(host) Sixty-six million years ago, an animal about the size of a rat was hunting down insects and searching for fruit among the evergreen leaves of the ancient relatives of the magnolia.

With a tiny narrow face and a long bushy tail, it probably looked a bit like a squirrel, but it wasn't.

Its name was Purgatorious, and it may be one of the world's earliest primates, an ancient relative of ours.

But maybe the most surprising thing about Purgatorious is where it was found: Eastern Montana, not far from where I am now.

And another species of Purgatorious has been found in Saskatchewan, Canada.

So let that sink in.

Early primates not only lived in North America, our primate family tree actually originated here.

Fossil primates have also been found from Central Alberta to Southern Texas and from California to Mississippi.

So if primates really did evolve in North America, then what happened to those early relatives of ours?

Like, why don't we have monkeys and tarsiers and lemurs wandering around the United States and Canada today?

Man, how cool would that be?

Well, the short answer is, North America was once a lot warmer and wetter, offering an ideal habitat for early primates.

But it didn't stay that way for long, and eventually, they all disappeared.

But the longer answer is that primates would eventually return to their home continent-- they just went the very long way around.

Today, non-human primates live on all the continents except Australia and Antarctica, and the ones that still live in North America are limited to Mexico and Central America.

No matter how and where they live, though, today's primates have some things in common, with the occasional exception.

We all have big, forward-facing eyes that are either completely surrounded by a ring of bone or walled off by a bony plate.

And for the most part, we all have nails instead of claws on our fingers and toes.

These traits, along with a few others, define the taxonomic order of primates, which includes humans, apes, monkeys, tarsiers, lemurs, and bush babies, to name just a few.

But once you start looking at the fossil record, you'll see that our primate ancestors looked pretty different.

For example, Purgatorious is a member of a group known as the plesiadapiforms.

They appeared around 66 million years ago, and the last of them vanished about 37 million years ago.

Many scientists consider plesiadapiforms to be the earliest primates.

But there are some traits that set them apart from the likes of you and me.

For one thing, most of them didn't have nails.

They had claws.

And while they did have big eyes like modern primates do, their eyes weren't as close together, which meant they didn't have quite the same level of depth perception.

Still, they did have bumpy, lumpy teeth to help crush fruit like many primates do.

And they had long fingers and toes that were good for grasping onto branches and tree trunks with mobile ankle joints to help them hang on.

So it's these traits that led many scientists to classify plesiadapiforms as the earliest primates.

And like so many primates today, plesiadapiforms mostly lived in warm, wet forests.

Ah, but here's the thing: 66 million years ago, those rain forests stretched far from the equator all the way up to the Arctic Circle.

And these vast rain forests and warm climates allow lots of different groups of primates to thrive throughout North America.

To wit, by the start of the Eocene epoch about 56 million years ago, North America was also home to omomyiforms, a group of tarsier-like primates, and adapiforms, which were more lemur like.

And these little primates were really diverse.

Several species often lived in the same area, like the three species of omomyiforms found in the Friars Formation of Southern California.

But being a rain forest specialist only works well when there are a lot of rain forests, and those aren't as common in North America as they used to be.

Why?

Well, because around 50 million years ago, way on the other side of the world, big changes were underway.

A chunk of the Earth's crust known as the Indian Plate rammed into Eurasia, starting the process that would eventually form the Himalayas.

And the weathering of these growing mountains helped pull carbon dioxide out of the air, which cooled the planet dramatically, nearly 12 degrees Celsius by about 35 million years ago.

And as temperatures changed, tropical environments retreated back toward the equator.

So by the time the Eocene epoch was over, North America no longer had the right habitat for primates.

Now, you'd think that this was the end of the story for North America's primates-- you would think.

Back in the 1960s, paleontologists found a handful of teeth and a jaw on the Pine Ridge Indian Reservation in South Dakota.

And these teeth were tiny.

The biggest of them was less than 4 millimeters long.

but they shared traits with our teeth.

They were short crowned and lumpy, built for crushing rather than slicing.

For a while, scientists weren't even sure that the owner of these teeth was a primate because, while some of its teeth are really similar to ours, they had some differences too.

The ones in back were smaller than the ones in front, and they had a few bumps that were unique.

But when more similar fossils were found, this time in Nebraska and Oregon, experts reached the conclusion that this animal was in fact a primate.

Just a really strange one.

And here's the thing: It lived 29 million years ago, almost ten million years after every other primate in North America went extinct.

So how was this primate able to survive when others didn't?

The answer, unfortunately, isn't clear.

After all, all we have is a handful of teeth.

But those teeth do tell us a few things.

First, they tell us that this animal was bigger than many other late North American primates, about the size of a small house cat as opposed to a rat.

And getting bigger is a pretty common evolutionary response to cooling temperatures, so maybe that could've helped it endure the changing climate.

Another interesting insight is that these teeth were found in what used to be an open woodland, or grassland with trees scattered around.

That might not sound like a very primate-friendly place.

But there are arboreal primates today that live in similar environments, like bush babies, which live in open woodlands in Africa.

And the bumpy nature of the teeth also tells us that this little primate was probably mostly eating fruit instead of the bush babies diet of tree gum, some insects, and maybe a little bit of fruit.

And this could have helped it survive longer, too, because it turns out that primates that eat fruit, at least without destroying the seeds, tend to be more evolutionarily successful because they spread their preferred food via their poop.

For example, during the end of the Eocene in Africa, primates that relied primarily on leaves started to become extinct, but the ones that ate fruit survived.

And that might be because primates that specialize in eating leaves don't contribute as much to the spread of their preferred food source.

So it's possible that this last North American primate made a decent living in a much drier, less forgiving forest environment than its ancestors did because it brought the trees it needed with it, spreading its own food through its poop, which is a phrase that I never thought I would say.

But whatever led to its initial success didn't last forever.

The climate continued to change, and as North America became drier, grasslands kept spreading.

While some primates in Africa have been able to adapt to a grassland environment, it appears that their North American counterparts simply couldn't, and as a result, 26 million years ago, it went extinct and primates disappeared from all of North America, but only for a while.

In 2016, a handful of primate teeth were found in the Panama Canal basin, and they belong to Panamacebus, a member of a family of monkeys that was only found in South America at the time.

But the teeth were about 21 million years old when North and South America were separated by ocean.

So how did Panamacebus get to North America?

Scientists suspect that it rafted there, maybe during or after a storm when it rode on a mat of plant material to the new continent.

It may sound strange, but for now, it's the best way to explain how primates could have crossed the ocean.

And even though Panamacebus managed to make it to Panama, it never made it any farther north, possibly because it, like so many other primates, was attached to living in the rain forest.

And it didn't last either.

Meanwhile, the monkeys found in South America today are most closely related to the monkeys that live in Africa.

And though it's a bit contentious, their arrival in South America is theorized to be the result of storm rafting too.

So what about the monkeys that live in Mexico and Central America today?

Where do they come from?

Well, genetic evidence suggests that they arrived from South America around 4 million years ago, after North and South America had become mostly attached.

And, like Panamacebus, they never made it farther north than the rain forests.

So you could say that the descendants of North America's first primates only recently made it back to their original home continent.

Their evolutionary journey took them around the world, from their likely origins in Montana and Canada at the start of the Cenozoic Era to Asia and Africa in the Eocene epoch, where they probably diversified into the ancestors of the major groups of primates alive today.

Then, eventually, they rafted from Africa back to the Western Hemisphere maybe between 37 and 44 million years ago, where they evolved into the families of primates that live in South America today.

And while all of that was going on, primates that stayed in North America disappeared, the victims of a changing environment.

It would take 22 million years for primates to really make it back to the North American mainland after North and South America reconnected just a few million years ago.

It was quite a trip.

With the return of monkeys to Central America, the North American continent had native primates again.

And then of course, we showed up, and we were adapted to thrive in a whole bunch of different environments, not just rain forests.

So it seems like this latest group of primates is probably here to stay.

I mean, I hope so.

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