One way to tell the story of human history is to just look at how people die.

I know that's a bit grisly, but just bear with me for a moment.

In the last 5,000 years, the single most deadly disease was smallpox.

Some scientists estimate that it killed billions of people before

the 21st century. But in the 1790s, a British physician named Edward Jenner took material from a

cow infected with cowpox and used it to inoculate a young boy. Since that fortunate but incredibly

unethical science experiment, vaccination, the word itself

coming from the Latin for cow, vodka, has spared millions of lives from an early death.

By the early 1900s, in rich countries like the U.S. where smallpox was fading out, another killer

emerged as the apex predator of humanity, bacterial infection.

According to the best records we have, almost all of the top causes of death in the late

19th century were bacterial, whether it was the gunky stuff in your lungs or the little

buggers in your gut. But thanks to the accidental discovery of penicillin in the 1920s and a heroic effort by

the U.S. to scale up that drug during World War II, bacterial infections have since plummeted.

Today, the top causes of death in the U.S. are not poxes or bacteria.

They are heart disease, cancer, stroke,

and Alzheimer's. These diseases are not typically premature killers. In many cases, they are more

like mortality's consolation prize. They are the consequences of not dying young. And this frames the challenge we face in modern medicine.

While we have made progress against this new class of villains, statins for our hearts,

immunotherapy for cancer, these killers are still killing us with remarkable frequency.

There is an idea in progress studies called the burden of knowledge.

Sometimes it looks like progress in a field, like science, is slowing down,

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