Researchers at Boston University are looking for a genetic link for Alzheimer’s. As part of this work, they studied 100-year-olds who show no signs of the disease. But, in the midst of their studies, they came across an even more interesting discovery—apparently; centenarians all share a group of genes that grants them their unusual longevity. The study authors caution that the test for the gene group is far from 100 percent accurate. And, of course, even if you have the longevity genes, if you smoke three packs of cigarettes a day, go through bottles of tequila, and eat Frosted Flakes and Big Macs all day, you’re still going to die relatively young. But it raises an interesting philosophical dilemma: some day it may be possible to get a blood test that will tell you how long you can live. If and when that day comes, will you get the test? And if you find out your body’s good for 100—or only 70—how will it change how you live?