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.