Each needed nothing the society did not already have, and arrived long after it could have.
Keep the latrine away from the well
- What was done
- Cities grew for centuries on shallow wells sunk among cesspits, although the rule to put waste away from the camp had been written down for well over two thousand years.
- Do instead
- Site every latrine at least 30 m from, and downhill of, every well, spring and stream.
- Evidence
- Deuteronomy 23:12–13 orders a place outside the camp and a spade to cover waste. In 1854 a cholera outbreak around London's Broad Street pump killed 616 people; the well sat less than a metre from a cesspit. John Snow traced the deaths to the pump, and an official inquiry rejected his conclusion the following year.
Needs: Find and hold water
Plant through the residue instead of ploughing the ground bare
- What was done
- For most of farming's history the ground was ploughed bare, burned, or left in bare fallow; the plough became the picture of farming itself.
- Do instead
- Keep at least 30 % of the soil covered with residue, mulch or a cover crop, open the ground only where the seed goes — a pointed planting stick makes the hole — and grow at least three different crops in sequence.
- Evidence
- These are the three principles by which FAO defines conservation agriculture: minimum soil disturbance, permanent organic cover of at least 30 %, and diversification across at least three crops. The cost of the alternative is on record: the Dust Bowl of the 1930s blew the topsoil off ploughed grassland across the southern Great Plains, and the United States founded its Soil Conservation Service in 1935 in response.
Needs nothing that is not already in hand.
Compost hot before it goes on food crops
- What was done
- Raw manure and night soil have been spread straight onto fields for as long as there have been fields, carrying the pathogens in them onto the food.
- Do instead
- Build the pile at a carbon-to-nitrogen ratio near 30:1, keep it as damp as a wrung-out sponge, and hold it at 55 °C or more for at least 15 days, turning it at least five times, before it goes near a crop that is eaten raw.
- Evidence
- 55 °C for 15 days with five turnings is the US EPA's standard for a windrow compost that has been treated to kill pathogens (40 CFR 503, Appendix B). A starting mix of 25:1 to 40:1 is the USDA NRCS composting standard; Cornell puts the ideal near 30:1.
Needs: Separate waste from water
Push-pull against stemborers and Striga
- What was done
- Cereal pests and the parasitic Striga weed were fought by hand-pulling and burning, and later with insecticides and herbicides.
- Do instead
- Drill Desmodium between the maize rows and plant three rows of Napier or Brachiaria grass round the plot: the Desmodium drives stemborer moths out and makes Striga seed germinate and die, and the grass border draws the moths in to lay their eggs where the larvae do not survive.
- Evidence
- In icipe's trials in East Africa, farmers using climate-smart push-pull harvested about 4 t of maize per hectare against 1.5 t without it, and fall armyworm infestation was more than 80 % lower (icipe). The layout is in icipe's step-by-step guide.
Needs nothing that is not already in hand.
Citrus and greens against scurvy
- What was done
- Navies and expeditions sailed on dried and salted food for three centuries. Lemon juice was recommended against scurvy by 1617, trialled in 1747, and issued in the Royal Navy only from 1795 — and the knowledge was then lost again.
- Do instead
- Give anyone living on stored food a raw vitamin C source every day: greens, sprouts, sauerkraut, potatoes or fruit. About 10 mg a day prevents scurvy.
- Evidence
- James Lind's 1747 trial on HMS Salisbury split 12 scurvy patients into six pairs; the pair given oranges and lemons recovered fastest, one fit for duty within six days. In the 1860s the Navy switched to West Indian lime juice, which carries less vitamin C and was stored for long periods, and scurvy returned on the British Arctic Expedition of 1875–76.
Needs: Forage, trap, fish, Preserve the harvest
Cook maize in alkali
- What was done
- Maize spread from the Americas to Europe, Africa and the US South after 1500 without nixtamalisation — the processing step that had made it a safe staple where it came from.
- Do instead
- Simmer every batch of maize in 1% slaked lime or wood-ash lye until the skins slip, steep it overnight and rinse it; eat beans with it.
- Evidence
- Pellagra was described in Spain in 1735 and became endemic in northern Italy. In the US South an estimated 3 million cases and 100,000 deaths followed between 1906 and 1940. Joseph Goldberger showed from 1914 that the cause was diet, not infection; niacin was identified as the missing factor in 1937. Mesoamerican evidence for nixtamalisation dates to about 1500–1200 BC.
Needs: Plant staples, Fire, and keeping it
Parboil rice before milling
- What was done
- From the late 19th century, mechanical mills made polished white rice cheap across Asia, and beriberi spread with it among those who ate the most of it: sailors, soldiers, prisoners and city workers.
- Do instead
- Soak and steam paddy in its husk before milling, or eat rice lightly milled; eat pulses or groundnuts with it.
- Evidence
- Japanese Navy: on the nine-month voyage of the training ship Ryūjō in 1882–83, 169 of 376 crew developed beriberi and 25 died. Kanehiro Takaki sent the Tsukuba on the same route in 1884 with barley, meat and milk added to the rice: 14 cases, all among men who had not eaten the new ration, and no deaths.
Needs: Plant staples, Pottery and the first kiln
Take the cooking fire out of the sleeping room
- What was done
- An open hearth on the floor of the one room where the family cooks, eats and sleeps, with the smoke left to find its way out through the thatch or a hole in the roof.
- Do instead
- Cook outdoors under a shade roof or in a separate cookhouse in warm climates; in cold climates give the hearth its own room and a flue, and never sleep beside a banked fire.
- Evidence
- WHO estimates household smoke caused 2.9 million deaths in 2021, over 309,000 of them children under five (WHO fact sheet, December 2025). Even vented stoves are assumed to release about 25 % of their emissions into the room (WHO Housing and health guidelines, 2018, table 8.7).
Needs: Fire, and keeping it, Shelter and body heat
Wash hands between patients
- What was done
- Doctors in 19th-century teaching hospitals went from dissecting corpses to examining women in labour without washing, and childbed fever killed mothers on their wards at several times the midwives' rate.
- Do instead
- Wash hands with soap before touching a woman in labour, and between every patient.
- Evidence
- In Vienna's General Hospital in 1846, the doctors' ward lost about 11% of mothers and the midwives' ward under 3%. Ignaz Semmelweis required hand-washing in chlorinated lime from May 1847, and the doctors' ward fell to about 1–2% within a year. His colleagues rejected the practice; routine hand hygiene in hospitals took decades more.
Needs: Soap
Kangaroo mother care for small babies
- What was done
- Small and premature babies were separated from their mothers into incubators where incubators existed, and mostly died where they did not.
- Do instead
- Keep a baby under 2 kg skin to skin on the mother's or another adult's chest, upright, day and night, breastfed on demand, from as soon after birth as possible.
- Evidence
- Developed in Bogotá in 1978 for lack of incubators. A WHO trial in five countries, published in 2021, found that starting continuous skin-to-skin contact immediately after birth in babies of 1.0–1.8 kg cut deaths in the first 28 days by about a quarter — 12.0% against 15.7%.
Needs nothing that is not already in hand.
Oral rehydration: salt, sugar and water
- What was done
- Until the 1970s, severe diarrhoea was treated with intravenous fluid where it existed and with nothing effective where it did not. Most of the dead were children.
- Do instead
- 1 litre of safe water, 6 level teaspoons of sugar and ½ level teaspoon of salt — or, without sugar, 50–80 g of rice flour boiled in the litre with the salt. Doses are in separate waste from water.
- Evidence
- The mechanism — glucose carries sodium, and water with it, across the gut wall — was described in 1960. In refugee camps during the 1971 Bangladesh war, oral rehydration held cholera deaths to 3.6% of cases, against about 30% in camps relying on scarce intravenous fluid. Child deaths from diarrhoea fell from around 4.6 million a year in 1980 to about 440,000 in 2021.
Needs: Make water safe
A float for everyone aboard
- What was done
- Ships were required to carry a lifejacket for every person only from 1914, when the first SOLAS convention followed the Titanic; in small boats the float is still the thing most often left ashore.
- Do instead
- From the first plank boat, carry a float for every person aboard — cork, sealed gourds, closed containers or a rated lifejacket — and wear it on cold or rough water.
- Evidence
- Of the 556 people killed in US recreational boating in 2024, 76 % drowned, and 87 % of those whose flotation was recorded wore none (USCG). The 1914 convention required lifejackets for every person aboard (IMO).
Needs nothing that is not already in hand.
Citrus against scurvy from the first long voyage
- What was done
- James Lind's trial of 1747 showed that oranges and lemons cured scurvy; the Royal Navy ordered lemon juice for every sailor every day only in 1795.
- Do instead
- Carry a daily source of vitamin C on every passage longer than a month — citrus or its juice, potatoes, sauerkraut, or grains and pulses sprouted aboard — and check the store is fresh.
- Evidence
- Less than about 10 mg a day for many weeks causes scurvy (NIH). After the 1795 order, scurvy had nearly disappeared from the Royal Navy by 1797 (James Lind Library).
Needs nothing that is not already in hand.
Lifeboats and lifejackets for everyone aboard
- What was done
- Required only from 1914, after the Titanic carried boats for 1,178 of more than 2,200 people.
- Do instead
- From the first passenger ship, boat places and a lifejacket for every person aboard.
- Evidence
- SOLAS 1914 made it law for every person aboard (IMO).
Needs: Plank boats, oars and sail
Measure in a wind tunnel before building
- What was done
- Early experimenters built full-size machines from published tables and learned from crashes; the Wrights built their tunnel only after their 1901 glider fell far short.
- Do instead
- Build a small wind tunnel and measure every wing shape before cutting a spar.
- Evidence
- The 1901 glider gave a third of the lift predicted (NASA); after two months in the tunnel, the 1902 glider made nearly 1,000 glides (National Park Service).
Needs: One metre, one kilogram, everywhere
Chlorinate the supply
- What was done
- Bleaching powder — chlorine absorbed into slaked lime — was made commercially from 1799, yet cities drank unchlorinated water for another century.
- Do instead
- After filtration, dose chlorine to leave at least 0.5 mg/l free chlorine after 30 minutes of contact, and at least 0.2 mg/l at the far end of the network.
- Evidence
- Maidstone in England disinfected its mains with bleaching powder during a typhoid outbreak in 1897. Jersey City began continuous chlorination of its supply in 1908, the first in the United States; a court challenge upheld it as safe and effective, and chlorination spread across American cities within a decade.
Needs: Acids, Lime