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Important: This report contains details that may be disturbing to some readers.
The son (or daughter) of one of our ancient ancestors, just three years old and still teething, walked through the wind-tossed grass of the South African savannah 2.8 million years ago.
The young Australopithecus africanus had no idea it was being watched from above. And, without anyone noticing its approach, a huge bird of prey swooped down, grabbed the child and killed it.
It is not known for certain which species of bird ate the human child, known as the "Taung boy". But the puncture marks over their eye sockets are consistent with the talons of eagles, which hunt their prey this way. Sometimes they store part of their game in a tree and take the rest back to their nest.
The Stone Age was a dangerous time to live. Megafauna reigned throughout the world.
The first humans lived alongside mammoths, mastodons, giant ground sloths, saber-toothed tigers, and enormous birds that preyed on children.
For tens of millions of years, between the fall of non-avian dinosaurs and the Great Ice Age, the skies were dominated by these giants. And his reign may have determined the course of human evolution in profound and overlooked ways.
Some of them are believed to have left their mark on the legends of birds that grabbed children. They remained in our culture across the planet long after real birds became extinct.
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Credit, Attie Gerber/Getty Images
Child-hunting eagles may be more than just ancient history.
There is a 19th century newspaper account from the US state of Tennessee about a child who was carried away by a "large gray eagle", which swooped down and "sank its immense claws into the boy's clothing".
A maid chased the bird, which flew away. And, just over 3 km away, the eagle deposited its prey on the ground for a moment.
A nearby hunter "shouted vigorously", startling the bird, and thankfully the "pretty, healthy, rosy boy" emerged from the experience unharmed.
Where did the monstrous birds come from?
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When the non-avian dinosaurs were wiped off the planet, the sky was covered in dust and most plants became extinct.
The animals had little food, except for seeds, which were ideal for birds. And, in the absence of predators, some small land birds with beaks have managed to evolve into giants.
Some of them were vegetarians, like the Dromornithidae of Australia, known as the "demon ducks of perdition". They were very similar to today's ducks, but 100 times larger and heavier than cows.
Some took flight to become enormous ocean predators, like Pelagornis sandersi, from South Carolina, now part of the United States. The species is the largest known flying bird to have ever lived on the planet and its enormous wingspan reached seven meters.
Others filled the vacancies with the extinction of the main terrestrial predators, such as tyrannosaurs. Where large prey is available, even larger predators develop.
These were the monstrous birds that our ancestors had to face.
Modern and ancient tracks
"Ever since primates appeared, there have been birds of prey," says primatologist Scott McGraw, from Ohio State University, in the United States. "And birds of prey have always targeted primates as prey, including us and our relatives."
The influence of ancient conflicts between our ancestors and giant birds can still be seen in wildlife today.
McGraw examined the remains of more than 600 modern primates killed by birds of prey, such as the African crowned eagle.
He discovered in the Taï forest in Côte d'Ivoire striking similarities to the claw marks left on the remains of the Taung boy.
In several skeletons, the monkeys had lesions on the orbital floor (a bony surface located inside the eye socket), "where the eagle had plucked the eyes out with its beak or claws," explains McGraw.
"One of our researchers went down to the fossil deposit, removed the Taung boy and concluded that the injury was identical."
Credit, Natural History Museum of Los Angeles County, 1981
McGraw believes that birds of prey routinely fed on our human ancestors and that predation by birds may have been one of the most important selective forces in the evolution of primates, the order to which humans belong.
"If we go back now and take a closer look at the sets of [human] fossils we've collected over the years, there's a good chance (now that we know what to look for) that we'll find other injuries caused by birds of prey," he explains.
"If what we're observing in Taï is any indication, this is normal."
How predatory birds shaped our evolution
There is little doubt in the paleoanthropological record that the first humans were prey animals, according to archaeologist James Cole, director of applied sciences at the University of Brighton in the United Kingdom.
"Particularly early hominins, like the baby Australopithecus africanus that was eaten by an eagle," he said.
Cole claims that our ancient ancestors were dinner for many predator species. "We were preyed upon, for sure."
Our predators included birds, leopards, hyenas and giant crocodiles. And the need to escape them would have been an important evolutionary pressure on our ancestors. Dining with giant birds is believed to have shaped our bodies and our minds.
Our ability to stand on two legs, for example, would have helped us visualize predators. Cooperation and altruism, interdependence and mutual protection may also have helped us.
Group size has become very important, according to Cole. For him, “there is safety in quantity”.
When it comes to escaping predatory birds, the larger the social group, the better, explains McGraw.
Pursuit predators, such as lions or wolves, actively pursue their prey. But birds of prey are often ambush predators.
They are stealthy and, in the case of crowned eagles, hide in trees until the right moment to attack arrives.
This indicates that the human tendency to socialize may have originated from the need to specifically escape predatory birds. With this, several people could be alert to possible surprise attacks, which is known as the "many eyes effect".
Credit, Paul Grace Photography Somersham/Getty Images
Cole highlights that larger groups may also have contributed to the emergence of the language. He explains that in a large group, "you start to have specialized roles."
“When you have some people doing one job while others do different activities, it requires coordination,” explains Cole. "And when a group begins to fragment like this, coordination cannot rely solely on line of sight."
For simple communications like hand gestures to work, people need to see each other, Cole points out. But when it's necessary to coordinate beyond line of sight (to warn of an approaching predator, for example), "that's when language really starts to gain importance."
So pressure to avoid death from above may have kickstarted the evolution of language, McGraw suggests.
Evidence shows that most primates use generalized alarms for different types of predators. The same call is used for lions and leopards, for example.
But with birds of prey, they respond to specific calls. And McGraw points out that this signaling behavior can be interpreted as a precursor to human language.
Meet the culprits: eagles and teratornis
It is believed that the largest encounter between giant predatory birds and our human ancestors took place on the American continent.
Ancient Americans would have crossed paths with teratornis, huge carnivorous birds similar to condors that could swallow their prey whole.
Towering above the ground, the wingspan of these birds was six meters. They were predators as well as scavengers.
These birds were so large that they could take off simply by spreading their wings and catching an updraft, according to Joanne Cooper, curator of bird anatomical collections at the Natural History Museum in London.
Teratornis reigned in the skies for about 25 million years, until their extinction about 10,000 years ago — well after the arrival of the first humans on the American continent.
Teratornis may have inspired the legends of thunderbirds, according to Cooper. In Native American mythology, the thunderbird has a colossal wingspan and is believed to control lightning and thunder.
The incredible teratornis (Aiolornis incredibilis) terrorized southern California and the Nevada region, in North America, with its wingspan of up to 5.5 meters.
Further north, in Oregon, Teratornis woodburnensis had a wingspan of four meters. This monster of the sky lived around 12 thousand years ago and its remains were found alongside mammoths, mastodons and giant sloths, as well as the first human beings.
Credit, Gunter Marx Photography/Getty Images
On the other side of the world, in New Zealand, there is the Maori legend of Te Hokioi, an immense eagle that kidnapped children. It is believed to have been based on a real species, the huge and extinct Haast's eagle, experts say.
The Haast's eagle was "basically a flying tiger," according to Cooper. It was about twice the weight of an adult harpy eagle, one of the largest eagles alive today.
The Haast's eagle preyed on another giant, but terrestrial bird: the moa, four meters tall.
The giant eagle would dive (as its weight provided considerable acceleration) and hit its prey in the back with its 10 cm long claws, knocking it completely to the ground.
“We saw huge claw marks on the pelvises of some moas,” explains Cooper. She highlights that Haast's eagle would have been capable of attacking humans.
"Children were certainly at risk," she said. "It must have been formidable and terrifying."
Perhaps it is also for this reason that the dominant legends about birds that kidnap children in Maori and North American cultures have persisted. And in Greek mythology, storks didn't deliver babies, they stole them.
"When these birds fly over us, they cast a shadow," explains Cooper, "and they cast a long cultural shadow across the world."
How we survived the giants
Giant predatory birds reigned over the planet's skies for about 50 million years, until, 2.6 million years ago, the Earth entered the Great Ice Age, in the Pleistocene period.
The Pleistocene was a time of severe climate fluctuations, which is believed to have driven human evolution.
On the other hand, at the end of that period (11,700 years ago), giant mammals were extinct and the largest predatory birds had also disappeared.
Scientists don't know for sure whether climate change or human hunters were responsible for the megafauna's disappearance. But the expansion of humans and the way we changed the ecosystem occurred simultaneously with the loss of up to 95% of all megafauna on the planet.
"We were trying to eat them or compete with them," explains Cooper. She indicates that perhaps this explains the tension between humans and birds of prey, which persists to this day.
"We're fascinated by them, we revere them, but we're not necessarily very happy living next to them."
With the end of the Pleistocene, the planet's climate began to stabilize. The glaciers retreated and humans began farming.
It was the dawn of a new era. The era of human beings.
Read the original version of this report (in English) on the BBC Earth website.
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