From Salk Institute:
LA JOLLA—By adolescence, your brain already contains most of the neurons that you’ll have for the rest of your life. But a few regions continue to grow new nerve cells—and require the services of cellular sentinels, specialized immune cells that keep the brain safe by getting rid of dead or dysfunctional cells.
Now, Salk scientists have uncovered the surprising extent to which both dying and dead neurons are cleared away, and have identified specific cellular switches that are key to this process.
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“It appears as though a significant fraction of cell death in neurogenic regions is not due to intrinsic death of the cells but rather is a result of the microglia themselves, which are killing a fraction of the cells by engulfment,” says Lemke. “In other words, some of these newborn neuron progenitors are actually being eaten alive.”
This isn’t necessarily a bad thing in the healthy brain, Lemke adds. The brain produces more neurons than it can use and then prunes back the cells that aren’t needed. However, in an inflamed or diseased brain, the destruction of living cells may backfire. More.
The problem is becoming clearer: There is no naturalist explanation for why life forms go to such trouble to create massive complexities in order to stay alive
Breathe deep and feel the randomness:
Seriously, it’s an under-considered problem. People want to do battle over how such complex patterns have arisen randomly, with the prize going to the Worst Mathematician Ever, Voodoo division. No one asks: What is the significance of the fact that life forms develop all these structures to assure their survival at ever higher degrees of complexity?
Come to think of it, if one can rank full professor just by being the Worst Mathematician Ever, Voodoo division, why bother with trivialities?