How well do you know how the world got better?

Vaccines

A 2024 study summarised by the WHO credited immunization with about 154 million lives over 50 years, more than any other single intervention measured.

Alexander Fleming

Alexander Fleming noticed a mould killing bacteria on a lab plate in 1928. Howard Florey and Ernst Chain later turned it into a usable drug.

154 million

The figure is about 154 million lives from 1974 to 2024, the equivalent of six lives every minute, with about 101 million of them infants.

Oral rehydration therapy

Oral rehydration therapy treats the dehydration caused by diarrhoea. The glucose lets the gut absorb water and salt even during severe illness. It may have saved more than 70 million children.

Smallpox

Smallpox, which killed about 300 million people in the 20th century alone, was declared eradicated in 1980. It remains the only human disease ever eradicated.

Banting and Best

Frederick Banting and Charles Best, with James Collip and J.J.R. Macleod, isolated insulin in Toronto in 1921 to 1922. The first patient treated was 14-year-old Leonard Thompson.

About half the world

Synthetic nitrogen fertilizer supports roughly half of the global population, about 48 percent as of 2008. Without it, today's food supply could not feed everyone.

Insecticide-treated bed nets

A 2015 Nature study found that of an estimated 663 million malaria cases averted, insecticide-treated bed nets were the single largest contributor, at 68 percent.

Jonas Salk

Jonas Salk's injected vaccine was declared safe and effective in 1955. He never patented it. Albert Sabin later developed the oral vaccine used in global eradication.

Over 99 percent

The WHO reports wild poliovirus cases have fallen by over 99 percent since 1988, from an estimated 350,000 a year to a handful, in just two countries.

Cowpox

Jenner noticed milkmaids who caught mild cowpox seemed protected from deadly smallpox. The word vaccine comes from vacca, Latin for cow.

About 43 percent

Economists Cutler and Miller calculated clean water was responsible for about 43 percent of the total fall in death rates across 13 US cities from 1900 to 1936.

1978

Louise Brown, the first baby conceived through in vitro fertilisation, was born on 25 July 1978. Millions of IVF births have followed.

Surgical anaesthesia

The public demonstration of ether anaesthesia at Massachusetts General Hospital, later called Ether Day, opened the era of painless surgery.

About 4 percent

The global under-five mortality rate has fallen from about 42.8 percent in 1800 to about 3.7 percent today, its lowest level ever recorded.

More than halved

The share of the world in extreme poverty has more than halved since 1990, one of the largest improvements in human living standards ever recorded.

Nearly 59 million

The WHO reports that measles vaccination averted nearly 59 million deaths between 2000 and 2024, more than any other vaccine over that span.

John Enders and Thomas Peebles

John Enders and Thomas Peebles isolated the measles virus and developed the first vaccine, licensed in 1963. Enders had earlier won a Nobel Prize for work that also enabled the polio vaccine.

83 million

The WHO estimates that global efforts to find and treat TB have saved about 83 million lives since the year 2000. TB still causes over 1.2 million deaths a year, so the work is far from over.

Robert Koch

Robert Koch identified the bacterium behind tuberculosis in 1882. The first real cure, the antibiotic streptomycin, did not arrive until 1943.

374,276

NHTSA estimates seat belts saved 374,276 lives in the United States from 1975 through 2017, including 14,955 in the single year 2017.

Nils Bohlin

The three-point seat belt was designed by Volvo engineer Nils Bohlin and introduced in 1959. Volvo opened the patent so every carmaker could use it.

300 million

The WHO states smallpox killed about 300 million people in the 20th century alone, before it became the first human disease ever eradicated, in 1980.

Sugar (glucose)

The mix is clean water, salt and sugar. The glucose is the key: it lets the gut absorb water and salt together even during severe diarrhoea.

The Haber-Bosch process

The Haber-Bosch process, developed by Fritz Haber and Carl Bosch between 1909 and 1913, combines nitrogen from the air with hydrogen to make ammonia for fertilizer. It supports roughly half the global population.

1928

Alexander Fleming spotted the mould on a lab plate in 1928. Howard Florey and Ernst Chain later turned it into a usable drug in the early 1940s.

About 101 million

The WHO reports that about 101 million of the 154 million lives saved by immunization from 1974 to 2024 were infants.

Leonard Thompson

The first patient successfully treated with insulin was 14-year-old Leonard Thompson, in Toronto in January 1922. He recovered within days.

About 73 years

Global life expectancy at birth is about 73.2 years, up from roughly 28.5 years in 1770.

$0.26

The price of a solar module fell from $128.27 per watt in 1975 to $0.26 in 2024, as manufacturing scaled and each doubling of capacity cut the price by about a fifth.

About 88 percent

About 87.7 percent of adults worldwide can read and write, up from around 12 percent two centuries ago.

$525

The cost to sequence a full human genome fell from $95,263,070 in 2001 to $525 in 2022, one of the fastest technology cost declines ever measured.

About 92 percent

About 91.6 percent of the world had access to electricity in 2023, up from 73.2 percent in 1998.

Halved

The global maternal mortality ratio fell from 429 deaths per 100,000 live births in 1985 to 212 in 2020, roughly a halving.

Two-thirds

Global AIDS deaths peaked at about 2.1 million in 2004 and fell to about 628,000 by 2024, more than two-thirds lower, as antiretroviral therapy reached the people who needed it.

Nearly three-quarters

About 73.7 percent of the world used safely managed drinking water in 2024, up from 61.3 percent in 2000, which still leaves roughly one in four people without it.

90 percent

The decadal death rate from natural disasters fell from 8.99 per 100,000 people in the 1900s to 0.59 in the 2020s, a drop of more than 90 percent, thanks to forecasting, early warning, and sturdier buildings.

About 9 years

The global average years of schooling for adults rose from 0.5 years in 1870 to 8.8 years by 2020.

About 43 percent

In 1800 about 42.8 percent of children, roughly four in ten, died before age five. Today the global figure is about 3.7 percent, the lowest ever recorded.

About 500

Reported paralytic polio cases fell from a peak of 65,737 in 1981 to 536 in 2023, as a global campaign closed in on the last strongholds.

More than 99 percent

The price of a million lumen-hours of light in Britain fell from about £29,674 in 1300 to £2.15 in 2023, a drop of more than 99.9 percent, as gas, electric bulbs and LEDs each produced far more light per unit of energy.

About 8 percent

The share of the world that is undernourished fell from 12.7 percent in 2000 to 8.2 percent in 2024, though it rose during the pandemic years before easing again.

About 10

Reported Guinea worm cases fell from a peak of 892,055 in 1989 to about 10 in 2025, leaving it on the brink of becoming the second human disease ever eradicated, after smallpox, and the first wiped out with no vaccine or drug.

12 seconds

The first controlled, powered flight at Kitty Hawk on 17 December 1903 lasted just 12 seconds, but it launched the age of aviation.

Armstrong and Aldrin

Neil Armstrong and Buzz Aldrin stepped onto the Moon on 20 July 1969, the first humans to walk on another world, while Michael Collins orbited above.

Wilhelm Roentgen

Wilhelm Roentgen discovered X-rays in 1895. Within weeks doctors were using them to find broken bones, and medicine gained a new set of eyes.

A double helix

In 1953 James Watson and Francis Crick published their description of DNA's double-helix structure, revealing how life stores and copies its own instructions.

The ozone layer

The 1987 Montreal Protocol phased out the chemicals destroying Earth's protective ozone layer. It is often called the most successful environmental treaty ever, and the ozone hole is now healing.

Tim Berners-Lee

Tim Berners-Lee published the first description of the World Wide Web and made it available to anyone on the internet on 6 August 1991.

About 3 billion

The first draft of the human genome, published in Nature in 2001, laid out roughly three billion letters of our shared genetic code.

Phase 3

Phase 1 checks safety in a few dozen people and phase 2 checks whether a drug does anything useful. Phase 3 is the big, controlled test that produces the evidence regulators use to approve it.

Treat it as an early clue, since most animal results never work in people

A result in mice is a promising signal, not a treatment. The large majority of therapies that work in animals fail once they reach human trials.

How big the difference is, which decides whether a real result actually matters

A result can be real but tiny. Effect size measures how large the difference is, which is what tells you whether it matters in real life.

What the risk went from and to in real numbers

A 50 percent relative cut can mean a fall from 2 in 100 to 1 in 100, a tiny absolute change. Always ask for the before-and-after real numbers.

A study shared before independent experts have reviewed it

A preprint is posted before peer review, the step where independent experts vet the work, so it deserves extra caution until that review has happened.

Not, on its own, that one causes the other

Correlation is not causation. Two things moving together can share a hidden cause or line up by chance, so “linked to” headlines rarely establish cause and effect.

Because one study is a data point, not a settled conclusion

A finding earns trust when independent scientists can repeat it. Until then a single study is one data point, not a conclusion.

How surprising the data would be if there were no real effect

A p-value is the chance of seeing data this extreme if there were no real effect. It is not the probability that a finding is true, a misreading the American Statistical Association warned against.

The plausible range around the number, that is, how precise or shaky it is

A confidence interval is the plausible range around a single result. A wide one means the number is shaky; a narrow one means it is precise.

A randomized controlled trial

A randomized trial assigns people to groups so the only systematic difference is the treatment. An observational study only watches, so it can show a link but not prove cause.

The J. Craig Venter Institute

In 2010 the J. Craig Venter Institute synthesized a whole bacterial genome from chemicals, placed it in an emptied cell, and watched it boot up and self-replicate, the first cell run by a human-made genome.

A ketogenic diet

Researchers are testing the ketogenic diet, used for a century to control epilepsy, for serious mental illness. A UCSF randomized trial found symptoms improved as patients stayed in ketosis.

Neanderthals

Hugo Zeberg and Svante Paabo showed the main genetic risk factor for severe COVID-19, a stretch of chromosome 3, was inherited from Neanderthals and is carried by about half of people in South Asia.

Removing a gallbladder

Trained on videos of the procedure, a Johns Hopkins robot removed a gallbladder through the whole operation on lifelike tissue, succeeding on all eight it attempted and adjusting as it went.

The African spiny mouse

African spiny mice regenerate lost skin, complete with hair follicles, glands and cartilage, almost scar-free, the clearest case of true regeneration in a mammal and a clue to switching it on elsewhere.

Astrocytes

Astrocytes, star-shaped cells that make up roughly half the brain's cells, were long thought to be mere support. New work shows activating them can strengthen connections and is needed to retrieve memories.

Eight

The mosaic-8 nanoparticle carries fragments of eight different SARS-like viruses at once, and in animals it raised antibodies that neutralized coronaviruses it had never been shown, the aim of a pan-sarbecovirus shot.