The longevity genes I work on are called “sirtuins,” named after the yeast SIR2 gene, the first one to be discovered. There are seven sirtuins in mammals, SIRT1 to SIRT7, and they're made by almost every cell in the body. Sirtuins instruct histone spooling proteins to bind up DNA tightly while leaving other regions to flail around. By doing so, they change the packaging of the DNA, turning genes off and on when needed. This is the mechanism sirtuins order our bodies to “buckle down” in times of