Exactly when our story began is still up for debate, but consensus agrees that humans first appeared in Africa some 2.3 million years ago with the evolution of Homo habilis from a species of Australopithecus.
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These early humans, whose name means ‘handy man’, were the first of our genus (Homo) and the first primate to use and manufacture stone tools - a hallmark of humanity.
Since then, many more human species have evolved and sought new territories away from Africa, travelling to all four corners of the world. As they did so, they’d have run into some truly terrifying beasts; some as large and powerful as tanks, and others no bigger than a small child yet just as deadly as creatures ten times their size.
A lot of these so-called ‘monsters’ survived alongside humans for many thousands of years, but nearly all of them eventually succumbed to extinction - many by our ancestors’ hands. These extinctions, which followed humans wherever they went, makes you re-evaluate who the real terrors of prehistory may have been.
Meet the prehistoric beasts that would have terrified early man
Smilodon
Of the roughly 70 different species of sabre-tooth cats, none are more well known than Smilodon - the most emblematic species of its diverse family and one of the last surviving sabre-tooth cats.
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Smilodon lived in the Americas during the Pleistocene (2.5 million to ~10,000 years ago), overlapping with those humans who first discovered the ‘New World’ roughly 23,000 years ago. Although they’re often called sabre-tooth tigers, Smilodon were not tigers; instead they belonged to a large, extinct family of big cats known as Machairodonts.
Like many other Machairodonts, Smilodon were built more like bears than today’s lions and tigers. They had stout, muscular hindlimbs and long, grasping forelimbs. Their most characteristic features, though, were their canines, which measured nearly a foot from root to tip. These adaptations made Smilodon formidable ambush predators that specialised in pouncing on their prey.
Humans lived alongside Smilodon for thousands of years, competing with them for similar prey such as mammoths, bison, and camels. Some think Smilodon may have even preyed on humans, though no direct evidence has yet been found.
There is, however, evidence of another large, prehistoric cat sinking their canines into the skull of one of our distant cousins, Paranthropus robustus, at a site in South Africa, dated to 1.8 million years ago. It’s not beyond the realms of imagination to think that Smilodon may have done the same to humans in the Americas.
Gigantopithecus
Just one look at this 10-foot-tall primate and it’s clear how it has earned itself the nickname, ‘the real life bigfoot’. Gigantopithecus lived in south China during the Pleistocene, inhabiting subtropical, evergreen forests. Only teeth and several jaw bones of this giant ape have so far been found, but from these researchers have been able to deduce its size, how it lived, and maybe even how it died.
Like their closest living relatives, orangutans, Gigantopithecus were vegetarians and survived largely on a diet of leaves, tubers, and fruits. We know this because of small stones, known as phytoliths, found on their teeth. A lot of these phytoliths come from fruits, figs in particular, and tell us that Gigantopithecus probably had a sweet tooth.
Unlike orangutans, Gigantopithecus - the largest of which likely tipped the scales at 270kg - were unsuited for an arboreal lifestyle and almost certainly dwelt on the forest floor, as gorillas do today. In doing so, it’s possible they may have clashed with our ancestors, Homo erectus, who arrived in this part of the world roughly 800,000 years ago.
Some researchers have suggested that competition between Homo erectus and Gigantopithecus may have led to the latter’s extinction 200,000 years ago. That said, a recent study - published in 2024 - provides evidence against this theory, concluding that climate change and a shrinking habitat ultimately spelt the end for Gigantopithecus.
Megalania
At 6m in length and weighing in at nearly 600kg, these giant lizards were perhaps the closest our ancestors got to meeting real life dinosaurs.
Megalania looked very similar to their close cousins Komodo dragons, with stocky, splayed limbs, large heads, and jaws full of serrated, blade-like teeth.
They probably also hunted like Komodo dragons, striking with lethal, venomous bites before moving in for the kill once their prey’s bloodstream was sufficiently full of toxin. It’s believed Megalania, which lived in Australia during the Pleistocene, preyed on a variety of megafauna, including the largest known marsupial ever - the forklift-sized Diprotodon.
For a long time it was thought Megalania died out before humans arrived in Australia, roughly 60,000 years ago. In 2015, however, a tiny, fossilised scale from a Megalania was found and dated to 50,000 years ago, suggesting humans may have lived alongside these beasts for thousands of years. As a result of this find, humans are now considered at least partially responsible for Megalania’s extinction. There’s evidence of humans driving lots of other large Australian animals to extinction too, including giant kangaroos, marsupial lions, and the enigmatic thylacine, or Tasmanian tiger.
Ground sloth
All six living species of sloth are exclusively arboreal, spending almost the entirety of their lives hanging upside down in trees. Their ancestors from the Pleistocene were a lot more diverse, grew to the sizes of elephants, and roamed the vast grasslands of the Americas.
There were roughly 30 species of ground sloths that may have overlapped with humans in the Americas. The biggest amongst them was Megatherium, a tank-sized sloth that stood almost 3.5m tall on its hind legs and tipped the scales at 4,000kg.
Megatherium, like many others of its kin, was a browser that ate predominantly foliage, twigs, and fruits from trees and shrubs. Not all ground sloths were such strict vegetarians, however; it’s thought that at least one, Mylodon, was an omnivore and may have occasionally feasted on abandoned caracases it stumbled across.
There’s lots of evidence of humans hunting ground sloths across the Americas, particularly Megatherium whose butchered bones have been found at many prehistoric sites. There’s also direct evidence of humans interacting with a ground sloth, likely Paramylodon, at a fascinating site located in White Sands National Park, New Mexico. At this site, researchers found human footprints inside a ground sloth footprint, suggesting they were either hot on its tail during a hunt, or dodging its attacks as they attempted to take it down.
Giant stork
During the Pleistocene, on an island in the Indonesian archipelago, there lived a ‘hobbit’. This hobbit belonged to a group of diminutive humans known as Homo floresiensis who lived on the island of Flores from one million to 50,000 years ago.
Homo floresiensis are thought to have been a product of island dwarfism - an evolutionary process where formerly large animals trapped on islands shrink as a result of poor or restricted diets. These tiny humans stood just 1.1m tall as adults and were far from the top predators on Flores.
That title went to the giant stork, Leptoptilos robustus - a 1.8m-tall, carnivorous bird that looked scarily similar to some of the most terrifying pterosaurs from the Mesozoic Era. Like some extant storks, Leptoptilos robustus were scavengers, but they may have also been active predators, hunting the large rats and Komodo dragons that lived on Flores.
Some also speculate they may have hunted Homo floresiensis, particularly juveniles who were probably small enough for these giant storks to swallow whole.
While Letoptilos robustus’ ancestors are thought to have been flightless, it’s widely agreed these storks were capable of flight. Whether they were strong enough to fly off with young hobbits, however, is another question.
Giant short-faced bear
It has long been theorised that this 950kg bear, which stalked the land bridge that once connected Russia to Alaska during the Pleistocene, may have prevented humans migrating into the Americas from Eurasia. This bear, appropriately named the giant short-faced bear (Arctodus simus), is widely considered the largest terrestrial carnivoran ever, larger than a polar bear and almost twice the size of a grizzly bear.
While the giant short-faced bear may have weighed close to a ton, it had a relatively slender build compared to many modern bears. This has sparked debate about its lifestyle, with some claiming it was a pursuit predator capable of running down prey at speeds of up to 51 kilometres per hour, and others suggesting it was a kleptoparasite - an animal that specialises in stealing kills from other predators.
The jury is still out on exactly how the giant short-faced bear filled its belly, but we do know that it came face to face with humans. At a site in Texas, towards the southernmost extent of their range, some Arctodus remains have been found that show signs of butchery.
It’s thought the bear in question probably died before humans found it and defleshed it. There’s also evidence at a site on Orcas Island, Washington, of humans caching bison carcasses underwater, perhaps in an attempt to mask the scent from the giant short-faced bears that were especially prevalent in this area of North America.
Crowned eagle
There’s still a species of crowned eagle alive today in Africa, Stephanoaetus coronatus. At just 4.5kg and with a wingspan of ~1.8m, crowned eagles are far from the largest eagles, yet their reputations as man-killers make them some of the most feared birds of prey on the planet. In modern times, there have been several eyewitness accounts of crowned eagles attacking, maiming, and even killing small children. A child’s skull was also found in the nest of a crowned eagle in Zimbabwe, according to a report published in 1982.
The best evidence of crowned eagles preying on humans, however, comes from prehistory, specifically South Africa 2.8 million years ago. The famous Taung Child fossil, a skull from a three-year-old Australopithecu africanus, displays damage consistent with an eagle attack. As well as scratches on the skull, two puncture holes were found in the child’s eye sockets. It’s thought that a crowned eagle, or at least a close relative, committed this particular murder.
Aside from humans, crowned eagles are known to prey on monkeys, antelopes, and hyraxes, snatching them from the ground with their unusually large talons and strong legs. Some records have documented crowned eagles carrying prey weighing more than 10kg up to their nests, making them one of the most powerful eagles ever relative to their body size.
Dire wolf
The dire wolves of George R.R. Martin’s epic fantasy series ‘A Song of Ice and Fire’ may be things of fiction, but the dire wolves of Pleistocene North America certainly weren’t. These extinct wolves were roughly 40% bigger than today’s grey wolves, and their jaws were packed with larger teeth with greater shearing ability. They also had the strongest bite force of any canid known, strong enough to bite through and grind up bones.
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It’s believed their large size and powerful jaws were adaptations for preying on many of the giant herbivores that shared their habitat in North America, such as ground sloths, mastodon, and bison. As well as competing with other predators for these herbivores, such as sabre-tooth cats and cave lions, dire wolves are thought to have also tussled with humans. Like humans of the time, and wolves of today, they probably hunted in coordinated groups, separating weaker prey from their herds before jumping in for the kill.
Lots of dire wolf remains are found at the famous La Brea Tar Pits in Los Angeles, natural tar traps that, during the Late Pleistocene, claimed the lives of thousands of animals, predators in particular. As other animals got trapped in these tar pits, predators like dire wolves came over to feast on their remains only to then find themselves trapped too.
Cave lion
Today, lions are restricted to pockets of savanna in sub-Saharan Africa. In the Pleistocene, their extinct relatives cave lions lorded over territory that stretched all the way from the Iberian Peninsula to North America, and included the British Isles. They were amongst the most successful predators that lived on the Mammoth Steppe - an icy tundra that covered large parts of the northern hemisphere for long periods during the Pleistocene. And it’s here, on the Mammoth Steppe, where they’d have run into our ancestors as the two competed for mammoths, mastodons, and reindeer.
Cave lions (Panthera spelaea) are very closely related to modern lions (Panthera leo) and are thought to have only diverged from a common ancestor as recently as 500,000 years ago, making them as closely related as us (Homo sapiens) and neanderthals (Homo neanderthalensis). They were almost twice the size of modern lions, though, and males lacked shaggy manes.
We know males didn’t have manes because of some incredible charcoal drawings left by humans on the walls of Chauvet Cave in southeast France, dated to roughly 35,000 years ago. These drawings aren’t the only evidence of our distant relatives venerating cave lions. In 1939 a 40,000-year-old ivory statue depicting a half-man, half-lion figure was found in Germany. Some think this statue may be evidence of early humans viewing cave lions as gods.
Other humans
We might be the only species of our kind left today, but during periods of the Pleistocene as many as eight human species lived concurrently across the world. Many of these species would have interacted with one another as their paths crossed, sharing knowledge, resources, and - if the DNA evidence is anything to go by - genes. It’s clear that our ancestors mated with neanderthals, for example, because we share roughly 2% of our DNA. We also share a significant proportion of DNA with denisovans, another prehistoric human species known from Asia.
Not all meetings between humans would have been so friendly, however. In fact, there’s evidence from several sites across the world of humans eating one another. At Gough’s Cave in Cheddar, Somerset, several human toe and rib bones have been found that bear marks made by human teeth.
Other clues of cannibalism include human jaw bones that have been severed from their skulls and deliberately broken in a similar way to the jaws of other animals. There’s also remains of skulls that some researchers think may have been used as drinking cups.
Whether or not these remains from Gough’s Cave are signs of humans eating one another as other food sources grew scarce, or perhaps as part of a funerary ritual, is unknown - but it sure is a terrifying image nonetheless!