Study.. This is how planet Earth would appear if modern humans did not exist
Human activity in the fields represents sprawling open farming, the ways that tie everything together.
Humanity’s footprint can be seen across the planet today, from the towering skyscrapers outlining our modern capitals to the pyramids and other ancient ruins of our past, but what would the world look like if humans had not existed before?
Live Science published a scientific paper that included data quoting scientists in which they painted a picture of pure wilderness and an abundance of species, from the familiar to the unfamiliar.
"I think it would be a much more botanical place with a wealth of animals, of great size spread across all continents except Antarctica," Trevor Worthy, a paleontologist and assistant professor at Flinders University in Australia, told Live Science.
A world without modern humans might also mean that our extinct human relatives, such as Neanderthals, would still exist. And they, no doubt, would have changed the landscape as well.
Humans shaped the world at the expense of many species, from the dodo (Raphus cucullatus) to the Tasmanian tiger (Thylacinus cynocephalus), which have driven us to extinction through activities such as hunting and habitat destruction.
The extinction rate on Earth today is more than 100 times what it would be without humans, according to the most conservative estimates, and has not been higher since the Cretaceous and Paleogene (K-Pg) extinction event that wiped out nearly 80% of animal species, including dinosaurs. Not floating, 66 million years ago, Live Science previously reported.
In other words, humans hit this planet like an asteroid, and the dust continues to settle as wildlife continues to deteriorate.
Serengeti System
Soren Forbe, senior lecturer in zoology at the University of Gothenburg in Sweden, believes that humans played a major role in the disappearance of many large mammals thousands of years ago. He led a 2015 study, published in the journal Diversity and Distributions, which suggested that without humans, Earth would be much like the modern-day Serengeti, an African ecosystem teeming with life.
In this scenario, extinct animals similar to those found in the Serengeti today - including elephants, rhinos and lions - would live across Europe. For example, instead of African lions (Panthera leo), there are still cave lions (Panthera spelaea), a slightly larger species that lived in Europe until about 12,000 years ago. Meanwhile, the Americas will be home to large relatives of elephants and bears, along with unique species, according to Forbe.
"In a world without humans, there would be much more diversity from large mammals, and if you saw more diversity from large mammals, you tend to see a more open habitat," Furby said.
Elephants and other large animals identify well when finding food, and will not tolerate unnecessary obstacles. "If you're old enough, it might be easier to knock on a tree and eat the fresh leaves on top of it," Furby said. But also, if there are a large number of large mammals, there is a tendency to have fewer wooded plants in the first place, he said.
Large animals, such as elephants, are known as megafauna. During the last Ice Age (2.6 million to 11,700 years ago), the world was rich in megafauna, but most of them died out with the end of the Ice Age, or in the thousands of years since.
For example, about 38 genera of large animals became extinct in North America at the end of the last Ice Age, according to a 2020 study published in the Proceedings of the National Academy of Sciences.
Over the past century, scientists have debated whether natural climatic changes or human activities, such as poaching, were the main reason for the decline of these large animals.
A study published in 2021 in the journal Nature concluded that climate change eventually wiped out woolly mammoths (Mammuthus primigenius) and other Arctic megafauna that survived the end of the Ice Age.
However, humans did hunt mammoths. Scientists who believe that humans may have been the main factor in their extinction, such as Furby, argue that mammoths survived climate change before humans appeared and would likely have survived to this day if not for the additional pressure that humans placed on them.
Christopher Dottie, associate professor and ecologist at Northern Arizona University, is modeling how large animals past and present transport seeds and nutrients through eating and defecation.
His work indicates that the transport of elements such as phosphorous, calcium and magnesium, which are important for life, was reduced by more than 90% through the extinction of large animals.
Dottie posits that without humans, the elements would be evenly distributed across the landscape. This means more fertile soil, which makes ecosystems more productive.
Humans tend to group the elements together through practices such as farming and creating fenced areas, so that these areas become less fertile over time compared to land systems, according to Doughty.
Greater fertility means plants can allocate their resources toward more fruits and flowers, so the world looks more vibrant and feeds more animals.
While it is difficult to determine how humans and megafauna affected climate change thousands of years ago with evidence obscured over time, it is much easier to judge our impact on Earth's climate today.
Through global warming, caused by activities such as burning fossil fuels, humans have raised the average global temperature by about 1.8°F (1°C) since the beginning of the 20th century. Therefore, the Earth would have been at least much cooler without us.
A 2016 study published in Nature concluded that human-caused warming will delay the next Ice Age by at least 100,000 years.
And it wasn't due for another 50,000 years, though, even without human delay, so it's unlikely that Earth would be in the middle of another ice age today if we didn't exist.
Humans are inevitable
It seems that scientists aren't sure why Neanderthals went extinct about 40,000 years ago, but due to interbreeding with Homo sapiens, parts of their DNA are present in some of us. There were likely multiple causes of Neanderthal death, but we're a prime suspect.
Chris Stringer, professor and research leader in human origins at the Natural History Museum in London, believes competition for resources was a factor in the Neanderthals' disappearance. "If we weren't around, if we didn't come to Europe 45,000 or 50,000 years ago, I think they would probably stay here," he told Live Science.
According to Stringer, Neanderthals had a complex life in Europe, similar to modern humans, but they had difficulty adapting to climatic changes and were relatively few in number, with low genetic diversity. This is bad news for any kind, as it is a sign of inbreeding and ill health. Neanderthals were likely "really in trouble, and when modern humans got there as well, I think that may have pushed them over the edge," Stringer said.
Source: Live Science
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