But while this discovery opens up new possibilities for medical science, the biggest question posed by the research—why some of our genes activate after we die—remains a mystery. Noble thinks clues may lie in the kinds of genes that are reanimating. Though none of the zombie genes seem to make any physical changes after death, many of them are related to activities that are normally closely regulated or inhibited. This includes the gene that tells cells to produce the beginnings of a spinal column — once you’ve already got a spine, you no longer need to grow a new one.

Other genes that activate after death are related to cancers. Perhaps in the absence of other genes that normally inhibit them, these genes seize the opportunity to reactivate, like teens throwing a party when their parents are out of town.

While the reason for the reactivation of these genes remains elusive, what’s clear is that death is a more nuanced process than previously thought. Death doesn’t mean that all the billions of cells in our bodies stop working, it just means that they stop working together. The hours and days during which these connections fall apart and life fizzles out are a new frontier for science.

“I call it the twilight of death, going from the organism’s death as a whole versus what happens to individual cells,” says Noble. “Where [is] the breakdown between cells and the whole functioning organism? That’s a big question. No one knows.”