Our guest is Steven Johnson, the bestselling author whose previous books include "Where Good Ideas Come From" and "The Ghost Map." He joins us to talk about his newest book, "Extra Life: A Short History of Living Longer," which is also currently appearing as a TV documentary series on PBS. "Extra Life" is a book that offers, per Kirkus Reviews, "a surprising look at why humans are living longer.... Entertaining, wide-ranging, and -- in light of Covid-19 -- particularly timely."