Did you know even bacteria get old? Scientists traditionally assumed that bacteria were immortal, since these single-celled organisms split into two apparently identical daughter cells, which in turn divide, and so on. We now believe that this is not true. Eric Stewart of Northeastern University, and his colleagues took fluorescent images of individual E. coli cells over ten generations. Each generation the E. coli cells divide down the middle, giving each daughter cell one new tip and an old tip from its mother, or grandmother, or some older ancestor.

"The conflict between maternal and fetus genes is one of the weirdest ideas in the modern theory of evolution."* According to evolutionary logic, the fetus "wants" to milk the mother for all it can get; the mother "wants" to restrict the fetus to what it needs to survive and save something for future offspring. The reason is that the fetus benefits from every bit of help the mother gives, while the mother's return on her investment diminishes with increasing investment, (i.e. ever greater investment won't necessarily increase her fitness).