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What is the world’s deepest cave?

Credit: Daily Sabah.

With a record depth of 2,212 meters (7,257 feet), the Verëvkina (Veryovkina) cave is the deepest cave measured thus far in the world. It’s located in the Arabika Massif in Abkhazia, a breakaway region of Georgia that is supported by Russia. Despite its complicated geopolitics, the region is home to not one but four of the deepest caves on Earth.

A decades-long history of exploration to reach the world’s deepest cave

Verëvkina was first discovered in 1968 by Soviet speleologists who only explored a section 115 meters deep (377 feet) and couldn’t comprehend the true scale of this gigantic cave system. In 1983, an expedition led by Oleg Parfenov climbed down a well that led the researchers to a new branch of the cave where they recorded a depth of 440 meters (1,443 feet). It was only much later, in the early 2000s, that new expeditions at Veryovkina were organized by the Moscow-based Perovo Speleo and Speleoclub Perovo caving organizations.

The work proved highly difficult and treacherous. The deeper the researchers went, the more it took for them to bring excavated material to the surface and the greater the mortal peril of collapse. After a few minor expeditions, the researchers finally broke through and reached new sections with a depth of over 1,000 meters (3,200 feet). This victory inspired Russian speleologists to keep exploring, launching expeditions every two to three months until they finally hit gold in 2017 and achieved the world's greatest depth for a cave system.

Using a series of camps along the way, it took expedition members more than four days to reach the terminal sump at a depth of 2,212 meters (7,257 feet). It takes roughly the same time to return to the surface, so the crew had to spend at least a week inside, which is a very long time for such an extreme environment. Due to the endless night, the cavers easily break their biorhythms, working at night and sleeping during the day. Thankfully, communication links with a surface base allow the cavers to contact the outside world and share updates about their progress.

The map is based on the profile by Perovskij speleo club (Moscow, pres. Aleksej Baraškov) of February 2020; surface contours and other data were obtained with the help of Perovo speleo team (also from Moscow, pres. Pavel Demidov). It was compiled February to July 2020 by Primož Jakopin - Klok, of DZRJL, Ljubljana Cave Exploration Society from Slovenia. Credit: Wikimedia Commons.

They had to descend thousands of feet on ropes and crawl through water- and mud-choked siphons. The cave goes down almost vertically and is full of wells with small horizontal passages. Starting from the depth of 800 meters (2,600 feet), water flowing through small tributaries splash water through the narrow passageways. This makes the cave extremely damp. The humidity is actually 100% and with a 4 °C to 7 °C temperature range, this means anyone descending will be freezing along the way.

Along the way, they collected samples of rare shrimp and scorpions, and possibly new species of microorganisms. There are also fossils, mainly imprinted on rocks, offering hints about how the cave's organisms might have looked millions of years ago, as well as how the cave itself and the surrounding mountains formed.

The caving heroes

Pavel Demidov in the camp -400 after the first rigging of Babatunda pit (155m). Veryovkina cave, 2016. Credit: Wikimedia Commons.

Pavel Demidov, the head of the record-holding expedition, was one of the first to reach it. He described Veryovkina "as if you have had a look at the far side of the Moon," referring to the alien environment of the cave. Right at the very bottom of the cave, there is a vast labyrinth

Demidov passed away on August 23, 2020, in Abkhazia while descending into an unexplored cave in the Arabika Mountain Range, not too far from Veryovkina. The 49-year-old man was killed by a large rock burst at a depth of 305 meters (1,000 feet).

Demidov's tragic death is illustrative of the kinds of dangers cavers face during their treks. In 2018, Demidov's team, which included Petr Lyubimov, Konstantin Zverev, Andrey Shuvalov, Evgeniy Rybka, and Andrey Zyznikov, as well as National Geographic photographers Robbie Shone and Jeff Wade, barely made it out alive after the cave was flooded. Heavy rains can cause water to collect, then, because of the volume, suddenly burst through cave openings.

Despite the extreme conditions, researchers continue to explore Veryovkina and other similar caves in Arabika Massive for various paleontology, biology, and microbiology projects. Some cave organisms may be beneficial to the development of antibiotics.

Four of the world's deepest caves are found in the astonishing Arabika Massive. Besides Veryovkina, these include Krubera-Voronja (2,199 m), Sarma (1,830 m), and Snezhnaja (1,760 m). This is no coincidence. All these caves are carved in karst terrain, which is a rugged landscape with a high elevation and very rich in soluble thick limestone.

#NameDepth (m)Length (km)Country
1Veryovkina Cave221213.5 km (8.4 mi)Abkhazia / Georgia
2Krubera-Voronja Cave219923.0 km (14.3 mi)Abkhazia / Georgia
3Sarma cave183019.2 km (11.9 mi)Abkhazia / Georgia
4Snezhnaja cave 176040.8 km (25.4 mi)Abkhazia / Georgia
5Lamprechtsofen173561 km (38 mi)Austria
6Gouffre Mirolda173313 km (8.1 mi)France
7Gouffre Jean-Bernard162526.6 km (16.5 mi)France
8Sistema del Cerro del Cuevón 15897 km (4.3 mi)Spain
9Wot-U-Got Pot 1560113 km (70 mi)Austria
10Sistema Huautla156089 km (55 mi)Mexico
11Chevé Cave153677.0 km (47.8 mi)Mexico
12Pantjuhinskaja Cave 15087.9 km (4.9 mi)Abkhazia / Georgia
13Sima de la Cornisa15076.4 km (4.0 mi)Spain
14Čehi 215055.5 km (3.4 mi)Slovenia
15Sistema del Trave 14419.1 km (5.7 mi)Spain
16Velebit caves14313.7 km (2.3 mi)Croatia
17Egma Sinkhole14293.1 km (10,000 ft)Turkey
18Boybuloq141514.8 km (9.2 mi)Uzbekistan
19Gouffre de La Pierre Saint-Martin 141083.6 km (51.9 mi)France, Spain
20Kuzgun Cave 14003.1 km (1.9 mi)Turkey
Top 20 world's deepest caves. Source: Wikipedia.

Thousands of other subterranean hidden marvels await discovery

Karst covers up to 25% of the Earth's land surface, and where there is karst, caves are bound to be close by. In fact, scientists believe there may be tens of thousands of undiscovered caves across the world. And some of them probably reach deeper than Veryovkina. The only limit is how far down groundwater can seep into limestone before the pressure becomes too great, and we know from the Soviet-era Kola Superdeep Borehole that this limit is far from being reached by a known cave.

The Kola Superdeep Borehole, the deepest hole in the world, drilled into the Earth from 1970 to 1994 until it reached a staggering depth of 12,262 meters (40,230 ft). Soviet geologists found water still circulating at depths of 6.9 km (4.3 miles), which is more than three times deeper than Veryovkina's cave floor.

One candidate for the title of the world's deepest cave is the Chevé Cave system, a sprawling underground complex in the Oaxaca region of Mexico, where water flow suggests it may descend nearly 2.57 km (1.6 miles) into the Earth. There may be many others waiting to be explored.

However, any super-deep caves are probably inaccessible from the surface and would require some drilling to reach them, provided that scientists can locate them. Remote sensing, such as electrical resistivity, seismic activity, and ground-penetrating radar only work up to a relatively shallow depth or don't have the necessary resolution to identify an underground passageway only a few feet in width.

But developing new methods to reach the world's deepest caves, however challenging, is worth it. Caves are filled with living organisms, particularly invertebrates and microbes, that could help scientists discover new antibiotics and other medicines. They are also time capsules of Earth's past climate, which refine climate models in order to have better projections of future trends.

Spanish cave paintings confirmed to have been made by the Neanderthals

Neanderthals in Europe weren’t the simple brutes they’re often portrayed as being, a new study suggests. It confirms that red ochre markings found in a Spanish cave were made by the Neanderthals and probably used for a symbolic or ritual purpose for thousands of years.

A general view and a close-up of a partly colored stalagmite tower in Cueva de Ardales. Image credits Africa Pitarch Martí et al., (2021), PNAS.

The Cueva de Ardales cave in Málaga, Spain, is one of the most impressive and well-preserved examples of Paleolithic cave paintings in southwestern Europe. More than a thousand different representations have been found here, indicative of the cave being inhabited by many generations of early humans.

One stalagmite here was painted red ochre thousands of years before the emergence of modern humans in Europe, according to a new paper, and offers us a glimpse into the history and culture of the Neanderthals.


It was first suggested that Neanderthals painted this stalagmite red in 2018, when an initial dating of the pigment showed it’s at least 64,800 years old. However, the results were contested, and “a scientific article said that perhaps these pigments were a natural thing,” explained co-author Francesco d’Errico for Agence France-Presse. It proposed that the markings were the result of iron oxide (iron) deposited by water infiltrating into the cave.

The new study shows that the deposition and composition patterns in this pigment are not consistent with natural processes. It was most likely applied through splattering (mixed with water) and blowing (in a powdered form).

Furthermore, the authors explain that pigment was repeatedly applied to the stalagmite over time, at least over ten millennia.

“[The findings] support the hypothesis that the Neanderthals came on several occasions, over several thousand years, to mark the cave with pigments,” said d’Errico, of the University of Bordeaux.

But they were likely not art in the way we understand the term. The markings themselves are different even from the cave art made by our ancestors thousands of years ago. Rather, the authors explain, these markings were “result of graphic behaviors intent on perpetuating the symbolic significance of a space.”

While the markings do seem to have been culturally or symbolically significant, we don’t actually know why, or what they meant. Even so, the study showcases how the Neanderthals were not necessarily as simple as we’ve come to think of them. They were capable of manufacturing and using advanced tools, making art, and using language.

The paper “The symbolic role of the underground world among Middle Paleolithic Neanderthals” has been published in the journal PNAS.

The world’s oldest known cave painting in Indonesia shows a chonky wild pig

The lush environment of Indonesia harbors some of the oldest known cave art. Now, it can officially boast having the oldest known cave art. Dated to 45,500 years ago, this prehistoric figurative painting depicts a Sulawesi warty pig — and researchers say there should be more like it in the area.

Dated pig painting at Leang Tedongnge. Maxime Aubert Credit: Maxime Aubert

Sulawesi is an Indonesian island east of Borneo. Rich in lush vegetation and karst environment, it would have been an excellent home for early humans. Unsurprisingly, then, the island has a long history of human occupation, with stone artifacts dating up to 194,000 years ago, possibly from a yet-unidentified ancient human species.

The Leang Tedongne cave, where the painting was discovered, lies in a narrow valley, enclosed by steep limestone cliffs — exactly the type of karstic landscape you’d expect to find caves in. Doctoral Student Basran Burhan came across the painting during 2017 surveys carried out with local authorities and members of the local Bugis community.

The cave is only accessible during the dry season as the valley gets flooded during rainy season. In fact, it’s so inaccessible that Bugis members told researchers the cave had never been seen by Westeners before.

Leang Tedongnge cave. The cave is located at the foot of a limestone karst hill. Credits: Brumm et al / Science Advances.

Measuring 136 by 54 centimeters (53 by 21 inches), the Sulawesi warty pig is painted in a single dark red color. It has a short crest of upright hair and a pair of horn-like warts, which help researchers identify the species of the pig. There are also two hand prints near the pig, as well as two partially preserved pigs, suggesting that it could have been a larger narrative scene.

The painting also features an artistic technique often found in ancient cave paintings, the researchers note in the study.

“It should be noted that the artists portrayed preorbital warts in the so-named twisted perspective. This is a common method of graphical representation in prehistoric art that entails using a single outline profile image of an animal to depict how it appears to an onlooker when observed from different viewpoints.”

“The pig appears to be observing a fight or social interaction between two other warty pigs,” said co-author Adam Brumm.

Sulawesi warty pigs have been hunted for tens of thousands of years in Indonesia, and have even been domesticated in some regions. It’s unsurprising then that these creatures feature prominently in cave art.

The researchers also analyzed a couple of other cave paintings, dating them and identifying the depicted species. The previous oldest cave art was dated from 43,900 years ago, also from Indonesia.

Could be even older

Since the maximum age that can be dated using carbon dating is 50,000 years, the cave painting was dated using another method: uranium dating. However, the team didn’t date the paint itself to prevent any damage, but rather the layer of calcite that formed on top of the painting. This means that the painting itself “could be much older because the dating that we’re using only dates the calcite on top of it,” they say.

Digital tracing of the rock art panel. Image credits: Brumm et al / Science Advances.

But even if the painting dates from so long ago, the people who made it were, by any definition, people. The team believes the artwork was made by Homo sapiens and not another, now-extinct human species like Denisovans (or another unidentified species) but cannot say this for certain at this moment. Regardless of what species made it, they were still people, researchers conclude.

“The people who made it were fully modern, they were just like us, they had all of the capacity and the tools to do any painting that they liked,” he added.

Since the depicted scene also features a couple of handprints, researchers are hoping to get some DNA samples and see what species created the art. In order to produce these handprints, the artists would have had to place their hand on the wall and then spit pigment over it — traces of that may yet be discovered, shedding new light on this ancient episode of human evolution.

The study has been published in Science Advances.

Artwork in Indonesia might be the new ‘oldest’ hunting scene by modern humans

Indonesia may be the home of the oldest cave paintings of hunting bands found in the world.

A section of the cave painting.
Image credits Griffith University via Gizmodo.

A new study reports on what appears to be a depiction of human-like figures hunting wild buffalo and pigs at the Leang Bulu’ Sipong 4 site in South Sulawesi, Indonesia. It was dated to be approximately 43,900-years old. If this estimate is true, it would make the artwork the oldest known example of figurative art drawn by modern humans.

For now, exactly what the scene is meant to represent is still up for debate, but it could also be the oldest depiction of a hunting scene to date.

Hunting or myth-telling

Cave art that precedes this one has been discovered both in Europe and Africa. However, the cave drawings in Europe, featuring animals, dots, geometric signs, and hand stencils, were almost certainly made by Neanderthals. The art-piece from Africa, a 73,000-year-old cross-hatched pattern drawn onto a smooth rock, is not a figurative work (i.e. not meant to represent a real scene or place).

The oldest known hunting scenes that we know were made by modern humans date back between 21,000 to 14,000 years ago and were found in Europe — including the famous drawing at The Shaft in Lascaux France. The new scene found in Sulawesi shows that the tradition of figurative cave paintings wasn’t necessarily born in Europe.

Due to the ravages of time, the 4-meter (13 ft) wide artwork isn’t fully visible. However, it seems to have been a single composition depicting tiny humans with spears and ropes hunting buffalo and pigs.

The oldest known hunting scenes that were made by modern humans date back somewhere between 21,000 and 14,000 years ago and were found in Europe — including the famous drawing at The Shaft in Lascaux France. The new scene found in Sulawesi shows that the tradition of figurative cave paintings wasn’t necessarily born in Europe.

The team was able to date the drawings using calcium carbonate growths that form naturally in limestone caves — the same growths that now obscure parts of the artwork. The tests returned an age of 43,900 years ago but, as these bits of mineral grew over the paints, the drawing itself could be much older.

Both modern and several kinds of archaic humans — including Homo erectus and the Denisovans — lived in the area at this time. While any one of them could have created the work, we know for a fact that modern humans would paint similar (and unrelated) scenes at later dates all over the world, making them the most likely candidate.

Ochre, hematite, and other natural pigments were used to paint the figures, the team explains. It showcases several therianthropes hunting or subduing six animals: two Sulawesi warty pigs and four dwarf buffaloes known as anoas, both of which were common to Sulawesi at the time.

“Although these animals were depicted in outline profile with irregular patterns of infill the figures were executed with a relatively high degree of anatomical realism and certain [anatomical features] of these species are clearly represented, such as, in the case of Sulawesi warty pig, its distinctive head crest, and, with the anoas, their characteristic straight, dagger-like horns,” corresponding author Adam Brumm told Gizmodo.

He adds that “we can’t ever know the real meanings of this cave painting,” the team is “fairly convinced” that it showcases a hunting scene; it could also be a depiction of myth or religious story due to the presence of the therianthropes.

The paper “Earliest hunting scene in prehistoric art” has been published in the journal Nature.

Archaeologists find first prehistoric figurative cave art in the Balkans

The cave art, which was first discovered in 2010, has now been shown to be truly figurative. It could be as old as 34,000 years old.

Composite of digital tracings of 1 Bison_2 ibex and 3 possible anthropomorphic figures from cave art – Credit Aitor Ruiz-Redondo

Ancient artists

An international team of researchers from Britain, France, Canada, Spain, and Croatia analyzed the cave paintings found in Romualdova Pećina (Romuald’s Cave), Croatia. Radiocarbon dating showed that these works are at least 17,000 years old, but judging by other indirect data (such as the dating of the cave sedimentary layers), the paintings might even date from 34,000 years ago. Further research will be conducted in order to establish the precise age of the rock art. But more important is the nature of these paintings. Although not very visible to the naked eye, digital recordings and image amplification techniques have revealed that the paintings represent a bison, an ibex, and two possible anthropomorphic figures.

These are clearly figurative paintings — depictions derived from real object sources and so is, by definition, representational — an important landmark of cultural evolution. The oldest known figurative art painting is over 40,000 (perhaps as old as 52,000) years old and represents an unknown animal. The dating results were only published one year ago. Meanwhile, the earliest known European figurative cave paintings are those of Chauvet Cave in France. These paintings date to earlier than 30,000 BCE (Upper Paleolithic) according to radiocarbon dating. However, these new findings represent the first such art found in the Balkan area.

“Rock art is key for understanding European Palaeolithic societies. Long thought to have been restricted to South-west Europe, recent discoveries on the Balkan Peninsula have expanded significantly the geographic distribution of Upper Palaeolithic figurative rock art, calling into question the idea of its limited distribution,” researchers write in the study.

Dr. Aitor Ruiz-Redondo, a British Academy-funded Newton International Fellow at the University of Southampton and postdoctoral researcher at the University of Bordeaux, further adds that the paintings offers an important clue to understand how different cultures were developed at the same time.

“The importance of this finding is remarkable and sheds a new light on the understanding of Palaeolithic art in the territory of Croatia and the Balkan Peninsula, as well as its relationship with simultaneous phenomena throughout Europe.”

Further research is currently being carried out at the cave.

Journal Reference: Ruiz-Redondo et al. Expanding the horizons of Palaeolithic rock art: the site of Romualdova PećinaAntiquity, 2019; 93 (368): 297 DOI: 10.15184/aqy.2019.36

Scientists find oldest figurative cave painting

A figurative painting, by definition, is a representation — an image of something else. Now, scientists have evidence that the first figurative painting was painted at least 35,000 years ago.

Ancient figurative cave art, 40,000 years old. Image credits: Pindi Setiawan.

The first artists

Since the 1990s, thousands of rock art images have been documented in the karst caves of the East Kalimantan, a province in the Indonesian portion of Borneo. This beautiful region is remote and difficult-to-access, and contains numerous caves, some of which contain remarkable drawings made by early humans. Fifty-two rock art sites have been recorded, generally in high-level caves that contain little other evidence of human habitation. Few sites in the region have been excavated and studies remain logistically difficult.

Now, researchers have used uranium dating to show that the paintings are much older than previously thought, and probably represent the oldest figurative paintings ever found.

The prehistoric paintings and drawings include thousands of depictions of human hands (“stencils”), animals, abstract signs and symbols, and related motifs. Previously, researchers have looked at the different styles of drawing, discovering three distinct phase:

  • The oldest style phase contains two different elements: large, reddish-orange-colored paintings of animals — mainly the Bornean banteng (Bos javanicus lowi), a type of wild cattle that still lives on the island — and hand stencils produced using a similar pigment;
  • The second phase is dominated by purple hand stencils, many of which are partly in-filled with painted lines, dashes, dots and small abstract signs that possibly represent tattoos or other marks of social identification;
  • The third phase features anthropomorphic figures, boats and geometric designs that are usually executed in black pigments.

Mulberry-colored hand stencils. Image credits: Kinez Riza.

Now, Maxime Aubert and colleagues from Griffith University studied a large, red-orange colored painting of an indeterminate animal from the first period. They used uranium dating to assess the age of the painting using a calcium carbonate sample.

[panel style=”panel-info” title=”Uranium Dating” footer=””]This is a radiometric dating technique to determine the age of calcium carbonate materials. It works by measuring the ratio between the radioactive isotope thorium-230 and its radioactive parent, uranium-234 within a sample. In the particular case of cave paintings, the difference between the type of dating can be extremely important.

“Radiocarbon dating is usually used to date the pigment layer itself, “Aubert explained. “It’s been applied in France for example to date the charcoal drawings in Chauvet cave. The problem it that it only provides a maximum age. The date is for the charcoal, not the marking event. In other words, if I walked into the cave today and pick up a 40,000 years old charcoal from the cave floor and draw an animal with it, it will date to 40,000 years.”

“The oldest cave art image we dated is a large painting of an unidentified animal, probably a species of wild cattle still found in the jungles of Borneo – this has a minimum age of around 40,000 years and is now the earliest known figurative artwork,” he added.


The stencil works were shown to be similar in age, suggesting that a Palaeolithic rock art tradition first appeared on Borneo between about 52,000 and 40,000 years ago.

The analysis also revealed that some 20,000 years ago, a major stylistic change happened: a new style emerged, featuring (rare) portrayals of humans. This coincided with the most extreme period of the ice age, though it’s not clear if the two events are connected.

The study also showcases another interesting parallel: previously, early cave paintings were predominantly found in Europe (particularly in today’s Spain), and they show quite a bit of resemblance to the ones found in Borneo. This suggests that a similar style evolved in at least two different populations, in very different parts of the world.

Limestone karst of East Kalimantan, Indonesian Borneo. Image credits: Pindi Setiawan.

“It now seems that two early cave art provinces arose at a similar time in remote corners of Palaeolithic Eurasia: one in Europe, and one in Indonesia at the opposite end of this ice age world,” said Associate Professor Adam Brumm, a Griffith archaeologist also involved in the study.

“What’s interesting is that it coincides with the arrival of modern humans in Europe but we know that modern humans arrived in Southeast Asia between 70,000 and 60,000 years ago,” Aubert adds.

However, while we now know that humans started making figurative art at almost the same time in two different parts of the world (western Europe and Borneo), we don’t really know who these artists were.

“Who the ice age artists of Borneo were and what happened to them is a mystery,” said team co-leader Dr. Pindi Setiawan, an Indonesian archaeologist and lecturer at ITB. Setiawan has studied the art since its discovery, and, along with ARKENAS rock art expert Adhi Agus Oktaviana, leads expeditions to the Kalimantan caves. “The new findings illustrate that the story of how cave art emerged is complex,” Oktaviana said.

But Aubert says that might soon change. While no archaeological digs have been carried out quite yet, digs are indeed planned for next year. Which means that we might soon find out who these peoples were, or at least what they lived like.

“We are going back next year and we will start archaeological excavations in order to find information about these unknowns artists. We also want to date more rock art in order to refine the minimum and maximum ages for each styles and also find out how long they lasted,” Aubert concluded.

The study has been published in Nature.

Early humans grew grains for beer, not bread, new study suggests

An ancient thirst for beer may have been why some early populations started growing grains, a new archaeological study suggests. The same study also pushes back the date for the oldest evidence of alcohol production.

Standing in the entrance to Raqefet Cave, where they found evidence for the oldest man-made alcohol in the world, are, from left, Dani Nadel, Li Liu, Jiajing Wang and Hao Zhao. Image credits: Li Liu / Stanford.

Natufian brew

The new evidence, brought to light by Li Liu, a professor of Chinese archaeology at Stanford, also brings forth an intriguing question: what came first, the beer or the bread? Normally, you’d think that of course, securing food comes before almost anything else — almost anything else.

Working in a cave in what is today Israel, Liu uncovered beer-brewing innovations that predate the use of cereals in the area by several millennia. That’s right, people were brewing beer while they were still living in caves.

“This accounts for the oldest record of man-made alcohol in the world,” Liu said.

The population responsible for these innovations is called the Natufians. The Natufians lived from 12,000 to 9,500 BC, and were a rather unusual culture: they were sedentary even before agriculture became a mainstay. They may also be the ancestors of the people who founded the earliest Neolithic settlements, although that’s not yet clear. At any rate, they were certainly one of the most remarkable peoples of the time.

The Natufians exploited wild cereals, made bread, and, as this new study showed, made beer. Researchers believe that the beer was not brewed to get a casual buzz, but rather to use it during ritual ceremonies.

“This discovery indicates that making alcohol was not necessarily a result of agricultural surplus production, but it was developed for ritual purposes and spiritual needs, at least to some extent, prior to agriculture,” Liu said about their findings.

The discovery was made after Liu analyzed residues from 13,000-year-old stone mortars found in the Raqefet Cave, a Natufian graveyard site located near what is now Haifa, Israel. She found evidence of a large-scale beer production operation — it came as a bit of a surprise, particularly as it wasn’t what she was looking for.

“We did not set out to find alcohol in the stone mortars, but just wanted to investigate what plant foods people may have consumed because very little data was available in the archaeological record,” said Liu, who is the Sir Robert Ho Tung Professor in Chinese Archaeology at Stanford’s School of Humanities and Sciences.

Ancient beer

It has to be said, we shouldn’t imagine the familiar golden, foamy brew — ancient beer looked and tasted much different to what we are used to seeing today. Ancient beer was most likely a porridge-like concoction, almost thick like a gruel. The Natufians also seemed to employ a three-stage brewing process, says Jiajing Wang, a doctoral student in the Department of East Asian Languages and Cultures and a co-author on the paper.

First, they’d take the starch from wheat or barley and germinate the grains in water, then strain and store them for a while — this created the malt base. Then, the malt would be mashed and heated, and finally, it would be left to ferment, with the magic being done by airborne, wild yeast.

Researchers tested this hypothesis by reproducing each step of the beer-producing process in their lab — you know, for science. Liu and Wang’s brewing experiments turned out to be quite similar with what was observed in the Natufian cave.

For now, no word on what it tastes, though.

The study has been published din the Journal of Archaeological Science.

Human hybrid — Ancient human relatives interbred with each other

Ancient human species interbred, new evidence suggests.

Digging in and analyzing in the Denisova Cave. Image credits: Bence Viola/Max Planck Institute for Evolutionary Anthropology.

A rather small and inconspicuous cave in the Altai mountains, Siberia, has revolutionized our understanding of ancient humans. The Denisova cave has yielded some of the most fascinating ancient artifacts and remains, including a new species of hominins — the Denisovans, named so after the cave itself.

The Denisovans were distinct but related to the Neanderthals. Since Neanderthal remains were also found in the cave, this led to speculation that the two groups were living and breeding together, but there was no direct proof — until now.

In a new study, a team of anthropologists describe a small piece of bone belonging to a child whose mother was a Neanderthal and father was a Denisovan. Not only is this an extremely important piece of evidence, but it’s also very unexpected — a needle in a haystack, anthropologically speaking.

“To find a first-generation person of mixed ancestry from these groups is absolutely extraordinary,” says population geneticist Pontus Skoglund at the Francis Crick Institute in London. “It’s really great science coupled with a little bit of luck.”

The new study was led by Viviane Slon and Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Along with their colleagues, they carried out a genetic analysis of the piece of bone, finding that 40% of DNA fragments from the specimen matched Neanderthal DNA, while another 40% matched Denisovan DNA. When they sequenced the sample’s mitochondrial DNA, they found that it comes from the Neanderthal lineage. Since mitochondrial DNA is only inherited from the mother, it means that the mother was Neanderthal, which means that the father was a Denisovan.

But there is another possibility: what if both parents were hybrids themselves?

Denisova Cave.

To figure out which of the two options were more likely, researchers looked at which sections matched which type of DNA. Again, the results aligned surprisingly well, clearly indicating that Denny — as the ancient human was unofficially named — was the direct offspring of two distinct humans, not hybrids. Denny is a first-generation hybrid, and the results, Skoglund told Nature, need to go directly into the history books.

It’s not clear how common interbreeding was, but it seems plausible that both Neanderthals and Denisovans would have jumped at the possibility of breeding with each other. So why haven’t we found more evidence for it, then?

There are a few reasons, starting with the fact that they come from different geographical ranges. In other words, Denisovans and Neanderthals might have simply not met all that often. Also, there’s a chance that hybrids wouldn’t have been fertile, preventing the two groups from truly merging.

Until some 40,000 years ago, Europe was home to both groups. The more well-known Neanderthals were more present in the West, while the elusive Denisovans retreated to the East.

The study was published in Nature.

Upper jaw bone with intact teeth, dated as being between 177,000 and 194,000 years old. Credit: Rolf Quam.

Oldest human fossil outside Africa suggests our species left the continent 100,000 years earlier than thought

Our species first evolved in Africa and then dispersed to Europe and Asia not in one massive exodus, but likely in multiple waves of migration over the last 200,000 years. Multiple lines of evidence collected in the past decade support this idea, the most recent of which being reported by researchers at Tel Aviv University who described a 200,000-year-old jawbone discovered in an Israeli cave. The jawbone is twice as old as any Homo sapiens fossil discovered outside of Africa.

Upper jaw bone with intact teeth, dated as being between 177,000 and 194,000 years old. Credit: Rolf Quam.

Upper jaw bone with intact teeth, dated as being between 177,000 and 194,000 years old. Credit: Rolf Quam.

The well-preserved upper jawbone containing eight intact teeth was found in the Misliya cave. Although the teeth are rather large compared to those of a modern human, researchers say the fossil undoubtedly belongs to a Homo sapiens, as reported in the journal Science. 

Along with the jawbone, excavations revealed stone tools and blades, which were fashioned by the cave’s crafty inhabitants to hunt and butcher gazelles, wild boars, turtles, and ostrich. Even pieces of an ancient matting made from plants that Misliya dwellers used to sleep on was found amongst the artifacts and fossils.

Radiocarbon analysis of both the fossil and tools suggests these are between 177,000 and 194,000 years old.

Up until recently, scientists used to think humans left Africa for Euroasia barely 60,000 years ago, where they quickly outclassed contemporary relatives like Neanderthals and Denisovans. But the evidence from recent years puts this singular ‘Out of Africa’ theory into question. For instance, there’s a trove of 100,000-year-old human teeth found in a cave in China, thousands of miles away from humanity’s cradle in Africa. Other similar findings were made in southeast Asia and even as far as Australia dated to 60,000 years ago. If humans had barely begun to exit Africa 60,000 years ago, how can we explain these other findings?

Now, Misliya breaks the mold of the classical theory when Homo sapiens first left Africa, suggesting that humans left the continent whenever the climate allowed it — or, conversely, when the climate forced them out. Prof. Israel Hershkovitz, who led the work at Tel Aviv University, thinks that humans came in and out of Africa frequently over the last couple hundred thousand years. The Misliya cave and others like it in present-day Israel were like “train stations” that exploring humans used on their way through Europe and Asia.

After settling Europe, modern humans out-competed Neanderthals into extinction, but not before interbreeding with them 50,000 years ago. To this day, all non-sub-Saharan humans carry 1-4 percent Neanderthal DNA. However, a recent DNA analysis of a Neanderthal leg bone discovered in a German cave suggests that interbreeding between the two species could have occurred as early as 200,000 years ago. Such a finding, peculiar as it seemed at first, now makes sense in light of the ancient Misliya jawbone.

It’s exciting to hear about such early excursions of our ancestors. Those must have been truly exciting times, but also very frightening and dangerous.

Our genes don’t lie, and according to population genetics studies, most modern-day populations outside Africa can trace their roots to a group that dispersed around 60,000 ago. It follows that earlier groups contributed very little, if anything, to our current lineage — most likely because they could not survive — to be fair, the odds weren’t really in their favor. It’s amazing, though, that after all this time, we can still piece together some of the long-lost history of our species’ most epic journey.

underwater cave

Longest underwater cave in the world found in Mexico

Not far from the beach resort of Tulum, Mexico, lies a cave system called Sac Actun — this may be the largest flooded cave in the world. The discovery was made by a team of divers who found a connection between two underwater caverns in eastern Mexico.

underwater cave

Credit: GAM.

Previously, Sac Actun was measured at 263 km but now, researchers working with the Gran Acuifero Maya (GAM) — a project concerned with preserving subterranean waters in the Yucatan peninsula — say the cave system communicates with the 83-km-long Dos Ojos system. This would make the entire system a unitary 347-km-long (216-mile) cave.

The connection between the two cave systems was identified after speleologists spent months navigating the intricate maze of underwater channels.

Like the vast majority of the planet’s cave systems, Sac Actun lies in limestone rocks. This karst setting occurs when acidic water starts to break down the surface of bedrock, causing cracks and fissures. In time, these fissures start getting bigger and bigger, until they create sinkholes or caves. It’s amazing to think about it, but these incredible features were created by groundwater. Since in the Yucatan area, where the Sac Actun system is located, groundwater is portrayed as flowing in underground rivers, caves also tend to be quite lengthy.

Map of the connection area between Nohoch Nah Chich and Dos Ojos regions. Cartography by Peter Sprouse.

GAM researchers underscore the importance of the finding in relation to the cultural heritage of the Maya civilization that dominated the area before the Spanish conquest.


Credit: GAM.

Many people are aware of the famous Mayan pyramids and other cultural landmarks. It’s a lesser known fact that the Mayan cities in which these relics were built drew upon an extensive network of sinkholes linked to subterranean waters known as cenotes. Some of these cenotes are known to have acquired a religious significance to the Maya, as well as their descendants.

“It allows us to appreciate much more clearly how the rituals, the pilgrimage sites and ultimately the great pre-Hispanic settlements that we know emerged,” Guillermo de Anda, director and underwater archaeologist on the Gran Acuifero Maya team, told Reuters.

Human bones in underwater Mexico cave dated to 13,000 years ago — thanks to a pelvis-stalagmite

In February 2012, researchers discovered a human skeleton in an underwater cave in Mexico. Their joy, however, was short-lived. Just days after photos were made public, unknown divers plundered the cave, stealing the complete skeleton and everything else they could find. They were never identified, the skeleton never located. Still, researchers managed to date a bone, based on measurements conducted on a stalagmite in the cave. The research findings have now been published in PLoS ONE.

Prehistoric human skeleton in the Chan Hol Cave near Tulúm on the Yucatán peninsula prior to looting by unknown cave divers. Picture: Tom Poole, Liquid Jungle Lab.

Settling a settlement debate

The earliest settlement in North America is still a matter of debate among anthropologists and archaeologists. The classical hypothesis is that the first migration took place 12,600 years ago through an ice-free corridor between retreating North American glaciers, over the Bering Strait which was still covered by an ice. That hypothesis is recently coming under more and more fire, with evidence from both North and South America suggesting that a migration took place earlier. However, that evidence is mostly hearths and artifacts — it’s extremely rare to find any human skeletons older than 10,000 years in the Americas. This is why this particular finding might be so important.

“The bones from the Chan Hol Cave near the city of Tulúm discovered five years ago represent one of the oldest finds of human bones on the American continent and are evidence of an unexpectedly early settlement in Southern Mexico,” says Prof. Wolfgang Stinnesbeck, who is an earth scientist at Heidelberg University.

The skeleton was found in a vast system of underwater carbonate bedrock caves filled alternatively with salt and sweet water. These caves, located near Tulúm on the Yucatán Peninsula, have proven a valuable trove for researchers. They contain archaeological, palaeontological and climatic information hidden there from the time before the flooding, which is extremely well preserved, according to Stinnesbeck.

“When my Mexican colleagues Arturo Gonzalez and Jerónimo Avilés showed me the first photos of the Chan Hol site, I immediately knew that we had something special,” says Stinnesbeck.

This is why, when the skeleton was stolen, it hurt even more. But scientists didn’t give up. They still had one bone to analyze — a pelvic bone that had since grown a stalagmite, a rock formation rising from the floor of a cave due to material deposited on the floor from ceiling drippings. Stalagmites are the floor counterpart of ceiling stalactites.

The ancient pelvis, as indicated by the orange arrow. Image credits: Wolfgang Stinnesbeck.

Left them a bone

Dating the bone was no easy feat, for all the potential it yielded. Bones this old have no more collagen, which is what is commonly used for dating bones. So instead, researchers took a different route: they dated it like a rock, not like a bone — something which was possible only thanks to the unique environment of the bone. They used the uranium, carbon, and oxygen isotopes in the bone itself and in the stalagmite that had grown through it. They then analyzed the oxygen and carbon isotope ratios, which are directly related to climate and precipitation data. This can be correlated to existing data, so the age of the stalagmite was estimated, and from it, the age of the bone. Researchers say it is at least 13,000 years old, which would add another nail in the coffin of the classic settlement theory.

More evidence would likely settle this debate once and for all, since this is still an indirect dating method, and more evidence likely lies in or around the cave system. But the area is threatened by growing tourism and urbanization in the area. It’s no coincidence that the skeleton was stolen after only a few photos, and researchers fear what is to happen to the cave if it is left unprotected. Whatever evidence may lie there could be gone forever.

This study fits in neatly with previous findings from the Paisley Cave in Oregon and Monte Verde, Chile, where there is evidence of early settlements.

Journal Reference: Wolfgang Stinnesbeck et al — The earliest settlers of Mesoamerica date back to the late Pleistocene.


Ancient sawed deer bone. Credit: Zupancich, A. et al. / Scientific Reports

Flints and bone from at least 300,000 years ago could be the first non-dietary tool use

Inside Qesem Cave (Photo: Ron Barkai, Tel Aviv University)

We owe all our species’ success to the aptness with which we use tools. Our opposable-thumbed hands, upright gait, and big brains were all fostered by evolution to accommodate the invention and use of tools. Some of the first evidence of tool use among hominids, our ancestors, can be traced back to some 2.5 million years ago. These primitive tools include flints — cutting instruments shaped from rocks — that were mainly used for hunting and butchering.

It’s not hard to imagine our ancestors using these flints for other purposes, other than cutting meat, but without direct evidence, it’s all speculation. The earliest such evidence might turn out to be flints and processed bones found in a cave in Israel. The animal bones seem to be sawed even though they were defleshed, suggesting a non-dietary purpose. The remains are between 300,000 and 420,0000 years old, and the tools themselves were fashioned by a yet to be identified Homo species.

Entering the cave of pioneers

The story of how the remains were found is just as remarkable. In the year 2,000, construction workers detonated explosives to clear a huge limestone boulder that was blocking a planned roadway outside of Tel Aviv in Israel. After the plume of dust faded, it was clear they had to abandon the road altogether for they opened the roof to a cave that was sealed off for more than 200,000 years.

Some of the tools found in the Qesem Cave. You can notice these had opening meant for a handle. Credit: Ron Barkai, Tel Aviv University.

Some of the tools found in the Qesem Cave. You can notice these had opening meant for a handle. Credit: Ron Barkai, Tel Aviv University.


Inside the Qesem Cave, as it is now known, archaeologists later found a treasure trove of artifacts, as well as hominid and animal remains. For instance, there’s a 300,000-year-old fireplace next to which tortoise shells were found. These roasted turtles are considered the oldest evidence of the consumption of cooked meat. The oldest knives and hand axes were also found here.

“By comparison,” said Professor Ron Barkai from Tel Aviv University who is the head of digging at Qesem Cave. “Europe only started seeing humans using knives 30,000 years ago. These knives were created 400,000 years ago. What happened here in Israel 400,000 years ago predates the rest of the world by hundreds of thousands of years

Ancient sawed deer bone. Credit: Zupancich, A. et al. / Scientific Reports

Ancient sawed deer bone. Credit: Zupancich, A. et al. / Scientific Reports

Concerning the people who used to live in the cave, things are a bit blurry. Only hominid teeth were found and absent other fossils, the cave’s occupants could have been  Homo erectus, Neanderthals or some yet to be identified species.

“This cave has been unusually well preserved,” said Avi Gofer, an archaeologist from Tel Aviv University, for Ynetnews. “The people who lived here were a huge revolution (in the history of humanity). What these people did here is completely different than what other humans were doing; in terms of chiseling technology, behavior, hunting techniques, organization, use of fire, and much more. In other words, there was an explosion of change (at Qesem Cave), and a lot of innovations.”

Gofer and colleagues recently published a paper in which they describe two sharpened flint tools and a deer bone with distinct saw marks. What’s out of the ordinary is that the marks didn’t result from butchering. The flint tools show bone residues while the marks on the bone were made after it was broken and defleshed, according to Real Clear Science.

“The results of this study allow us to argue that at Qesem Cave, hominins were bringing selected body parts of hunted game to the cave and, after the meat, fat, and marrow were consumed, they occasionally used the discarded animal bones for non-dietary purposes,” the researchers write.

“The data presented here represents an innovative behaviour, practised between 420 and 300 kya, possibly the oldest evidence related to intentional non-dietary modification of bone through the use of specific stone tools,” they added.

This is only one piece of the puzzle. We still need to know who were the members of this early homo intelligentsia. Whoever they were, it’s clear they were way ahead of their time.

Krzysztof Starnawski first dived in the cave 20 years ago. Now, he led the team that found that "Hranice Abyss" is the world's deepest underwater cave. Credit: Marcin Jamkowski/National Geographic

World’s deepest underwater cave discovered in Czech Republic — explorers still haven’t reached the bottom

Krzysztof Starnawski first dived in the cave 20 years ago. Now, he led the team that found that "Hranice Abyss" is the world's deepest underwater cave. Credit: Marcin Jamkowski/National Geographic

Krzysztof Starnawski first dived in the cave 20 years ago. Now, he led the team that found that “Hranice Abyss” is the world’s deepest underwater cave. Credit: Marcin Jamkowski/National Geographic

A team of Polish and Czech explorers reports that the flooded limestone cave of Hranicka Propast, or Hranice Abyss, located in the eastern part of the Czech Republic, is the deepest underwater cave in the world. The Czech Speleological Society says the cave is at least 404 meters deep. In reality, it could be much deeper since the submersible robot used by the explorers had to pull out before it could spot the bottom.

The team was led by Polish explorer Krzysztof Starnawski. In 2015, Starnawski strapped on scuba gear and passed through a narrow slot of the cave. He managed to dive to 265 meters down without reaching the cave’s bottom. This prompted him to learn more but diving that deep required him to spend over six hours in a decompression chamber. That’s annoying, not to mention dangerous, so the team decided to use a remotely-operate underwater robot (ROV) to record the depth of Hranicka Propast.

The control panel of the ROV. Credit: Krzysztof Starnawski Expedition

The control panel of the ROV. Credit: Krzysztof Starnawski Expedition

Last week, Starnawski’s team dived to about 200 meters deep and from there on released the ROV which descended to about 404 meters deep — the full length of its chord. Although the robot went as deep as it could, the bottom of the cave was still nowhere in sight, prompting the team to speculate it could be much deeper.

“During this push, the most important part of the job was done by the robot,” he said.

“I scuba dived down to 200 metres just before the ROV’s deployment to put in the new line for the robot to follow.

“The goal was to give the ROV a good start from there to the deepest part of the cave.

“The results were astonishing,” he added.

Schematic showing the various pathways and crevices of the Hranicka Propast cave. It ends with "???" because they've yet to map the bottom. Credit: Krzysztof Starnawski / Facebook

Schematic showing the various pathways and crevices of the Hranicka Propast cave. It ends with “???” because they’ve yet to map the bottom. Credit: Krzysztof Starnawski / Facebook

Even so, Hranicka Propast beat the previous record holder, a flooded sinkhole in Italy called Pozzo del Merro, by 12 meters.

The team plan of exploring the Czech cave even further — this time they’ll use a longer rope.

National Geographic was the first to report this story and was also partially responsible for the funding. 


Gene mutation helped early humans cope with smoke infested caves, but not Neanderthals


Credit: Pixabay

Pennsylvania State University researchers claim they’ve uncovered a gene that helps humans cope with the toxicity of smoke. This gene wasn’t found in specimens belonging to Neanderthals or Denisovans, two other hominin species which were contemporary with homo sapiens for thousands of years before becoming extinct.

A smokey edge

The researchers posit that this mutation must have given humans an evolutionary edge against the two other species. Some 50,000 years ago, humans, Neanderthals and Denisovans lived mostly in caves where fires must have clouded everything in smoke.

When we eat grilled meat or inhale smoke, toxic byproducts like polycyclic aromatic hydrocarbons (PAHs) are absorbed by the body which cause DNA mutations, cancer or sudden death. Luckily, when PAHs enter the body enzymes are produced to break down the chemicals and flush them out. If there’s too much smoke, however, the body goes into enzyme production overdrive, which triggers the formation of a number of even more toxic byproducts — but not if you have a gene mutation in the aryl hydrocarbon receptor, found in the in the middle of the ligand-binding domain.

All modern humans have this mutation, but when the researchers led by Gary Perdew, the John T. and Paige S. Smith Professor in Agricultural Sciences, Penn State, sequenced the DNA of three Neanderthals and one Denisovian they couldn’t find any. Not having this mutation could have made all the difference — from a hundred to a thousand-fold more aryl hydrocarbon receptor ligand sensitivity.

“For Neandertals, inhaling smoke and eating charcoal-broiled meat, they would be exposed to multiple sources of polycyclic aromatic hydrocarbons, which are known to be carcinogens and lead to cell death at high concentrations,” said Perdew in a statement. “The evolutionary hypothesis is, if Neandertals were exposed to large amounts of these smoke-derived toxins, it could lead to respiratory problems, decreased reproductive capacity for women and increased susceptibility to respiratory viruses among preadolescents, while humans would exhibit decreased toxicity because they are more slowly metabolizing these compounds.”

The same tolerance also helped humans pick up some bad habits, like smoking tobacco, the researchers wrote in their paper published in Molecular Biology and Evolution

All hominids included in this study knew how to make fire. In fact, a previous study found Neanderthals were clever enough to use manganese dioxide — a substance commonly used in batteries today — to light their camps. The first hominid to use fire was likely Homo erectus, a species which regularly made use of the blaze to cook, fend off predators, provide warmth and possibly ritualistic purposes 1.9 million years ago. Any species which followed H. erectus must have learned to light and maintain fires as well.

“Cooking with fire could have allowed our ancestors to incorporate a broader range of foods in our diets, for example, by softening roots and tubers that might otherwise have been hard to chew,” Perry said. “Cooking could also help increase the digestibility of other foods, both in chewing time and reduced energetic investment in digestion.”

“Besides heating and cooking, humans used — and still use — fire for landscape burning and as part of hunting and gathering, and now as part of agriculture,” he added.

I would caution, however, readers that this is still a tentative hypothesis. After all, the researchers could only look at three Neanderthals and a Denisovan. A lot more DNA from more specimens should be sequenced before any definite conclusion can be made. Already, some critics aren’t convinced.

“Neanderthals were the ultimate cave-dwelling fire users. If there was some selective disadvantage against this, then they would have died out a long time before they did. But they were actually one of the more successful stories in human evolution and lasted a really long time compared to other hominids,” David Wright, an archaeologist at Seoul National University and the University of York, told The Guardian.

“That somehow Homo erectus and Neanderthals and dozens of other hominid species couldn’t handle sitting around a fire, it doesn’t make any sense to me,” he added. “The problem is it’s really difficult to test, because we can’t take a Neanderthal and sit them next to a fire to see how they react.”

How caves form and the different types of caves

Ahh, the cave, cradle of humanity since time immemorial. Early humans sought them for shelter, plastered their walls with paintings, made them into the first temples. And even after we’ve moved out, they still captivate and terrify us — unknown, but somehow familiar.

Without caves, our life might have been very different now. So how did they come about? How does a cave form? Well, in a lot of different ways, really. Caves come in different sizes and shapes, and the way they’re created depends on the type of cave. Most often, they form when water dissolves limestone, but they can also be shaped by waves, even lava.

So don your hardhats and pull your learning pants on, because I’m going to tell you all about:

The Types of Caves

Solutional caves

Son Doong Cave in Vietnam, the largest cave ever found, is a solutional cave. It’s big enough to have its own ecosystem.
Image credits Doug Knuth

These are the structures people most readily associate with the idea of a cave, and for good reason. They’re the most numerous, the largest and most often-encountered structures. If you’ve ever been spelunking or seen a cave in a movie chances are it was a solutional cave. The secret to their abundance is two-fold: for starters, the rocks that house them are found throughout the globe, and the chemical elements required to shape them are abundant. As Andrei wrote:

“Solutional caves are generally formed in limestone or other similar rock such as gypsum or dolomite. They form when acidic water dissolves the rock, seeping through the bedding planes.”

Let’s consider a geological environment of soil over a bedrock of limestone, as solutional caves are most frequently found in this type of rock. Limestone is a carbonatic rock, formed over millions of years from the remains of coral, zooplankton, shells or bones, all mashed up together. This material gets bunched up and subjected to huge pressure, fusing into solid rock.

The main mineral found in limestone is calcium carbonate, or CaCO3, a mixture of calcium and carbon trioxide, an unstable compound. While limestone is pretty resilient and nice to look at, it tends to be relatively brittle and fractures a lot due to tectonic stress. Its chemical makeup also makes it susceptible to attack by acids which break up the calcium carbonate into calcium compounds (Ca + the non-metal that forms the acid), carbon dioxide (CO2), and water (H2O).

Limestone cave in Australia.
Image credits Andrew McMillan

[panel style=”panel-info” title=”Fun geology fact” footer=””]Rubbing a diluted solution of acid onto a geological sample is still the easiest way to determine if there are any carbonatic compounds in the rock. If so, the solution will bubble and foam quite vigorously.[/panel]

These conditions work together to make limestone an ideal place for cave formation. In nature water invariably becomes acidic by mixing with carbon dioxide molecules (H2O+CO2=H2CO3) forming a solution of carbonic acid. Part of this can happen in the atmosphere as rain pours down, but most of the mixing takes place in the soil which is rich in CO2 left over from decaying organic matter.

This solution trickles down through the soil and cracks in the limestone until it reaches the water table. Here it starts to eat through the rock, forming channels. In an almost cruel twist of geological fate, while limestone dissolves it releases the exact components needed to make more carbonatic acid. This chain reaction and the extra acids that seep in from the surface keep expanding the cavern until the water table level drops. If this happens, water with dissolved calcium compounds will trickle down to the new area of dissolution, forming stalactites and stalagmites.

And looking awesome.
Image via pixabay

If on the other hand water remains mobile throughout dissolution, the caves take on the appearance of an underground drainage system, a landscape known as karst.

Something like this, but underground.
Image credits Jonathan Wilkins

It takes a few million years for a solutional cave to form.

Lava caves

While dissolution caves are formed by hollowing out preexistent packets of rock, lava caves form at the same time as the geological environment around them — and so, they’re considered to be primary caves. They’re centered around areas of volcanic activity and resemble huge underground rock pipes.

Lava River Cave in Arizona.
Image credits Volkan Yuksel

And in a way, that’s just what they are. Molten rock that reaches the surface (called lava) can form sprawling cave networks while it flows down the path of least resistance. The material is very hot initially, but as the outer layer of lava starts to cool it solidifies into a shell of rock. This process insulates the lava within and starts at the base of the flow (because the rock it’s pouring over is a better thermal conductor than air,) forming a through-like structure through which the hot lava at the center keeps on flowing. Over time, material clings to the edges of this through and solidifies, eventually closing into a pipe-like structure.

Because this shell of rock is solidified from a flowing material its inner walls are neat, almost polished, with horizontal conduits on the inner side that channel the flow. Once the lava supply starts to dwindle the cave cools down and thermal constriction starts fragmenting the walls. The pressure of volcanic gasses in the cave, however, support the roof from collapsing. As these gasses mix with air from vents in the roof resulting oxidation processes sometimes generate enough heat to re-fuse the ceiling, solidifying it. Sometimes, this process can lead to the formation of stalactites as molten material drips from the ceiling.

Long exposure picture of a lava tube near Bend, OR. The lighting is artificial. Image credits to Michael Harms.

Long exposure picture of a lava tube near Bend, Oregon. The lighting is artificial.
Image courtesy of Michael Harms.

These structures are called lava tubes, and it’s important to note that they form on the surface and are later covered with sediments. They often have lava streams solidified along their floors. The most common access points into these caves are areas with collapsed ceiling.

Similar processes form inflationary caves or vertical conduits underground, which can be big enough to qualify as caves. The former are areas where lava pushed on neighboring rock then receded, leaving domes of solid rock behind. The latter are formed in areas where lava escaped to the surface.

Sea caves

Erosion is the process by which soil or rock is removed from their original structures by surface factors. Dissolution can be viewed as a particular case of erosion, but we’ve already talked about those.

Sea caves are also formed by water. But, while dissolution caves get hollowed out through chemical reactions, sea caves are constructed by wave-powered erosion, either above or below the waterline. They can be found on the shoreline, as the name implies, but also inland, in areas that were once close to the sea but have since dried up — in parts of Norway, for example. They can form in all types of rock: igneous, metamorphic or sedimentary.

This Minecrafty beauty is named Fingal’s Cave, Scotland. It is a sea cave formed through basalt pillars.
Image via reddit user narwalmart

Waves form these structures by sheer attrition, throughout millions of years of battering with particle-rich water. As such, they tend to form in weaker areas of the rock, such as fault lines in igneous or metamorphic rocks or bedding plane contacts in sedimentary rocks. Once waves open a fissure through the rocks, the process becomes much faster — confined to a narrower space, the water and suspended particles exert more pressure on the walls and pressurize the gasses within, acting like a wedge.

Their walls are usually chunky and jagged, as erosion breaks off irregular slabs of rock from them. Some sea caves, however, have circular shapes with smooth walls and are filled with pebbles. This is caused by the waves taking on a circular motion inside the caves as they wash in and out, grinding the pebbles against the walls and smoothing them down.

Such as this beautiful cave in the Algarve region, Portugal.
Image via Imgur

Because erosion is a continuous process, removing rock bit by bit, sea caves are prone to collapse, leaving behind a “littoral sinkhole.”

Caving in

There are many other kinds of caves, each one with its own story to tell. Each one tells of how an area’s geology interacts with the world above it, being shaped by it over countless centuries. But, the paintings our ancestors adorned them with, the lines of sooth they burned into their walls stand testament to how they can, in turn, shape the world around them.

The main types of caves, according to science

Caves have sparked our imaginations and played a crucial role in human evolution, but for all their enticing history, most people still don’t know what they are and how they form. There are several ways of classifying caves. I’ll just run you through the main ones before detailing all of them:

  • solutional caves are generally formed in limestone or other similar rock such as gypsum or dolomite. They form when acidic water dissolves the rock, seeping through the bedding planes.
  • lava caves are also called primary caves because they form at the same time as the surrounding rock. Sometimes lava flow creates a hollow tube, which results in the cave.
  • sea caves are quite self-explanatory – they’re formed by the sea, due to the constant activity of waves. They can be both over and under water.
  • glacier caves are caves not in rock, but in glaciers.

There are also several more uncommon types of caves which we’ll discuss further. For now, it’s time to get our hands dirty.


Cave where the remains of Homo floresiensis, an ancient hominid, were found. Photo by Rosino.

What caves are

Before we start looking into the types of caves with more detail, let’s analyze just what caves are. Not any hole in an underground space is a cave. In order for it to be called a cave, the structure must be natural and large enough for a human to enter. This part of the definition isn’t so strict, though.

Caves can be formed by various geological processes and therefore, can vary greatly in size and structure.

Solutional caves

limestone cave

Limestone cave. Photo by Andrew McMillan.

These are by far the most common caves – for most people, they’re probably synonymous with caves.

Solutional caves form in carbonatic rocks, most commonly limestone, but also chalk, dolomite, marble, salt, and gypsum. Regardless of the type of rock, the process is similar. As water falls on the ground, it accumulates carbon dioxide from the atmosphere, becoming a very weak acid. But even this “weak acid” can create great things over time: as the water percolates through the rock, it dissolves more and more, creating bigger and bigger voids.

how caves form

How caves form, via British Geological Survey.

It does take a lot of time, however – we’re talking geological time. This is why solutional caves often have formations like stalactites and stalagmites. Limestone caves especially have many formations, and they’re also the biggest and most impressive caves.

Lava caves

Primary or lava caves form at the same time as the rock around them, as a result of volcanic activity.

Thurston Lava Tube in Hawaii Volcanoes National Park, Hawaii.

Thurston Lava Tube in Hawaii Volcanoes National Park, Hawaii. Photo by Frank Schulenburg

Lava caves are almost always lava tubes, formed by flowing lava. As the lava flows, it cools down and creates a solid crust. Liquid lava continues to flow beneath that crust, and most of it flows out, leaving behind a hollow tube. Lava tubes aren’t formed only on Earth, but also on the moon and on Venus.

In some rarer circumstances, these caves can form outside of lava tubes. Rift caves, lava mold caves, open vertical volcanic conduits, and inflationary caves can all form due to volcanic activity.

Sea caves

Sea caves are found on shores all around the world, also usually in carbonatic rocks.

sea cave

Painted Cave, a large sea cave, Santa Cruz Island, California. Photo by Dave Bunnell.

The constant action of waves attacks the weaker part of the rocks and in time, starts to erode them. Sand and tiny bits of gravel can also amplify the corrosion. A special case of sea caves is called littoral caves, where the waves act on very weak areas, such as faults or bedding plane contacts. The waves “speculate” the rock’s weakness and can create a cave much faster.

Glacier caves

Until now, we’ve talked about rocky caves – but caves can also form in glaciers.

glacier cave

A partly submerged glacier cave on Perito Moreno Glacier. The ice facade is approximately 60 m high

They are similar to solutional caves, but it can form much faster. Melting ice and flowing water within the glacier can create surprisingly large ice caverns, which are regarded as caves. Though they are sometimes referred to as “ice caves,” that term is normally reserved for rocky caves with year-round ice formations inside.

Other types of caves

As we mentioned above, there are other types of caves too, but they’re much rarer.

  • Fracture caves form when a soluble layer, such as gypsum, dissolves. After the layer disappears, the rocks around it can collapse, creating a fracture cave.
  • Talus caves are formed by the openings among large boulders that have fallen down into a random heap. They should be avoided as they’re usually unstable and dangerous.
  • Eolian caves are formed, like their name says, by the wind. They form only in deserts, driven by the sandblasting effect of silt or fine sand being blown against a rock face. They can be surprisingly large and impressive.
  • Anchialine caves are usually coastal and contain a mixture of freshwater and saline water (usually sea water). They occur in many parts of the world and often have highly specialized, endemic fauna.


“Cave of Forgotten Dreams” may be earliest painting of volcano eruption

Volcanic eruptions have fascinated and frightened people for millennia, and many have tried to describe them in different ways. Whether it was through paintings, text or documentaries, we’ve all seen volcanoes described in one way or another. But for people 30,000 years ago, that was a much more difficult challenge. Now, researchers believe they have found the earliest such depictions.

Spray-shaped drawings in an inner gallery of the Chauvet cave may depict a volcanic eruption. Left: general view; right: traced detail, with an overlaid charcoal painting of a giant deer species removed (lower right). Image credits: . Genty (left)/V. Feruglio/D. Baffier (right)/CC BY 4.0

The famous Chauvet cave is one of the most well known and well studied caves in the world. Hosting the earliest and best preserved figurative cave paintings in the world, as well as other evidence of Upper Paleolithic life, it’s a Mecca for anthropologists. The Werner Herzog documentary ‘Cave of Forgotten Dreams’ made it equally famous for the public.

Replica after painting in the Chauvet Cave. Image via Wikipedia.

Replica after painting in the Chauvet Cave. Image via Wikipedia.

Fearsome woolly rhinoceroses, cave lions and bears dominate Chauvet’s imagery, but the most spectacular image is a giant deer species, Megaloceros (the first image). This deer drawing is surrounded by mysterious spray-like imagery; what it represents remains a mystery. Now, Sebastien Nomade, a geoscientist at the University of Paris-Saclay in Gif-Sur-Yvette, France, who led the study believes he’s found the answer: volcanoes.

“I think they make a pretty good case that it’s potentially a depiction of the kind of volcano that one sees on the landscape,” says Michael Petraglia, an archaeologist at the University of Oxford, UK. Depictions of natural events in rock art are rare, he notes, but this could be because they are too abstract or because researchers simply haven’t looked. “Maybe there’s more of this out there than we have realized.”

Image via Wikipedia.

[Also Read: Did you know? Prehistoric Art – The Trois Frères Cave]

It’s not the first time volcanoes have been associated with the cave. After all, Chauvet is located a mere 35 kilometers (21 miles) as-Vivarais volcanic field, a well-known site containing more than a dozen extinct volcanoes. The problem was timing – previous studies put the volcanic eruption way before humans arrive and made drawings in Chauvet. Now, through isotopic analysis, Nomade’s team believes the last series of eruptions took place between 19,000 years and 43,000 years ago – a timing window which fits with human existence in the cave. He also says that the cave provided a safe vantage point to the chaos unleashed by the volcanoes.

“You just have to climb the small hill on top of Chauvet, and looking north you see the volcanoes. During the night you could see them glowing and you could hear the sound of the volcanic eruption.”

Axel Schmitt, a geoscientist at Heidelberg University in Germany whose team studied the eruption near Çatalhöyük, says that the dating of the eruptions near Chauvet is solid, but it seems to me like we still need some more evidence. Sure, the timing fits, it could be a depiction of a volcanic eruption but it doesn’t have to be. After all, it’s still a matter of artistic interpretation.

Amateur archaeologists find 560,000 year old human tooth

A half a million year old human tooth was discovered in France in a place called Tautavel, one of Europe’s most important prehistoric caves. Anthropologists hailed the discovery as an extremely important one, with chief researcher Tony Chevalier calling it a “major discovery”.

Volunteer archaeologists Camille and Valentin pose for the cameras in the Arago cave. Camille, 16, found the adult tooth, which dates back 565,000 years

Volunteer Camille, 16, was working with an archaeology student when they found the tooth. They are among the hundreds of archaeology trainees or volunteers come to dig out the Tautavel cave, searching for evidence of early human inhabitants.

Older human fossils are known in Europe (dating back to 1.2 million years ago), but this one bridges a gap in the fossil evidence in the Lower Paleolithic. Thousands of other finds were made in the same site, including tools and bones from animals, especially horses, reindeers and buffalos.

“We believe these men have lived for a long time in the cave or have regularly come back into it,” Chevalier said. “We also know that the area was quite cold at the time. It was a steppe, with no trees. There had to be some long periods with snow.”

The owner of the tooth – a very worn lower incisor – lived during a much colder climate than today’s; he and his people hunted horses, bisons and reindeer, and used tools. They took cover in caves.

“A large adult tooth – we can’t say if it was from a male or female – was found during excavations of soil we know to be between 550,000 and 580,000 years old, because we used different dating methods,” paleoanthropologist Amelie Viallet told the AFP news agency. “This is a major discovery because we have very few human fossils from this period in Europe,” she said.

Earth-loving Hades: meet the centipede from Hell

Deep below ground level, 3,500 feet (1000 meters) down a Croatian cave, scientists have discovered a new species of centipede. They named this incredibly resilient creature Geophilus hadesi – earth loving Hades – in honor of Hades, the Greek God of the underworld and ruler of Hell.

The entrance of cave Munižaba. Photo: D. Bakšić.

Centipedes are elongated arthropods with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Except for one species having 96 legs (48 pair), centipedes always have an odd number of pairs of legs—for example, 15 or 17 pair (30 or 34 legs), therefore no centipede has exactly 100 legs. They also have long curved claws which they use to grasp their prey and long antennae which help them find the prey in the dark environment in which they live in. However, as their discoverers explain, we don’t know that many details about their lifestyle, or about any cave-dwelling creatures really.

“When I first saw the animal and its striking appearance, I immediately realized that this is a new, hitherto unnamed and highly adapted to cave environment species. This finding comes to prove once again how little we know about the life in caves, where even in the best prospected areas, one can still find incredible animals,” Pavel Stoev, lead author of a study on the newly discovered creatures, said.

Geophilus hadesi sp. n. Habitus of male specimen. Photo taken in situ in the Lukina jama – Trojama cave system, at -980 m below the surface

Like other species, Geophilus hadesi hunts smaller invertebrates, including worms, spiders and larvae. Because it lives in caves with little light, it lacks pigmentation. The species is part of a group called geophilomorphs who spend their entire lifecycles dwelling in caves (only two centipede species are known to do this).

“The change of a species’ appearance is usually a result of a long evolution that is likely to have happened [over] the course of millions of years,” said Stoev, who noted that the Hades centipede has also adapted to the deep caves’ cold temperatures, which can drop as low as 37 degrees Fahrenheit (3 degrees Celsius).

The centipede was discovered in the caves under Velebit, a massive mountain that stretches over 90 miles in the Dinaric Karst, while the other geophilomorph centipede, Geophilus persephones was discovered in the 1990s in a cave in France. Scientists aren’t sure what pushed these species to move to caves in the first place.

Entrance of cave Lukina jama. Photo: M. Jekić

“It could be a dramatic change in the outside temperatures and overall conditions that forced less-adaptive organisms to seek shelter underground where the conditions are more stable and less dependent on the outside fluctuations,” Stoev said.

The discovery of the centipede is yet another reminder that we still have much to understand about the environment and the biodiversity in caves.

You can read the entire scientific article for free, here.


New bug species discovered in world’s deepest cave

lustration of Duvalius abyssimus. / Sinc - José Antonio Peñas

lustration of Duvalius abyssimus. / Sinc – José Antonio Peñas

A new species of ground beetle perfectly adapted to extreme environments has been discovered in the world’s deepest cave system, the Krubera-Voronja, in Russia. The insect is about a quarter of an inch long and blind. In fact, given there isn’t light whatsoever reaching it, the bug has evolved extended antennae and a body that has no pigment.

The cave, known as Krubera-Voronya, is considered the “Everest of the caves”. The total length of cave passages reaches 13,232 m, and at its deepest point is -2,191 m below the Earth’s surface or about the same as the height of seven Eiffel Towers. Undeterred by the inhospitable conditions – ambient temperature is around seven degrees Celsius and the water is freezing cold – various expeditions have explored the caves in Russia and came back with invaluable insights.

The subterranean community is home to various (weird) creatures. The cave biota is composed of troglobionts and also epigean species that can penetrate until -2140 m. Some of the unique species found here include a transparent fish living in water of two degrees and at a depth of two thousand meters. The new beetle species, named Duvalius abyssimus, joins the fine list for Krubera-Voronya’s biota.

Check out some of the breathtaking photos of Krubera-Voronya below.