Picture an orchestra that has been playing the same symphony for years. At first all the musicians play in tight coordination, but over time someone starts lagging behind or coming in at the wrong moment. The notes are the same, but the music is no longer what it was. That is how it goes with the cells in our body: as we age, they make more and more mistakes in running their genes.
Scientists have come up with a way to measure these mistakes. They look at many cells and work out how far each cell deviates from the common norm. The bigger the deviation, the worse the cell follows the program. It turned out that in stem cells, which renew tissues, errors increase with age. But in cells that have already finished their development, there is no such increase.
This knowledge will help doctors assess the aging of the body by looking at cells, without resorting to complex tests. And perhaps in the future we will learn to help cells play in sync again.
In mouse hematopoietic stem cells, dyscoordination rises with age almost linearly: in 30-month-old mice it is on average 40% higher than in 1-month-old mice. Yet terminally differentiated monocytes show no such increase, even though they age too.
In Greg Egan's novel Permutation City, people digitize their consciousness but run into the problem of copy degradation from accumulated random errors. A similar idea underlies this work: cellular aging can be seen as a gradual loss of fidelity in reproducing the program, not just as a change in the program itself.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.