How ancient reptile footprints are rewriting the history of when animals evolved to live on land
Scientists in Australia have identified the oldest known fossil footprints of a reptile-like animal, dated to around 350 million years ago.
The discovery suggests that after the first animals emerged from the ocean around 400 million years ago, they evolved the ability to live exclusively on land much faster than previously assumed.
'We had thought the transition from fin to limb took much longer,' said California State University paleontologist Stuart Sumida, who was not involved in the new research.
Previously the earliest known reptile footprints, found in Canada, were dated to 318 million years ago.
The ancient footprints from Australia were found on a slab of sandstone recovered near Melbourne and show reptile-like feet with long toes and hooked claws.
Scientists estimate the animal was about 2 1/2 feet (80 centimeters) long and may have resembled a modern monitor lizard. The findings were published Wednesday in Nature.
The hooked claws are a crucial identification clue, said study co-author and paleontologist Per Ahlberg at Uppsala University in Sweden.
'It's a walking animal,' he said.
Only animals that evolved to live solely on land ever developed claws. The earliest vertebrates -- fish and amphibians – never developed hard nails and remained dependent on watery environments to lay eggs and reproduce.
But the branch of the evolutionary tree that led to modern reptiles, birds and mammals – known as amniotes -- developed feet with nails or claws fit for walking on hard ground.
'This is the earliest evidence we've ever seen of an animal with claws,' said Sumida.
At the time the ancient reptile lived, the region was hot and steamy and vast forests began to cover the planet. Australia was part of the supercontinent Gondwana.
The fossil footprints record a series of events in one day, Ahlberg said. One reptile scampered across the ground before a light rain fell. Some raindrop dimples partially obscured its trackways. Then two more reptiles ran by in the opposite direction before the ground hardened and was covered in sediment.
Fossil 'trackways are beautiful because they tell you how something lived, not just what something looked like,' said co-author John Long, a paleontologist at Flinders University in Australia.
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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Science and Educational Media Group and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.
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The Independent
an hour ago
- The Independent
Researchers discover two new species after genetic testing
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Daily Mail
a day ago
- Daily Mail
Look familiar? Scientists reveal what Neanderthals and Denisovans would look like TODAY if they hadn't gone extinct
For the last 40,000 years, Homo sapiens have been the only human species walking the Earth. Our ancient ancestors died out thousands of years ago, leaving behind nothing but fossils, a few scattered artefacts, and lingering traces in our DNA. But what if things had turned out differently? MailOnline has asked the experts to find out what the world might look like if the Neanderthals and Denisovans hadn't gone extinct. Surprisingly, they say that our distant evolutionary cousins might not be all that different to modern humans today. However, they might have had a hard time fitting in with our fast-paced, highly social societies. Dr April Noel, a palaeolithic archaeologist from the University of Victoria, told MailOnline: 'The idea that Neanderthals were hunched over, dim-witted individuals with no thought beyond their next meal is no longer tenable. 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Neanderthals and modern humans interbred when we overlapped and would likely continue to into the future. Scientists say that male Neanderthal and Homo sapiens female couples would have had the highest likelihood of producing fertile hybrid offspring (AI-generated impression) Could modern and ancient populations merge? Scientists say it is extremely likely that Homo sapiens, Neanderthals, and Denisovans would eventually merge if no species went extinct. The resulting species would have genetic traits from all three groups. Since modern humans reproduce faster and build larger communities, they would likely represent more of the genetic material. This is essentially what happened to these species in the past. Our modern genome contains traits passed on from breeding with these ancient species before they disappeared. But Dr Zeberg points out that Denisovan genes are responsible for 'high altitude adaptation for Tibetans and some influence on lip shape in Latin American populations.' 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Modern humans developed genes that allowed us to become more sociable, develop larger social networks, and work with our fellow humans. Dr Noel says: 'Unlike their modern human contemporaries, Neanderthals lived in small, fairly isolated groups. 'If there was an accident that killed a number of their hunters or some other crisis occurred, they did not always have others to reach out to. As a result, their numbers would drop below what you need to be sustainable.' Dr Noel points out that research into Neanderthal genes suggests they were less cognitively flexible, had greater difficulties processing language, and lacked genes related to self-awareness, creativity, and behaviours intended to benefit others. 'In the highly connected world we all live in, I think Neanderthals would have been left behind, or at least, left out,' says Dr Noel. In a world where Neanderthals lived alongside other human species, this could really change the way society was structured. Professor Spikins says that while modern humans became 'tamer, more playful and more friendly to each other,' those changes came alongside 'being a bit easily led'. She adds: 'If Neanderthals were better at not "following the herd" and more of those tendencies were present, I bet much of our world would be different; they might not be easily swayed by social media!' How would the world be different? If Neanderthals and Denisovans hadn't gone extinct thousands of years ago, the world might be a very different place. From the evidence we have of these ancient species, we know that they lived in much smaller communities and had a far more limited impact on the land. In fact, Dr Zeberg points out that modern humans appear to be unique in the way that we modify the world around us through agriculture and large cities. One strange consequence of this is that a world where Homo sapiens are not dominant might mean a world without pets. There is no evidence that Neanderthals and Denisovans attempted to nurture relationships with animals through domestication - that means no horses, cats, dogs or even modern agricultural species like cattle and sheep. But with more of our relative anti-social genes, humanity may also have avoided some of its more destructive tendencies. Professor Spikins says: 'If Neanderthals had been the ones to survive, we might not have the problem we have with climate change, as their tendency to be more isolated within their separate groups might have limited how technology spread and got used, and how much the environment got exploited.' THE DENISOVANS EXPLAINED Who were they? The Denisovans are an extinct species of human that appear to have lived in Siberia and even down as far as southeast Asia. The individuals belonged to a genetically distinct group of humans that were distantly related to Neanderthals but even more distantly related to us. Although remains of these mysterious early humans have mostly been discovered at the Denisova Cave in the Altai Mountains in Siberia, DNA analysis has shown the ancient people were widespread across Asia. Scientists were able to analyse DNA from a tooth and from a finger bone excavated in the Denisova cave in southern Siberia. The discovery was described as 'nothing short of sensational.' In 2020, scientists reported Denisovan DNA in the Baishiya Karst Cave in Tibet. This discovery marked the first time Denisovan DNA had been recovered from a location that is outside Denisova Cave. How widespread were they? Researchers are now beginning to find out just how big a part they played in our history. DNA from these early humans has been found in the genomes of modern humans over a wide area of Asia, suggesting they once covered a vast range. They are thought to have been a sister species of the Neanderthals, who lived in western Asia and Europe at around the same time. The two species appear to have separated from a common ancestor around 200,000 years ago, while they split from the modern human Homo sapien lineage around 600,000 years ago. Last year researchers even claimed they could have been the first to reach Australia. Aboriginal people in Australia contain both Neanderthal DNA, as do most humans, and Denisovan DNA. This latter genetic trace is present in Aboriginal people at the present day in much greater quantities than any other people around the world. How advanced were they? Bone and ivory beads found in the Denisova Cave were discovered in the same sediment layers as the Denisovan fossils, leading to suggestions they had sophisticated tools and jewellery. Professor Chris Stringer, an anthropologist at the Natural History Museum in London, said: 'Layer 11 in the cave contained a Denisovan girl's fingerbone near the bottom but worked bone and ivory artefacts higher up, suggesting that the Denisovans could have made the kind of tools normally associated with modern humans. 'However, direct dating work by the Oxford Radiocarbon Unit reported at the ESHE meeting suggests the Denisovan fossil is more than 50,000 years old, while the oldest 'advanced' artefacts are about 45,000 years old, a date which matches the appearance of modern humans elsewhere in Siberia.' Did they breed with other species? Yes. Today, around 5 per cent of the DNA of some Australasians – particularly people from Papua New Guinea – is Denisovans. Now, researchers have found two distinct modern human genomes - one from Oceania and another from East Asia - both have distinct Denisovan ancestry. The genomes are also completely different, suggesting there were at least two separate waves of prehistoric intermingling between 200,000 and 50,000 years ago. But what they did not expect to find was individuals from East Asia carry a uniquely different type.
BBC News
2 days ago
- BBC News
CrowdScience Why are twins special?
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