Hey! Make sure to check out the most recent episode of our podcast,
Eons: Mysteries of Deep Time.
In this episode, I’ll take you through a whodunit detective story that spans more than a century
as we try to figure out who was behind the most famous fake human fossil.
Check it out now wherever you get your podcasts!
Mischievous laughter echoes across the African
savannah as a group of spotted hyenas cluster around a carcass.
These predators make the most of their prey,
ripping off flesh and cracking open bones for their marrow.
Their bone-crushing jaws give them a unique niche in their environment, allowing them to
scavenge the remains of animals brought down by other predators when their own hunts fail.
But hyenas weren’t always able to eat bones. In fact, only a few million years ago,
they lived very different lives.
The hyenas of today come from tree-living ancestors similar to modern civets,
which kinda look like a cross between a cat and a mongoose.
And for a brief window of time, hyenas were the “top dogs” of Eurasia and
Africa - radiating into species that looked and lived like modern
African wild dogs and jackals...despite being more closely related to cats.
But once the real dogs arrived, the true heyday of hyena diversity was over…but
they didn’t disappear completely.
This is the tale of two hold-out hyenas and how their fall
left us with the handful of species we know today.
Today, most hyenas are only found in Africa,
but they first originated in Europe during the Miocene epoch, about 17 million years ago.
And despite their dog-like appearance, they’re actually on the cat side of the
Carnivoran family tree, along with things like civets and mongooses...
Which explains why the ancient ancestors of hyenas shared a lot of features with these animals.
The oldest fossil of a member of the hyena family that we’ve ever found is called Protictitherium.
Unlike modern hyenas, it was arboreal and had retractable claws that likely helped it climb
and hunt small prey.
But its descendants would ultimately leave the trees for a more terrestrial life,
eventually losing those retractable claws and developing longer legs,
a more powerful sense of smell, and stronger teeth.
And these changes would shape the evolutionary history of hyenas.
Or should we say the two evolutionary histories of hyenas.
One lineage would lead to most of the hyenas we know today: the powerful bone-crackers.
But the other would occupy the ecological
niche that’s currently filled by wolves and wild dogs -- predators that chase down their prey.
Most of these dog-like species,
animals like Ictitherium, were practically mirror-images of living jackals and wolves.
While they could probably break bones with their teeth,
they were not as specialized for it as modern hyenas.
And for much of the rest of the Miocene, these dog-like hyenas,
along with some of the earliest bone-crackers and the last of the ancient tree-living taxa,
were the dominant predators across Europe, Africa, and Asia.
Think for a second about the world we live in today.
In some ecosystems, like in the western United States,
you have mountain lions as ambush predators, wolves as pursuit predators,
and weasel-relatives like martens and fishers living in the trees.
Now, imagine that, along with members of all those different carnivore families,
there were also hyenas in those ecological niches -- that was the Miocene.
But this explosion of hyena diversity wouldn’t last for long.
The arrival of real dogs - the canids - from North
America around 8 million years ago began to put pressure on the dog-like hyenas.
And as the Miocene shifted toward the Pliocene Epoch around 5 million years ago,
the climate became much drier, which caused grasslands and savannas to expand.
When the forests disappeared, so did the last of the ancient arboreal hyena-relatives.
Most of the dog-like hyenas also began to decline as their prey became much scarcer
and the incoming canids filled in niches faster than the hyenas could recover.
But there was one dog-like genus that held out - a hyena that doubled-down on being a
pursuit predator: Chasmaporthetes, also known as the running hyena.
It had much longer legs than its bone-cracking contemporaries for chasing down fast prey,
but it wasn’t specialized for eating bone like modern hyenas.
And this niche worked for Chasmaporthetes as it survived into the Pleistocene Epoch,
and ranged throughout Africa and Eurasia.
It was even able to do something no other hyena-relative could do:
make it to the Americas. Its fossils have been found as far north as the Arctic Circle
and as far south as Texas, Florida, Arizona, and Mexico.
And it managed to do this even though canids were already present,
including some of the last so-called bone-crushing dogs – the borophagines.
But even this wasn’t enough to keep Chasmaporthetes around forever.
It went extinct around 780,000 years ago,
probably due to competition with newer species of canids and short-faced bears.
Meanwhile, back in Eurasia and Africa, bone-cracking hyenas had started their rise.
The expansion of grasslands and changing climate at the start of the Pliocene, around 5 million
years ago, that led to the decline of the ancient arboreal hyenas and most of the dog-like hyenas...
Also favored animals that could eat almost every bit of their prey, bones and all.
So, while the dog-like hyenas had become long-legged runners,
the bone-cracking hyenas went in another direction.
They’d developed large, powerful teeth and incredibly strong jaw muscles, along with
much longer forelimbs that allowed them to carry off larger pieces of food at the cost of speed.
These hyenas ranged throughout Eurasia and Africa, with the biggest species being Pachycrocuta.
It first appeared around 7 million years ago,
overlapping with the tail-end of the reign of the dog-like hyenas.
Pachycrocuta was very similar to the modern spotted hyena,
but around 20% larger, making it on average the size of a lioness.
But we also have evidence for bigger individuals - some potentially as large
as the extinct American lion; possibly up 150 kg!.
And based on its morphology, it wasn’t very fast, but it had the strongest bite force of
any hyena, which would have been useful for cracking the bones of megafauna.
This probably made Pachycrocuta very successful, as its fossils have been
found as far west as France, as far east as eastern China, and down into Africa.
And Pachycrocuta lasted longer even than Chasmaporthetes...
But it, too, went extinct around 400,000 years ago as the megafauna that it relied on became scarcer,
and it found itself steadily replaced by the smaller and
more mobile spotted hyena - which is still around today.
Pachycrocuta and Chasmaporthetes were examples of two different ways to be a hyena - ones
that took the specialized features of each of their lineages to the extremes.
The surviving hyenas, on the other hand, were the ones that stuck to more stable niches.
The modern bone-cracking hyenas could thrive on smaller prey and carrion, while the last of
the dog-like hyenas, the aardwolf, adapted to feed on colonial insects, like termites.
The evolutionary story of hyenas is a tale of boom and bust,
from their rise to dominate many different carnivore niches in the Miocene,
to their fall as conditions changed and competitors appeared.
While the living hyenas might not be as big or powerful as their ancestors,
we can say one thing about them for sure: as survivors, they got the last laugh.
Before you go – What can somebody who is completely blind teach you about video games?
How did anime become a 25 billion dollar industry?
And why are these guys putting underwear on goats?
Subcultured, a brand new documentary series from PBS, answers those questions and so many more,
exploring lesser known communities and folx that have had a major impact on the mainstream.
Check it out over on PBS Voices, link in our description, and let them know that Eons sent you.
We’ve gotta thank this month’s Eontologists for laughing with us:
Become an Eonite at patreon.com/eons and you can get fun perks like submitting a joke for
us to read, like this one from Sarah M
Which prehistoric reptile delivers mail?
A Postosuchus.
And don't forget we also have merch! Just search Eons at DFTBA.com
And as always thanks for joining me in the Konstantin Haase studio.
Subscribe at youtube.com/eons for fantastic fossils!