When Humans Were Prey

In 1924, a worker at a limestone quarry in
the town of Taung, South Africa made an incredible discovery. It was the fossilized skull of a juvenile
hominin, a member of the human lineage that includes us and all of our ancestors that
came after our split with chimpanzees and bonobos. That little skull became the type specimen
for Australopithecus africanus, and it would become one of the most important fossils in
the study of human evolution. Today, the specimen is known as the Taung
Child. Its discovery revolutionized our thinking
about our past for a number of reasons. For one thing, at about 2.8 million years
old, it was the first fossil evidence that our early human ancestors originated in Africa. But there was something else. The skull had been found among lots of bones
from other, mostly small animals, and many of them had been badly damaged, as if the
animals had been butchered. So for decades, these fossils were read by
experts as evidence that hominins like Australopithecus weren’t fruit-eating apes — they were carnivorous
hunters, so-called “predatory ape-men.” It would be more than 80 years before scientists
would realize that, in fact, the Taung site was not proof that australopithecines were
hunters. Instead, it was actually evidence that the
hominins themselves were being hunted. No one noticed it at the time, but the skull
of the Taung Child bore the telltale marks of violent trauma: puncture holes in the base
of the eye sockets, a depressed fracture in the top of the skull, and scratches on the
sides. These would eventually prove to be the hallmarks
of a predator that no one suspected. But this child’s skull is just one example
of the evidence that, not too long ago, our early human ancestors were under constant
threat of attack from predators. And it turns out that this difficult chapter
in our history may be responsible for the adaptations that allowed us to become so successful. We may be who we are today, because of the
time when we were prey. The notion that our ancestors were once hunted
by other animals would have come as a surprise to the anthropologist who first studied the
Taung Child. His name was Raymond Dart, and he proposed
that one of the driving forces of human evolution was what he called “the thirst for blood.” To Dart and many anthropologists of his time,
the impulse to kill prey was seen as a deeply ingrained part of our heritage. Dart observed baboons that appeared to “spontaneously”
hunt down prey, and he noted that living hunter-gatherers seemed to be hunters first and gatherers second. So, Dart built the case that australopithecines
were ravenous carnivores, as more and more fossils emerged that seemed to support his
model. One such fossil was unearthed in a South African
cave in 1949: the bony skullcap of a juvenile hominin with two very suspicious puncture
marks. This partial cranium belonged to a young member
of Paranthropus robustus dating to between 1.8 and 1.5 million years ago. It was found alongside other fossil mammals,
like antelope and baboons, many of which were also damaged or had only their skulls preserved. The child’s skull was labelled SK 54, and
it had suffered two punctures at the back of the head. And the bone on the inside of the cap, where
those punctures were, flaked upward – indicating that the victim was probably alive, or only
very recently dead, when it was attacked. At the time, a science writer named Robert
Ardrey took this fossil as evidence of interpersonal violence: SK 54, he said, was the victim of
two blows to the back of the head with a pointed object, by another hominin. Soon, the idea began to take hold that our
evolution was deeply shaped by violence, including between humans. Ardrey gave this idea the rather sensational
name of “The Killer Ape Theory.” Dart described it as “the predatory transition
from ape to man.” And this view seemed to get another big boost
from a discovery made at a South African cave site called Makapansgat. The cave was found to be filled with the bones
of Australopithecus africanus and many other mammals – most of which, like at the Taung
site, were broken. Raymond Dart studied more than 7000 remains
from this site and was struck by the fact that the fossils consisted almost entirely
of skulls and neck vertebrae. So he concluded that the fractures on these
bones were evidence of blows by hunters and that the high proportion of skulls meant that
the hominins were taking the heads of their prey as trophies — including the heads
of their own species. But within the field of anthropology, changes
were in the works. Just as the Killer Ape Theory was reaching
its peak of popularity, more scientists began to suspect that we had actually spent most
of our evolutionary history being prey of other, better hunters. Enter the American anthropologist Sherwood
Washburn. While doing research on a game reserve in
Africa, he noticed how modern predators ate carcasses selectively – eating the soft, meaty
parts and leaving skulls, jaws, and upper vertebrae behind. It struck him that this was the same pattern
of bones that Dart saw at the sites of supposed hominin “headhunters”. Washburn also observed hyenas carrying off
parts of carcasses and stashing the bones around their dens – again, creating a pattern
like the one Dart was seeing in the South African caves. Washburn published his observations in 1957,
and argued that australopithecines weren’t headhunters – instead, they were the prey
of carnivores like hyenas. This was a major turning point in our understanding
of our evolutionary history. For decades, Dart and his contemporaries had
been studying human nature in the violent social context of World Wars I and II, so
it made sense that they understood our history as being shaped by aggression. But while they stuck to that model, younger
anthropologists began to explore Washburn’s ideas. And his work made enough of an impact that
when another damaged hominin fossil was found — this time at Olduvai Gorge, Tanzania, in
1960 — other hominins were not considered the top suspects. In this case, the fossil was OH8, a slightly
mangled partial left foot of Homo habilis, discovered by anthropologist Louis Leakey. The ankle bone had tooth marks on it, and
Leakey’s wife and partner, Mary Leakey, concluded the marks came from a carnivore
that was probably not a hyena, but nor was it another hominin. So by the mid-1960s, anthropologists were
at least starting to think that hominins could’ve been prey. Then, in 1970, paleontologist C.K. Brain revisited
the cave site where SK54, that skullcap with the puncture wounds, had been found. He wanted to try to figure out why all of
those fossils had accumulated where they had. And he realized that the fossils weren’t
signs of hominins hunting, much less fighting each other. Instead, he argued, those fossils had been
the victims of a hungry ancient leopard. For one thing, he pointed out, modern leopards
often stash their kills in the trees that grow around these types of caves. And the bones often end up dropping down into
the caves. But the more convincing evidence was that
the puncture wounds in SK54 perfectly matched the lower canine teeth of a leopard. Which means some big cat must have attacked
Sk 54, and dragged it by its head up into a tree, its bones later falling into the cave. So, just like with Washburn, Brain’s observations
of the behavior of living carnivores were fundamental to rethinking whether our hominin
ancestors were the hunters or the hunted. Big cats and hyenas turned out to be very
good at making just the kinds of bone assemblages that Dart had seen in those South African
caves. And once anthropologists started thinking
about how bones become deposited and preserved in different settings, it seemed less likely
that small hominins like the australopithecines were mighty, bloodthirsty killers. And this new thinking eventually worked its
way back to that crucial, early hominin fossil: the Taung Child. In 1995, researchers took another look at
the fossils from that site, and noticed a whole new set of clues. For example, they noticed that the nature
of the damage to the Taung skull was similar to that found on the skulls of baboons found
there. And they were struck by the fact that the
other bones were generally of small animals. And, there were also the remains of large
eggshells in the area. So the team proposed that the Taung Child,
along with the other animals found with it, were in fact the victims of a large bird. They found even more convincing evidence in
2006, when they compared the Taung Child’s skull to those of modern monkeys that had
been preyed upon by eagles. The gouges and punctures in the base of its
eye orbits matched the damage done to those monkey skulls. So the Taung Child was likely killed by an
ancient, giant bird of prey. Likewise, remember OH8, the Homo habilis foot
found by the Leakeys? Well in 2012, researchers took a second look at
that fossil, too, and noticed something new. The puncture wounds in the bone had two extra
grooves in them that matched the ridges found on the teeth of crocodiles. Crocs are ambush predators, and those kinds
of attacks leave characteristic marks and patterns of damage on the bones of their prey,
which, again, matched the damage done to that Homo habilis. We’ve come a long way from Raymond Dart’s
ideas about bloodthirsty hominins. Today it seems that our evolution was shaped
less by our need to kill than by our need not to be killed. After all, Africa in the Pliocene and Pleistocene
was a dangerous place for our fossil ancestors and relatives. And with selective pressure comes adaptation
and evolution. So the evolutionary legacy of that time when
we were prey is enshrined in our bodies today. Having become larger than our ancestors, for
example, has helped protect us from birds and smaller mammal predators. And some experts argue that becoming bipedal
allowed us to better scan the horizon for threats, to move quickly while carrying food
or infants, and just generally look bigger. Plus, with our hands freed up, we could also
throw things at potential predators, which chimps still do today, though not as well
as we can. Some experts also point out that speech has
given us the ability to plan, rather than to just react. Living primates have alarm calls that are
specific to certain predators, but speech allows us to figure out in advance what to
do when we hear one of those calls. But, it’s worth pointing out: the Taung
Child, SK54, and OH8 were all bipedal hominins – and they still got eaten. So other researchers have suggested that maybe
our evolutionary legacy from that dangerous time is simply our ability to cooperate. Hominins would have needed to live in groups,
and also to work together to ward off threats. And studies have shown that our brains are
still activated in specific ways when we do things like play cooperative games, triggering
our reward centers when we work together. By contrast, studies of chimps have shown
that they don’t help others, even when there is no cost to doing so. But even if all of these adaptations evolved
out of a need to defend ourselves from predators, they obviously didn’t work every time. Researchers in Poland recently discovered
the finger bones of a Neanderthal child who lived just 115,000 years ago. And those bones were covered with dozens of
small, distinctive holes that could only have come from passing through the digestive tract
of a large bird. So, as recently as the Late Pleistocene, our
ancestors were still being preyed upon, or maybe scavenged, by birds, just like the Taung
Child was. But being able to recognize the signs of predation
in our past has marked a major shift in how we think about ourselves — one that allowed
us to better understand the selective pressures that helped make us who we are today. Thanks as always, fam, and extra big thanks
to our current Eontologists, Jake Hart, Jon Ivy, John Davison Ng and everyone’s favorite
hominin, STEVE! Do you want to join them and have me maybe
mispronounce your name and make fun of you? Then go to patreon.com/eons and make your
pledge! Now, what do you want to learn about? Leave the dude a comment, and don’t forget
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