The short answer: in the last fifty thousand years nearly every large land animal on the planet, meaning anything over about 44 kilograms (100 pounds), died out, continent by continent. Australia lost its giants around 45,000 years ago, the Americas lost about three quarters of their large mammals around 13,000 years ago, Madagascar lost its elephant birds and giant lemurs between about 1,000 and 700 years ago, and New Zealand lost all nine species of moa within about 150 years of people arriving. Each wave lines up, roughly, with the arrival of humans. Most researchers now accept that humans played at least a contributing role alongside a changing climate. How much varies by place: New Zealand is beyond argument, Australia is genuinely disputed.
Twenty thousand years ago a walk in the woods meant something. There were armadillos the size of a family car, sloths that stood four meters tall and pulled branches down like a man picking apples, and beavers as big as bears. There were lions in America and rhinos in England. Nearly all of it is gone, in a geological eyeblink. And here is the part you will not like: on continent after continent, it went at about the moment people turned up. Here is what died, where, when, and how much of it the evidence actually pins on us.
What counts as megafauna?
In this argument, megafauna means land animals over about 44 kilograms, roughly 100 pounds. That is a threshold, not a magic line; it is simply where the pattern shows up. And the pattern is blunt: the bigger the animal, the more likely it is not here any more. Rats, lizards and small birds came through fine. It is the large-bodied animals that vanish. The reason is arithmetic. Big animals breed slowly, one calf at a time, years apart, with decades to reach adulthood. So you do not need to slaughter them. You only need to kill them slightly faster than they replace themselves, and keep doing it for a very long time, without ever noticing.
Sources: Quaternary extinction event; Late-Quaternary megafauna extinctions: patterns, causes, ecological consequences, Cambridge Prisms: Extinction, 2024
What happened to Australia's megafauna?
Australia is where people first arrive somewhere that has never seen anything like them, around 45,000 years ago. Waiting for them: Diprotodon, a wombat the size of a rhinoceros at up to about 2.7 tonnes. Procoptodon, a short-faced kangaroo standing about two meters tall. Thylacoleo, the marsupial lion, with the strongest bite for its size of any mammal we know of. Genyornis, a flightless bird twice the weight of an emu. Megalania, a monitor lizard far bigger than any alive today. Within a few thousand years of people arriving, essentially all of it is gone.
Now the honest part. Australia is the hardest case to prove. The dating is difficult, the climate was shifting too, and serious researchers still argue about how much of it was us. But the coincidence is uncomfortable, and it is about to become a pattern.
Sources: Diprotodon; Thylacoleo; Australian megafauna
Which giant animals lived in America?
The Americas, around 13,000 years ago, is the big one. The Columbian mammoth. The mastodon. Smilodon, the sabre-toothed cat. Megatherium, a ground sloth four meters tall that weighed as much as an elephant. Glyptodon, an armadillo relative about the size and rough shape of a small car, and its cousin Doedicurus, which carried a spiked club on the end of its tail. Arctodus, the short-faced bear, which some estimates put at around a tonne. The American lion. The dire wolf. Castoroides, a beaver the size of a black bear. Around three quarters of North America's large mammals disappeared, and South America lost even more. The timing lines up, roughly, with people spreading through both continents. Roughly, because when people first reached the Americas is itself still argued over.
The climate side has a real case here, and it should be heard: a 2021 study in Nature Communications found that megafauna decline in North America tracked climate change better than it tracked human population growth. That is the strongest paper on the other side of the argument, and you deserve to know it exists.
Sources: Megatherium; Glyptodon; Arctodus; Castoroides; Stewart et al., Nature Communications, 2021
Did horses come from America?
Yes, and this is the fact that gets people. Horses evolved in North America. Not Asia, not Arabia: America. So did camels. Both were native American animals for millions of years, and both died out there completely. Horses survived only because some had wandered across into Asia. Camels survived because some had wandered into Asia and others into South America, where their relatives are the llamas. So when Spanish ships unloaded horses in the sixteenth century, those animals were not invaders. They were coming home, after roughly ten thousand years away. Nobody tells you that at the rodeo.
Sources: Evolution of the horse; Camelid; Mustang
Why did Europe and Asia keep more of their big animals?
Eurasia is different, and the difference matters. The losses there were real but slower and less complete: the woolly mammoth, the woolly rhinoceros, the cave bear, the cave lion, and Megaloceros, the so-called Irish elk, which was neither Irish nor an elk and carried antlers up to about three and a half meters across. But Europe and Asia kept more than the Americas did. There are still bison, bears, wolves and moose. The likely reason is that humans and their relatives had already been in Eurasia for hundreds of thousands of years. The animals there had time to learn what we were. Hold on to that idea; it comes back in Africa.
Sources: Woolly mammoth; Irish elk
When did the elephant birds of Madagascar die out?
Here it stops being archaeology and starts being recent. Madagascar had the elephant birds, the heaviest birds that have ever lived, around three meters tall, with an egg that held about as much as 150 chicken eggs. It had giant lemurs, not the small ones bouncing about in documentaries but lemurs the size of gorillas. It had dwarf hippos and a giant tortoise. Most of it disappeared between about a thousand and seven hundred years ago. That is not prehistory. There were cathedrals. Somebody somewhere was already complaining about the youth of today. The evidence points to a double blow: a drying climate that put the animals under strain, and then people and their livestock arriving on top of it.
Sources: Aepyornis; Subfossil lemurs; The Conversation; Science, double whammy
How fast did the moa go extinct?
New Zealand is the case nobody argues about. It was the last significant landmass people reached: Polynesian settlers arrived around 1250 to 1300. Waiting for them were the moa, nine species of enormous flightless bird, the largest standing about three and a half meters with its neck up, and Haast's eagle, the largest eagle known, which hunted moa by dropping on them at speed. Within about 150 years every moa was gone, all nine species, and one study put the founding human population at fewer than about 2,500 people. Not an army. A village. The eagle went with them, because it ate moa and there were no moa left. There are middens holding the remains of huge numbers of birds. This one is us, it was fast, and it is documented.
Sources: Moa; Mongabay, 2014; Haast's eagle; The Moa the Merrier, 2023
Were mammoths alive when the pyramids were built?
Yes, and it embarrasses everybody. You think of the mammoth as impossibly ancient: cave paintings, ice, a lost world. A population survived on Wrangel Island in the Arctic Ocean, cut off when the sea rose, until about 4,000 years ago. The Great Pyramid was finished around 2560 BC, roughly 4,500 years ago. Egypt had pharaohs, writing and bronze, and there were mammoths walking about on an island at the same time. And that one does not fit the story neatly, so here it is straight: the last mammoths do not look hunted. The chemistry of their bones suggests a small, isolated, fairly stable population wiped out by something abrupt, probably an extreme weather event. Bad luck, not spears. Sometimes the answer is not you. Do not get comfortable. It is mostly you.
Sources: ScienceDaily, 2019; Quaternary Science Reviews, 2019, the isotope record; Live Science
Did humans or climate kill the megafauna?
That is the fight, it has been running for more than two hundred years, and it is not fully settled. The climate case is serious: the end of the last ice age reorganized the whole planet, habitats moved, vegetation changed, and large specialized animals are exactly what that kills. The overkill case is that the extinctions track the arrival of humans far better than they track any single climate event. And the overkill side's strongest point is this: there had been ice ages before, many of them, and the same animals came through the earlier ones. What was different about the last one was not the ice. It was us.
The honest position now is that most researchers accept at least a contributing role for humans, and recent work has been shifting further that way. It varies by place. And humans versus climate was probably always the wrong way to frame it. Picture an animal already squeezed by a shifting climate into a smaller range and a smaller population, and now add a new predator that is clever, cooperative and armed, and has never been part of its world. Neither finishes it alone. Together they do it easily. Anyone who tells you it was one or the other, you impatient little snack cake, has stopped reading.
Sources: The Conversation, the debate narrows; Late-Quaternary megafauna extinctions review, Cambridge Prisms: Extinction, 2024
Why does Africa still have elephants and rhinos?
Africa is the exception, and the exception is the evidence. It still has elephants, rhinos, hippos, giraffes, buffalo and lions, the only place left that looks even slightly like the world used to look everywhere. The long-standing explanation, put forward by Paul Martin in the 1960s, is co-evolution: African animals grew up alongside us. Our ancestors had been in Africa for millions of years, getting gradually more dangerous, so its animals had time to learn a healthy fear of the small clever thing that walks upright. Everywhere else, we arrived already finished, with no warning at all. There is a caveat, as there always is: a 2018 study in Science found that some African megaherbivores began declining millions of years before our ancestors ate much meat, which points at falling carbon dioxide and spreading grasslands instead. So co-evolution is not the whole explanation. But the correlation holds around the world, India included: the longer animals had lived alongside us, the more of them survived.
Sources: Faith et al., Science, 2018; ASU summary; Yale, on India
What did we lose when the big animals died?
Not just the animals. What they did. A large animal is not a decoration; it is infrastructure. Elephants knock down trees and keep grassland from turning into scrub. Enormous herbivores spread seeds too big for anything else to carry, in guts big enough to move them for miles. Some trees alive today bear fruit that no living wild animal can properly spread. The avocado is the famous example, a fruit apparently built for a mouth the size of a ground sloth's, and the ground sloth is not answering. Big animals also move nutrients: they eat in one place, walk a long way and deposit it elsewhere, which on a continental scale is a circulatory system. We cut most of the arteries.
Sources: Evolutionary anachronism, after Janzen and Martin, 1982; Trophic cascade
The world you inherited
Every wilderness you have ever seen is a reduced one. The national park that moved you, the documentary that made you feel small, the forest you called untouched: all of it is what was left over. Nobody alive has ever seen a complete ecosystem. Not you, not your grandparents, not theirs. There is a name for taking whatever was left when you showed up and calling it normal: shifting baseline syndrome, coined by the fisheries scientist Daniel Pauly in 1995. And none of this was done on purpose. Nobody in Australia 45,000 years ago decided to remove the Diprotodon. Nobody in New Zealand called a meeting about the moa. Every one of them was feeding a family and having a perfectly ordinary day. The damage only shows up from a long way up, looking down at ten thousand years at once.
Source: Shifting baseline
Which one would you bring back first? Tell us under the video on Facebook.
Questions people ask
What killed the Ice Age megafauna?
Most researchers now accept a combination: a changing climate at the end of the last ice age, and hunting by newly arrived humans, with the balance different on each continent. The extinctions track human arrival closely, and the same animals had survived earlier ice ages.
When did the megafauna go extinct?
In waves. Australia lost most of its giants around 45,000 years ago, the Americas around 13,000 years ago, Madagascar between about 1,000 and 700 years ago, and New Zealand's moa within about 150 years of people arriving around 1250 to 1300.
Did horses originate in North America?
Yes. Horses and camels both evolved in North America and both died out there. Horses survived in Asia and were brought back to the Americas by Spanish colonists in the sixteenth century.
Were mammoths alive when the pyramids were built?
Yes. A population of woolly mammoths survived on Wrangel Island in the Arctic Ocean until about 4,000 years ago, after the Great Pyramid of Giza was finished around 2560 BC.
Why does Africa still have so many large animals?
The long-standing explanation is that African animals evolved alongside humans and their ancestors for millions of years and learned to fear them. Research since 2018 shows climate and grassland spread also drove earlier declines, but around the world, the longer animals lived alongside humans, the more of them survived.
Sources
Every claim above was sourced before the episode was narrated. Where researchers still disagree, as over Australia and the Americas, it says so, and the strongest paper on the climate side is cited rather than left out. The main papers:
- Janzen and Martin (1982). Neotropical anachronisms: the fruits the gomphotheres ate. Science 215.
- Faith et al. (2018). Plio-Pleistocene decline of African megaherbivores: no evidence for ancient hominin impacts. Science 362.
- Stewart, Carleton and Groucutt (2021). Climate change, not human population growth, correlates with Late Quaternary megafauna declines in North America. Nature Communications 12.
- Late-Quaternary megafauna extinctions: patterns, causes, ecological consequences (2024). Cambridge Prisms: Extinction.
Keep reading
Support the show
Every episode of Man Explains Everything is sourced line by line before a word is recorded. The shop at manexplainseverything.com has the shirts, caps, mugs and stickers with the insults on them, the sound pack and the sketch cards, and the money goes to the show. Or skip the shirt and support the show directly.