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They are among the most recognizable animals on Earth, yet their history is far more surprising than their appearance suggests.
Their ancestors lived tens of millions of years ago, and since then, they traded the ability to fly to become some of the world’s best swimmers.
Today, they inhabit environments ranging from frozen polar landscapes to tropical islands, with extraordinary adaptations that let them survive against incredible odds.
Learn more about penguins on this episode of Everything Everywhere Daily.
Penguins are some of the most well-known and beloved animals on Earth, yet most people know surprisingly little about them.
Penguins belong to the order Sphenisciformes and the family Spheniscidae, which includes all living penguins. They are flightless seabirds most closely related to petrels and albatrosses, rather than other flightless birds such as ostriches.
The 18 commonly recognized living species are divided into six genera, reflecting their evolutionary relationships.
Almost all penguins live in the Southern Hemisphere, save for a few minor exceptions, which I’ll get to in a bit.
Early penguin species could fly, but they thrived in the ocean. The ancestors of modern penguins began using their wings to fly underwater to hunt prey, much like a modern puffin.
Below the waves, the birds found it much easier to feed with the seemingly endless food supply of fish. For millions of years, these ancestral proto-penguins were stuck in the middle: they could fly and swim, but they weren’t the best at either.
Early penguins evolved in a much warmer world, where abundant marine food favored birds that could swim and dive efficiently. Over time, natural selection favored shorter, more powerful wings for underwater propulsion, eventually making aerial flight impossible.
Evolution reshaped their wings from long, flexible, hollow flight structures to short, stiff, dense, powerful ones suited to the sea. Shorter, more muscular, and denser wings allowed early penguins to sink, gain speed and agility amid the powerful currents.
This transition was explained by National Geographic’s Brian Handwerk, who said: This involved a progressive reduction in wing size, making diving more efficient and flying less so. Penguin bones also thickened over the ages, as lighter bones that make it easier for birds to fly gave way to denser bones, which may have helped make them less buoyant for diving.
Penguins evolved their distinctive swimming adaptations about 60 million years ago, probably around present-day New Zealand.
Evolution also gave penguins thermal adaptations that let them survive in Earth’s harshest environment.
While penguins are best known as living in Antarctica, penguins’ geographic range and evolutionary story extend far beyond the Southern Ocean. Penguins live along the coasts of South America, South Africa, Australia, New Zealand, sub-Antarctic islands, and even in the Galápagos. Some Galápagos penguins can cross the equator but rarely go beyond 1 degree north.
One of evolutionary biology’s great mysteries is how these species survive in such different climates.
In Antarctica, emperor and Adélie penguins have evolved substantial fat reserves, specialized circulatory systems that conserve body heat, and remarkably effective insulating plumage. Beneath their waterproof outer feathers lies a dense layer of downy feathers that helps them survive some of the coldest conditions on Earth.
At some point in their evolutionary history, some early proto-penguins were carried north by currents and ended up on the coast of South America.
These birds faced the opposite problem of Antarctic penguins as some of them settled near the equator in temperate and tropical regions. Over time, northern birds shed some of their dense feathering and girth as they evolved smaller body sizes.
Populations that ended up in the Galápagos and South Africa developed behavioral hacks to stay cool, such as burrowing in moist volcanic ash and spending much of the day in the cool ocean currents.
Most people would be surprised to learn how large their ancestors were. Recent fossil evidence was noted by Smithsonian Magazine’s Margaret Osborne, who noted: The largest known penguin to ever waddle the Earth was a 340-pound behemoth—more than three times the size of the largest penguins alive today. The massive, flightless seabird swam in the oceans around New Zealand more than 50 million years ago.
As their bodies shrank over time, penguins became excellent swimmers, which they needed to avoid predators as penguins are a primary food source for killer whales, leopard seals, and several shark species.
Evading these predators requires profound swimming and diving skills. While speed varies by species, penguins swim at a robust 10-15 mph (23 km/hr), far slower than their apex predator, the killer whale, at 30 mph (50km/h), making agility and diving speed crucial.
Antarctica’s emperor penguin can dive an astonishing 500 meters (1,800 feet) and hold its breath for nearly 30 minutes. For perspective, most modern submarines can’t dive that deep.
When an Emperor penguin dives to this depth, its body pulls off a remarkable survival trick. As penguins descend, increasing water pressure compresses their air sacs, while specialized adaptations in their lungs and airways help them withstand the pressure. Penguins can also slow their heart rate to a crawl and shut off blood flow to nonessential organs.
They must sink to these depths to reach the food that form the foundation of their diet: squid, fish, and krill.
While penguins’ hunting and diving skills are essential for survival, their highly coordinated social structure may be even more important. Despite their evolution, Antarctic penguins cannot survive the continent’s gale-force winds and plunging temperatures alone.
To cope, Emperor penguins pack themselves into massive huddles, with thousands of birds working together to stay warm. Penguins on the outside rim of the huddle rotate inward in shifts, while those who enjoyed the warmth of the interior move out.
Perhaps the most astonishing aspect of their social development is the emperor penguin’s parental relationship. Each couple produces a single egg during the coldest part of the Antarctic winter.
Shortly after the female lays the egg, she must transfer the egg to the male. The egg cannot touch the ice for more than a few seconds, or the embryo will freeze to death. The birds must transfer the egg from the mother’s feet to the father’s brood pouch for storage.
Once the handoff is complete, the female embarks on a grueling trek across the frozen landscape back to the open ocean to feed. The mother gorges herself, eating as much as she can for up to 8 weeks so that she can return with regurgitated food for the hatched penguin.
For the next 2 months, the male demonstrates incredible endurance as he balances the egg on his feet, cocooned in the warmth of the brood pouch.
During this period, the male fasts for weeks, surviving on stored body fat. If the mother arrives late and the chick hatches before she returns, the father can secrete a special milk from his esophagus to sustain the newborn. When the mother returns, she exchanges vocalizations with her partner to recognize him and let him know she’s ready to feed the young penguin.
Adélie penguins in Antarctica live in large colonies. The Adélies don’t breed on the ice, preferring to build rock nests to protect their eggs rather than the emperor’s foot-balancing act on ice sheets. Adélie rookeries run on chaos: penguins routinely steal pebbles from one another and then verbally express their displeasure, making quite a ruckus and even swatting at each other with their wings.
Pebble stealing is part of a complicated mating ritual in which penguins court each other with the smoothest pebble they can find, even if someone else is using it.
The world’s largest known penguin colony is at Cape Adare in Antarctica, home to more than half a million breeding pairs of Adélie penguins.
Penguin social patterns outside Antarctica differ. Rookeries in more temperate climates are like giant penguin cities. Penguins closer to the equator don’t need to huddle for warmth, so they are often more spread out.
Zavodovski Island in the South Sandwich Islands once held the title of world’s largest rookery, with well over a million penguins. However, over the past 15 years, the chinstrap penguin population on Zavodovski has plummeted by about 60% to fewer than 500,000 pairs.
The devastation of the region’s small marine life, particularly the krill population, is driving the decline, as krill have moved closer to Antarctica in search of colder waters.
Many chinstrap penguins can no longer migrate far enough to catch krill, leaving nesting penguins to starve when they can’t return with enough food to feed their young.
Human societies have a long history with penguins.
Archaeological excavations of M?ori communities, along with oral traditions, highlight the penguin’s importance to the region. The Maori and and people in Patagonia commonly hunted penguins for food and oil.
The first European contact with penguins likely dates to Portuguese mariner Vasco da Gama’s 1497 passage around the Cape of Good Hope. Da Gama noted in his journal that they resembled flightless geese and were easy to hunt for food.
As exploration continued, explorers and later whaling ships hunted penguins in large numbers for food during their voyages, causing population declines. The effects of depopulation were particularly visible in the Falkland Islands and the islands around the South Georgia archipelago.
In the 19th century, pressure on penguin populations worsened as people used them as an oil source, primarily for lighting. Historical records from the Falkland Islands offer a grim appraisal of how European fishermen and whalers used penguins, often setting up boiling pots on the shore to process their catch immediately.
Their records noted: It was reckoned that 9 good penguins (Rockhoppers) could boil down to a gallon of oil (best done when they first came ashore to breed and were fat and oily).
When the men of the ill-fated Endurance expedition, led by Ernest Shackleton, were stranded in Antarctica, they survived by eating penguin meat.
In the course of my travels, I’ve had the pleasure of seeing most penguin species firsthand in the wild. I’ve seen them in Australia, South Africa, New Zealand, the Falkland Islands, the Galapagos, South Georgia Island, and Antarctica.
One of the most stunning things I’ve seen was a quarter million king penguins on the shores of South Georgia Island. They showed no fear of humans, as they have no predators on land. They would come right up to you and check you out.
The area was incredibly loud with penguins squawking, and it smelled terrible with penguin poop, vomit, and dead birds.
Yet whenever I meet someone for the first time and they ask what my favorite place I’ve been is, I always pull out my photo of the penguins of South Georgia Island.
Penguins are a remarkable example of how evolution can take an animal in an entirely unexpected direction. By sacrificing the ability to fly, their ancestors became masters of a different environment, turning their wings into powerful swimming tools.
Along the way, they developed extraordinary adaptations for diving, surviving extreme temperatures, and raising their young in some of the harshest places on Earth.
From the towering emperor penguin to the tiny fairy penguin, they demonstrate how a single evolutionary lineage can diversify into remarkably different forms.
Penguins may look awkward on land, but in the water, they are among nature’s most well adapted animals.