What if modern civilisation were to collapse tomorrow? What could you do to provide for yourself – what could any of us do – if food no longer magically appeared in the supermarket, or clothes on shop hangers, or the power-grid and gas and water supplies vanished? If you were to wake up after a global catastrophe that toppled civilisation, with the vast majority of humanity gone, what would you be able to do to help the post-apocalyptic community recover? What knowledge would you need not only to avert another dark age, but accelerate the rebooting of a technological civilisation from scratch?
1. Survive the immediate aftermath
Food will remain preserved for decades in tin cans on the shelves of deserted supermarkets, so your primary concern will not be sustenance. The one piece of information that will help you more than any other in the immediate aftermath is germ theory – the idea that contagious diseases are spread by invisibly small organisms invading your body. As with any disaster, disease will be a particular concern – given the unrecovered corpses and contaminated water supplies. Drinking water can be sterilised by boiling, of course, but this takes a lot of time and fuel. Water can be disinfected with iodine tablets foraged from any camping store, or even household bleach or swimming pool chlorine, greatly diluted. Filter murky water through a drum filled with layers of charcoal and sand before you disinfect it. Just washing your hands can prevent a huge number of gastrointestinal and pulmonary diseases, and in the longer term, as you settle down again, you must ensure that your water supply is not contaminated upstream by your own, or anyone else's, excrement. It seems simple enough, but even this wasn't appreciated as late as the mid-19th century.
2. Leave the cities
Aside from the stench of corruption and risk of disease, modern urbanised areas simply won't be habitable once the technological bubble that supports them bursts with the apocalypse. With the failure of the power grid and gas supplies, modern apartment blocks would be nigh-on impossible to heat and cook in. And where would you go for fresh water? You will need to make scavenging forays into the cities, but post-apocalyptic life would be much easier after moving to the countryside, in a traditional house with fireplaces. A coastal region near a large wood will offer you access to a wide range of natural resources.
3. Reinstate agriculture
The "grace period" offered by the left-overs of our civilisation will only last so long, and by the time the packaged food starts running out you need to have rebooted agriculture for yourself. The Millennium Seed Bank, located in Wakehurst, West Sussex, is the largest plant conservation project in the world and would offer the perfect backup file for civilisation. Simple tools such as ploughs and harrows could be scavenged, or created by repurposing steel items with a simple forge, but the essential trick, one that evaded medieval farmers, is how to maintain the fertility of your fields over the years. Without industrially synthesised fertilisers, your best option for replenishing nitrates in the soil is by rotating leguminous plants – peas, lentils, clover, alfalfa – with your cereal crops. Dissolving bones in acid will provide phosphates, and spreading crushed chalk or limestone will counter rising soil acidity.
4. Food surplus
The vital enabler since the dawn of civilisation has been the ability not just to grow food, but to preserve it for consumption later, to see you through the winter, accumulate reserves and support whole settlements. The key principle behind all food preservation is to modify its internal environment to hinder the growth of spoilage micro-organisms such as bacteria or moulds. Drying, salting and saccharine jams all work by limiting the availability of moisture. Increasing the acidity (pickling) prevents much microbial growth, but the opposite approach of using highly alkaline conditions should be avoided as it turns fats in food into foul-tasting soapy compounds. You can also preserve food with extremes of temperature – heat-inactivation for pasteurising milk, or exploiting the gas laws to construct a refrigerator or freezer.
5. A shirt on your back
Until the recent invention of synthetic polymers, domesticated species have provided us with not only a reliable food source but the means to clothe ourselves and avoid dying of exposure. Hide is treated to produce leather and natural animal and plant fibres are twisted into thread and then woven into fabrics. Plant sources include the pithy stem of flax (for linen) and the fluffy fibres surrounding the seeds of cotton. Animal fibres can be gathered from the hair of pretty much any furry mammal, although sheep or alpaca wool is most common, and one prevalent insect source is the cocoon of the Bombyx mori moth: silk. If needs be, a clump of fibres can be teased out and rolled into a thin thread with your fingertips. The crucial technology for weaving is the loom, and can be as rudimentary as a rectangular framework. Look at the weave of the top or jumper you are wearing. Two sets of fibres, at right angles, are interlaced over and under each other: the thicker warp threads give structural strength and are filled in with the weft. Spinning and weaving also gives you strong ropes and canvas for sails or windmills.
6. Reboot the chemical industry
The progress of civilisation is often thought of in terms of advances in mechanical prowess – waterwheels and windmills then steam engines, turbines and internal combustion engines. But establishing a capable civilisation is just as much about proficiency in providing the necessary substances and materials for the functioning of society. Before the late 19th century and the exploitation of coal and then crude oil, the source of chemical feedstocks – acids, alcohols, solvents, tars – was by dry distillation of wood; baking timber in an airtight container and collecting the vapours released as it was converted into charcoal. One of the most vital classes of substances throughout history has been the alkalis, such as potash (potassium carbonate) soaked out of wood ashes or soda (sodium carbonate) soaked out of seaweed ashes. These are critical for reacting with fats and oils to make soap, disassembling plant matter to make paper, and in the production of glass.
7. Transport
As with food and other substances and materials, there will be a huge amount of petrol and diesel left behind after the apocalypse: vast underground lakes beneath every service station and in petrochemical storage tanks. But this reserve will not last forever, and will deteriorate over time. You'll be able to cannibalise spare parts to keep cars, trucks, and other mechanisation going, but you'll need to produce your own biofuels. Rendered animal fat or plant oil reacted with methanol (wood alcohol, distilled from heated timber) and lye (made by reacting soda with quicklime from roasted chalk or limestone) produces biodiesel. You can even fuel a car directly with wood, using a procedure called "gasification" that was common in the second world war. Timber is partially combusted in a closed metal canister, the heat breaking down the wood to release combustible gases like hydrogen and methane, which can be filtered and piped directly into the engine cylinders.
8. The Greatest Invention
Selected tips on how to keep yourself alive and begin rebuilding civilisation will only get you so far. The greatest invention of them all, the piece of the modern world that must above all else be preserved through the cataclysm, is the scientific method. It is only by thinking rationally, closely observing the world around you, and asking carefully constrained questions of nature – running experiments – that you will be able to decide which explanatory story (or hypothesis) is more likely to be correct. This knowledge-generating machinery of science is phenomenally successful and will enable the post-apocalyptic society to reconstitute all that is known today. It is science that built our modern world, and it is science that you will need to rebuild again.
• Lewis Dartnell's The Knowledge: How to Rebuild Our World from Scratch is due from Bodley Head. Go to the-knowledge.org
