Expert reveals why human lifespan has doubled in 100 years

CNN’s Bianna Golodryga speaks to Steven Johnson, author of “Extra Life: A Short History of Living Longer,” about some of the discoveries and innovations that have led to the average human life expectancy almost doubling over the last century.CNN’s Bianna Golodryga speaks to Steven Johnson, author of “Extra Life: A Short History of Living Longer,” about some of the discoveries and innovations that have led to the average human life expectancy almost doubling over the last century.