To stay young, kill zombie cells

Single-Cell Analysis of Human Pancreas Reveals Transcriptional Signatures of Aging and Somatic Mutation Patterns

As rats age, their chirping generally becomes less frequent. (A similar phenomenon seems to occur in humans: Research done by William Fry, a professor emeritus at Stanford University School of Medicine, has found that kindergarteners laugh 300 times a day, whereas adults laugh just 17 times.) However, rats who were tickled often when young usually retain their tendency to chirp later in life.