Illustration of an extinct Glyptodon. This is an armadillo-like giant that lived during the last Ice Age. (Image credit: Daniel Eskridge/Stocktrek Images via Getty Images)
The footprint of humanity can be seen all over the globe today, from the tall skyscrapers that make up our modern metropolises to ancient monuments like the pyramids. Our sprawling open fields and roads linking them together are also a result of human activity. What would the world look like without humans?
Scientists paint a picture that depicts a beautiful wilderness with a variety of species. Trevor Worthy, a paleontologist who is also an associate professor at Flinders University, Australia, said that he believes it would be more vegetated with a greater variety of animals spread across all continents, except Antarctica.
Our extinct human relatives, the Neanderthals and our modern humans, might still be alive in a world without them. They would have undoubtedly changed the landscape.
Related: What was the first species that humans drove to extinction in history?
Humans have shaped the planet at the expense many species, including the dodo (Raphuscucullatus), and the Tasmanian Tiger (Thylacinus cucullatus), which we drove extinct through hunting and habitat destruction.
According to Live Science, the Earth's extinction rate is now more than 100 times higher than it would have been without humans. This was in addition to the fact that the Cretaceous-Paleogene extinction event (K-Pg), which wiped out around 80% of animal species, 66 million year ago, has not been reported previously. This means that humans have hit the planet like an asteroid and the dust continues to settle as wildlife continues its decline.
Worthy stated that his great-great grandfather was able observe thousands of parakeets in natural landscapes. My father saw several hundred and my grandfather only saw one. I am lucky to see two in the forest.
Human-driven decline in nature suggests that Earth would be much wilder without us. Some lost giants like moas stand out more than others. Over millions of years, this group of ostrich-like birds, some measuring up to 11.8 feet (3.6 meters) high, was created in New Zealand. Worthy says that all nine moa species were extinct within 200 years of humans arriving on the birds' lands 750 year ago.
Recent examples of large animals that have been extinct are the giant moasts and Haast’s eagles. Their extinctions can be attributed to human activities such as unsustainable hunting or introduction of invasive species in new habitats. These are indicators of how our relationship with large mammals may have been elsewhere.
It is crucial to ensure the survival of large animals if you want to speculate about an Earth without people, because these creatures have such a significant impact on landscapes.
A composite image showing wildlife in the Serengeti. (Image credit to ugurhan via Getty Images
Soren Faurby is a senior lecturer of zoology at University of Gothenburg, Sweden. He believes that humans played a major role in the disappearance of large mammals dating back thousands of years. A 2015 study he led, published in Diversity and Distributions, suggested that Earth would look a lot like the modern-day Serengeti, an African ecosystem teeming full of life.
Related: How long will most species survive before becoming extinct?
This scenario would see extinct animals that are similar to the ones found today in the Serengeti, including elephants, rhinos, and lions, living across Europe. Instead of African lions, (Panthera Leo), there would be cave lions instead (Panthera Spelaea), which are slightly larger and lived in Europe for about 12,000 years. Faurby says that the Americas would house elephant relatives and huge bears as well as unique species like giant ground sloths and Glyptodon, which are car-sized armadillo relatives.
Faurby explained to Live Science that there would be more large mammals in a world without humans.
Elephants and large animals like elephants are very determined about finding food and will not tolerate any obstructions. Faurby stated that if you are large enough it may be easier to knock down a tree and then eat the leaves. He also said that if there are many large mammals, then there is less wooded vegetation.
The room's hairy elephant
Megafauna is a term for large animals such as elephants. The world was rich in megafauna during the Pleistocene (2.6 million to 11.700 years ago), but many died off as the ice era ended or over the millennia. According to a 2020 study published in Proceedings of the National Academy of Sciences, 38 genera of large mammals went extinct in North America after the last ice age. Overhunting and natural climate change have been the major causes of large animal declines over the past century.
A Nature 2021 study concluded that climate change eventually decimated woolly mammoths (Mammuthus primigenius), and other Arctic-dwelling megafauna, which survived the end Pleistocene. The warming climate had made it too dry for the plants they ate to survive.
Humans did, however, hunt mammoths. Faurby and other scientists believe that humans are the main factor in mammoths' extinction. They argue that mammoths were able to survive climate changes before humans arrived and could have survived until today if they weren't under the extra pressure from humans.
Related: How could 2 degrees of warming make a difference to the planet?
Illustration of woolly mammoths traversing snow-covered hills. (Image credit: Daniel Eskridge/Shutterstock)
Christopher Doughty is an associate professor at Northern Arizona University and ecosystem ecologist. He models how large animals, both past and present, move nutrients and seeds around by eating and urinating. His research suggests that the transport of essential elements like phosphorus, calcium, and magnesium has declined by more than 90% due to the extinctions of large animals.
Doughty believes that elements would be distributed more evenly across the landscape if there were no humans. This would result in more fertile soil which would increase ecosystem productivity. Doughty stated that if elements are less cohesive in ecosystems, productivity will be lower.
According to Doughty, humans tend to cluster elements together through practices like agriculture and the creation fenced-off zones. These areas are less fertile over time than wild systems. Higher fertility means that plants can use their resources to produce more fruits and flowers. This could make the world more vibrant and provide more food for animals.
It's possible that the climate is different. While it's hard to know how megafauna and humans may have affected climate changes thousands of years back, it's easier to assess our current impact on Earth's climate. Global warming, which is caused by human activities like burning fossil fuels, has raised the average temperature of the world by 1.8 degrees Fahrenheit (1degree Celsius) since the start of the 20th century. Without us, Earth would have been about 1.8 degrees Fahrenheit (1 degree Celsius) cooler.
A Nature study in 2016 concluded that human-caused global warming will delay an ice age by at most 100,000 years. The ice age wasn't due until another 50,000 years. However, it was not due until that time if humans weren't present.
Humans are inexorable
Modern humans (Homo sapiens) are not the only hominins. Taking us out of the equation may have allowed for Neanderthals. Although scientists aren't certain why Neanderthals died out around 40,000 years ago (because they interbred and H. sapiens), some parts of their DNA still exist in some of ours. While there were many possible reasons Neanderthals died, the main reason is that we are one of them.
Chris Stringer is a professor at the Natural History Museum in London and a research leader on human origins. He believes that Neanderthals disappeared because of competition for resources. He told Live Science that if they hadn't existed, if they hadn't arrived in Europe 45,000 years or 50,000 years ago I believe they would still be here."
Related: What if Neanderthals hadn't gone extinct?
At the Natural History Museum in London, a male Neanderthal replica. (Image credit: Chettaprin.P/Shutterstock.com)
Stringer stated that Neanderthals lived complex lives in Europe and had similar characteristics to modern humans. However, they were unable to adapt to climate change and were very few in numbers with low genetic diversity. This is bad news for all species as it indicates inbreeding, ill health and is a sign of inbreeding. Stringer stated that Neanderthals were probably "already in trouble" and that modern humans may have contributed to their current state of affairs.
Humans may not have been as stubborn as Neanderthals. Scientists still have to learn more about the Denisovans, another human lineage that existed around the same time period as modern humans and Neanderthals. This lineage is closer to Neanderthals in appearance and genes, but it is distinguished from Neanderthals due to its large molars.
Denisovans are likely to have interbred with humans as evidence of Denisovan DNA is found in modern-day humans in Oceania and New Guinea. This finding suggests that Denisovans were in Southeast Asia, possibly interacting with the ancestors that settled further east. Science published a 2012 study. Denisovans also partnered with Neanderthals in Siberia, where the fossilized remains of a Denisovan-Neanderthal hybrid were found, Live Science previously reported .
Together with fossil evidence, these Denisovan interactions suggest that they had a wider geographic range than Neanderthals and were therefore more adaptable than the Neanderthals. Stringer also believes that DNA evidence suggests that Denisovans likely had more genetic diversity than Neanderthals. They might have been a better option for survival than the Neanderthals.
Both Neanderthals or Denisovans are important because they could have traced a similar path as H. sapiens, which moved from hunting-gathering to agriculture after the last ice age.
Stringer stated that there is no reason why Neanderthals and Denisovans wouldn't have been able to do it eventually, provided they had enough time. He suggested that they may have overcome potential intellectual weaknesses, though it's not certain they did. Maybe the world would not look so different.
Stringer stated that they could also be making the same mistakes as us. "Global warming could still have occurred, but not with us driving it. "Who knows?"
Original publication on Live Science