The Island of Huge Hamsters and Giant Owls

Summary

This script delves into the intriguing phenomenon of insular gigantism and dwarfism, as evidenced by the late Miocene epoch's Mikrotia fauna of Mediterranean islands. It narrates the evolutionary journey of these 'odd little giants', from their isolation on islands leading to significant size changes, to their eventual extinction due to rising sea levels. The script highlights the real-life powers of natural selection, showcasing creatures like the giant Deinogalerix and the enormous birds of prey, illustrating how island environments can dramatically alter species over time.

Takeaways

• 🌊 Greek and Roman mythologies are filled with tales of exotic islands inhabited by strange and terrifying creatures.
• 🐾 In the late Miocene epoch, there were real islands in the Mediterranean Sea with unusual, large-sized animals.
• 🏝️ The island animals were considered giants compared to their mainland ancestors but were actually small by today's standards.
• 🔍 Geographic isolation can lead to the evolution of new species with unusual sizes, both larger and smaller than their ancestors.
• 🇮🇹 In 1969, Dutch paleontologists discovered a rich fossil deposit in Gargano, Italy, revealing the existence of the Mikrotia fauna.
• 🦉 The Mikrotia fauna included oversized owls, hamsters, and hedgehogs, which were different from their mainland counterparts.
• 🌱 The absence of large predators and competitors on the islands allowed for the development of insular gigantism in some species.
• 🔄 Foster's Rule, identified by J. Bristol Foster, states that isolated environments often see large animals getting smaller and small animals getting larger.
• 🦔 Deinogalerix, a hedgehog-like creature, evolved from a small insectivore to a larger predator capable of hunting larger prey.
• 🦅 Large birds of prey, such as Tyto gigantea and Garganoaetus, evolved on the islands, possibly due to an evolutionary arms race with larger prey.
• 🌊 The extinction of the Mikrotia fauna is likely due to rising sea levels that reduced their island habitats, leading to their inability to adapt.

Q & A

What was the significance of the Mediterranean islands during the late Miocene epoch?

The Mediterranean islands during the late Miocene epoch were significant because they were home to a unique group of animals that had evolved to be either much larger or smaller than their mainland counterparts due to geographic isolation. This phenomenon is a result of natural selection and is known as insular gigantism or insular dwarfism.

What is the Mikrotia fauna?

The Mikrotia fauna refers to a group of animals found in the fossil deposits of the Gargano Peninsula and Scontrone in Italy. These animals were characterized by their unusually large or small body sizes compared to their mainland relatives, due to the effects of insular gigantism and insular dwarfism.

What role did geographic isolation play in the evolution of the animals on the Mediterranean islands?

Geographic isolation played a crucial role in the evolution of the animals on the Mediterranean islands by allowing them to evolve independently from their mainland counterparts. This isolation led to the development of new species with unusual sizes, either much larger or smaller, due to the absence of predators, competitors, or other ecological pressures.

What is Foster’s Rule, and how does it relate to the animals of the Mikrotia fauna?

Foster’s Rule, identified by biologist J. Bristol Foster in 1964, states that in isolated environments, large animals frequently get smaller, and tiny animals often become larger. This rule is exemplified by the Mikrotia fauna, where some animals evolved to be much larger than their mainland relatives, while others became smaller.

What were some of the peculiar animals found in the Mikrotia fauna?

Some of the peculiar animals found in the Mikrotia fauna include extra-large owls, alarmingly big hamsters, supersized hedgehogs, and large birds of prey like Tyto gigantea and Garganoaetus. There were also large herbivores like the Hoplitomeryx, which had saber-like fangs and five horns on their heads.

What was the impact of the rising sea levels on the Mikrotia fauna?

The rising sea levels about 5.3 million years ago dramatically shrank the island habitats of the Mikrotia fauna, leading to their extinction. The islands were flooded, reducing the available resources and habitat, which likely contributed to the extinction of these unique animals.

How did the animals on the Mediterranean islands adapt to their new environments after becoming isolated?

After becoming isolated on the Mediterranean islands, many animals started to follow different evolutionary paths. Some stayed small or even shrank, while others responded to the absence of large predators and competitors by getting much larger. This allowed them to exploit new ecological niches and resources that were unavailable on the mainland.

What is the significance of the discovery of the Mikrotia fauna fossils in the study of evolution?

The discovery of the Mikrotia fauna fossils is significant in the study of evolution as it provides concrete evidence of how geographic isolation can lead to the development of new species with unusual body sizes. It illustrates the power of natural selection and the adaptability of species in response to their environments.

What was the role of the giant owl Tyto gigantea in the ecosystem of the Mediterranean islands?

The giant owl Tyto gigantea likely played a significant role as a top predator in the ecosystem of the Mediterranean islands. Its large size and powerful beak would have allowed it to hunt and consume larger prey than its mainland counterparts, contributing to the balance of the island's food web.

How did the animals on the Mediterranean islands become isolated from the mainland?

The animals on the Mediterranean islands became isolated from the mainland due to changes in sea levels. During periods of lower sea levels, land bridges connected the islands to the mainland, allowing animals to migrate. However, as sea levels rose, these land bridges were submerged, turning the high spots into islands and cutting off the connection to the mainland.

Outlines

00:00

🏝️ Evolutionary Giants on Mediterranean Islands

This paragraph delves into the fascinating world of the Miocene epoch, where islands in the Mediterranean Sea were home to a unique array of giant-sized creatures, which were actually quite small compared to their mainland ancestors. The text explains how geographic isolation can lead to the evolution of new species with unusual sizes, either miniaturized or gigantic. The discovery of a rich fossil deposit in Gargano, Italy, revealed an eclectic collection of oversized animals, now known as the Mikrotia fauna. The absence of large European mammals in these fossils and the presence of unusually large smaller animals suggest that these areas were once isolated islands. The paragraph also touches on the concept of insular dwarfism and insular gigantism, illustrating the power of natural selection through the example of the Pygmy mammoth.

05:02

🦉 Insular Gigantism and the Evolution of Island Beasts

The second paragraph explores the phenomenon of insular gigantism further, focusing on the Mikrotia fauna of Gargano and Scontrone. It discusses how the isolation of these areas during periods of low sea levels led to the evolution of large-sized animals, such as Deinogalerix, a shrew-like hedgehog, and Tyto gigantea, a giant owl. The text explains how these animals adapted to their environment, with some becoming top predators in the absence of large terrestrial carnivores. It also introduces the concept of an evolutionary arms race between predators and prey, leading to the growth of both groups. The paragraph highlights the unique adaptations of various animals, such as the Garganornis, a large, flightless bird, and the Hoplitomeryx, a hoofed mammal with distinctive features.

10:06

🌊 Extinction and the Legacy of the Mikrotia Fauna

The final paragraph brings the story of the Mikrotia fauna to a close by discussing their eventual extinction. Around 5.3 million years ago, a significant rise in sea levels due to the influx of Atlantic water through the Strait of Gibraltar led to the shrinking of the island habitats, which likely contributed to the extinction of these unique creatures. The paragraph also mentions the tectonic uplift that later reconnected Gargano and Scontrone to the mainland. It concludes by emphasizing the natural history aspect of these events, distinguishing them from mythology, and highlighting the importance of the fossil record in understanding the evolutionary processes that shaped these ancient island inhabitants.

Keywords

💡Island

An island is a landmass surrounded by water and relatively small in size. In the context of the video, islands are significant as they provide isolated environments that can lead to unique evolutionary developments. The script mentions an island or group of islands in the Mediterranean Sea where unusual giant creatures evolved due to geographic isolation.

💡Geographic Isolation

Geographic isolation refers to the separation of a group of organisms from the rest of their species by physical barriers, such as bodies of water or mountain ranges. This concept is central to the video's theme, as it explains how the island populations evolved independently, leading to the emergence of 'giant' creatures that were actually much larger than their mainland ancestors.

💡Evolution

Evolution is the process by which species of organisms change over time through genetic variation and natural selection. The video discusses how geographic isolation on Mediterranean islands led to evolutionary changes, resulting in the growth of certain species to unusually large sizes, a phenomenon known as insular gigantism.

💡Insular Gigantism

Insular gigantism is a biological phenomenon where species on islands tend to evolve into larger forms compared to their mainland relatives. The video uses this term to describe how animals like the Deinogalerix, a shrew-like hedgehog, grew significantly larger when isolated on islands.

💡Fossil

A fossil is the preserved remains or traces of animals, plants, and other organisms from the remote past. The script discusses the discovery of fossils in Gargano, Italy, which provided evidence of the existence of the large island creatures discussed in the video.

💡Paleontologists

Paleontologists are scientists who study the history of life on Earth through the examination of plant and animal fossils. In the script, a group of Dutch paleontologists discovered the rich fossil deposits in Gargano, leading to insights into the ancient Mediterranean island life.

💡Mikrotia Fauna

The Mikrotia fauna refers to a group of animals that were discovered in the fossil deposits of Gargano and Scontrone, characterized by their unusually large size for their species. The term is derived from the rodent Mikrotia, which was part of this fauna and is used in the video to describe the unique ecosystem of these ancient Mediterranean islands.

💡Foster's Rule

Foster's Rule is a principle in evolutionary biology that states that in isolated environments, large animals often become smaller, and small animals become larger. The video explains how this rule is exemplified by the Mikrotia fauna, where small animals evolved into much larger forms due to their island isolation.

💡Deinogalerix

Deinogalerix is a genus of large, shrew-like creatures from the hedgehog family that lived during the Miocene epoch. The video uses Deinogalerix as an example of insular gigantism, highlighting how it evolved into a much larger predator on the isolated islands compared to its mainland ancestors.

💡Tyto Gigantea

Tyto gigantea is a species of giant owl that lived during the Late Miocene and is known from the fossil deposits in Gargano. The video mentions this species to illustrate the concept of insular gigantism, as it was significantly larger than any mainland owl of its time.

💡Garganoaetus

Garganoaetus is a genus of large birds of prey that inhabited the Miocene Mediterranean islands. The script discusses two species of this bird, with the larger one rivaling the size of today's golden eagle, as an example of how predatory birds also evolved larger sizes in response to the island environment.

💡Hattomys Gargantua

Hattomys gargantua is a species of giant hamster that lived on the Mediterranean islands during the Miocene epoch. The video describes this species as an example of insular gigantism, noting that it was three times heavier than modern hamsters and represents a significant size increase from its mainland relatives.

💡Hoplitomeryx

Hoplitomeryx is a genus of hoofed mammals with unique features such as saber-like fangs and five horns on their heads. The video mentions this genus to illustrate the diversity of the Mikrotia fauna and how different species of varying sizes could coexist without direct competition due to different dietary niches.

Highlights

Greek and Roman mythology inspired by real-life Mediterranean islands with unique fauna during the Miocene epoch.

Islands were home to 'giant' beasts that were actually small, such as large hamsters and hedgehogs the size of house cats.

Geographic isolation led to the evolution of species with unusual sizes due to the absence of predators and competitors.

Dutch paleontologists discovered rich Late Miocene Epoch fossil deposits in Gargano, Italy, in 1969.

Gargano fossils lacked large mammals found elsewhere in Europe, featuring instead an eclectic collection of oversized smaller animals.

The Mikrotia fauna of Gargano and Scontrone was likely due to these areas being geographically isolated as islands.

Insular environments can lead to insular dwarfism or insular gigantism, as per Foster’s Rule.

Deinogalerix, a hedgehog-like creature, evolved from small to the largest land-dwelling hunter in its ecosystem.

Giant owls and birds of prey, such as Tyto gigantea and Garganoaetus, evolved on these islands due to a lack of competition.

Evolutionary arms race between predators and prey led to the growth of both groups on the islands.

Gargano's Garganornis, a flightless bird similar to ducks and geese, adapted to a terrestrial lifestyle due to island isolation.

Hoplitomeryx, a 'prongdeer' with saber-like fangs and five horns, exemplified size variation among island mammals.

The extinction of the Mikrotia fauna was likely due to the flooding of their island habitat around 5.3 million years ago.

Tectonic uplift in the early Pleistocene reconnected Gargano and Scontrone with the mainland.

Natural history, not mythology, explains the existence of odd-sized Mediterranean island creatures.

Fossil remains serve as evidence of the unique evolutionary processes on ancient Mediterranean islands.

Transcripts

Greek and Roman mythology is full of stories about exotic islands that were home to weird

and fearsome monsters -- like one-eyed ogres, seductive sirens, and man-eating giants.

And I’m here to tell you: Back in the late Miocene epoch, there was in fact an island--or

maybe a group of islands-- in the Mediterranean Sea that was populated with fantastic giant

beasts.

But, these giants were actually … pretty small.

Some of them you might even consider cute.

There were enormous hamsters.

And big, fat waterbirds that could neither fly nor swim.

And animal like hedgehogs that were as big as house cats.

These organisms were only giants compared to their ancestors, which had lived on the

European mainland.

But once they became isolated on these Mediterranean islands, some of these little critters attained

massive body sizes.

That’s because geographic isolation is a powerful force in evolution.

Sometimes, when a population of animals gets cut off from many of its normal predators

or competitors, it gives rise to new species of unusual sizes.

Sometimes, they turn out to be miniaturized versions of their ancestors.

Other times, giants!

The tale of these Mediterranean island beasts of the Miocene is no myth.

It’s a lesson in the very strange, but very real, powers of natural selection.

In 1969, a group of Dutch paleontologists were working in Gargano, a region on the eastern

coast of Italy, when they discovered deep fissures, or cracks, in the limestone quarries

and road cuts there.

And these cracks turned out to be full of fossils!

For millions of years, it seemed, animals had been stumbling into these fissures, like

natural traps, starting about 8 million years ago.

The result was an amazingly rich fossil deposit, a snapshot of life in this place in the Late

Miocene Epoch.

But a few things about the Gargano fossils turned out to be really … odd.

For one thing, scientists were confused about the fossils they didn’t find.

Elsewhere in Europe, deposits from the late Miocene tend to contain a lot of large mammals

-- like extinct elephants, cats, and perissodactyls, the group of hoofed mammals that includes

horses.

But at Gargano, none of those animals were anywhere to be found.

Instead, researchers uncovered an eclectic and bizarre bestiary, including fossils of

smaller animals that seemed ... overgrown.

There were extra-large owls, alarmingly big hamsters, and supersized hedgehogs.

This strange assortment of animals came to be known as the Mikrotia fauna.

And for decades, the Gargano Peninsula --along with a handful of nearby towns -- were the

only places on the planet where these creatures were known.

Then in the 1990s, fossils of some of those same, peculiar animals turned up at Miocene

sites near Scontrone, a town in central Italy.

So, what exactly were these animals?

Why were the Miocene animals of Gargano and Scontrone so different from their counterparts

in the rest of Europe?

For paleontologists, the most likely explanation was that these areas must’ve been cut off

-- geographically separated -- from the rest of Europe.

Specifically, they were probably islands -- or maybe parts of the same island.

This would explain not only why these animals appear just at those sites; it would also

account for the strange body sizes of animals that were ordinarily quite small.

I’ve talked before about how, in island environments, large-bodied animals often get

smaller over time.

In the case of Columbian mammoths on the Channel Islands of California, for example, the absence

of large predators, combined with limited food, led natural selection to favor smaller

body sizes.

So, after thousands of years, some of the giant Columbian mammoths had developed into

what scientists consider a new, separate and smaller species: the Pygmy mammoth!

This phenomenon is known as insular dwarfism.

But it’s only part of the story about how island environments can tinker with animals’

body plans.

The flip-side is what happened to some of the animals of Gargano and Scotrone: Insular

Gigantism.

Both processes are part of what’s known as Foster’s Rule, identified by biologist

J. Bristol Foster in 1964.

Essentially, Foster’s Rule says that in isolated environments, large animals frequently

get smaller -- and tiny animals often become larger.

And this is what happened to many animals in the Mikrotia fauna.

And it happened because their habitat allowed it to happen.

Much like the modern Channel Islands, the regions of Gargano and Scontrone in the deep

past were higher in elevation than the surrounding areas.

So as sea levels rose and fell over millions of years due to changes in climate, these

places became isolated from the rest of Europe, and then reconnected, many times.

And it may have been during one of these periods of low sea levels when some ancestors of the

island giants first made their way to Gargano and Scontrone.

Researchers think that, about 30 million years ago, in the Oligocene Epoch, a global cooling

trend lowered sea levels in the Mediterranean and elsewhere, forming a land bridge between

the mainland and these two spots.

But then, about 15 million years ago, the climate warmed again and sea levels rose,

turning those high spots into islands and severing their connection to the mainland.

So, maybe the ancestors of the Mikrotia fauna simply walked across the land bridge before

it became submerged.

But other scientists have proposed that most of them arrived much more recently -- just

around 8 million years ago -- when the island or islands were properly isolated.

In that case, it’s thought that the animals might have rafted on piles of floating debris--like

logs, branches, and palm leaves -- much in the same way that the ancestors of South America’s

rodents are thought to have migrated from Africa!

Either way, once they’d reached their new island habitats, many of the animals started

to follow different evolutionary paths.

Some stayed small, and some may have actually shrunk.

But others responded to their new environment by getting downright huge.

Just look at Deinogalerix, a shrew-like member of the hedgehog family that’s found only

in these Mikrotia fossil deposits.

Early species of this genus were about 30 to 45 centimeters long, making them only slightly

bigger than a modern European hedgehog.

But over time, bigger and badder Deinogalerix started to evolve alongside them.

The largest species--found only in the most recent deposits--was some 60-centimeters long!

And even though it was a member of the hedgehog family, Deinogalerix had teeth that were more

like those of cats and dogs.

Using its long, pointy incisors and crushing cheek teeth, the largest of this genus probably

behaved like a badger or raccoon, hunting much bigger prey than its ancestors ever could.

And it did, simply because it could!

Back on the mainland, the ancestors of Deinogalerix needed to stay small in order to avoid all

the large predators.

But in this island environment, there were very few large, terrestrial carnivores.

So without the selective pressure to remain small, Deinogalerix was free to expand in

size and take advantage of new niches.

Its ancestors probably specialized in eating insects, but this animal could’ve also hunted

other, larger prey, like vertebrates.

In the process, it emerged as one of the area’s biggest land-dwelling hunters.

This was Foster’s Rule in action!

But a big old hedgehog-like thing still had some competitors--and natural enemies.

Because, these islands were also home to some unusually large birds of prey.

Take the giant owl known as Tyto gigantea, which appeared on Gargano in the Late Miocene.

We don’t know for sure which species it evolved from, but we do know that there was

nothing near its size on the mainland.

Based on its fossils, scientists think Tyto gigantea may have had a wingspan of two meters

or more -- twice the size of a living barn owl.

Likewise, the islands were also home to a bird of prey known as Garganoaetus, which

included two species.

The larger one probably rivaled today’s golden eagle in size, and it’s only found

in more recent deposits.

So this suggests that Garganoaetus, like the giant owl, developed a bigger body size over

time.

But here’s a question: On an island with few other predators, why would these birds

of prey get so large?

Wouldn’t that just mean they’d need more food?

Well, some researchers think that on these islands of giants, both predators and prey

were engaged in a sort of evolutionary arms race.

Research has shown that the modern barn owl can’t swallow any rodents whose heads are

longer than 17 millimeters.

But by being bigger, these birds would’ve had an easier time hunting--and gulping down--the

local rodents, which were also getting quite hefty.

For example, there’s the burrowing rodent Mikrotia, the Gargano native that gave this

whole group its name.

One species of Mikrotia had a skull that was twice the size of a modern rat’s head, suggesting

the rest of the animal was pretty big too.

There was also a giant species of dormouse -- which are usually tiny and adorable -- but

this one weighed about a kilogram….Which still sounds pretty cute to me!

And then there was Gargano’s strange, giant hamster Hattomys gargantua.

It was three times heavier than today’s common hamster and much bigger than the any

species that lived on the mainland at the time.

Mind you, not all of these island animals expanded in size over time.

Small and normal-sized birds and rodents coexisted with giant species.

But some rodents definitely got bigger, either because they simply could or because it let

them expand into new dietary niches.

And as they grew, the birds of prey also evolved larger sizes in order to hunt and eat them.

This same phenomenon occurred among other kinds of birds, too.

Take the case of Garganornis, first reported in 2013.

Garganornis belonged to the same family of birds as ducks and geese.

But it weighed between 15 and 22 kilograms, up to twice as much as a large Canada goose.

Unlike modern geese and ducks, its toes and lower leg bones were really short, suggesting

that it spent most of its time walking on land and not paddling in the water.

And judging by the bones in its wings, it probably couldn’t fly, either.

So, researchers think that Garganornis adapted to take advantage of its island’s lack of

big, herbivorous mammals.

By growing bigger and staying on land, it may have been able to broaden its niche and

forage on a wider range of terrestrial plants, while its size could’ve helped it fend off

some of those birds of prey.

And size adaptations seemed to have benefitted some larger mammals on the island, too.

One herbivore known exclusively from Mikrotia deposits was the truly strange Hoplitomeryx,

a genus of hoofed mammals with saber-like fangs and five horns on their heads.

Five!

And there were lots of different species of this so-called “prongdeer” that varied

a lot in size.

By one estimate, the smallest only weighed around 5 to 6 kilograms, while the biggest

may have tipped the scales at 113 kilograms.

And species of different sizes seem to have lived at the same time, which kind of makes

sense.

DIfferent sizes would make different food sources available to each species.

This would’ve not only kept the “prongdeer” from competing with each other, it could also

have prevented from from overgrazing their little island.

But there was a change on the horizon that none of the weird and beautiful Mikrotia fauna

could adapt their way out of.

About 5.3 million years ago, a massive amount of Atlantic water passed through the Strait

of Gibraltar--which had once been lifted above sea level.

This flooded the Mediterranean.

Rising water levels dramatically shrank the little giants’ island habitat, which is

probably what drove them to extinction.

Just a few million years later, in the early Pleistocene, some areas of central and southern

Italy went through a period of tectonic uplift.

That reunited Gargano and Scontrone with the rest of the mainland, where they remain today.

So, competition, food availability, predator/prey relationships, and niche expansion: any or

all of these things can, very gradually, make either pygmies or giants out of animals that

are isolated on islands.

It’s not mythology!

It’s natural history!

And we have their fascinating fossil remains to remind us of the odd little giants that

once roamed those ancient Mediterranean islands.

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