It can take eons for large-scale shifts in the genetic code to happen, but the genes we already have can be switched on or off within a matter of hours. Epigenetics is how green grasshoppers can turn themselves black after a grassland fire to better camouflage against the charred soil582 and how our body determines the number of active sweat glands we have in our skin based on whether we’re born in the tropics or in a colder setting.583 Epigenetics is good news.
