I've just finished the rewrite of Troy: The Ancient Dead, the concluding part of the trilogy. Bit of a relief, to be honest. The latter half of the book is full of talk of the end of civilisations - the Hittites have fallen, Troy is ruined, and there's a leftover fragment of the Minoans that gets Odysseus thinking about all this. It's got me thinking too, about all the dangers our own 21st century culture faces.
Meteor impact, for example. There are claims that a "shotgun" impact destroyed the Indus valley people, when pieces of an asteroid rained down in the Indian Ocean. But in the past civilised areas were too few and small for this to happen often. Today we know the risk better, and the impact of Shoemaker-Levy 9 on Jupiter on 1994 shows us how bad it could be.
Or super-volcanoes. Toba in Indonesia was the most recent to erupt, about 75,000 years ago, but the best known is probably Yellowstone, in the USA. It erupts every 600,000 years or so and is due anytime. The results would be catastrophic - vast clouds of ash settling on the ground, more in the air blocking sunlight to create a volcanic winter, sulphur mixing with water to produce sulphuric acid which we'd breathe in, and so on. It would likely affect the whole Northern Hemisphere, and kill billions.
Or a pandemic. You can take your choice on this one; Ebola, swine flu or bird flu, Marburg, Sabia, Mapucho - or something else we haven't noticed yet, perhaps. Our mobile lifestyles mean that air travel provides thousands of very rapid vectors along which a disease would spread. Back in the 1500s the Spanish brought smallpox to the Americas, and in the ensuing decades up to 80% of the local people, with no immunity to the virus, died from it. Something similar is quite possible today. Any serious virus to which humans have no immunity could do it, and history shows pandemics break out quite often.
All of these three threats are almost certain to happen, given time. But even so, the greatest threat to human cultures is probably still ourselves. I don't mean nuclear war, or biological weapons run amok. I just mean the seemingly endless, crippling stupidity of people.
Got an unspoiled wilderness? We'll strip-mine it for coal, or mine tin and leave the tailings to poison the river. We'll use pesticides on our fields which are made using oil, so we leave a petrochemical sheen on rivers. When we need new housing we'll overlook the brownfield sites in cities, and build instead on fields outside. And worst of all we'll breed and breed, without any apparent thought for the consequences.
In my school days there were 4 billion people on Earth. Today there are more than 7 billion and the number is still growing. All of them need food and water, clothes to wear, a home, the prospect of a job and some kind of decent life. How will we sustain them? How we will cope when the number reaches 8 billion, then 9?
Civilisation throughout history have fallen because they outgrew their ability to feed themselves. The Mayans of Guatemala, the early Chinese of the Yellow River area, probably even the Achaean Greeks I've just been writing about. We're not immune, just because we have computers and neon lights, and tell each other that "it couldn't happen now". Of course it could. The rules which applied to them still apply to us.
It's a bit less dramatic than seeing a culture wiped out by invading dragons, or by invaders with wicked spikes on their chariot wheels. But I suspect that living through it would feel quite dramatic enough.