It's happened before, now some claim it's happening again.
In 1200BC, the world's most advanced civilisations — Egypt, Assyria, Cannan — were burnt to the ground all at once.
It was the era of the Biblical Exodus and the poet Homer's Trojan War.
A convergence of catastrophes made these nations weak. And it's happening again.
"We're f**ked," says eminent biologist, Paul Ehrlich, whose 1968 book The Population Bomb triggered international debate.
Speaking to news.com.au, Professor Ehrlich was pulling no punches.
"We've talked for a long time about the coming collapse. Now we're in it. Every sign says so."
He has joined with Flinders University ecologist Professor Corey Bradshaw to present their global systems change modelling to Australia's politicians. And the predictions are not pretty.
"We can limit the damage, but we can't avoid it," Professor Bradshaw says.
"That's what gets me out of bed in the morning. If all that I've been doing gives my daughter maybe another 10 years without a major resource conflict, I've done my job — both as a parent and as a scientist."
They're adding their voices to a growing groundswell of alarm being sounded by researchers the world over.
It's not all just based on computer projections. It's founded in history. And it provides a terrifying road map of what is coming next.
CLEAR AND PRESENT DANGER
It took the Freedom of Information Act to learn what Australia's Defence Force chief Angus Campbell fears. He warns Australia is in "the most natural disaster-prone region in the world".
"Climate change is predicted to make disasters more extreme and more common," he says. "Deploying troops on numerous disaster relief missions, at the same time, may stretch our capability and capacity. Defence may also be increasingly called upon to support stabilisation, governance or peacekeeping activities."
Former Defence Force chief Chris Barrie is also proclaiming his dread. Specifically, that of a rising tide of climate refugees.
"I once suggested to government we might be talking 100 million people," Admiral Barrie warns for later this century.
"One hundred million people when we're only 40 million people — you can get the enormity of this problem. Frankly, it would be beyond our resources."
Such fears are not new. They echo pleas heard 3200 years ago. The Egyptians. The Hittites. The prosperous city-state of Ugarit.
Surviving diplomatic correspondence paints a grim picture.
A clay tablet from a Hittite governor (in modern-day Turkey) sent to his ally, the Syrian city-state of Ugarit, urges: "You have written to me: 'Ships of the enemy have been seen at sea!'… Well, you must remain firm. Indeed, for your part, where are your troops, your chariots stationed? Are they not stationed near you? … Surround your cities with walls. Bring infantry and chariotry in. Be on the lookout for the enemy and make yourself very strong!"
It didn't work.
They appear to have come from as far afield as the western Mediterranean — 4000km away. They were escaping circumstances becoming all too familiar in our own world.
"The politicians on both sides have absolutely no clue what the issues are today," Professor Ehrlich says. "And they have absolutely no clue what's coming. When you picture the refugee situation in Europe and realise that the population of Africa is going to come close to quadrupling."
Professor Bradshaw points to statistical modelling showing a two-to five-fold increase in African refugees for every 1 per cent increase in population.
"If you tried to take that through and extrapolate it to the end of the century … you're looking at between 80 and 120 million refugees coming out of Africa every year alone. Just Africa."
What's causing this mass migration?
Professor Bradshaw calls it "density feedback".
"As you increase a population, what happens is that you approach an environment's carrying capacity," he says.
Populations — be they human, elephant, bug or bacteria — naturally grow towards the level their local environment can sustain. Once they approach and pass that level, their wellbeing falls. So a population correction must restore the balance of supply and demand.
And supply isn't reliable.
A TIME OF FIRE
"I contend that every major human conflict in history has an ecological underpinning," argues Professor Bradshaw.
"Now, there may be complications and political corollaries on top of this. But really, if you look down at the base reason, major conflicts are nearly always over a resource conflict, and that resource is environmental."
In the Bronze Age, it was rain. It's happening again.
Professor Bradshaw says the need for freshwater is already unsettling world politics. There's the fight over the Murray-Darling. There's the damming of the Mekong.
"Why did China take over Tibet?" he rhetorically asks. "It wasn't because they're just imperialists. It is because that's where their water comes from. China is one of the most water-stressed countries in the world because it has 1.5 billion people trying to grow their own food."
Entire European nations fled their homelands because of a catastrophic Bronze Age drought. Crops failed, year after year. Fires ravaged the landscape. Cities and towns could no longer be fed. Their occupants had no choice but to set out in search of a new land.
"It wasn't just about wealth accumulation," Professor Bradshaw says. "It was about subsistence. And when you start to mess with subsistence, people get very concerned for their lives."
Not that the Middle East was all that better off.
Pollen analysis. Sediment cores. Oxygen-isotopes from cave stalactites. All serve to confirm the onset of a 300-year drought.
Again, written records confirm this. They also point to the strength of international relations.
"I have caused grain to be taken in ships, to keep alive this land of Hatti," Pharaoh Merneptah proclaimed in an inscription. This was international disaster relief.
"It is a matter of life or death!" the Hittite king appealed to Ugarit over an urgent shipment of barley.
But, soon, even the breadbasket nations were struggling.
One letter to an Ugarit-based entrepreneur declares: "There is famine in your house; we will all die of hunger. If you do not quickly arrive here, we ourselves will die of hunger. You will not see a living soul from your land."
For centuries, the Mediterranean civilisations thrived around an international network of copper and tin.
Kings ruled by the strength of bronze. Magnates grew wealthy mining and transporting its components (sound familiar?). A vast array of supporting and complementary trade grew up around it all.
But, then, as now, came technological disruption.
Then, it was iron.
Iron ore was common. But it took the discovery of how to smelt it for the new technology to take off. And, once it did, there was no longer any need for bronze.
Like the internet, iron was a disrupter. It up-ended the old, centralised economic and power networks.
The elites in their Bronze Age palaces saw the value of their trade fall away. Their diplomatic influence waned. They saw a rapid proliferation of arms beyond their own loyal soldiers.
Then came a loss of faith among their subjects.
God-kings didn't seem so godly anymore. God-kings weren't upholding the social bargain that put them in power. God-kings were rapidly becoming redundant.
It was a similar story for international trading corporations. Their monopolies were becoming worthless. They could no longer pay proper wages. And then there was the raiding Sea Peoples.
"When you've got refugees flooding into a system that has more resources, there's more competition, or at least even the perception of competition," Professor Bradshaw says.
"When there's more competition for fewer resources, you're going to get more entrenched views, both left and right. It works both ways. And, therefore, there is conflict."
WORLD WAR ZERO
The international trading hub of Ugarit was suddenly and violently destroyed about 1190BC.
Its treaties weren't worthless. But its allies were also fighting for survival.
"When your messenger arrived, the army was humiliated and the city was sacked," one of the last tablets made in Ugarit reads. "Our food on the threshing floors was burnt, and the vineyards were also destroyed. Our city is sacked. May you know it! May you know it!"
Ugarit was never rebuilt. The international network it served did not recover. Thick layers of rubble, ash and bronze arrows point to a similar fate for most Eastern Mediterranean cities.
The superpower of Egypt was the last bastion standing.
When Ramses III took the throne in 1184BC, Egypt was under siege. Trade routes were falling, one by one. The neighbouring Libyans were probing his borders. Then, in 1177BC, the greatest assembly of Sea Peoples yet appeared off the coast.
In the Battle of the Delta, Ramses III won a comprehensive victory.
Egypt stood firm.
But it was not without cost. Ramses lost control of Canaan to tribes that would become known as the Philistines. And Egypt's economy was gutted.
It no longer had easy access to goods it did not possess itself. Standards of living inevitably fell.
Over the next century, the once-great superpower steadily crumbled into dust.
The Sea People's didn't destroy everything. Disgruntled populations took care of the rest.
The biblical city of Megiddo — also known as Armageddon — was one of the very last to fall, sometime around 1130BC. It was a cosmopolitan city, with trade goods found there from far afield.
But the good life was well and truly over by 1130BC. Mycenae was no more. The Hittites had fallen. Ugarit was in ruins. Egypt was mortally wounded.
The networks that had sustained Megiddo's economy had collapsed. So, the social contract between the population and their rulers broke down.
The priests and kings were supposed to intercede with the gods for rain. They were supposed to repel invaders.
Since they were achieving neither, what need was there for such a governing class?
It was a revolution being played out across the Middle East.
The fate of the mountain capital of the Hittite empire, Hattusa, had long puzzled archaeologists. It is hundreds of kilometres inland — out of reach of invaders from the sea. It was abandoned at some point about 1180BC. But only its temples and palaces were destroyed.
Now it seems the empire could no longer feed or employ such a remote centre. So the population starved, revolted, and moved on.
Can such a scenario be transferred to the modern era?
"I'm actually very concerned," Professor Bradshaw says. "I have a 12-year-old daughter. Is she going to experience major war and conflict that directly threatens her? Is she going to have to live under siege, with World War II kind of scarcity of resources? Is she going to have to live with the threat of bombs being dropped every day?
"I suspect that's going to be ultimately what happens. It's a quest for the last remaining resources, and the strongest will prevail."
What is collapse? It is a different thing to different people, says Professor Bradshaw.
"Some people think a collapse is World War III and people eating each other in the streets, whereas, at the other extreme definition, collapse is just a continuous recession."
And that, he says, is the choice we now face.
The world overstretched. And the more we stretch it, the harder it will snap back.
"You have to agree that there is a problem and we need to fix it," he says. "It's our fault. Yes, we did it … We've got to give our children the tools to be able to get out of it. And that's why being entrenched with particular ideologies is being most unfair to the next generation. That's the worst part for me."
Drought triggered the fall of the Bronze Age. There's no longer enough rain to support us.
"The effort it takes to acquire resources is getting exponentially larger simply because we've used up all the easy stuff," Professor Bradshaw says. "Yes, and technology can help to a certain extent. But every additional human being makes it exponentially harder to provide those resources for that same standard of living."
In the Bronze Age, international corporations were replaced by wandering traders. Cities were replaced by towns. Stone houses became mud huts. The lost golden age rapidly passed into myth.
Would it be the same for the modern world?
"What keeps coming back is that there are so many possibilities for a collapse," Professor Ehrlich says. "For instance, if it's the debt pyramid that goes down, there probably will be electricity in some places and computers that survive.
"If, on the other extreme, a large-scale nuclear war occurs … I don't think there will be electricity anywhere. So most of humanity's knowledge is just going to be lost. Then, who knows?"
A NEW DAWN?
With the fall of the Bronze Age kingdoms, large-scale societies were not to be seen again for centuries. But out of this dark age would come inventions such as alphabets, refined iron tools and improved agriculture.
Professors Bradshaw and Ehrlich are less sure about next time.
"If the Romans had nuclear weapons, we wouldn't be here because the barbarians coming over the walls would have been more than enough excuse to use them," Professor Ehrlich says.
And he says the social and political will to prevent the return of such "barbarians" — or Sea Peoples — doesn't exist.
"We might be able to support — at a Mexican standard of living — about three and a half billion people. But since we're way past seven, now, the idea of stabilising the population is just a non-starter."
That's the core of the problem. Too much consumption. And our capacity to sustain this population is contracting.
"It's got to be shrunk, and it's got to be shrunk humanely. The way to shrink it humanely to start is to give absolutely full opportunity, full legal rights and so on to women everywhere and make sure that everybody has modern contraception and safe backup abortion. That's just ground zero. If you don't believe in that, then you're just saying, OK, leave it to our great-grandchildren to pay the full price."
The drain on our resources won't end anytime soon.
"We've done the modelling," adds Professor Bradshaw. "It'll take centuries, not decades, to have the population equilibrate to something that would be more in tune with the local carrying capacity, irrespective of the technology that remains.
"So that means that there will be a lot of suffering."
It's an apocalyptic vision.
"That's the sort of thing that people don't want to hear — politicians sure as hell don't want to hear it," Professor Ehrlich says. "But, with the grid down, you can't pump petrol, and you can't move trains without electricity, and everybody will starve to death, basically. The big issue is, will there be enough left after the collapse so you can get some kind of a reset."
"I don't have any real hope," Professor Ehrlich adds. "But I don't see any choice but to keep trying. Yeah, you know, you can't be certain what the future is going to show."