all this out themselves, even if it means finding out the hard way.

If mammoths lived in a similar manner, the males likely fell into pits and asphalt pools more often because they had nobody to teach them until it was too late. A higher tolerance for risk may have also made them more likely to try stepping on the weird black stuff in the grass, since without a matriarch or green traffic cone to warn them, they weren’t sufficiently wary of what now seems like an obvious danger.


My third grader asked: What’s the asphalt made of?

liquid asphalt bubbling up in Hancock Park
Liquid asphalt bubbling up in Hancock Park, Los Angeles.

While male mammoths were apparently adept at getting stuck in all kinds of hazards, the pachyderms in what would become Los Angeles were stuck in a natural asphalt, which is the lowest grade of crude oil. This oil is a layer of decomposed, pressurized marine plankton, first laid down five to 25 million years ago. The bubbles are generally methane gas, although microorganisms in the oil help create hydrogen sulfide, which adds a notable “rotten egg” smell.

It’s not clear how ancient mammoths missed the bubbles and the smell, but once dust and leaves covered the surface of a shallow oil pool, it seemed to only take a few steps to completely ensnare mammoths and other megafauna.

Source: Woolly Mammoth Bachelors Skew the Fossil Record by Carl Engelking, D-brief