Thanks to advances in medicine and technology, more of us will live to see our grandchildren to adulthood.
As noted by Laura Carstensen, director of Stanford University's Center on Longevity, Americans have added more years to life expectancy in the past century than in all of human evolution to this point. In the mid-1800s in the U.S., most people on average lived to their mid-30s. By the end of the 20th century, that number had jumped to 77, and today it's 78. "Four, five, maybe a total of six generations within the same family can be alive at the same time today," Carstensen said.