Penguins ruled the Southern Ocean before whales, once grew as large as gorillas
After the asteroid extinction wiped out dinosaurs, penguins reached the Southern Ocean's food chain apex before whales and sharks, dominated for about ten million years before ceding the throne, transforming into today's endearing small creatures.
The video won't play here. Listen to the audio instead:
The argument · tap a timestamp to hear it
Penguins are dinosaurs—birds are the flying branch of dinosaurs
Guest Steve Brusatte explains that dinosaurs were once as diverse as mammals—one dinosaur lineage shrank, grew wings, learned to fly, and became birds, equivalent in status to bats among mammals. The difference is that all other dinosaurs went extinct, leaving only birds to survive. When you see penguins, sparrows, and crows, you're looking at real dinosaurs, not metaphorically ‘dinosaur-like’ creatures.
— Steve BrusatteThe earliest penguin fossils had already lost the ability to fly
The oldest known penguin fossils are 61-63 million years old, appearing shortly after the asteroid extinction of dinosaurs. These fossils had already abandoned aerial flight, with wings evolved into paddle-like flippers specialized for underwater swimming. Penguins completed the evolutionary ‘trade of flight for swimming’ as soon as they entered the fossil record, rather than gradually degenerating over time.
— Steve BrusattePenguins' homeland may have been a sunken continent
All known oldest penguin fossils come from New Zealand, which is merely the remaining portion above water of an ancient continent mostly sunken underwater—Zealandia. Zealandia was once connected to Australia and Antarctica, with granite bedrock and distinct boundaries consistent with continental geology, but plate tectonics submerged most of it beneath the sea. After the asteroid impact, land still protruded from Zealandia, and with mammals nearly absent, birds became the apex of the food chain there; penguins likely originated here.
— Steve BrusattePenguins dominated the Southern Ocean before whales and sharks
When the asteroid extinction eliminated dinosaurs, marine apex predators like mosasaurs and plesiosaurs also vanished, leaving a gap at the top of the Southern Ocean food chain. This gap wasn't filled by the later orcas and great sharks—at that time, whale ancestors were still small even-toed ungulates living on land, requiring another ten million years or so before entering the sea. The first to truly claim the throne were penguins; only the fossil record can tell us this, something genetic analysis of modern animals alone cannot reveal.
— Steve BrusatteGiant penguins were roughly the size of gorillas
The giant penguin nicknamed ‘Colossus’ may have weighed about 300 kilograms, equivalent to a gorilla. From its fossil, the creature is still recognizable at a glance as a penguin—upright stance, long beak for catching fish and squid—just magnified many times over. Penguins were not originally the endearing small creatures of today; the small penguins we see now are actually the result of a ‘second reduction in size’.
— Steve BrusatteThe penguin reign was actually brief, and they eventually ceded power
Penguins' time at the apex of the food chain was not long, roughly ten million years, after which they were replaced by evolved orcas and large sharks; the reasons remain unclear. But Brusatte emphasizes this was not a devastating defeat—penguins were not ‘conquered’ but rather transitioned into a new lifestyle, becoming the endearing small creatures we see today, symbols of polar ice. He compares this history to an empire that flourished briefly but brilliantly.
— Steve BrusatteGastornis was herbivorous, not the top predator everyone believed
Gastornis, with its fierce appearance and robust hooked beak, was long thought to be an apex meat-eating predator, similar to terror birds. But about ten years ago, paleontologists conducted oxygen and carbon isotope chemical analysis of its bones—the principle being ‘you are what you eat,’ with herbivores and carnivores leaving different chemical signatures. The results showed Gastornis was actually herbivorous, a conclusion that shocked many but also confirmed the suspicions of some scholars. What exactly it ate with that enormous skull remains a mystery.
— Steve BrusatteFlying giant birds filled the pterosaur niche, but it remains empty today
Pterosaurs in the dinosaur age were giant yet could fly, once thought to be beyond what birds could achieve, since flight requires active chest muscle wing-beating, which becomes impossible at enormous size. But fossils show that a group called pelagornithids actually did this, with wingspans reaching about 20 feet, double that of today's largest flying bird, the albatross. They relied more on soaring than flapping, gliding on the wind like pterosaurs. These giant birds survived for over 60 million years until extinction about 2.5 million years ago—before humans appeared. Since then, no species has evolved to fill this ecological niche of ‘soaring giant birds,’ and it remains empty.
— Steve BrusatteIn their own words · checked verbatim
when you look at a sparrow or you look at a crow or you look at a penguin, it doesn't look anything like a T-Rex, like a Triceratops, but dinosaurs were a very diverse group.
Steve Brusatte4:03
it took the whales, the dolphins, the big sharks. It took them a while to reach the top of the food chain. Something else tops the food chain first.
Steve Brusatte17:43
One of them is called the Colossus penguin. That's the nickname, and that says it all. It is a nickname that this penguin very much deserves.
Steve Brusatte19:50
elephant birds, 10 feet tall. They weighed 1,600 pounds, laid eggs the size of watermelons.
Steve Brusatte31:24
we are what we eat. And so you can actually tell something about the diet of a species or an individual based on the chemistry of the bones and the teeth.
Steve Brusatte35:30
these giant birds that are called pelagornithids. And some of them had wingspans of about 20 feet.
Steve Brusatte38:38
Nothing in the last two and a half million years has evolved to fill that niche. So that means that giant hang glider kite pterodactyl niche right now is vacant.
Steve Brusatte40:45
Figures
| Asteroid extinction event date | 66 million years ago | 5:03 |
| Species death rate in extinction event | approximately 75% | 29:21 |
| Giant penguin (Colossus) weight | approximately 300 kilograms, equivalent to a gorilla | 19:50 |
| Duration of penguin apex food chain reign | approximately 10 million years | 23:57 |
| Elephant bird size | 10 feet tall, weighing 1600 pounds | 31:24 |
| Demon duck body mass | approximately 100 times that of a Canada goose | 33:28 |
| Pelagornithids wingspan | approximately 20 feet, double that of the albatross | 38:38 |
| Pelagornithids extinction | approximately 2.5 million years ago | 39:40 |
Glossary
- Zealandia
- An ancient continent mostly sunken underwater, of which New Zealand is the remaining portion above sea level.
- Waimanu
- The oldest known penguin fossil genus, dating back approximately 61-63 million years.
- pelagornithids
- An extinct group of giant soaring seabirds with wingspans reaching about 6 meters.
- Gastornis
- An ancient European giant bird once mistaken for a top predator, now revealed to be herbivorous.
How to listen
Science enthusiasts interested in prehistoric evolution and the dinosaur-to-bird transition, especially those curious about whether penguins or whales dominated the ocean first.
Opening and mid-segment History Hit subscription ad segments can be skipped.