Editor's note: This conversation originally aired May 19, 2021
For most of human history, the average life expectancy was about 30 years. Over just a couple of centuries, major advancements in science and medicine have allowed us to more than double our life expectancy. That gives most of us, if we’re lucky, an additional 20,000 more days of life than our ancestors — in short, an extra life.
Just in the last 20 years, the percentage of people living to over 100 has quadrupled. We must be doing something right. Life-saving developments like antibiotics, vaccines, pasteurization and even seatbelts have changed the course of human history.

Globally, that’s not without its drawbacks as the planet faces overpopulation and existential threats like climate change. Still, our guest says that the doubling of life expectancy should be considered “the most important development in human society over the last hundred years.”
Steven Johnson tells the story behind how we got here in the new book, “Extra Life: A Short History of Living Longer.”
Guest
Steven Johnson, bestselling author of 13 books, including "Extra Life: A Short History of Living Longer," which is also the subject of a four-part PBS series.