News Article | April 25, 2017
In 2013, Lee Berger at the University of the Witwatersrand in Johannesburg and his colleagues made an extraordinary discovery – deep inside a South African cave system they found thousands of bones belonging to a brand new species of early human — and now we finally may know when this species lived and how it fits into our evolutionary tree. By 2015 it was becoming clear that the new species, which was named Homo naledi, was unlike anything researchers had discovered before. Although parts of its skeleton looked identical to our modern human anatomy, it had some features that were strikingly primitive – including a skull that was only slightly larger than that of a chimpanzee. But Berger and his colleagues had trouble establishing how old the H. naledi fossils were. Without that piece of information, most other researchers agreed that the true significance of H. naledi for understanding human evolution was unclear. Guesses have varied from as old as 2 million years to as young as 100,000 years. Today, news broke that Berger’s team has finally found a way to date the fossils. In an interview published by National Geographic magazine, Berger revealed that the H. naledi fossils are between 300,000 and 200,000 years old. “This is astonishingly young for a species that still displays primitive characteristics found in fossils about 2 million years old, such as the small brain size, curved fingers, and form of the shoulder, trunk and hip joint,” says Chris Stringer at the Natural History Museum in London. Here, we address some of the implications of the announcement, as we wait for the full publication of the results. Why has it taken so long to establish the age of the fossils? It can be surprisingly difficult to work out how old fossil bones are. Many of the techniques researchers can use require the isotopic analysis of bone samples. Berger and his colleagues are reluctant to use these techniques, because they involve destroying small samples of precious fossil material. Another option is to date the rock or sediment that blankets the layer in which the fossils are found. Ancient lava flows, in particular, contain chemical signatures that are perfect for isotopic dating. But the H. naledi remains were found in a cave in which there were no easily dated sedimentary layers covering the fossils. Researchers can also work out the rough age of the fossils by looking at the fossil remains of other species found alongside them, if the age of those other species has already been established. The cave in which the H. naledi fossils were found contains virtually no bones from other species, though, making this approach a nonstarter. So how did Berger and his colleagues work out the age of the fossils? We don’t know yet. The scientific papers in which this information will be revealed haven’t been published. The National Geographic interview mentions that Berger and his colleagues have found a second cave chamber containing more H. naledi remains – perhaps these additional fossils were preserved in a context that made dating less challenging. If the fossils are 300,000 to 200,000 years old what does that mean? Our earliest hominin ancestors lived at least seven million years ago. The first species to look a little like modern humans appeared between about two and three million years ago. But our own species – Homo sapiens – evolved about 200,000 years ago. So, if H. naledi lived 300,000 to 200,000 years ago that’s a remarkable discovery. It means that a species of human with some surprisingly primitive features – including a tiny skull and brain – survived into the relatively recent past. Conceivably, H. naledi might even have met early members of our species, H. sapiens. One could even speculate we had something to do with it going extinct. Does the age help us to work out where H. naledi fits in the human evolutionary tree? It probably depends on whom you ask. Based purely on its strange anatomy, H. naledi seems to belong somewhere near the very base of the “true human” family tree – an idea suggested in some studies of the fossils. But we know that the first early humans appeared more than two million years ago. If H. naledi is just 300,000 years old, some researchers might argue that it can’t belong to the base of our family tree. It’s too young. Perhaps it even had a modern-looking ancestor and later evolved primitive-looking features. But it is, in fact, still perfectly possible that H. naledi really does belong somewhere near the base of our human evolutionary tree. The species might have evolved more than two million years ago, as one of the earliest “true” humans, and then survived, unchanged, for hundreds of thousands of years. “It could lie close to the origin of the genus Homo, suggesting that this is a relic species, retaining many primitive traits from a much earlier time,” says Stringer. Berger has previously talked about this possibility. He says H. naledi might be like a human version of the coelacanth – a primitive fish with ancestors that first appeared 400 million years ago but that is still found in oceans today. Is there any precedent for that idea in the human fossil record? Yes – potentially. About a decade ago researchers working on the opposite side of the world, in Indonesia, made another astonishing discovery: they found remains of another ancient human species with a tiny chimp-sized head that also lived just a few hundred thousand years ago. It is named Homo floresiensis – although it is better known by its nickname: the “hobbit”. Researchers have been arguing about H. floresiensis’s place in the human family tree for years. Last week, one paper revived the idea that H. floresiensis can trace its roots back to a very early species of human called H. habilis that we know lived in Africa more than two million years ago. The idea is that a population of H. habilis left Africa about two million years ago and gradually moved across Asia, ultimately reaching Indonesia. If this idea is correct, H. floresiensis falls on one of the lowest branches in the “true” human family tree despite its young age, because it evolved directly from the primitive H. habilis. In other words, species of evolutionarily primitive humans might, in some circumstances, be able to survive for hundreds of thousands of years. “There are obvious parallels with the late survival of H. floresiensis in Indonesia, but in that case island isolation probably accounts for its longevity,” says Stringer. “How did a comparably strange and small-brained species linger on in southern Africa, seemingly alongside more ‘advanced’ humans?” What happened to H. naledi in the end? There are no answers to this question yet. But if the fossils really are just 300,000 to 200,000 years old there is at least one possible scenario. Our species, H. sapiens, evolved in Africa about 200,000 years ago. If those early H. sapiens reached southern Africa shortly afterwards, they might have contributed to the extinction of H. naledi. Again there is precedent for this. The fossil record elsewhere in the world shows that H. sapiens left Africa and gradually spread across Eurasia. As it did so, H. sapiens arrived in areas already populated by ancient humans – species like the Neanderthals. Within a few thousand years of H. sapiens arriving in these new areas, the indigenous species of ancient humans disappeared, apparently outcompeted by H. sapiens. Even the hobbit, H. floresiensis, seems to have suffered this fate. The most recent information suggests it went extinct 50,000 years ago – about the same time that H. sapiens arrived in this part of Indonesia. H. naledi might have the dubious honour of being the earliest ancient human species to have been driven to extinction by the spread of our species. But this is still speculation at the moment. Read more: Homo naledi: Unanswered questions about the newest human species
News Article | April 17, 2017
Scientists have long wondered what the earliest dinosaur relatives looked like. Most assumed they would resemble miniature dinosaurs, about the size of chickens, and walk on two legs. The discovery of Teleocrater rhadinus, however, has forced scientists to reassess their ideas. Based on a fossil unearthed in southern Tanzania, these early relatives were carnivorous animals that measured approximately 7-10 feet long, with long necks and tails. Rather than walking on two legs, they walked on four crocodilian-like legs. The finding, published today in the journal Nature, fills a gap in the fossil record. "The research sheds light on the distribution and diversity of the ancestors of crocodiles, birds, and dinosaurs," said Judy Skog, a program director in the National Science Foundation's (NSF) Division of Earth Sciences, which funded the research. "It indicates that dinosaur origins should be re-examined now that we know more about the complex history and traits of these early ancestors." T. rhadinus predated dinosaurs, living more than 245 million years ago during the Triassic Period. It shows up in the fossil record right after a large group of reptiles known as archosaurs split into a bird branch (leading to dinosaurs and eventually birds) and a crocodile branch (leading to alligators and crocodiles). T. rhadinus and its kin are the earliest known members of the bird branch of the archosaurs. "The discovery of such an important new species is a once-in-a-lifetime experience," said Sterling Nesbitt, a paleobiologist at Virginia Tech and lead author of the Nature paper. The late paleontologist F. Rex Parrington first discovered T. rhadinus fossils in Tanzania in 1933. The late Alan J. Charig, then-curator of fossil reptiles, amphibians and birds at the Natural History Museum of London, was the first to study those original specimens in the 1950s. Charig could not determine whether the creature was more closely related to crocodilians or to dinosaurs, largely because the specimens lacked ankles and other bones. The new specimens, found in 2015, clear up those questions. The intact ankle bones and other parts of the skeleton helped scientists determine that the species is one of the oldest members of the archosaur tree and had a crocodilian look. Nesbitt and his co-authors chose to honor Charig's work by using the name he selected for the animal, Teleocrater rhadinus, which means "slender complete basin" and refers to the animal's lean build and closed hip socket. "The discovery of Teleocrater fundamentally changes our ideas about the earliest history of dinosaur relatives," said Nesbitt. The team's next steps are to return to southern Tanzania to find missing parts of the T. rhadinus skeleton. "It's so exciting to solve puzzles like Teleocrater, where we can finally tease apart tricky mixed assemblages of fossils and shed light on broader anatomical and biogeographic trends in an iconic group of animals," said Michelle Stocker, a paleobiologist at Virginia Tech and co-author of the paper. Other co-authors include: Richard Butler at the University of Birmingham; Martin Ezcurra at Museo Argentino de Ciencias Naturales; Paul Barrett at the Natural History Museum of London; Kenneth Angielczyk at the Field Museum of Natural History; Roger Smith at the University of the Witwatersrand and Iziko South African Museum; Christian Sidor at the University of Washington; Grzegorz Niedzwiedzki at Uppsala University; Andrey Sennikov at the Borissiak Paleontological Institute and Kazan Federal Univeristy; and Charig. The National Geographic Society Young Explorer program and other institutions also funded the research.
News Article | May 3, 2017
Scientists have directly dated Stone Age rock paintings in southern Africa reliably for the first time. Their work reveals that early hunter-gatherer peoples created art at three sites in the region, some 5,700 years ago (A. Bonneau et al. Antiquity 91, 322–333; 2017). And the findings open the door for archaeologists and other researchers to date thousands more rock paintings in this part of Africa — and so piece together the lives and development of ancient people there. The study focused on paintings in present-day Botswana, South Africa and Lesotho created by the San people, whose direct descendants still live in the area. The San have been much studied, but many mysteries remain about how they lived, and how they interacted with other groups — such as early farmers. “If we are able to date depictions of livestock and material goods associated with incoming groups, we may be able to start unravelling the nature of interactions between groups in this early contact,” says David Pearce, an archaeologist and director of the Rock Art Institute at the University of the Witwatersrand in Johannesburg, South Africa, and a co-author of the latest study. Just under 2,000 years ago, Pearce says, pastoral and farming people independently arrived in South Africa, where they came into contact with hunter-gatherer groups such as the San. “We know relatively little about these groups because of the paucity of archaeology.” Rock paintings show that these groups interacted, but, because the paintings were discovered at sites that contain no other artefacts, they have not been reliably dated. “What we’ve been doing previously existed out of time,” says Pearce. He adds that, although “we know a lot about what the paintings mean”, scientific techniques have not been widely applied to archaeological findings in the region. Many experts had assumed that the black paint used in African pictures was based on manganese compounds and that the rock art would therefore have contained too little carbon to be reliably dated, he says. As a result, techniques developed in Europe and elsewhere have not previously been applied in Africa. Yet southern African rock art is highly influential. “It was ethnographies of San bushmen art that provided many of the models for social interpretation of the art we still use today,” says Alistair Pike, an archaeologist at the University of Southampton, UK, who was not involved in the research. And pictures left by the San and others could help researchers to put dates on other significant events, including the development of early religious rituals. Dating rock pictures is itself a tricky art. Extracting useful samples damages paintings, and it is hard to distinguish original materials from modern contaminants. Over the years, compounds that contain carbon build up on top of the pictures and interfere with radiocarbon dating. And it’s not enough to know that a sample contains carbon: charcoal used in paint, for example, could pre-date a painting by centuries and so affect the result of the carbon tests. “While doing the characterization of the different paints, we realized that the San people used three different materials to make black paints: charcoal, soot and carbon-blacks, which are burnt fat or grease,” says Adelphine Bonneau, a postdoctoral researcher at Laval University in Quebec, Canada, who is lead author on the study. Soot and carbon-blacks would have had to be produced a few hours before being used — and that meant they could be tested to give an accurate date. It was this fact that formed the basis of her team’s multi-stage technique. First, Bonneau and her colleagues took tiny samples — less than one square millimetre — and determined their chemical composition. If they found testable carbon, the researchers took a larger sample. They cleaned away centuries of accumulated surface compounds such as calcium oxalate, which contaminate test results, and then carbon-dated the sample. Georges Sauvet, an archaeologist with the Emile Cartailhac Prehistoric Art Research and Study Center at the University of Toulouse-Jean Jaurès in France, questioned the efficacy of the cleaning process, saying: “They seem to be reticent to show clearly that they have totally removed the calcium oxalate, and I don’t know why.” Pike welcomed the technique and the results, but warned that it might not be suitable for older sites with more organic contaminants. “Were these paintings older, I would be more cautious in accepting these results,” he says. But young sites made from similar materials could be dated using this method. “I hope that the team are able to continue to provide dates for paintings in Africa,” Pike adds. “The earliest forms of symbolic expression are known from Africa, so perhaps there are older paints in Africa that have yet to be found, or yet to be dated.”
News Article | April 23, 2017
NEW ORLEANS, LOUISIANA—A remarkably complete skeleton introduced in 2010 as “the best candidate” for the immediate ancestor of our genus Homo may just be a pretender. Instead of belonging to the human lineage, the new species of Australopithecus sediba is more closely related to other hominins from South Africa that are on a side branch of the human family tree, according to a new analysis of the fossil presented here last week at the annual meeting of the American Association of Physical Anthropologists. When fossils from several individuals’ skeletons were found in a collapsed cave in Malapa, South Africa, in 2008, their discoverer, paleoanthropologist Lee Berger of the University of the Witwatersrand, noted that they helped fill a key gap in the fossil record 2 million to 3 million years ago when some upright-walking australopithecine evolved into the earliest member of our genus, Homo. But the oldest Homo fossils, at 2.4 million to 2.9 million years, are scrappy, and a half dozen more primitive hominins may have been walking around Africa at roughly the right time to be the ancestor. Researchers have hotly debated whether their direct ancestor was the famous 3.2-million-year-old fossil Lucy and her kind, Australopithecus afarensis from Ethiopia, or another australopithecine. With its fossils dated to 1.98 million years ago, Au. sediba is too young to be directly ancestral to all members of the genus Homo. But Berger and his colleagues proposed in 2010, and again in 2013 in six papers in , that given the many humanlike traits in Au. sediba’s face, teeth, and body, the Malapa fossils were a better candidate than Lucy or other East African fossils to be ancestral to Homo erectus, a direct human ancestor that appeared 1.8 million years ago. In a talk here, though, paleoanthropologist Bill Kimbel of Arizona State University in Tempe analyzed the most complete skull of Au. sediba and systematically shot down the features claimed to link it to early Homo. Kimbel noted that the skull was that of a juvenile—a “7th grader”—whose face and skull were still developing. In his analysis, with paleoanthropologist Yoel Rak of Tel Aviv University in Israel, he concluded that the child already showed traits that linked it most closely to the South African australopithecine Au. africanus, a species that lived in South Africa 3 million to 2.3 million years ago. And had it survived to adulthood, its humanlike facial traits would have changed to become even more like those of Au. africanus. For example, the breadth of the young Au. sediba’s cheekbones appears narrow, as in early Homo. But by studying other australopithecine, ape, and Homo fossils to see how features of the cheekbones change as individuals grow and chewing muscles develop, Kimbel and Rak could predict how the boy’s face and skull would have looked if he’d grown up to be an adult. The resemblance to Au. africanus is so striking, in fact, that Kimbel thinks Au. sediba is a closely related “sister species” of Au. africanus—and not a long-lost human relative. “We don’t believe … that Au. sediba has a unique relationship to the genus Homo,” says Kimbel. Other researchers who have long been skeptical that Au. sediba was an ancestor of Homo found Kimbel’s talk persuasive: “Spot on,” says paleoanthropologist Bernard Wood of George Washington University in Washington, D.C. Paleoanthropologist Ian Tattersall of the American Museum of Natural History in New York agrees with Kimbel that Au. sediba is most closely related to Au. africanus and that neither species is ancestral to early Homo. But paleoanthropologist Darryl de Ruiter of Texas A&M University in College Station, a co-author with Berger on the 2013 paper describing the skull, says he and his former graduate student reached “the opposite conclusion” when they used computational methods to project how the skull would have changed as it matured. “I disagree with his impression that the changes that [the skull] would have undergone had it lived to adulthood would be so extensive as to make it appear like Au. africanus,” said de Ruiter, who heard Kimbel’s talk. The only way to know what an adult Au. sediba’s skull and face really looked like, he says, is to find one: “The ultimate resolution of the question must await the long-hoped-for recovery of the adult cranium of Au. sediba.”
News Article | March 2, 2017
Elephants sleep an average of two hours a day — the shortest-known sleep time of any mammal on land, a new study has found. They also regularly go almost two days without shuteye, a research team from the University of the Witwatersrand in South Africa discovered. African elephants are the largest terrestrial animal, and evidence suggests that larger mammals are likely to sleep less. Many other studies, however, only probed their sleep in captive environments and also mistook mere rest for sleep. Lead researcher and professor Paul Manger and his colleagues tracked two free-roaming African elephant matriarchs living in Botswana’s Chobe National Park for 35 days. They outfitted the subjects with an actiwatch — much like the fitness and health tracker Fitbit — to monitor sleep accurately and a GPS collar with a gyroscope to track and monitor position. “[M]easuring the activity of the trunk, the most mobile and active appendage of the elephant, would be crucial, making the reasonable assumption that if the trunk is still for five minutes or more, the elephant is likely to be asleep,” said Manger in a statement. The two elephants turned out to sleep two hours a day on average, with the sleep occurring mostly at pre-dawn. They went without sleep for up to 46 hours, traveling long distances of about 30 kilometers during those times, likely because of threats such as poaching or predation. According to data, sleep in these wild creatures appear to be unrelated to sunrise or sunset, but rather are tied to environmental factors such as temperature and humidity. They could also sleep while either standing up or lying down, which happened only every three or four days and for around an hour. It was in lying down that the elephants could reach rapid eye movement (REM) or dream sleep, which is believed to be vital for memory consolidation. “The elephant has well-documented long-term memories,” explained Manger, “but does not need REM sleep every day to form these memories.” The findings were discussed in the journal PLOS ONE. Probing sleep in animals proves critical not only for stumbling upon new information for better wildlife conservation and management practices. In an important nature reserve in Central Africa, researchers recently found that around 25,000 or 81 percent of the forest elephant population had been wiped out by poaching. The remote, 2,900-square-mile Minkébé in Gabon, supposedly the frontliner in the battle against poaching that buoys the ivory demand in Asia, saw its elephant population disappearing fast from 2004 to 2014. It is threatened not just by Gabonese poachers, but by hunters from neighboring nations such as Cameroon. These animal sleep studies also offer a better understanding of our own sleep as humans. While it remains a mystery why we sleep, new research considers sleep a way to forget certain things learned throughout the day in order to grow neural connections that will store new memories. A four-year experiment detected the shrinking of synapses or neural connections in mice while they slept, therefore positioning sleep as a way for the brain to keep learning new things and forming new memories. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.
News Article | February 15, 2017
An ancient continent that was once sandwiched between India and Madagascar now lies scattered on the bottom of the Indian Ocean. The first clues to the continent’s existence came when some parts of the Indian Ocean were found to have stronger gravitational fields than others, indicating thicker crusts. One theory was that chunks of land had sunk and become attached to the ocean crust below. Mauritius was one place with a powerful gravitational pull. In 2013, Lewis Ashwal at the University of the Witwatersrand in South Africa and his colleagues proposed that the volcanic island was sitting on a piece of old, sunken continent. Although Mauritius is only 8 million years old, some zircon crystals on the island’s beaches are almost 2 billion years old. Volcanic eruptions may have ejected the zircon from ancient rock below. Now, Ashwal and his team have found zircon crystals in Mauritius that are up to 3 billion years old. Through detailed analyses they have reconstructed the geological history of the lost continent, which they named Mauritia. Until about 85 million years ago, Mauritia was a small continent — about a quarter of the size of Madagascar — nestled between India and Madagascar, which were much closer than they are today. Then, India and Madagascar began to move apart, and Mauritia started to stretch and break up. “It’s like plasticine: when continents are stretched they become thinner and split apart,” says Martin Van Kranendonk at the University of New South Wales in Australia. “It’s these thin pieces that sink below the ocean.” There is evidence that other volcanic islands in the Indian Ocean, including the Cargados Carajos, Laccadive and Chagos islands, also sit on fragments of Mauritia. More and more remnants of other old continents are being uncovered, says Alan Collins at the University of Adelaide in Australia. Several pieces have recently been found off Western Australia and underneath Iceland, he says. “It’s only now as we explore more of the deep oceans that we’re finding all these bits of ancient continents around the place.”
News Article | March 1, 2017
Why we sleep is one of the enduring unanswered mysteries of modern science. Along with such activities as eating, protecting oneself and reproducing, sleep is one of the major biological imperatives of existence. Although being asleep precludes these other activities, all animals do sleep. Some, like whales, dolphins, seals and certain birds, do it in a very unusual manner, sleeping with only half their brain at a time, while some sleep quite a lot and others less so. "While there are many hypotheses regarding the function of sleep, the ultimate purpose of sleep is yet to be discovered," says Prof. Paul Manger, from the School of Anatomical Sciences at Wits University. The lack of sleep can -- even over a relatively short term - lead to brain damage, and in the longer term death, as can be seen in the human conditions fatal familial insomnia and sporadic fatal insomnia. Generally, larger animals tend to sleep less than smaller animals, but do elephants fit this trend? Behavioural studies of elephant sleep in zoos record that they sleep around four hours per day and can sleep standing up or lying down -- but how much do they sleep and how do they sleep in their natural environment? Working in the Chobe national Park in Botswana, Manger, Dr Nadine Gravett and Dr Adhil Bhagwandin at the University of the Witwatersrand, along with their colleagues from the NGO Elephants Without Borders, Botswana, and the University of California, Los Angeles, made use of small activity data loggers, scientific versions of the well-known consumer fitness and wellness tracker, Fitbit, to study the sleeping patterns of elephants in the wild. "We reasoned that measuring the activity of the trunk, the most mobile and active appendage of the elephant, would be crucial, making the reasonable assumption that if the trunk is still for five minutes or more, the elephant is likely to be asleep," says Manger. The team outfitted two matriarch elephants, noting when they used their trunk by an implanted activity data logger, when they moved around and - by installing a GPS collar with a gyroscope around their necks - where and when they were lying down to sleep. The main finding of the study, recently published in the journal PLOS ONE, was that the two matriarch elephants slept only two hours per day on average, and this sleep occurred mostly in the early hours of the morning, well before dawn. "The data also indicates that environmental conditions (temperature and humidity, but not sunlight) are related to when the elephants fell asleep and when they woke up (which happens well before dawn)," says Manger. "This finding is the first that indicates that sleep in wild animals is likely not to be related to sunrise and sunset, but that other environmental factors are more crucial to the timing of sleep." The team also found that the wild elephants could sleep while standing up, or while lying down. Lying down to sleep only happened every three or four days and for about an hour, and it is likely that when the elephants were lying to sleep were the only times they could go into REM, or dreaming, sleep, meaning elephants possibly don't dream on a daily basis like we do, but may dream only every few days. "REM sleep (or dreaming) is thought to be important for consolidating memories, but our findings are not consistent with this hypothesis of the function of REM sleep, as the elephant has well-documented long-term memories, but does not need REM sleep every day to form these memories," says Manger. Lastly, they found that the two elephants, when disturbed by such things as predators, poachers, or a bull elephant in musth, could go without sleep for up to 48 hours, and following the start of the disturbance would walk up to 30 km from where the disturbance occurred. This put a great deal of distance between the elephant herd and any source of danger, but at the expense of a loss of a night's sleep. "Understanding how different animals sleep is important for two reasons. First, it helps us to understand the animals themselves and discover new information that may aid the development of better management and conservation strategies, and, second, knowing how different animals sleep and why they do so in their own particular way, helps us to understand how humans sleep, why we do, and how we might get a better night's sleep."
News Article | March 2, 2017
Wild African elephants sleep for the shortest time of any mammal, according to a study. Scientists tracked two elephants in Botswana to find out more about the animals' natural sleep patterns. Elephants in zoos sleep for four to six hours a day, but in their natural surroundings the elephants rested for only two hours, mainly at night. The elephants, both matriarchs of the herd, sometimes stayed awake for several days. During this time, they travelled long distances, perhaps to escape lions or poachers. They only went into rapid eye movement (REM, or dreaming sleep, at least in humans) every three or four days, when they slept lying down rather than on their feet. A way to lift an elephant's mood How to put an elephant to sleep Prof Paul Manger of the University of the Witwatersrand, South Africa, said this makes elephant sleep unique. "Elephants are the shortest sleeping mammal - that seems to be related to their large body size," he told BBC News. "It seems like elephants only dream every three to four days. Given the well-known memory of the elephant this calls into question theories associating REM sleep with memory consolidation." Elephants living in captivity have been widely studied. To find out more about their sleeping habits in the wild, Prof Manger and his research team fitted the scientific equivalent of a fitness tracker under the skin of the animals' trunks. The device was used to record when the elephants were sleeping, based on their trunk staying still for five minutes or more. The two elephants were also fitted with a gyroscope to assess their sleeping position. Both elephants were followed for five weeks, giving new insights into their natural sleep patterns. "We had the idea that elephants should be the shortest sleeping mammal because they're the largest," said Prof Manger. "Why this occurs, we're not really sure. Sleep is one of those really unusual mysteries of biology, that along with eating and reproduction, it's one of the biological imperatives. We must sleep to survive." Generally, smaller-bodied mammals sleep for longer than larger ones. For example, sloths sleep for around 14 hours a day, while humans sleep for around 8 hours. How elephants survive on so little sleep remains a mystery. The researchers are planning follow-up studies on more elephants, including males. They also want to find out more about REM sleep in elephants. REM sleep is believed to be critical in laying down memories. It is a type of sleep seen across the animal kingdom, in mammals and birds and even lizards. Most mammals go into REM sleep every day.
News Article | March 1, 2017
It’s another sleepless night in the savannah. Wild elephants average just 2 hours of sleep a night, making them the lightest-known snoozers of any mammal. Previous studies have looked at such habits in captive elephants, which sleep for 3 to 7 hours a day. But with more dangers and pressure to find food, wild animals tend to sleep less. So Paul Manger at the University of the Witwatersrand, Johannesburg in South Africa and his colleagues set out to monitor sleep in wild African elephants in Chobe National Park in northern Botswana. The most reliable way to measure sleep is to use electrical recordings of the brain, but this isn’t possible in elephants. Their thick skulls mean that surface electrodes are ineffective, and putting electrodes under the skull would require invasive surgery. Instead, the researchers fitted motion sensors to elephants’ trunks. The trunk is the most active part of the elephant’s body, and is rarely idle while the animal is awake. “We figured when it hadn’t been used for 5 minutes, the elephant was probably asleep,” says Manger. The team monitored two matriarchs for 35 continuous days. The elephants slept for an average of 2 hours a night, not in a single slumber but in four to five short bursts – a pattern known as polyphasic sleep. Most of their sleep occurred between 1.00 and 6.00 am, and the elephants snoozed in different places every night. On four days, the elephants didn’t get any shut-eye at all, resulting in them being awake for up to 48 hours continuously. During these periods, they travelled long distances of around 30 kilometres, possibly to evade lions or poachers. But they didn’t appear to compensate with extra sleep after going a night without. Although the sample size is very small, Manger thinks these findings give a reasonably reflective view of wild elephants’ typical sleep habits. “I think what we’ve got is pretty close to the mark,” he says. “Obviously it would be nice to do a lot more animals, but there are ethical considerations and the bottom line is getting enough funding.” The elephants also wore a collar with a gyroscope attached to it, which told the researchers whether they were standing up or lying down. Each elephant slept lying down on only 10 of the 35 days. This finding implies that the animals spent very little time in rapid-eye-movement (REM) sleep, the stage when we have vivid dreams that is thought to be important for memory consolidation. During REM, the muscles usually relax, making it impossible to remain standing. Either elephants only experience REM every few days, or they can enter this phase in short bursts of 5 to 10 seconds while standing, as birds do, says Manger. Alternatively, like whales and dolphins, they may not need REM at all. “We’re not sure which of those is true yet and that’s something we’d like to follow up and discover,” he says. Bigger animals generally tend to sleep less, probably because they have to spend so much time eating. “Elephants can eat up to 300 kilograms of food a day, so obviously it takes a long time for the trunk to get all that into their mouths, and that leaves less time for sleep,” says Manger. But even among large mammals, elephants seem to be light sleepers. The considerably larger grey whale sleeps for 9 hours a day and the giraffe for almost 5 hours. The domestic horse, at nearly 3 hours, is its closest rival. The use of trunk motion to infer sleep state is clever, says John Lesku at La Trobe University in Melbourne, Australia, but he adds that it will be important to learn more about how posture and trunk movement reflect waking, sleeping and REM sleep. “For instance, ruminants can stand, have their eyes partially open and even continue to chew their cud during non-REM sleep, raising the possibility that elephants might have more sleep than appreciated,” he says. Read more: Why brainy animals need more REM sleep after all; Sleep and dreaming: The how, where and why
News Article | March 2, 2017
—If you’ve ever felt tired and overworked, be thankful you’re not an elephant. The lumbering giants may get by on at little as two hours a night, according to scientists. The first sleep study of wild elephants, published in journal PLOS ONE on Wednesday, concluded that elephants may get less sleep than any other mammal, including new human parents. What’s more, they regularly skip nights and often sleep standing up, leaving little chance to dream. The research contributes to a growing understanding of the relationship between body size and sleep time, but complicates science’s quest to understand the ultimate purpose of sleep. Scientists had previously observed captive elephants sleeping 4 to 6 hours a day, but catching some extra z’s while unemployed and with nothing to do in an enclosed area perhaps isn’t so surprising. Wild animals have to feed themselves, avoid threats, and in the case of the two matriarch subjects of this study, lead their herd. "Sleep needs to be studied in an animal's natural environment if we are truly to understand it," said Paul Manger, a research professor in the School of Anatomical Sciences at the University of the Witwatersrand in South Africa who led the study, in an interview with Reuters. To get a more accurate picture of wild behavior, researchers tagged two female leaders known as matriarchs with a gyroscope-equipped GPS collar to track location and position, and surgically implanted a benign Fitbit-like movement tracker into each elephant’s trunk. Embedding an electrical device to monitor the brain directly into the animals’ thick skulls was deemed to be too invasive, so researchers used trunk movement as an approximation of wakefulness, the New Scientist reports. “We reasoned that measuring the activity of the trunk, the most mobile and active appendage of the elephant, would be crucial, making the reasonable assumption that if the trunk is still for five minutes or more, the elephant is likely to be asleep,” said Dr. Manger in a press release. The month-long study found that the elephants slept an average of two hours each day, a full hour less than the previous mammalian record holder, the domestic horse. Those two hours generally fell in the early hours before dawn and were spread out over four to five short nap sessions, like Spaniards but with more siestas. On multiple occasions, the animals walked through the night, staying awake for up to two days straight and covering distances as far as 19 miles. Researchers suspect they may have been avoiding predators such as lions or poachers. Unlike most humans, the elephants didn’t log any extra catch-up time the day after an all-nighter. When the giants did sleep, it was in a different spot each night, and often standing up. Because they only laid down for about an hour every three to four days, researchers concluded that elephants don’t enter REM sleep daily like humans. While dreaming, most mammals relax their muscles, making it difficult to stand. However, Manger told New Scientist that birds can dream in sub-minute bursts, and whales and dolphins appear to go without REM sleep entirely. Since this investigation only studied trunk movement, it’s impossible to know for sure when and if the elephants dreamt. “We’re not sure which of those is true yet and that’s something we’d like to follow up and discover,” he said. The short sleep time didn’t come as a surprise, though. The relationship between body size and sleep duration is still debated, but the authors used data on other captive plant-eating mammals to predict that elephants would sleep about 2.5 to 3 hours per day. It seems that larger animals tend to sleep less, perhaps because they have to spend so much time eating. What was more surprising was the possibility that elephants don’t dream very often. The purpose of sleep remains mysterious, but one proposed function is the re-writing of memories during REM. “REM sleep (or dreaming) is thought to be important for consolidating memories, but our findings are not consistent with this hypothesis of the function of REM sleep, as the elephant has well-documented long-term memories, but does not need REM sleep every day to form these memories,” said Manger. In the paper, the team wrote that the “current study has produced a number of exciting and interesting results,” but highlights a few potential biases in their data. The study recorded sleep times in only two individuals, and matriarchs at that. As any president can confirm, leaders don’t often get to sleep in. One was also nursing a 1-year-old calf. However, they also suspect that using trunk movement may have lead to an overestimate of sleep time, including those moments when the animal was motionless but hadn't yet drifted off. Despite these drawbacks, Manger thinks the team’s results are representative. “I think what we’ve got is pretty close to the mark,” he told New Scientist. “Obviously it would be nice to do a lot more animals, but there are ethical considerations and the bottom line is getting enough funding.