Every season of Eons ever, ranked from best to worst by thousands of votes from fans of the show. The best seasons of Eons!

Trilobites are famous not just because they were so beautifully functional, or because they happened to preserve so well. They’re known the world over because they were everywhere!

The Trouble With Trilobites

During the Cretaceous Period, dinosaurs were more diverse, more fierce, and more strange than ever. But something else was happening under the feet of the terrible lizards: for the first time in history, there were flowers.

When Did the First Flower Bloom?

There are animals in the fossil record that challenge some of our most basic ideas about what animals are supposed to look like. If there ever was a monster on this planet that was worthy of the name, it might have been the Tully Monster.

The Tully Monster & Other Problematic Creatures

If you take it as a given that extinct dinosaurs were all weird and wonderful, then you gotta at least consider that Stegosaurus was one of the weirdest and wonderfulest.

Stegosaurs: Tiny Brains & Thagomizers

We know a lot about dinosaurs but there’s one question that has plagued paleontologists for decades: what color were they?

What Colors Were Dinosaurs?

Smilodon was a fearsome Ice Age cat, the size of a modern-day tiger, that had a pair of fangs nearly 18 centimeters long. But it was only the last and largest of the great sabertooths: ridiculously long canines had already been a trend for millions of years by the time Smilodon was prowling around. And you know what? Those giant teeth just might make a comeback.

The Story of Saberteeth

What if we told you that there was a time when oxygen almost wiped out all life on Earth? 3 billion years ago, when the world was a place you’d never recognize, too much of a good thing almost ruined everything for everybody.

That Time Oxygen Almost Killed Everything

Today, we’re familiar with two types of flying vertebrates -- birds and bats. But over 66 million years ago, there was a giraffe-sized reptile that soared through the sky.

The Biggest Thing That Ever Flew

With its lizard-like appearance and that distinctive sail on it back, Dimetrodon is practically the mascot of the Palaeozoic Era, a time before flowers, birds, mammals, and even crocodiles. But if you take a close look at this sail-backed animal, you might see a little bit of yourself.

Dimetrodon: Our Most Unlikely Ancestor

Natural history is full of living things that were long thought to have gone extinct only to show up again, alive and well. Paleontologists have a word for these kinds of organisms: They call them Lazarus taxa.

The Extinction That Never Happened

There are many fossils that challenge our ability to form even the most basic idea of how a living thing looked, or lived, or functioned. One of the longest-running of these mysteries involved a 270-million-year-old sea creature called Helicoprion that once swam the seas around the supercontinent of Pangea.

The Strange Case of the Buzzsaw Jaws

Insects outnumber humans by a lot and we only like to think we're in charge because we're bigger than they are. But insects and other arthropods weren’t always so small. About 315 million years ago during the Carboniferous Period, they were not only abundant: they were enormous.

The Age of Giant Insects

Fossil fuels are made from the remains of extinct organisms that have been exposed to millions of years of heat and pressure. But in the case of coal, these organisms consisted largely of some downright bizarre plants that once covered the Earth, from Colorado to China.

History's Most Powerful Plants

Part of why we’re so fascinated with extinct dinosaurs it’s just hard for us to believe that animals that huge actually existed. And yet, they existed! From the Jurassic to the Cretaceous Periods, creatures as tall as a five-story building were shaking the Earth.

How Did Dinosaurs Get So Huge?

Besides the blue of the oceans, the dominant color of our planet, as we know it, is green. But imagine a time when the Earth looked a little … purple.

When The Earth Was Purple

Crocodiles, horseshoe crabs and tuatara are animals that have persisted for millions of years, said to have gone unchanged since the days of the dinosaurs. But even the most ancient-looking organisms show us that evolution is always at work.

'Living Fossils' Aren't Really a Thing

We know whales as graceful giants bound to the sea. But what if we told you there was actually a time when whales could walk.

When Whales Walked

Our image of dinosaurs has been constantly changing since naturalists started studying them about 350 years ago. Taken together, these pictures can tell us a whole lot about just how much we have learned. Let's explore the history of dinosaur science as seen through the history of dinosaur art.

An Illustrated History of Dinosaurs

By looking at the layers beneath our feet, geologists have been able to identify and describe crucial episodes in life’s history. These key events frame the chapters in the story of life on earth and the system we use to bind all these chapters together is the Geologic Time Scale.

A Brief History of Geologic Time

More than 4 billion years ago, the crust of the Earth was still cooling and the oceans were only beginning to form. But in recent years, we’ve started to discover that, even in this hellish environment, life found a way.

The Search for the Earliest Life

Over the past 20 years, dinosaurs of all types and sizes have been found with some sort of fluff or even full-on plumage. These fuzzy discoveries have raised a whole batch of new questions so we're here to tell you everything we know about dinosaurs and feathers.

The Facts About Dinosaurs & Feathers

Imagine an enormous, lush rainforest teeming with life...in the Arctic. Well there was a time -- and not too long ago -- when the world warmed more than any human has ever seen. (So far)

The Last Time the Globe Warmed

Probably twice the size of a modern gorilla, Gigantopithecus is the greatest great-ape that ever was. And for us fellow primates, there are some lessons to be learned in how it lived, and why it disappeared.

What Happened to the World's Greatest Ape?

420 million years ago, a giant feasted on the dead, growing slowly into the largest living thing on land. It belonged to an unlikely group of pioneers that ultimately made life on land possible -- the fungi.

When Giant Fungi Ruled

What if I told you that, more than two billion years ago, some tiny living thing started to live inside another living thing … and never left? And now, the descendants of both of those things are in you?

How Two Microbes Changed History

About 5 million years ago, a new predator made its way from the south and onto the coastal plains of North America. It was a giant, flightless, carnivorous bird and came to be known by one of the coolest and most richly earned nicknames in all of paleontology: the terror bird.

The Time Terror Birds Invaded

In the late 1800s, paleontologists in Nebraska found huge coils of hardened sand stuck deep in the earth. Local ranchers called them Devil's Corkscrews and scientists called them Daemonelix. It was clear these corkscrews were created by some form of life, but what?

Untangling the Devil's Corkscrew

90 million years ago, an ancient snake known as Najash had...legs. It is by no means the only snake to have limbs either. But what’s even stranger: we’re not at all sure where it came from.

The Great Snake Debate

The study of natural history is the study of how the world has changed but Earth itself is in a constant state of flux -- because the ground beneath your feet is always moving. So if we want to know how we got here, we have to understand how "here" got here.

The Whole Saga of the Supercontinents

The first era of our current eon, the Paleozoic Era, is probably the most deceptively fascinating time in Earth’s history. With near constant revolutions in life, punctuated by catastrophic extinctions, it is also one of the most chaotic.

From the Cambrian Explosion to the Great Dying

We don’t know which living thing was the very first to arrive at the totally revolutionary process that is sexual reproduction but we can follow the history of how (and why) sex became a thing.

How Sex Became a Thing

Fossils found around the world suggest that multi-cellular life was not only present before the Cambrian Explosion, it was much more elaborate and diverse than anyone thought. This is the story of the sudden burst of diversity that marked the dawn of truly complex life on our planet.

The Other Explosion You Should Know About

Where did turtles come from? And how did the they get their shells? The answers to these questions would eventually cause scientists to rethink the entire history of reptile evolution.

How the Turtle Got Its Shell

We traveled to Bozeman, Montana to meet with Dr. Ellen-Thérèse Lamm who explores ancient life by studying it at the cellular level. Kallie and Dr. Lamm discuss how she does this, and what she’s learned by putting dinosaur bones under a microscope.

What a Dinosaur Looks Like Under a Microscope

For decades, one of the most abundant kinds of fossils on Earth, numbering in the millions of specimens, was a mystery to paleontologists. But geologists discovered that these mysterious fossils could basically be used to tell time in the deep past.

The Most Useful Fossils in the World

We're back in Bozeman, Montana this week talking to Amy Atwater, Collections Manager at the Museum of the Rockies. MOR has among the largest collections of North American dinosaurs in the United States. We talk to Amy about her job and the collection she manages.

Inside the Dinosaur Library

The search for our origins go back to a single common ancestor -- one that remains shrouded in mystery. It’s the ancestor of everything we know and today scientists call it the last universal common ancestor, or LUCA.

What Was the Ancestor of Everything?

The ancestors of modern, squishy cephalopods like the octopus and the squid all had shells. In ancient times, their shell was their greatest asset but it eventually proved to be their biggest weakness.

How the Squid Lost Its Shell

Two extinct relatives of horses and rhinos are closely related to each other but have strikingly different body plans. How did two of the same kind of animal, living in the same place, end up looking so different?

How the Chalicothere Split In Two

Reptiles emerged from the Paleozoic as humble creatures, but in time, they grew to become some of the largest forms of life ever to stomp, swim, and soar across the planet. This Age of Reptiles was a spectacular prehistoric epic, and it all took place in a single era: the Mesozoic.

The Age of Reptiles in Three Acts

In 1912, a fossil collector discovered some strange bone fragments in the eerie, beautiful Cretaceous Bahariya rock formation of Egypt. Eventually, that handful of fossil fragments would reveal to scientists one of the strangest dinosaurs that ever existed -- the world’s only known semi-aquatic dinosaur.

The Weird, Watery Tale of Spinosaurus

After taking you on a journey through geologic time, we've arrived at the Cenozoic Era. Most of the mammals and birds that you can think of appeared during this era but perhaps more importantly, the Cenozoic marks the rise of organisms that look a lot like us.

From the Fall of Dinos to the Rise of Humans

At the beginning of the Triassic Period, with the continents locked together from pole-to-pole in the supercontinent of Pangea, the world is hot, flat, and very, very dry. But then 234 million years ago, the climate suddenly changed for the wetter.

That Time It Rained for Two Million Years

The Triassic was full of creatures that look a lot like other, more modern species, even though they’re not closely related at all. The reason for this has to do with how evolution works and with the timing of the Triassic itself: when life was trapped between two mass extinctions.

Why Triassic Animals Were Just the Weirdest

There are fossils of viruses, of sorts, preserved in the DNA of the hosts that they’ve infected. Including you. This molecular fossil trail can help us understand where viruses came from, how they evolved and it can even help us tackle the biggest question of all: Are viruses alive?

Where Did Viruses Come From?

385 million years ago, a group of fish would undertake one of the most important journeys in the history of life and become the first vertebrates to live on dry ground. But first, they had to acquire the ability to breathe air.

When Fish First Breathed Air

Tyrannosaurus rex was big, Tyrannosaurus rex was vicious, and Tyrannosaurus rex had tiny arms. The story of how T-Rex lost its arms is, itself, pretty simple. But the story of why it kept those little limbs, and how it used them? Well, that’s a little more complicated.

How the T-Rex Lost Its Arms

Over the first season of PBS Eons, we’ve explored the history of Earth from the very origins of life right up to the Cenozoic Era that we’re in now. To celebrate our first anniversary together, we’d like to answer some of your most frequently asked questions.

FAQs From Our First Year

Insects were the first animals to ever develop the ability to fly, and, arguably, they did it the best. But this development was so unusual that scientists are still/working on, and arguing about, how and when insect wings first came about.

When Insects First Flew

In 1800s, miners began working in exposed deposits of mud near the town of Messel, Germany. They were extracting oil from the rock and along with the oil, they found beautifully preserved fossils of animals from the Eocene. What happened to these Eocene animals? And why were their remains so exquisitely preserved?

The Mystery of the Eocene’s Lethal Lake

420 million years ago, some fish were more medieval. They wore armor, sometimes made of big plates, and sometimes made of interlocking scales. But that armor may actually have served a totally different purpose, one that many animals still use today.

When Fish Wore Armor

Experts are still arguing over whether Archaeopteryx was a true bird, or a paravian dinosaur, or some other kind of dino. But regardless of what side you’re on, how did this fascinating, bird-like animal relate to today’s birds? It turns out its teeth were a clue that this story goes all the way back to what we now call the non-avian dinosaurs.

When Birds Had Teeth

The ancestors of modern horses became so successful that they spread all over the world, to Europe, Asia, South America, and Africa. But in their native range of North America, they’ll vanish for 10,000 years. Until another strange mammal brings them back.

How Horses Took Over North America (Twice)

One of the most dynamic, transformative, and potentially dangerous features in North America is also responsible for some of the continent’s most amazing fossil deposits. It’s a supervolcano we now call Yellowstone.

How a Supervolcano Made the Cenozoic’s Coolest Fossils

A huge and diverse subfamily of dogs, the bone-crushers patrolled North America for more than thirty million years, before they disappeared in the not-too-distant past. So what happened to the biggest dogs that ever lived?

The Rise and Fall of the Bone-Crushing Dogs

This is not a Game of Thrones fan fiction episode. Dire wolves were real! And thousands of them died in the same spot in California. Their remains have taught us volumes about how they lived, hunted, died and way more about any animal’s sex life than you’d ever want to know.

Life, Sex & Death Among the Dire Wolves

Fossilized footprints have proved that human ancestors were already striding across the landscape 3.6 million years ago. But who started them on that path? What species pioneered this style of locomotion? Who was the first to walk?

When We First Walked

Paleontologists have been studying and drawing totally different conclusions about the fossil LH PV18 for almost a decade. Is it just one of many specimens of a theropod called Tarbosaurus bataar or is it an entirely different theropod named Raptorex kriegsteini? In order to answer this question, you have to understand the many ways in which we can--and can’t--determine the age of a fossil.

Did Raptorex Really Exist?

In 1993, scientists cracked open a piece of amber, took out the body of an ancient weevil, and sampled its DNA. Or, at least, so we thought. It took another few decades of research, and a lot of take-backs, before scientists could figure out how we could truly unlock the genetic secrets of the past.

Can We Get DNA From Fossils?

Temnospondyls were a huge group of amphibians that existed for 210 million years. And calling them ‘diverse’ would be putting it mildly. Yet in the end, two major threats would push them to extinction: the always-changing climate and the amniote egg.

When Giant Amphibians Reigned

Purgatorius, a kind of mammal called a plesiadapiform, might’ve been one of your earliest ancestors. But how did we get from a mouse-sized creature that looked more like a squirrel than a monkey -- to you, a member of Homo sapiens?

Your Place in the Primate Family Tree

Due to an odd quirk of genetics and some unique evolutionary circumstances, two humans who lived at different times in the distant past managed to pass on a very small fraction of their genomes to you. And to me. To all of us.

The Two People We're All Related To

The best evidence we have suggests that, while Caviomorpha originated in South America, they came from ancestors in Africa, over 40 million years ago. So how did they get there?

When Rodents Rafted Across the Ocean

Ratites have spread to Africa, Australia, New Zealand, and South America. And there are fossils of Ratites in Europe, Asia, and North America too. That’s a lot of ground to cover for birds that can’t fly. So how did Ratites end up all over the world?

When Birds Stopped Flying

Camels are famous for adaptations that have allowed them to flourish where most other large mammals would perish. But their story begins over 40 million years ago in North America, and in an environment you’d never expect: a rainforest.

When Camels Roamed North America

The story of sloths is one of astounding ecological variability, with some foraging in the seas, others living underground, and others still hiding from predators in towering cliffs. So why are their only living relatives in the trees?

How Sloths Went From the Seas to the Trees

If you’ve ever been to, or lived in, or even flown over the central swath of North America, then you’ve seen the remnants of what was a uniquely fascinating environment. Scientists call it the Western Interior Seaway, and at its greatest extent, it ran from the Caribbean Sea to the Canadian Arctic.

When Sharks Swam the Great Plains

Today, our closest evolutionary relatives, the apes, live only in small pockets of Africa and Asia. But back in the Miocene epoch, apes occupied all of Europe. Why aren’t there wild apes in Europe today?

When Apes Conquered Europe

For more than 10 million years, Megalodon was at the top of its game as the oceans’ apex predator...until 2.6 million years ago, when it went extinct. So, what happened to the largest shark in history?

Why Megalodon (Definitely) Went Extinct

Not too long ago, our early human ancestors were under constant threat of attack from predators. And it turns out that this difficult chapter in our history may be responsible for the adaptations that allowed us to become so successful.

When Humans Were Prey

Blood is one of the most revolutionary features in our evolutionary history. Over hundreds of millions of years, the way in which blood does its job has changed over and over again. As a result, we animals have our familiar red blood. But also blue blood. And purple, and green, and even white.

How Blood Evolved (Many Times)

As more and more fossil ancestors have been found, our genus has become more and more inclusive, incorporating more members that look less like us, Homo sapiens. By getting to know these other hominins--the ones who came before us--we can start to answer some big questions about what it essentially means to be human.

The Humans That Lived Before Us

The mammoths fossils found on the Channel Islands off the coast of southern California are much smaller than their relatives found on the mainland. They were so small that they came to be seen as their own species. How did they get there? And why were they so small?

The Island of Shrinking Mammoths

In order to understand where hearts came from, we have to go back to the earliest common ancestor of everything that has a heart. It took hundreds of millions of years, and countless different iterations of the same basic structure to lead to the heart that you have today.

The Evolution of the Heart (A Love Story)

Strange geologic landmarks in the Pacific Northwest are the lingering remains of a mystery that took nearly half a century to solve. These features turned out to be a result one of the most powerful and bizarre episodes in geologic history: this region experienced dozens of major, devastating floods over the course of more than 7,000 years.

How 7,000 Years of Epic Floods Changed the World

Back in the late Miocene epoch, there was an island--or maybe a group of islands-- in the Mediterranean Sea that was populated with fantastic giant beasts. It’s a lesson in the very strange, but very real, powers of natural selection.

The Island of Huge Hamsters and Giant Owls

The California condor is the biggest flying bird in North America, a title that it has held since the Late Pleistocene Epoch. It's just one example of an organism that we share the planet with today that seems lost in time, out of place in our world.

The Giant Bird That Got Lost in Time

The tools made by our human ancestors may not seem like much when you compare them to the screen you’re looking at right now but their creation represents a pivotal moment in the origin of technology and in the evolution of our lineage.

When We First Made Tools

Sea scorpions thrived for 200 million years, coming in a wide variety of shapes and sizes. Over time, they developed a number of adaptations--from crushing claws to flattened tails for swimming. And some of them adapted by getting so big that they still hold the record as the largest arthropods of all time.

When Giant Scorpions Swarmed the Seas

The ability to make and use fire has fundamentally changed the arc of our evolution. The bodies we have today were, in many ways, shaped by that time when we first tamed fire.

When We Tamed Fire

The short-faced bears turned out to be remarkably adaptable, undergoing radical changes to meet the demands of two changing continents. And yet, for reasons we don’t quite understand, their adaptability wasn’t enough to keep them from going extinct.

The Mystery Behind the Biggest Bears of All Time

In the Eocene Epoch, there was a reptile that had teeth equipped for biting through flesh, its hind legs were a lot longer than its front legs and instead of claws, its toes were each capped with hooves. How did this living nightmare come to evolve?

The Croc That Ran on Hooves

From our deepest origins in Africa all the way to the Americas, by looking at the fossils and archaeological materials we have been able to trace the path our ancestors took during thee short window of time when we took over the world.

When We Took Over the World

All of today’s big cat species evolved less than 11 million years ago and yet their evolutionary history remains an almost total mystery. But scientists have recently discovered a major clue about the origins of the big cats, one that could provide a whole new starting place for solving this puzzle.

The Ghostly Origins of the Big Cats

Throughout the Pleistocene Epoch, the range of the woolly rhino grew and shrank in sync with global climate. So what caused the climate -- and the range of the woolly rhino -- to cycle back and forth between such extremes?

The History of Climate Cycles (and the Woolly Rhino) Explained

Despite the name, we don’t know where the so-called “hell pigs” belong in the mammalian family tree. They walked on hooves, like pigs do, but had longer legs, almost like deer. They had hunched backs, a bit like rhinos or bison. But as is often, if not always, the case, there is some evolutionary method to this anatomical madness.

The Hellacious Lives of the "Hell Pigs"

As a scientific concept, evolution was revolutionary when it was first introduced. With the help of all three of our hosts and the Smithsonian National Museum of Natural History’s new Deep Time Hall, we’ll try to explain how evolution actually works and how we came to understand it.

How Evolution Works (And How We Figured It Out)

Synapsids were the world’s first-ever terrestrial megafauna but the vast majority of these giants were doomed to extinction. However some lived on, keeping a low profile among the dinosaurs. And now our world is the way it is because of the time when the synapsids struck back.

When the Synapsids Struck Back

The marine reptiles Ichthyosaurs arose after The Great Dying, which wiped out at least 90 percent of life in the oceans, changing the seas forever and triggering a new evolutionary arms race between predator and prey.

When Ichthyosaurs Led a Revolution in the Seas

We all belong to the only group of hominins on the planet today. But we weren’t always alone. 100,000 years ago, Eurasia was home to other hominin species, some of which we know our ancestors met, and spent some quality time with.

When We Met Other Human Species

Over 600 million years ago, sheets of ice coated our planet on both land and sea. How did this happen? And most importantly for us, why did the planet eventually thaw again? The evidence for Snowball Earth is written on every continent today.

How Volcanoes Froze the Earth (Twice)

They have survived every catastrophe and every mass extinction event that nature has thrown at them. And by being the little, filter-feeding, water-cleaning creatures that they are, sponges may have saved the world.

How Earth's First, Unkillable Animals Saved the World

Megaloceros was one of the largest members of the deer family ever to walk the Earth. The archaeological record is full of evidence that our ancestors lived alongside and interacted with these giant mammals for millennia. But what happened when they did interact, when humans met this megafauna?

When Giant Deer Roamed Eurasia

Paleontologists have spent the better part of two decades debating whether Coelophysis ate its own kind. It turns out, the evidence that scientists have had to study in order to answer that question includes some of the strangest and grossest fossils that any expert would ever get to see.

Was This Dinosaur a Cannibal?

The myth of the Missing Link--the idea that there must be a specimen that partly resembles an ape but also partly resembles a modern human--is persistent. But the reality is that there is no missing link in our lineage, because that’s not how evolution works.

The Missing Link That Wasn’t

In 1964, a paleontologist named John Ostrom unearthed some fascinating fossils from the mudstone of Montana. Its discovery set the stage for what’s known today as the Dinosaur Renaissance, a total re-thinking of what we thought we knew about dinosaurs.

The Raptor That Made Us Rethink Dinosaurs

Bats pretty much appear in the fossil record as recognizable, full-on, flying bats. And they show up on all of the continents, except Antarctica, around the same time. So where did bats come from? And which of the many weird features that bats have, showed up first?

When Bats Took Flight

When pterosaurs first took flight, you could say that it marked the beginning of the end for the winged reptiles. Because, strangely enough, the power of flight -- and the changes that it led to -- may have ultimately led to their downfall.

How Pterosaurs Got Their Wings

Just a few thousand years ago, the island of Madagascar was inhabited by giant lemurs. How did such a diverse group of primates evolve in the first place, and how did they help shape the unique environments of Madagascar? And how did they get winnowed down, leaving only their smaller relatives behind?

When Giant Lemurs Ruled Madagascar

Before the start of the Eocene Epoch about 56 million years ago--Antarctica was still joined to both Australia and South America. And it turns out that a lot of what we recognize about the southern hemisphere can be traced back to that time when Antarctica was green.

The Best Seasons of Eons

The Best Seasons of Eons

Season 1

Season 2

Season 3

Season 4

Season 5

Season 6