On Your Birthday, You’re Not Celebrating What You Think - Issue 42: Fakes
▻http://nautil.us/issue/42/fakes/on-your-birthday-youre-not-celebrating-what-you-think
Have you had a birthday recently? Feeling old? Don’t worry—there’s a good chance that you’re younger than your infant self. As an adult, you have billions more new cells and trillions of times more new molecules than you had in your body when you were born. Your body now has day-old cells, year-old cells, and only a relatively small proportion of decades-old cells (found in parts of your brain). Most of your body is much younger than the day you were born. What’s more, it’s not entirely clear what “old” actually means. The rate of cell multiplication and molecular turnover in your body varies from organ to organ. In our brain, most of the cells do not divide at all, even though many of the molecules that compose those cells can change or be replaced. Cells in other organs might divide every (...)