B. A Benayoun

In the aged skin of a male mouse, every third hair follicle is left without a nerve, like a house whose electrical line has been pulled away. The socket itself is intact: the neurons, tucked away in nerve ganglia along the spine, have not gone anywhere. They are alive and have no intention of dying.

Inside a cell there is an orchestra, with every molecule playing its part. But sometimes a conductor walks in who doesn't just change the tempo, but rewrites the notes right on the music stands. That conductor turned out to be LINE-1, a mobile element capable of copying itself into the genome.