Up until the second half of the twentieth century, it was generally accepted that organisms grow old and die “for the good of the species” — an idea … - David A. Sinclair

If you've had your genome analyzed, you can check if you have any of the known variations of FOXO3 that are associated with a long life.40 For example, having a C instead of a T variant at position rs2764264 is associated with longer life. Two of our children, Alex and Natalie, inherited two Cs at this position, one from Sandra and one from me, so all other genes being equal, and as long as they don't live terribly negative lifestyles, they should have greater odds of reaching age 95 than I do, with my one C and one T, and substantially greater than someone with two Ts.

What I'm suggesting is that the SIR2 gene in yeast and the SIRT genes in mammals are all descendants of gene B, the original gene silencer in M. superstes.30 Its original job was to silence a gene that controlled reproduction.

When the Sir2 enzyme is sitting on the mating-type genes, they remain silent and the cell continues to mate and reproduce. But when a DNA break occurs, Sir2 is recruited to the break to remove the acetyl tags from the histones at the DNA break. This bundles up the histones to prevent the frayed DNA from being chewed back and to help recruit other repair proteins. Once the DNA repair is complete, most of the Sir2 protein goes back to the mating-type genes to silence them and restore fertility. That is, unless there is another emergency, such as the massive genome instability that occurs when ERCs accumulate in the nucleoli of old yeast cells.