PE3 Oligocene

Summary

The Oligocene epoch marked a significant era in primate evolution, with the emergence of the first monkeys, or anthropoids. As Earth's climate cooled due to continental drift affecting ocean currents, new habitats and selective pressures led to the development of these primates. Fossil evidence from Fayum, Egypt, reveals the earliest monkeys, the Oligopithicids, dating back 35 million years. These primates dispersed globally, with some, the Parapithecids, migrating to South America to become New World monkeys, while others evolved into Old World monkeys, apes, and humans. Dental formulas differentiate these groups, with 2-1-3-3 for New World monkeys and 2-1-2-3 for Catarrhines, including humans.

Takeaways

• 📅 The Oligocene epoch saw rapid development of new primate adaptations and the first appearance of monkeys.
• 🌍 The Earth's climate changed dramatically during the Oligocene due to continental drift affecting ocean currents.
• ❄️ Cooling of the Earth during the Oligocene led to new habitats and natural selective pressures, resulting in new adaptations.
• 🐒 Monkeys, or anthropoids, emerged during the Oligocene and replaced many prosimians.
• 🦴 Fossil evidence from the Fayum region in Egypt shows the earliest monkeys appeared around 35 million years ago.
• 🌊 Monkeys rapidly dispersed across the Old World and to South America within 10 million years of their emergence.
• 🚢 Some Oligopithicids rafted across the Atlantic Ocean to South America, evolving into Platyrrhines, or New World monkeys.
• 🦍 Most Oligopithicids remained in Africa and evolved into Propliopithecids, leading to Old World monkeys, apes, and humans.
• 🔬 Aegyptopithecus, dating to about 30 million years ago, is the earliest example of a Catarrhine with a 2-1-2-3 dental formula.
• 🦷 New World monkeys retained the primitive 2-1-3-3 dental formula, while Old World monkeys, apes, and humans have the derived 2-1-2-3 dental formula.

Q & A

What significant primate adaptation emerged during the Oligocene epoch?

The first monkeys, or anthropoids, emerged during the Oligocene epoch.

How did continental drift impact the Earth's climate during the Oligocene?

Continental drift altered the distribution of ocean currents, which affected the Earth's climate by redistributing heat and cold, leading to a cooler global climate.

What was the impact of the Oligocene climate change on land habitats and primate evolution?

The cooler climate during the Oligocene changed land habitats, leading to new environmental pressures and the emergence of new primate adaptations, including the first monkeys.

Where is one of the best places to find fossil primates from the Oligocene period?

One of the best places to find fossil primates from the Oligocene period is the Fayum region in Egypt.

What does the fossil record from Fayum tell us about primate evolution during the Oligocene?

The Fayum fossil record shows that monkeys first appeared around 35 million years ago and that they quickly dispersed to different parts of the world, including South America.

What are Parapithecids, and what is their significance in primate evolution?

Parapithecids are an early group of monkeys that migrated to the Americas and evolved into the modern New World monkeys (Platyrrhines) found in Central and South America today.

What distinguishes Platyrrhines from other primates?

Platyrrhines, or New World monkeys, are distinguished by their primitive dental formula of 2-1-3-3.

Who were the Propliopithecids, and what did they evolve into?

Propliopithecids were a group of early monkeys that stayed in the Old World and eventually evolved into Old World monkeys, apes, and humans.

What is the significance of Aegyptopithecus in primate evolution?

Aegyptopithecus, dating to about 30 million years ago, is the earliest example of a Catarrhine monkey with the derived dental formula of 2-1-2-3, indicating a different evolutionary branch from New World monkeys.

How do the dental formulas of New World and Old World monkeys differ?

New World monkeys (Platyrrhines) have a primitive dental formula of 2-1-3-3, while Old World monkeys, apes, and humans (Catarrhines) have a derived dental formula of 2-1-2-3.

Outlines

00:00

🌏 Oligocene Climate Shift and Primate Evolution

The Oligocene epoch marked a significant period in primate evolution, characterized by a dramatic climate change due to continental drift affecting ocean currents. This cooling trend led to habitat alterations, prompting natural selection to drive new adaptations among primates. The first monkeys, or anthropoids, emerged during this time, with the fossil record providing crucial insights into their evolution. Notably, the Fayum Depression in Egypt, once a swampy forest, now a desert, has yielded fossils that reveal the development of early monkeys around 35 million years ago. These early primates, known as Oligopithecids, dispersed rapidly across the globe, with evidence of their presence in South America within 10 million years of their first appearance.

05:01

🐒 Dispersal and Evolution of Early Monkeys

A subset of the early monkeys, the Parapithecids, is identified as the ancestors of modern Platyrrhines, or New World monkeys, native to Central and South America. The migration of these monkeys to the Americas is estimated to have occurred between 35 and 26 million years ago, as evidenced by the oldest fossil records in Argentina. This transatlantic journey likely involved a small group of Oligopithecids drifting across on rafts, encountering new selective pressures in South America that led to their evolution into distinct New World monkey species. Meanwhile, the majority of the Oligopithecids remained in the Old World, evolving into Catarrhines, which include Old World monkeys, apes, and humans. Aegyptopithicus, dating back to 30 million years ago, represents the earliest Catarrhine monkey with a derived dental formula, setting it apart from its New World counterparts.

10:01

🦷 Dental Evolution: New World vs. Old World Primates

The dental formula serves as a distinguishing feature between New World and Old World primates. New World monkeys and their ancestors possess a primitive dental formula of 2-1-3-3, which is indicative of their early evolutionary stage. In contrast, Old World monkeys, apes, and humans, collectively known as Catarrhines, exhibit a more derived dental formula of 2-1-2-3. This divergence in dental patterns underscores the separate evolutionary paths of these primate groups following the migration event. Aegyptopithicus, identified as the earliest Catarrhine, further solidifies the distinction between the two groups, highlighting the significance of dental evolution in primate classification and understanding their adaptive radiation.

Keywords

💡Oligocene

The Oligocene is an epoch of the Paleogene period, characterized by significant climatic changes and the emergence of new primate adaptations. In the video, it is highlighted as the time when the first monkeys appeared, marking a pivotal moment in primate evolution. The script mentions how the Earth's climate during the Oligocene, influenced by continental drift and ocean currents, led to habitat changes that spurred natural selection and the development of new species.

💡Natural Selection

Natural selection is the process by which species adapt to their environment through the differential survival and reproduction of individuals due to variations in their traits. In the context of the video, natural selection is key to understanding how new primate adaptations, such as the first monkeys, emerged in response to environmental pressures during the Oligocene epoch.

💡Continental Drift

Continental drift refers to the movement of Earth's continents relative to each other, which has significant effects on global climate and ecosystems. The video script explains how continental drift during the Oligocene impacted ocean currents, leading to a cooling of the Earth and changes in habitats that influenced the evolution of primates.

💡Ocean Currents

Ocean currents are the continuous movement of ocean water in a specific direction, driven by various factors including temperature, salinity, and wind. In the video, it is explained that changes in ocean currents due to continental drift played a role in the Earth's cooling during the Oligocene, which in turn affected the habitats and the course of primate evolution.

💡Fayum

Fayum refers to a region in Egypt known for its fossil beds that provide crucial evidence for understanding primate evolution during the Oligocene. The script mentions the Fayum area as a swampy, forested region during the Oligocene, which has since yielded many fossils, including the earliest evidence of monkeys.

💡Oligopithecids

Oligopithecids are an extinct family of primates that represent the earliest known anthropoids or monkeys. The video script identifies Oligopithecids as the first monkeys that appeared around 35 million years ago, with fossil evidence from the Fayum region, and who rapidly dispersed to different parts of the world.

💡Parapithecids

Parapithecids are a subgroup of Oligopithecids that migrated to the Americas. The script explains that these primates are ancestral to modern Platyrrhines, the New World monkeys found in Central and South America, and that their migration across the Atlantic occurred between 35 and 26 million years ago.

💡Platyrrhines

Platyrrhines are a taxonomic group of monkeys that are native to the New World, specifically Central and South America. The video script describes how Parapithecids, which migrated to the Americas, evolved into the Platyrrhines we see today, characterized by a unique set of evolutionary pressures and adaptations.

💡Propliopithecids

Propliopithecids are an early group of primates that are considered to be the ancestors of modern Catarrhines, which include Old World monkeys, apes, and humans. The video script discusses how Propliopithecids evolved in the Old World, distinct from the Parapithecids that migrated to the Americas.

💡Catarrhines

Catarrhines are a group of primates that include Old World monkeys, apes, and humans. The term is derived from the Greek word 'κατά' meaning 'down' and 'ῥίς' meaning 'nose', referring to their downward-pointing nostrils. In the video, Catarrhines are described as having evolved from Propliopithecids in the Old World and are characterized by a specific dental formula.

💡Dental Formula

Dental formula refers to the layout of teeth in mammals, typically expressed as the number of incisors, canines, premolars, and molars on each side of the jaw. The video script explains the significance of the dental formula in distinguishing between New World monkeys (2-1-3-3) and Old World monkeys, apes, and humans (2-1-2-3), with Aegyptopithicus being the earliest example of a Catarrhine with the latter formula.

Highlights

The Oligocene epoch saw rapid development of new primate adaptations and the first monkeys.

Earth's climate changed during the Oligocene due to continental drift impacting ocean currents.

Ocean currents play a crucial role in distributing heat and cold across the Earth.

The Earth cooled off during the Oligocene, changing habitats and leading to new adaptations.

Natural selection reshaped primate populations in response to new environmental pressures during the Oligocene.

The Fayum fossil beds in Egypt provide crucial evidence for primate evolution during the Oligocene.

The earliest fossil evidence for monkeys dates back to 35 million years ago in Fayum.

Oligopithicids were the earliest anthropoids and monkeys.

Oligopithicids dispersed rapidly across the Old World and the Americas within 10 million years.

Parapithecids migrated to South America and are ancestral to modern Platyrrhines.

The earliest fossil evidence for ancestral Platyrrhines in South America dates to 26 million years ago.

A small number of Oligopithicids likely rafted across the Atlantic to reach South America.

The majority of Oligopithicids stayed in the Old World and evolved into Catarrhines, including apes and humans.

Aegyptopithicus, dating to 30 million years ago, is the earliest known Catarrhine monkey.

Catarrhines have a derived dental formula of 2-1-2-3, unlike the primitive 2-1-3-3 formula of New World monkeys.

The dental formula distinction helps differentiate between New and Old World monkeys.

Transcripts

PROFESSOR: The next epoch of the Paleogene is the Oligocene,

and it's during the Oligocene that we

see a rapid development of new kinds of primate adaptations.

And it's during this period that we get the first monkeys.

The Earth's climate changed somewhat dramatically

during the Oligocene, not quite as dramatic

as when the asteroid hit--

you can't get much more dramatic than that--

but more gradual and more natural.

Actually, it's thought to be the result

of continental drift impacting the distribution of ocean

currents.

Ocean currents are one of the ways

that the Earth radiates heat and distributes

heat and cold from warm places to cold places and vice versa,

so that as continents were moving around,

they interrupted the distribution

of these temperature differences.

And as a result, the Earth cooled off.

When it cooled off, that changed the habitat

that was present in different ecologies on land.

And with a new set of natural selective pressures

present in the environment, we see natural selection

taking existing populations and reshuffling

the deck a little bit.

We see new adaptations emerge in response

to these new environmental circumstances.

And one of the new adaptations that we

see emerge for the first time during this period

are monkeys, anthropoids.

Some prosimians survive, of course,

because we still have prosimians with us today.

But a lot of prosimians, a lot of those euprimates

that were alive during the Eocene,

go extinct during the Oligocene.

These monkeys replace them, and we now

have a new primate adaptation present on the planet.

We understand primate evolution through the fossil record.

And one of the best places to obtain fossil primates

from this period is at a place in Egypt called Fayum.

The Fayum fossil beds are now out in the desert,

in the Sahara.

It's very dry, but during the Oligocene, they were--

this area was a swampy, forested region

on the shores of a great inland sea that has since receded.

There were lots of different creatures

from the period alive there, and it's from these fossil beds

that we have obtained the information that

shows us how monkeys evolved during this period.

This is a picture from your book showing what kinds of things

were alive in the Fayum region during the Oligocene period.

We have different mammals, different reptiles, birds.

We have some marsupials, and if you look in the upper left,

we have some monkeys.

And this is the earliest evidence

we have for this particular primate adaptation--

shows us that it emerged during this period.

The earliest fossil evidence we have from monkeys at Fayum

dates to about 35 million years ago.

This makes them the earliest anthropoids, the earliest

monkeys, and we call these the Oligopithicids.

Within 10 million years, different subgroups

of these Oligopithicids have migrated to different parts

of the world.

We find monkey remains in South America,

in Argentina within 10 million years

and throughout Africa and in other places in the Old World

during that time frame as well.

So the earliest evidence we have is about 35 million years ago

in Fayum, but what we see is a pretty rapid dispersal

of this new kind of primate, these new monkeys,

across not only the Old World but across the Atlantic

into the Americas as well.

On the previous slide, we introduced

the terms Propliopithecids and Parapithecids.

And on this slide, we're going to explain what those are

and what the evolutionary significance of them is

and which primates that we have alive today

are descended from these two different groups.

I mentioned on the previous slide

that we have a group of this Oligopithicid

migrate across the Atlantic Ocean into the Americas,

and we have evidence for these within about 10 million years

of the emergence of monkeys.

These guys were known as the Parapithecids,

and they are ancestral to modern Platyrrhines.

Platyrrhines origins is the taxonomic group

of monkeys that are found only in the New World.

These are New World monkeys that we find in Central and South

America today.

The earliest fossil evidence we have for ancestral Platyrrhines

comes from Argentina and dates to about 26 million years ago.

So if monkeys first evolved about 35 million years ago

in Africa, and we find monkeys 26 million years ago

in South America, that means that this migration

must have taken place at some point

between 35 and 26 million years ago.

How did that happen?

Well, the animation that you'll do for your extra credit

exercise explains this very well.

But suffice it to say, we think that some small number

of these Oligopithicids rafted across what was then

a much narrower Atlantic Ocean, arriving in South America, what

is now South America, sometime prior to 26 million years ago

and, by doing so, encountered an entirely different set

of evolutionary pressures, different natural selective

features.

There wasn't as much competition.

There were different kinds of food that were available.

And these monkeys, now in this new environment

with its own unique set of circumstances,

evolved into the New World monkeys that we see today.

However, that was only a small part of the overall population.

If a handful of them migrated across the Atlantic

on rafts accidentally, then that means

that the vast majority of these Oligopithicids

stayed in the Old World, stayed on

the other side of the Atlantic.

These continue to evolve based on

the natural selective pressures that

were present in that region--

the suite of competitors, the suite of predators,

the kinds of food that were available.

These evolved into what we call today Catarrhines.

These earlier populations, known as the Propliopithecids,

eventually became what we now call Old World monkeys.

We also include in Catarrhines apes and humans,

which evolved in the Miocene and the Pliocene sometime later.

So to sum it up, we have this population of monkey

that appears in Africa about 35 million years ago.

Some small number of these accidentally

float across the Atlantic and colonize the Americas.

This group is called the Parapithecids,

and they evolve into the modern New World monkeys

that we see in Central and South America today.

However, most of them remained in Africa,

remained on the other side of the Atlantic.

We call that group the Propliopithecids,

and they evolved into Old World monkeys, monkeys

that we find in Africa and Asia today,

and eventually apes and humans.

We don't know exactly when the Parapithecids migrated

to South America.

We do know that they were there by about 26 million years ago.

We have somewhat better data as to when

the earliest Catarrhines, the earliest

Propliopithecids, and then Catarrhines,

evolved in the Old World.

There is a specimen that was found in the 1960s at Fayum

that we now call Aegyptopithicus.

It dates to about 30 million years ago

and is the earliest example we have of a Catarrhine monkey.

Catarrhines, as we discussed on the last slide,

are today represented by Old World monkeys, apes,

and humans.

Catarrhines, importantly, also have the derived dental formula

of 2-1-2-3.

Aegyptopithicus, at about 30 million years ago,

is the first monkey that we see with this 2-1-2-3 dental

formula.

Now, remember that New World monkeys today have the 2-1-3-3

primitive dental formula.

Those Parapithecids that migrated to the Americas

and eventually evolved into the modern New World monkeys

that we find in Central and South America today--

well, all of those monkeys, the modern ones and their earliest

ancestors, have that primitive 2-1-3-3 dental formula.

So whenever the ancestors of modern New World monkeys

migrated to the Americas, when they did,

they brought with them that 2-1-3-3 primitive dental

formula.

We know that because all New World monkeys today still have

that primitive 2-1-3-3 dental formula.

However, in the Old World, Aegyptopithicus is the earliest

example of continued evolution of a different branch that

would ultimately become Catarrhines and is the first

to have this 2-1-3-3--

2-1-2-3 dental formula.

I know it can seem kind of confusing,

but if you just break it out by geography--

New World monkeys, 2-1-3-3, Old World monkeys, apes,

and humans, every primate that is Indigenous to the other side

of the Atlantic, 2-1-2-3--

it's a little easier to remember.