Ancient footprints from Australia reveal earliest-known reptile
(Reuters) -Seventeen footprints preserved in a slab of sandstone discovered in southeastern Australia dating to about 355 million years ago are rewriting the history of the evolution of land vertebrates, showing that reptiles arose much earlier than previously known.
The fossilized footprints, apparently made on a muddy ancient river bank, include two trackways plus one isolated print, all displaying hallmark features of reptile tracks including overall shape, toe length and associated claw marks, researchers said. They appear to have been left by a reptile with body dimensions similar to those of a lizard, they said.
The footprints reveal that reptiles existed about 35 million years earlier than previously known, showing that the evolution of land vertebrates occurred more rapidly than had been thought.
"So this is all quite radical stuff," said paleontologist Per Ahlberg of the University of Uppsala in Sweden, who led the study published on Wednesday in the journal Nature.
The Australian footprints were preserved in a sandstone slab measuring about 14 inches (35 cm) across that was found on the banks of the Broken River near the town of Barjarg in the state of Victoria.
The story of land vertebrates started with fish leaving the water, a milestone in the evolution of life on Earth. These animals were the first tetrapods - meaning "four feet" - and they were the forerunners of today's terrestrial vertebrates: amphibians, reptiles, mammals and birds. Footprints in Poland dating to about 390 million years ago represent the oldest fossil evidence for these first tetrapods, which lived an amphibious lifestyle.
These creatures were the ancestors of all later land vertebrates. Their descendants split into two major lineages - one leading to today's amphibians and the other to the amniotes, a group spanning reptiles, mammals and birds. The amniotes, the first vertebrates to lay eggs on land and thus finally break free of the water, cleaved into two lineages, one leading to reptiles and the other to mammals. Birds evolved much later from reptile ancestors.
The Australian footprints each are approximately 1-1.5 inches (3-4 cm) long. They appear to have been left by three individuals of the same reptile species, with no tail drag or body drag marks. No skeletal remains were found but the footprints offer some idea of what the reptile that made them looked like.
"The feet are rather lizard-like in shape, and the distance between hip and shoulder appears to have been about 17 cm (6.7 inches). Of course we don't know anything about the shape of the head, the length of the neck or the length of the tail, but if we imagine lizard-like proportions the total length could have been in the region of 60 cm to 80 cm (24 to 32 inches)," Ahlberg said.
"In terms of its overall appearance, 'lizard-like' is probably the best guess, because lizards are the group of living reptiles that have retained the closest approximation to the ancestral body form," Ahlberg added.
The modest size of the earliest reptiles stands in contrast to some of their later descendants like the dinosaurs.
This reptile probably was a predator because plant-eating did not appear until later in reptilian evolution. The bodies of herbivorous reptiles tend to be big and clunky, whereas this one evidently was lithe with long, slender toes, Ahlberg said.
The researchers also described newly identified fossilized reptile footprints from Poland dating to 327 million years ago that broadly resemble those from Australia. Those also are older than the previous earliest-known evidence for reptiles - skeletal fossils from Canada of a lizard-like creature named Hylonomus dating to around 320 million years ago, as well as fossil footprints from about the same time.
The reptile that left the Australian footprints lived during the Carboniferous Period, a time when global temperatures were similar to today's, with ice at Earth's poles but a warm equatorial region. Australia at the time formed part of the ancient supercontinent Gondwana and lay at the southern edge of the tropics. There were forests, partly composed of giant clubmoss trees.
"The tracks were left near the water's edge of what was probably quite a large river, inhabited by a diversity of big fishes," Ahlberg said.
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Fossils show two types of ancient human ancestors lived at the same place and time. One was possibly an unknown species
Ancient, fossilized teeth, uncovered during a decades-long archaeology project in northeastern Ethiopia, indicate that two different kinds of hominins, or human ancestors, lived in the same place between 2.6 million and 2.8 million years ago — and one of them may be a previously unknown species. The discovery provides a new glimpse into the complex web of human evolution. Ten of the teeth, found between 2018 and 2020, belong to the genus Australopithecus, an ancient human relative. Meanwhile, three teeth, found in 2015, belong to the genus Homo, which includes modern humans, or Homo sapiens. The results were published Wednesday in the journal Nature. Such an overlapping of two hominins in the fossil record is rare, which had previously led scientists to believe that Homo appeared after Australopithecus, rather than the two being contemporaries. Australopithecus species walked upright much like modern humans, but had relatively small brains, closer in size to those of apes. The emergence of Homo species, with their larger brains, is easy for people today to view as some sort of evolutionary upgrade on a path to modern humanity. But the coexistence of the two demonstrates that hominins developed, and lived, in multiple varieties at once. 'This new research shows that the image many of us have in our minds of an ape to a Neanderthal to a modern human is not correct — evolution doesn't work like that,' said study coauthor Kaye Reed, research scientist and president's professor emerita at the Institute of Human Origins and emeritus professor at the School of Human Evolution and Social Change at Arizona State University, via email. 'Here we have two hominin species that are together. And human evolution is not linear, it's a bushy tree, there are life forms that go extinct.' Since 2002, Reed has been a codirector of the Ledi-Geraru Research Project, which is focused, in part, on searching for evidence of early Homo species. In 2015, the team announced the discovery of the oldest known Homo jawbone at 2.8 million years old. It has also searched for later evidence of Australopithecus afarensis, which first appeared 3.9 million years ago, but there is no sign of these ancient human relatives in the fossil record after 2.95 million years ago — suggesting they went extinct before Homo's first appearance. Australopithecus afarensis is best represented by the famed fossilized remains of Lucy, discovered in 1974 in Ethiopia. Lucy was shorter than an average human, reaching about 3.3 feet (1 meter) in height, had an apelike face and a brain about one-third the size of a human brain. Her fossil showcased a mixture of humanlike and apelike traits and provided proof that ancient human relatives walked upright 3.2 million years ago. When the team discovered the Australopithecus teeth during two separate digs in 2018 and 2020, it compared them with species such as afarensis and another hominin group known as garhi, but they didn't match up. Instead, the scientists believe the teeth belong to a previously unknown species of Australopithecus that walked the Earth after Lucy — and alongside an early Homo species. 'Once we found Homo, I thought that was all we would find, and then one day on survey, we found the Australopithecus teeth,' Reed said. 'What is most important, is that it shows again, that human evolution is not linear. There were species that went extinct; some were better adapted than others, and others interbred with us — we know this for Neanderthals for sure. So anytime that we have another piece to the puzzle of where we came from, it is important.' Cracks in Earth's surface The teeth were found in Ethiopia's Afar region, a key place for researchers seeking answers about human evolution. A variety of preserved fossils have been found there as well as some of the earliest stone tools, Reed said. The Afar region is an active rifting environment — the tectonic plates beneath its earth are actively pulling apart and exposing older layers of sediment that shed light on almost 5 million years of evolution, Reed said. 'The continent is quite literally unzipping there, which creates a lot of volcanism and tectonics,' said study coauthor Christopher Campisano, associate director and associate professor at the Institute of Human Origins and associate professor at the School of Human Evolution and Social Change at Arizona State, in a video the school released. 'At 2 1⁄2, 3 million years ago, these volcanoes spewed out ash that contain crystals called feldspars that allow us to date the eruptions that were happening on the landscape when they're deposited.' The Australopithecus teeth documented in the new study were dated to 2.63 million years ago, while the Homo teeth are from 2.59 million and 2.78 million years ago. But the team is cautious about identifying a species for any of the teeth until it has more data and more fossils. 'We know what the teeth and mandible of the earliest Homo look like, but that's it,' said Brian Villmoare, lead study author and associate professor in the department of anthropology at the University of Nevada, Las Vegas, in a statement. 'This emphasizes the critical importance of finding additional fossils to understand the differences between Australopithecus and Homo, and potentially how they were able to overlap in the fossil record at the same location.' The Australopithecus teeth broadly resembled those of the afarensis species in contour and the size of the molars, but features of the cusps and canine teeth had not been previously seen in afarensis or garhi teeth, Villmoare said. The teeth were also different in shape than those of any Homo species, or of the ancient human relative Paranthropus, known for its large teeth and chewing muscles. 'Obviously these are only teeth,' Villmoare said, 'but we are continuing field work in the hopes of recovering other parts of the anatomy that might increase resolution on the taxonomy.' Even just finding the teeth was a complicated task, according to Campisano. 'You're looking at little teeth, quite literally, individual teeth that look just like a lot of other of the little pebbles spread on the landscape,' he said in the video. 'And so, we have a great team of local Afars that are excellent fossil hunters. They've seen these things their entire lives walking around the landscape.' A blip for evolution The new study is important because it provides insight into a time frame from 3 million to 2 million years ago, a mysterious period in human evolutionary studies, said Dr. Stephanie Melillo, paleoanthropologist and assistant professor at Mercyhurst University in Pennsylvania. Melillo was not involved in this research, but she has participated in the Woranso-Mille Paleontological Research Project in the Afar Triangle of Ethiopia. Part of the problem in learning about this stretch of prehistory is how ancient layers of dirt were deposited over the course of history in eastern Africa. 'Erosion in rivers and lakes were at a low level and only a little bit of dirt was deposited in the Afar,' Melillo wrote in an email. 'That deposited dirt contains the fossils — of our ancestors and all the animals that lived with us. When there is little deposition, there are few fossils.' A key feature helping archaeologists to understand humanity's evolution are structural basins, or 'bowls' on Earth's surface that naturally collect layers of sediment better than the surrounding landscape does — like the Turkana Basin stretching across southern Ethiopia and northern Kenya, Melillo said. Previous research has found evidence to suggest that Homo and Paranthropus coexisted there 1.5 million years ago. The new study focuses on the Afar Depression, a basin to the north of the Turkana. 'This contribution by Villmoare and colleagues demonstrates that in the Afar there was also some other species around with Homo — but it isn't Paranthropus,' Melillo said. 'Instead, they identify this 'non-Homo' genus as Australopithecus. They do a very convincing job of demonstrating why the new fossils are not Paranthropus.' The study adds to growing evidence that Australopithecus was not roaming the Afar Depression alone, she said. A mysterious coexistence When Australopithecus and Homo were alive, the Afar Region, now mostly a semidesert, had much more seasonal variation in rainfall than it does today, Reed said. Millions of years ago, the environment there was still dominated by a dry season, but it was interrupted by a brief wet season. Rivers that carried water across the landscape existed for only part of the year. Few trees grew near the river, and the environment nearby was largely wetlands and grasslands. 'We have a fossil giraffe species that was eating grass, which probably indicates they were stressed as they eat trees and bushes almost every place else,' Reed said. 'Were the hominins eating the same thing? We are trying to find out by examining isotopes in their teeth and microscopic scratches on their teeth.' Understanding whether or not Homo and Australopithecus had the same food sources could paint a portrait of how our ancient ancestors shared or competed for resources, Reed said. The team also wants to try to identify which hominin made the stone tools found at the site. At the moment it's impossible to tell exactly how the two hominins coexisted, but Reed said she is hoping that future findings will provide more answers. 'Whenever you have an exciting discovery, if you're a paleontologist, you always know that you need more information,' Reed said. 'You need more fossils. More fossils will help us tell the story of what happened to our ancestors a long time ago — but because we're the survivors we know that it happened to us.' 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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Ancient, fossilized teeth, uncovered during a decades-long archaeology project in northeastern Ethiopia, indicate that two different kinds of hominins, or human ancestors, lived in the same place between 2.6 million and 2.8 million years ago — and one of them may be a previously unknown species. The discovery provides a new glimpse into the complex web of human evolution. Ten of the teeth, found between 2018 and 2020, belong to the genus Australopithecus, an ancient human relative. Meanwhile, three teeth, found in 2015, belong to the genus Homo, which includes modern humans, or Homo sapiens. The results were published Wednesday in the journal Nature. Such an overlapping of two hominins in the fossil record is rare, which had previously led scientists to believe that Homo appeared after Australopithecus, rather than the two being contemporaries. Australopithecus species walked upright much like modern humans, but had relatively small brains, closer in size to those of apes. The emergence of Homo species, with their larger brains, is easy for people today to view as some sort of evolutionary upgrade on a path to modern humanity. But the coexistence of the two demonstrates that hominins developed, and lived, in multiple varieties at once. 'This new research shows that the image many of us have in our minds of an ape to a Neanderthal to a modern human is not correct — evolution doesn't work like that,' said study coauthor Kaye Reed, research scientist and president's professor emerita at the Institute of Human Origins and emeritus professor at the School of Human Evolution and Social Change at Arizona State University, via email. 'Here we have two hominin species that are together. And human evolution is not linear, it's a bushy tree, there are life forms that go extinct.' Since 2002, Reed has been a codirector of the Ledi-Geraru Research Project, which is focused, in part, on searching for evidence of early Homo species. In 2015, the team announced the discovery of the oldest known Homo jawbone at 2.8 million years old. It has also searched for later evidence of Australopithecus afarensis, which first appeared 3.9 million years ago, but there is no sign of these ancient human relatives in the fossil record after 2.95 million years ago — suggesting they went extinct before Homo's first appearance. Australopithecus afarensis is best represented by the famed fossilized remains of Lucy, discovered in 1974 in Ethiopia. Lucy was shorter than an average human, reaching about 3.3 feet (1 meter) in height, had an apelike face and a brain about one-third the size of a human brain. Her fossil showcased a mixture of humanlike and apelike traits and provided proof that ancient human relatives walked upright 3.2 million years ago. When the team discovered the Australopithecus teeth during two separate digs in 2018 and 2020, it compared them with species such as afarensis and another hominin group known as garhi, but they didn't match up. Instead, the scientists believe the teeth belong to a previously unknown species of Australopithecus that walked the Earth after Lucy — and alongside an early Homo species. 'Once we found Homo, I thought that was all we would find, and then one day on survey, we found the Australopithecus teeth,' Reed said. 'What is most important, is that it shows again, that human evolution is not linear. There were species that went extinct; some were better adapted than others, and others interbred with us — we know this for Neanderthals for sure. So anytime that we have another piece to the puzzle of where we came from, it is important.' Cracks in Earth's surface The teeth were found in Ethiopia's Afar region, a key place for researchers seeking answers about human evolution. A variety of preserved fossils have been found there as well as some of the earliest stone tools, Reed said. The Afar region is an active rifting environment — the tectonic plates beneath its earth are actively pulling apart and exposing older layers of sediment that shed light on almost 5 million years of evolution, Reed said. 'The continent is quite literally unzipping there, which creates a lot of volcanism and tectonics,' said study coauthor Christopher Campisano, associate director and associate professor at the Institute of Human Origins and associate professor at the School of Human Evolution and Social Change at Arizona State, in a video the school released. 'At 2 1⁄2, 3 million years ago, these volcanoes spewed out ash that contain crystals called feldspars that allow us to date the eruptions that were happening on the landscape when they're deposited.' The Australopithecus teeth documented in the new study were dated to 2.63 million years ago, while the Homo teeth are from 2.59 million and 2.78 million years ago. But the team is cautious about identifying a species for any of the teeth until it has more data and more fossils. 'We know what the teeth and mandible of the earliest Homo look like, but that's it,' said Brian Villmoare, lead study author and associate professor in the department of anthropology at the University of Nevada, Las Vegas, in a statement. 'This emphasizes the critical importance of finding additional fossils to understand the differences between Australopithecus and Homo, and potentially how they were able to overlap in the fossil record at the same location.' The Australopithecus teeth broadly resembled those of the afarensis species in contour and the size of the molars, but features of the cusps and canine teeth had not been previously seen in afarensis or garhi teeth, Villmoare said. The teeth were also different in shape than those of any Homo species, or of the ancient human relative Paranthropus, known for its large teeth and chewing muscles. 'Obviously these are only teeth,' Villmoare said, 'but we are continuing field work in the hopes of recovering other parts of the anatomy that might increase resolution on the taxonomy.' Even just finding the teeth was a complicated task, according to Campisano. 'You're looking at little teeth, quite literally, individual teeth that look just like a lot of other of the little pebbles spread on the landscape,' he said in the video. 'And so, we have a great team of local Afars that are excellent fossil hunters. They've seen these things their entire lives walking around the landscape.' A blip for evolution The new study is important because it provides insight into a time frame from 3 million to 2 million years ago, a mysterious period in human evolutionary studies, said Dr. Stephanie Melillo, paleoanthropologist and assistant professor at Mercyhurst University in Pennsylvania. Melillo was not involved in this research, but she has participated in the Woranso-Mille Paleontological Research Project in the Afar Triangle of Ethiopia. Part of the problem in learning about this stretch of prehistory is how ancient layers of dirt were deposited over the course of history in eastern Africa. 'Erosion in rivers and lakes were at a low level and only a little bit of dirt was deposited in the Afar,' Melillo wrote in an email. 'That deposited dirt contains the fossils — of our ancestors and all the animals that lived with us. When there is little deposition, there are few fossils.' A key feature helping archaeologists to understand humanity's evolution are structural basins, or 'bowls' on Earth's surface that naturally collect layers of sediment better than the surrounding landscape does — like the Turkana Basin stretching across southern Ethiopia and northern Kenya, Melillo said. Previous research has found evidence to suggest that Homo and Paranthropus coexisted there 1.5 million years ago. The new study focuses on the Afar Depression, a basin to the north of the Turkana. 'This contribution by Villmoare and colleagues demonstrates that in the Afar there was also some other species around with Homo — but it isn't Paranthropus,' Melillo said. 'Instead, they identify this 'non-Homo' genus as Australopithecus. They do a very convincing job of demonstrating why the new fossils are not Paranthropus.' The study adds to growing evidence that Australopithecus was not roaming the Afar Depression alone, she said. A mysterious coexistence When Australopithecus and Homo were alive, the Afar Region, now mostly a semidesert, had much more seasonal variation in rainfall than it does today, Reed said. Millions of years ago, the environment there was still dominated by a dry season, but it was interrupted by a brief wet season. Rivers that carried water across the landscape existed for only part of the year. Few trees grew near the river, and the environment nearby was largely wetlands and grasslands. 'We have a fossil giraffe species that was eating grass, which probably indicates they were stressed as they eat trees and bushes almost every place else,' Reed said. 'Were the hominins eating the same thing? We are trying to find out by examining isotopes in their teeth and microscopic scratches on their teeth.' Understanding whether or not Homo and Australopithecus had the same food sources could paint a portrait of how our ancient ancestors shared or competed for resources, Reed said. The team also wants to try to identify which hominin made the stone tools found at the site. At the moment it's impossible to tell exactly how the two hominins coexisted, but Reed said she is hoping that future findings will provide more answers. 'Whenever you have an exciting discovery, if you're a paleontologist, you always know that you need more information,' Reed said. 'You need more fossils. More fossils will help us tell the story of what happened to our ancestors a long time ago — but because we're the survivors we know that it happened to us.' Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. Solve the daily Crossword
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Never-before-seen cousin of Lucy might have lived at the same site as the oldest known human species, new study suggests
When you buy through links on our articles, Future and its syndication partners may earn a commission. Roughly 2.6 million-year-old fossilized teeth found in Ethiopia might belong to a previously unknown early human relative, researchers say. The teeth are from a species of Australopithecus, the genus that includes Lucy (A. afarensis). But these newly discovered teeth don't appear to belong to any known species of Australopithecus, according to a new study published in the journal Nature on Wednesday (Aug. 13). What's more, at the same site the researchers found extremely old teeth from Homo, the genus that includes modern humans (Homo sapiens). These teeth may belong to the oldest known Homo species on record, which scientists haven't yet named, the study found. These new discoveries show that at least two lineages of early hominins — a group that includes humans and our closest relatives — coexisted in the same region around 2.6 million years ago, the researchers said. Discoveries at Ledi-Geraru archaeological site The researchers found the teeth at the Ledi-Geraru archaeological site in northeastern Ethiopia, which is known for earlier groundbreaking discoveries: a 2.8 million-year-old jawbone that's the oldest known human specimen, as well as some of the oldest known stone tools made by hominins, which date to 2.6 million years ago. Paleontologists and archaeologists hypothesize that the region was an open and arid grassy plain during this period, based on grass-eating animal fossils from that time. The area offered resources Homo and Australopithecus could use, Frances Forrest, an archaeologist at Fairfield University in Connecticut who was not involved with the new research, told Live Science in an email. Grasslands and rivers would have provided water to drink, plants to eat and large animals to hunt. Related: 'Huge surprise' reveals how some humans left Africa 50,000 years ago But the unusually rich fossil record in this area could also be because of excellent preservation of remains, due to volcanic eruptions, for example — not necessarily that this was a hominin hotspot, Forrest said. Australopithecus and Homo teeth In the new study, the researchers used layers of volcanic ash above and below the newly discovered fossils to determine their age. Of the 13 teeth discovered, the team found 10 are 2.63 million years old and belonged to an unidentified species of Australopithecus, which for now the researchers are calling the Ledi-Geraru Australopithecus. Previously, researchers had found remains in the region from A. afarensis and Australopithecus garhi. But the newfound teeth look different from the teeth of those species. "It doesn't match any of these, so it could be a new species," study co-author Kaye Reed, a paleoecologist at Arizona State University, told Live Science. However, the research team hasn't officially named it as a newly identified species because the teeth don't have any especially unique features. "In the fossil record, researchers usually define a new species by finding anatomical traits that consistently differ from those of known species," Forrest said, adding that the evidence from this discovery is too limited to define a new species. The researchers also identified two teeth that are 2.59 million years old, and one that is 2.78 million years old, all belonging to the genus Homo, which Reed believes are from the same species as the oldest known Homo specimen — the jawbone discovered in Ledi-Geraru — although this hasn't been confirmed. Image 1 of 2 Study authors J. Ramón Arrowsmith and Christopher J. Campisano examine the geology of the area near the new fossils. Image 2 of 2 An aerial view of the Ledi-Geraru excavation site, home of the newly discovered fossilized teeth, and where the oldest known Homo specimen has been uncovered. The new discovery means at least three hominin species were living in this region of Ethiopia before 2.5 million years ago: the Homo and Australopithecus species these teeth belong to, as well as A. garhi. At the same time, A. africanus lived in South Africa, and Paranthropus, another hominin genus, lived in what is now Kenya, Tanzania and southern Ethiopia. This evolutionary trial-and-error within the extended hominin family is why humans' evolutionary tree is considered "bushy" rather than linear. "It has become clear over the last decade or so that during most of our evolutionary history … there have been multiple species of human relatives that existed at the same time," John Hawks, an anthropologist at the University of Wisconsin-Madison who was not involved in the new research, told Live Science. "The new paper tells us this is happening in Ethiopia … [in] a really interesting time frame, because it's maybe the earliest population of our genus Homo." Next steps The research team is now studying the enamel on the newfound teeth, as their chemistry can reveal what these species were eating. This may shed light on whether these hominins were eating the same things and competing for similar resources. "Right now, we can say very little with certainty about direct interaction between Australopithecus and Homo," Forrest said. "We know that both genera sometimes overlapped in time and space, but there is no behavioral evidence linking the two." RELATED STORIES —300,000-year-old teeth from China may be evidence that humans and Homo erectus interbred, according to new study —78,000-year-old footprints from Neanderthal man, child and toddler discovered on beach in Portugal —Stunning facial reconstructions of 'hobbit,' Neanderthal and Homo erectus bring human relatives to life Chimpanzees and gorillas live in some of the same forests, Hawks pointed out, but they're mostly geographically separated from each other, not living side by side. The fact these early hominins may have lived closer together than primates typically do now is interesting, Hawks said. "They probably weren't eating the same things," Reed noted. "But right now we don't really know." The researchers are also searching for more information and fossils at the site. "Everything we find is a piece in the puzzle of human evolution," Reed said. Human evolution quiz: What do you know about Homo sapiens?
