Ancient glacier finding reveals clues to how complex life on Earth evolved, scientists say
More than half a billion years ago on a frigid, ice-covered Earth, glaciers stirred up ingredients for complex life by bulldozing land minerals and then depositing them in the ocean, according to a new study.
Inch by inch, as massive glaciers crept over frozen land toward an ice-covered sea, they scoured the ground beneath them, gouging and scraping rocks from Earth's crust. When the glaciers eventually melted, they released a torrent of terrestrial chemicals into the ocean, researchers recently reported. Minerals swept up on land by this 'glacial broom' altered marine chemistry and infused oceans with nutrients that they say may have shaped how complex life evolved.
This ancient period of deep freeze, known as the Neoproterozoic Era, or 'Snowball Earth,' lasted from about 1 billion to 543 million years ago. During that time, landmasses consolidated into a supercontinent called Rodinia and then broke apart again. Earth's earliest forms of life, such as microbes, cyanobacteria, sponges and seafloor-dwelling organisms, populated the oceans. After the end of the Neoproterozoic came the rise of more complex life, with the first appearance of marine creatures sporting armor, shells and spikes.
Scientists have attributed this evolutionary boom to increased oxygen levels in Earth's atmosphere and in shallow ocean waters. And now, research published Tuesday in the journal Geology suggests the flowing of ancient glaciers may have directly shaped chemical changes in the ocean that were critical for the evolution of complex organisms.
Studying Snowball Earth offers a window into our planet's past, but it also presents valuable insights into modern climate change, lead study author Dr. Chris Kirkland said.
'Our deep time geological record indicates how changing one part of Earth affects another,' he said. Right now, the dramatic warming of the planet that marks the human-fueled climate crisis is happening at breakneck speed compared with these ancient processes that took millions of years.
'This rapid pace limits Earth's ability to naturally regulate itself, underscoring the urgency of addressing anthropogenic climate change.'
Glacier movement, or glaciation, is known to scrape up and ferry terrestrial sediments into oceans, lakes and rivers, forming the basis of aquatic food webs. However, researchers who study ancient Earth were previously uncertain whether Neoproterozoic glaciers moved at all, let alone enough to erode the ground beneath them and transfer minerals into the sea.
'It had been hypothesized that widespread glacial erosion of continental interiors could be caused by the Snowball Earth ice,' said Kirkland, a professor in the School of Earth and Planetary Sciences at Curtin University in Perth, Australia. 'However, aspects of this idea were not clear because that ice may not have moved or moved only slightly or indeed even flowed.'
Kirkland and his colleagues found answers in Scotland and Northern Ireland, where they studied sediments from rock formations dating to the Neoproterozoic. The team looked at zircons — crystallized minerals that are exceptionally durable and can weather extreme geological events. Zircons also contain uranium; by measuring the stages of uranium's decay in zircons, geologists use the minerals as chronometers for studying Earth's past.
The researchers examined sediments dating to the time when Earth was covered with ice, and from the 'hothouse Earth' period millions of years later when the ice was gone, and found the mineral composition of Snowball Earth sediments differed dramatically from that of later sediments.
'We recovered distinctive patterns in the populations of these mineral grains,' Kirkland told CNN in an email. 'In essence the 'DNA' fingerprint of these sedimentary rocks changed.'
The findings appear to bolster the notion of active glaciation 'somewhat,' said Dr. Graham Shields, a professor of geology at University College London. Shields was not involved in the new research. However, the study did not include data from a significant glacial interval called the Marinoan, which marked the end of Snowball Earth, he told CNN in an email. Shields was also cautious about directly linking glacial erosion to the evolution of complex life.
'This connection has been proposed before but it is controversial because the linkage is assumed rather than explained,' Shields said. 'Dramatic landscape change causing the emergence of macroscopic animals is a neat idea, but the paper introduces a hypothesis about glacial erosion/weathering that can be tested, rather than settling the debate.'
Rocks from the time of Snowball Earth contained older minerals, but also featured a range of mineral ages, hinting that the rocks were exposed and eroded over time by the scraping movement of glaciers. This evidence told the scientists that the glaciers of the Neoproterozoic were mobile. Younger rocks, from when Snowball Earth was thawing, had a narrower range of mineral ages, and more fragile grains were absent, suggesting flowing water had dissolved material that was previously ground down.
At the waning of the Neoproterozoic, one of the known changes in ocean chemistry was a rise in uranium. Other research had previously explained this increase as resulting from the rise in atmospheric oxygen, 'however, our data imply that the delivery of chemical elements into the oceans also played a role in this,' Kirkland said.
'The 'lost' dissolved component in these rocks is seen 'popping back up' in changes in ocean chemistry at this time,' he added. By mapping these changes in terrestrial and marine environments, 'we are imaging the transfer of chemical elements through the Earth as a system.'
The scientists reported that major glaciation events took place at least twice between 720 million and 635 million years ago. By the end of the Neoproterozoic, as Earth's icy cover began to thaw, major chemistry shifts were taking place in Earth's atmosphere and oceans.
'The end of these glaciations is marked by rapid increases in atmospheric and oceanic oxygen, possibly due to enhanced weathering of exposed rock surfaces and increased nutrient fluxes into the ocean,' Kirkland said. Such changes could have infused nutrient cycles and provided emerging life with the boost it needed to evolve into more complex forms.
'The idea that glacial debris from Neoproterozoic ice ages provided nutrients to support early animal evolution has been around for a while,' said Dr. Andrew Knoll, a professor emeritus of Earth and planetary sciences at Harvard University, who was not involved in the new research. However, questions remain about whether the minerals poured into the ocean by Neoproterozoic glaciation would have been enough to spur long-term environmental changes with biological consequences, Knoll told CNN in an email.
Other research previously suggested that the impacts of glaciation events, such as the ones described in the new study, 'might well have only transient consequences — a bolus of nutrients raising primary production and perhaps increasing oxygen levels, before relaxing back to the earlier state of the environment,' Knoll said. The new findings are 'an interesting addition to the conversation,' he added. 'But the conversation continues.'
From the Neoproterozoic to the present, similar processes shape climate change, including the role played by carbon dioxide (CO2) and the behavior of feedback loops, when a process feeds into an existing aspect of Earth's climate system and intensifies it. Ancient climate evidence also illuminates what happens during climate tipping points — when a threshold is crossed, triggering large-scale changes that are often irreversible.
Today, Earth is heating up rapidly rather than cooling gradually over time. It took millions of years for glaciation to overtake the planet during Earth's snowball phase, while modern warming is accelerating over mere decades, 'much faster than past natural climate shifts,' Kirkland said.
However, climate change's global progress is still mapped by studying the interplay of CO2 buildup, feedback loops and tipping points, he added.
'We can see how different parts of the planet are interrelated via chemical links,' he said. 'Change one part of the system, other parts also change.'
Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American and How It Works magazine.
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Animal stories Ancient creatures Africa Retail consumerFacebookTweetLink Follow It stands to reason that a 95 million-year-old tooth shipped to my home would have a rich past. But what ensued after I bought it online for about $100 revealed how, for such relics and those who covet them, the present is in some ways much more complicated. I always wanted to own a fossil, and once the algorithm picked up on that desire, ads flooded my Instagram feed. It then became impossible to resist the thrill of purchasing a piece of one of the largest predators that ever existed: Spinosaurus, a semiaquatic meat-eater that could reach almost 60 feet (about 18 meters) in length — longer and heavier than Tyrannosaurus rex. When the package arrived, in a pretty glass dome and with a preprinted certificate of authenticity that stated it came from North Africa, the long pointy tooth looked the part to my untrained eyes: yellowish brown, with varying textures and a stonelike appearance. 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It was unearthed in 1990 and sold at auction in 1997 for $8.36 million after a long legal battle over its ownership. Even though Chicago's Field Museum of Natural History purchased Sue and still has it on display, the pooling together of private funds led to its acquisition and kick-started the era of big-ticket fossil auctions. Seventy-one T. rex specimens are now in private hands, versus 61 held by public trusts, according to a recent study. Peter Lovisek, a fossil broker and curator at Fossil Realm, a gallery in Ottawa, said a key turning point for the market — 'where these pieces began to be seen as cultural icons, artworks, investment assets' — was the auction of a 40-foot-long T. rex named 'Stan,' which sold for $31.8 million in 2020. The media frenzy surrounding Stan, which is part of a planned exhibition at the upcoming Natural History Museum Abu Dhabi in the United Arab Emirates, brought fossils into the mainstream, Lovisek added. 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Morocco is not the only country imposing restrictions on fossil exports with the goal of preserving its cultural heritage. Export bans are also in place in Argentina, Brazil, China and Mongolia. 'All around the world, different countries have different laws. In the UK and the US, if you find something on your land, you can do whatever you want with it,' while in some parts of South America, for example, the person who discovers an artifact has a weaker claim, Maidment said. Brazilian fossils in particular, according to a law established in 1942, don't belong to the finder, noted Taissa Rodrigues, a professor of paleontology at the Federal University of Espirito Santo in Brazil. 'It belongs to the country,' Rodrigues said. 'That means, if you find a fossil, you're not its owner, so that's why you're not allowed to sell it, because it's not up for you to decide.' 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So it's a huge, huge problem.' Morocco's Ministry of Energy Transition and Sustainable Development, which regulates 'the fields of geology, minerals, hydrocarbons and energies,' has not responded to CNN's requests for comment. The full extent of the questionable movement of fossils across borders is hard to pin down, but it has included important specimens such as Ubirajara jubatus, a feathered dinosaur species first described in a now-retracted 2020 paper from a one-of-a-kind skeleton that had allegedly been illegally exported to Germany from Brazil. Germany's State Museum of Natural History Karlsruhe returned the rare remains to Brazil in 2023 among a wave of similar high-profile repatriations, including a 56 million-year-old crocodile fossil that Morocco recovered from the United States. A few years earlier, in 2015, actor Nicolas Cage returned a T. rex skull he bought for $276,000 at auction in 2007 to the Mongolian government. It's more difficult for smaller, less expensive fossils that have been illegally exported to make it back to their country of origin, although in 2022 French customs returned nearly 1,000 fossils from the Araripe Basin in Brazil that had been stolen to be sold online. Neither Martill nor John Nudds, an honorary lecturer in the department of Earth and environmental sciences at the UK's University of Manchester, would go as far as calling my fossil illegal. 'There's a bit of a gray area,' Martill said. 'I can't technically go there and dig fossils without the permission of the ministry in Rabat.' But he added that locals 'can dig fossils, they can cut fossils, they can polish fossils, and tourists can buy the fossils. And if you go to any fossil fair, you'll find Moroccan fossils for sale, and that will include Spinosaurus teeth.' Nudds said he knows of at least one reputable wholesaler based outside Morocco that sells 'an awful lot' of Spinosaurus teeth exactly like mine. 'That's why I'm pretty confident that these are OK to come out of Morocco,' he said. Part of the reason why fossils may occupy a legal gray area, Nudds added, is some ambiguous wording in UNESCO's 1970 Convention, which was designed to prevent the illegal export of items of cultural importance across many categories. The category that includes fossils is described as 'Rare collections and specimens of fauna, flora, minerals and anatomy, and objects of palaeontological interest.' According to Nudds, the wording makes it unclear whether the objects of paleontological interest are in their own category, which would include all fossils, or if they are part of the 'rare collections,' which would not. But when it comes to my tooth, he said he believes that unless the shop I bought it from has smuggled the item out of Morocco, then it is selling it legally, even if it bought it from a smuggler. 'There may be an ethical issue,' Nudds said, 'and there may be a moral or even a scientific issue, but not a legal issue.' Elmahdi Lassale, CEO of M2 Rocks & Minerals, a Moroccan wholesaler and exporter of minerals and fossils that sells directly to retailers in the US, UK and Europe, confirmed that under Moroccan law, since 2020, fossils are classified as geological heritage. Excavating and exporting them isn't strictly off-limits, according to Lassale, but to do so commercially, a license must be obtained from the Ministry of Energy Transition and Sustainable Development as well as a validated customs certificate. In practice, it means that before each export, Lassale sends the ministry a list of the individual items he wants to sell. 'Normally we just send the descriptions and the names of the items,' he added, 'but sometimes they ask to send a real specimen, to see it in person.' When I asked if he deals in Spinosaurus teeth, he said he doesn't, because it's unlikely that the ministry would approve their export. 'If we talk about dinosaur bones or teeth, it's (almost) impossible to export from Morocco (even) with a license,' Lassale said. Among the items he gets permission to export are trilobites, ammonites, shark teeth, and Mosasaur and Plesiosaur teeth and vertebrae. However, he said he is aware that other fossils do get out of the country via 'illegal suppliers' as well as 'through informal shipments via tourist luggage and small couriers, creating a mixed online market of documented and undocumented specimens abroad.' He estimated the total trade of fossils in Morocco to be worth $30 million to $40 million annually, including official and unofficial exports, and that about 80% of fossils are exported. In a large trade show such as the one in Tucson, he said, there will be on average around 200 Moroccan fossil dealers. Martill and Nudds viewed my fossil during separate video calls. 'You've got a genuine fossil, but I think it's a repair,' Martill said. 'There's a possibility that the tip belongs to a different specimen. You can see some glue — they often find broken examples, and they will just do sympathetic repairs.' However, the human cost of obtaining even an imperfect specimen can be serious, he said. 'Let me tell you now that the man who dug that out of the ground risked not only his life but his lungs as well,' Martill said, adding that he has gone into fossil mines in Morocco and spent time with miners. The fossil trade in Morocco is the main source of income for more than 50,000 people, including diggers, miners, artisans, middlemen and wholesalers who go on to export the fossils, according to a 2018 study. Martill said he believed my tooth came from Hassi el Begaa, a village in the Kem Kem region. 'This is a place where the mines go in from the side of the hill,' Martill said. 'They go in horizontally, for maybe 50 to 100 meters (164 to 328 feet). They then turn to the left or the right, and that's when you lose any hint of sunlight. You're well underground, and the place is incredibly dusty. The miners are often working without masks. They have little head torches, and they dig with tiny crowbars fashioned out of the steel that you use to reinforce concrete. They're not sophisticated tools. 'They do this all day long and then shovel out all of the sand in a wheelbarrow, tip it down the side of the hill and look for the fossils. They're working extremely hard — they're hand-digging a mine,' Martill added. Taking all that into account, he said, what I paid for my tooth fossil 'is probably pretty cheap.' Lassale agreed the fossil diggers in Morocco often work in challenging conditions, including temperatures as high as 40 degrees Celsius (104 degrees Fahrenheit), and with minimal protective equipment, while earning about 120 to 180 Moroccan dirhams (about $13 to $20) daily. He added that his company only partners with artisans and cooperatives that provide safety measures such as shade tents, water and protective goggles to workers, though he said such practices are not common industrywide. 'It's very easy to make a lot of money with this, but it's not easy to dig out minerals or fossils — small artisans, they put their health at risk' to support their families, Lassale said. He noted that mines and shafts dug to reach fossil deposits have been known to collapse sometimes, causing fatalities. 'Unfortunately, we hear about that every year — not just fossil but also mineral mines,' he said. Would I be in trouble if my fossil tooth turned out to be illegal? Experts told me I likely wouldn't, even if the specimen had been illegally exported — the responsibility would likely be on the wholesaler. But things could be different for fossils from countries that have strong restrictions on fossil exports. That's why experts recommend prospective buyers avoid anything advertised from countries such as Brazil, Argentina, China or Mongolia. 'I guess the best advice would be to only buy something if you can see it and hold it in your hand,' Nudds said. 'If you're going to buy online, then maybe avoid those countries which do ban exports, because that's where you're more likely to find forgeries.' Fakes don't seem to be widespread, but they're more common on the cheaper end of the market, according to Lovisek of the Fossil Realms gallery in Canada. 'There's so much scrutiny with the higher end, that the real problem is not forgery, but misrepresentation — claiming there's less restoration than there is, or claiming it's more real bone than there is,' he said. Other than such deceptions or distortions, when it comes to how to purchase a fossil properly, experts offered guidance that would apply to buying pretty much anything online: Do your research, look for a reputable seller, and ask for paperwork or proof that the item is sold legally and ethically. Perhaps the more important question is should you buy a fossil at all? I still look at the Spinosaurus tooth on my bookshelf and marvel that it's the oldest thing in my house by at least 94 million years. But given the complexities around fossils' cultural status and scientific relevance, the dangerous working conditions in some excavation areas, and the fact that many countries are now recovering fossils exported illegally, it's no surprise that the answer to that question has stirred disagreement, even within my small cohort of paleontologists. 'Do not buy your fossils online,' said Maidment of London's Natural History Museum. 'Unless you can absolutely verify that they are being sold legally, and that they're in your country legally, it's best to just not to do it at all. My view of fossils — it's something that belongs to all of us. It's part of our heritage. It shouldn't be something that one person owns.' Martill has a different view, particularly for smaller, less rare specimens that don't hold as much value for researchers. 'There are billions of fossils in the ground. There's no point in them staying in the ground. And scientists like me, there's only so much that you can do with one isolated dinosaur tooth. It's a common fossil; it's scientifically uninteresting,' he said. 'I think it's great that you can have a fossil. You got something there which is 90 to 100 million years old,' Martill added. 'There is a possibility that you could buy a tooth and actually own a piece of the fantastic history of the life on Earth.' Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.
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- CNN
Mexico's bat man on saving the ‘most unfairly treated animals on Earth'
EDITOR'S NOTE: Call to Earth is a CNN editorial series committed to reporting on the environmental challenges facing our planet, together with the solutions. Rolex's Perpetual Planet Initiative has partnered with CNN to drive awareness and education around key sustainability issues and to inspire positive action. Bats have a bad reputation. Myths, folk tales, and negative media coverage mean people often link these flying mammals to vampires or blame them for disease outbreaks. But bat populations around the world are in decline, and without them, ecosystems lose key benefits like pest control, pollination and seed dispersal. Through education, research and advocacy, Rodrigo Medellín, a senior professor of ecology at the University of Mexico, has made it his mission to change the way people see these animals. Medellín's fascination with bats began at the age of 13, when he held one in his hands for the first time. 'That's when I decided to dedicate my life to their study and protection,' he says. Since then, caves have become his happy place. 'The peace, the darkness, the silence apart from the bat squealing. I feel relaxed in a cave and all I do is I try to convey this feeling to the people that are with me,' says Medellín, who is part of the Rolex Perpetual Planet Initiative and has won multiple awards for his work. He also founded of the Latin American Network for Bat Conservation, and Global South Bats, a network of bat scientists. There are over 1,400 bat species, which account for around a fifth of all known mammal species across the globe. They are the only mammals capable of powered flight, rather than just gliding, which allowed them to spread across the globe. They use highly developed echolocation to navigate and find prey at night, with some able to sense objects as small as human hair. Although certain species live for over 30 years, bats reproduce slowly – typically one pup per year. This makes it difficult for populations to recover from decline. 'They are very mysterious. Many people fear them, attack them, or despise them. They are probably the most unfairly treated animals on Earth,' says Medellín. Bats are often seen as symbols of evil and darkness, largely due to their association with vampires and the supernatural in Western folklore. Throughout history in Christian Europe, the bat has been associated with the devil, evil spirits, and witches. Eastern cultures tend to view them much more positively. For instance, in Chinese culture, they are considered symbols of luck and happiness. Still, the perception of bats has worsened with the emergence of Covid-19, which some believe originated in bats and they are often viewed negatively due to their association with diseases. 'Bats are certainly not fuller of diseases than your dog or cat. That has been horribly exaggerated,' Medellín explains. One of the most impactful services bats provide is pest control. Medellín notes that just one species along Mexico's northern borders numbers up to 30 million individuals, collectively devouring about 300 tons of insects every night. But they do much more than keep insects in check. Fruit-eating bats play a crucial role in spreading seeds as they fly long distances in search for food. 'By dropping seeds far from the parent tree, they help regenerate forests, maintain plant diversity, and support the life cycles of countless other organisms. The restoration of forests relies very heavily on bats,' Medellín says. Bats are also key pollinators for a wide range of plants, according to Medellín, including agave, the plant used to make tequila. Despite their critical ecological roles, populations worldwide face many challenges, most of which are caused by human activity. Habitat loss, wind turbines, pesticide use, and most recently, white nose syndrome – a fungal disease – have all taken a serious toll. As a result, many species are now listed as endangered or threatened. 'Imagine what happens if we lose bats overnight,' Medellín says. 'Without them, crops would be ravaged by hungry insects, and mosquito populations would surge, drastically changing our way of life.' He is committed to convincing people that bats are important for their everyday wellbeing and believes that greater awareness could transform attitudes and turn fear into fascination. Through initiatives like bat-friendly agave farming, long-distance migration tracking and international conservation networks, he's working to protect bat populations while highlighting their role in pollination, pest control and ecosystem health. 'I give people facts, images, evidence, and automatically they fall in love with bats,' he says. 'In my experience, anyone who had any contact with bats maintains that contact and starts expanding it.' 'If there is anybody who is still afraid of bats, I would like to invite you to learn a bit more,' he adds. 'They are going to win your heart.'
