Browse all 68 episodes in this season, including available images, air dates, runtimes, ratings and episode summaries from TMDB.
Episode 1
Around 10,000 years ago, somewhere in Africa, a microscopic parasite made a huge leap. With a little help from a mosquito, it left its animal host - probably a gorilla - and found its way to a new host: us.
Episode 2
The Snake Detection Hypothesis proposes that the ability to quickly spot and avoid snakes is deeply embedded in primates, including us - an evolutionary consequence of the danger snakes have posed to us over millions of years.
Episode 3
We often think of dinosaurs as either preying on other dinos or mammals, or as plant-eaters -- but in ecosystems today, those aren’t the only two options. So why would we expect dinosaurs to have only been carnivores or herbivores, with the occasional omnivore thrown in the mix?
Episode 4
As revolutionary as teeth were, they would go on to disappear in some groups of vertebrates. But why?
Episode 5
Do our modern horses descend from just one domesticated population, or did it happen many times, in many places? Answering these questions has been tricky, as we’ve needed to bring together evidence from art, archaeology, and ancient DNA…Because, as it turns out, the history of humans and horses has been a pretty wild ride.
Episode 6
Today, all mammals from humans to bats have five fingers or fewer. Yes, even whales, whose finger bones are hidden in their fins. Birds have four or fewer and amphibians get the best of both worlds, often having four digits on their “hands” and five on their “feet.” But no species of vertebrates have more than five digits, let alone eight!
Episode 7
There used to be SO MANY sharks...where did they go?
Episode 8
Dire wolves aren’t actually wolves but what they are might be even cooler.
Episode 9
Could humans survive during the Precambrian?
Episode 10
Don’t be fooled by convergent evolution.
Episode 11
Why do human knees suck?
Episode 12
And it’s been reported that one of the geologists started it on purpose?
Episode 13
The ecological niche of apex predators was empty on Hateg Island, waiting to be occupied by something large, mobile, and powerful enough to fill it.
Episode 14
TMDB has not published a written overview for this episode yet.
Episode 15
Would you have survived the K-Pg Impact?
Episode 16
A truly enormous ichthyosaur around the size of a modern sperm whale, reached its size within just a few million years of taking to the water - a blink of an eye in evolutionary time.
Episode 17
Thylacines are definitely extinct!
Episode 18
Hyenas weren’t always able to eat bones. In fact, only a few million years ago, they lived very different lives.
Episode 19
TMDB has not published a written overview for this episode yet.
Episode 20
The bird that evolved twice!
Episode 21
TMDB has not published a written overview for this episode yet.
Episode 22
TMDB has not published a written overview for this episode yet.
Episode 23
I will pass on the parasitic mind-controlling mushroom, thanks
Episode 24
We tend to think that evolution only goes in one direction— toward getting bigger and more advanced. But that’s not always the case. This tiny, simple animal, the Myxozoans, (yes, animal!) evolved from something bigger and more complex.
Episode 25
TMDB has not published a written overview for this episode yet.
Episode 26
While sour taste's original purpose was to warn vertebrates of danger, in a few animal groups, including us, its role has reversed. The taste of danger became something it was dangerous for us to avoid.
Episode 27
Only a handful of Denisovan fossils have been identified. In the absence of actual body fossils, it’s impossible for us to reconstruct their morphology, right?
Episode 28
TMDB has not published a written overview for this episode yet.
Episode 29
TMDB has not published a written overview for this episode yet.
Episode 30
TMDB has not published a written overview for this episode yet.
Episode 31
While we’ve been farming for around 10,000 to 12,000 years, the ancestors of ants have been doing it for around 60 million years. So when, and how, and why did ants start … farming?

Episode 32
A mysterious, large feline roamed Eurasia during the last ice age. Its fossils have been found across the continent, and it’s been the subject of ancient artwork. So what exactly were these big cats?
Episode 33
Fossil evidence suggests Diictodon used burrows to breed, and that a parent stayed behind to feed and protect their young. And the parent that stayed behind? It might’ve been the male.
Episode 34
There’s something weird going on at the Cleveland-Lloyd Dinosaur Quarry in what’s now Utah.
Episode 35
Does Homo erectus beat out Homo sapiens?
Episode 36
Sometimes modern problems require ancient, evolutionary solutions.
Episode 37
What was this ancient pup’s last meal?
Episode 38
The newest oldest saber-toothed mammal
Episode 39
In the quest to understand how evolution basically built the woolly mammoth, we may have found the blueprints for building them ourselves.
Episode 40
Paleodictyon, a hexagonal-patterned fossil, is a bit of a mystery. We don’t even know if it’s a trace fossil, or the organism itself. So… what could it be?

Episode 41
In 2003, microbiologists made a huge discovery. One that would force us to reconsider a lot of what we thought we knew about the evolution of microbial life: giant viruses.
Episode 42
Microbiology goes macro with a new giant bacterium!
Episode 43
Spinosaurus had dense bones!
Episode 44
Guemesia: a new no-arm dino

Episode 45
This giant millipede was the largest known invertebrate to ever live on land. So how did it get so big??

Episode 46
Despite the profound changes we’ve made here in recent history, the epic saga of Los Angeles' natural history is still visible - and even striking - if you know where and how to look for it.

Episode 47
Today, billions of people around the world start their day with caffeine. But how and why did the ability to produce this molecule independently evolve in multiple, distantly-related lineages of flowering plants, again and again?
Episode 48
One of the biggest earthquakes humans ever experienced happened around 3800 years ago in what's now northern Chile.
Episode 49
We have no idea where they were all this time, or who stole and returned them and why.
Episode 50
Flesh-eating bees exist!
Episode 51
Archaeologists have discovered an ancient art workshop

Episode 52
There is one - and only one - group of mammals that doesn’t have alpha-gal: the catarrhine primates, which are the monkeys of Africa and Asia, the apes, and us.

Episode 53
Mystacodon is the earliest known mysticete, the group that, today, we call the baleen whales. But if this was a baleen whale, where was its baleen? Where did baleen come from? And how did it live without it?

Episode 54
This fungus was actually manipulating ants’ movements, forcing them to do something they’d never ordinarily do, something strange, yet specific…
Episode 55
Did you know that fossils can get sick? – Specifically with Pyrite Disease
Episode 56
Disaster in the great plains!
Episode 57
80 years ago, a bunch of fossils of ancient humans disappeared.
Episode 58
Congrats! You just found a wombat burrow. And the cubes are its poop.
Episode 59
Wisdom teeth can be such a pain
Episode 60
Paranthropus got chomped by a leopard
Episode 61
We didn’t always wear clothes!
Episode 62
Ancient sperm whale heads belonged on every shark-cuterie board
Episode 63
Mercury, Venus, and Mars are all super low on water – so where did ours come from and why do we have so much of it? We think our water came from a few unlikely sources: meteorites, space dust, and even the sun.
Episode 64
Around the time that some of our fishapod relatives were crawling out of the water, others were turning around and diving right back in.
Episode 65
We might’ve been wrong about how this saber-toothed cat looked
Episode 66
Sometimes evolution is completely predictable.
Episode 67
Shanidar 1 got by with a little help from his friends
Episode 68
Here are two ways to get a fossil species named after you.