Daily Meh is an edited stream of consciousness, by Simen.

Why a person doesn't evolve in one lifetime - The body's complicated cell-making process may help to avoid cancer.

There’s no reason in principle that individual cells in multicelled creatures couldn’t evolve, just as whole organisms do, writes Nature. In practice, though, mutant cells that don’t do their jobs so well tend to replicate faster, and that’s, you know, bad. The only place this is good is in the immume system, since it needs to be able to handle new diseases. Unfortunately:

One drawback of this, however, is that it would be expected to make the immune system more prone to cancers. And that seems to be so: leukaemia and lymphoma are cancers associated with the immune system, and they seem to be more common in younger people than many other cancers, suggesting that the failure to suppress evolution allows its problems to show up rather quickly.

(Thanks, 3 Quarks Daily.)