People flock to the Paleo diet in order to eat like our ancestors—but incidentally, the original paleo diet drove a flock of birds to extinction, as researchers from the University of Colorado at Boulder have discovered the first reliable evidence that humans (Homo sapiens) played an enormous role in the extinction of massive flightless birds in Australia some 50,000 years ago.

The bird, which is known as Geryornis newtoni, was nearly seven feet tall and weighed a whopping 500 pounds. They appeared to have lived in across a large portion of Australia—that is, until humans arrived.

The particular evidence uncovered by the CU-Boulder team—burned eggshells—was found to date to this time period.

“Eggshells were found in 200 sites across much of the arid zone of Australia, from the west coast to the central deserts,” said Dr. Gifford Miller, professor of Geological Sciences at CU-Boulder and co-author of the paper which can be found in Nature Communications.

These eggshells were burned, but not just by a wildfire; patterns indicated that the birds’ 3.5-pound eggs were in fact cooked by humans, thereby directly decreasing the numbers of the birds’ progeny and likely playing an important role in their extinction.

“We consider this the first and only secure evidence that humans were directly preying on now-extinct Australian megafauna,” said Miller in a statement.

The proof in the pudding

The team used radiocarbon dating, which indicated that the shells were no younger than 47,000 years old. They verified this date using a fascinating technique known as optically stimulated luminescence (OSL) dating. The OSL technique can determine when certain types of crystalline materials—like the quartz grains in the eggshells—were last exposed to sunlight. In the case of the G. newtoni eggs, sunlight had been missing for some 44,000 to 54,000 years.

So the burned egg shells were old, and fit right into the time period of when humans settled in Australia. But how do we know they were actually cooked by humans? The answer came from protein.

“When we found ‘blackened’ eggshells we wanted to know for sure if the black colour was due to burning or staining,” Miller said. “Birds include about 3% protein in their eggshells, presumably to make the calcite less brittle.”

Amino acids—which are the buildings blocks of protein—are sensitive to heat. So by analyzing the amino acid content across the eggshells, they could determine whether the egg had been consumed by a wildfire or cooked by humans.

“We found that fully blackened eggshells had no amino acids left at all (temperatures above 500°C), and most importantly, eggshell fragments blackened at only on end had no amino acids at the blackened end, but concentrations almost the same as unheated eggshell at the opposite ends,” Miller continued.

“This can only be explained if the fragment was touching a very hot source (an ember) for a short period of time. And some fragments in the same cluster were not heated at all. We conclude that the only explanation is that humans harvested the giant eggs, built a fire and cooked them (which would not blacken them) then discarded the fragments in and around their fire as they ate the contents.”

This theory is strengthened by the fact that most burned eggshell fragments were found in tight clusters without other eggshells nearby—and that the amount of protein decomposition in some clusters showed that the heat affecting the eggs varied by as much as 1,000 degrees Fahrenheit.

“We can’t come up with a scenario that a wildfire could produce those tremendous gradients in heat,” Miller added.

Australia had scary fauna even 50,000 years ago

Of course, a 500-pound bird wasn’t the only type of megafauna (huge animals) around Australia at the time. A 1,000-pound kangaroo, a 25-foot long lizard, and a Volkswagen-sized tortoise all were there to greet the first humans. Shortly after our advent 50,000 years ago, though, more than 85 percent of Australia’s mammals, birds, and reptiles that weighed more than 100 pounds went extinct.

Which could mean that humans didn’t just change the fate of G. newtoni.

“We only have evidence for predation on the one species of Megafauna, Genyornis,” explained Miller. “But this is the first direct evidence of such predation, and as such it adds more evidence to a likely human role in megafaunal extinction.”

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Feature Image: An illustration of a giant flightless bird known as Genyornis newtoni, surprised on her nest by a 1 ton, predatory lizard named Megalania prisca in Australia roughly 50,000 thousand years ago. (Credit: Illustration by Peter Trusler, Monash University)

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