As we get older we look wrinkly on the outside, although we feel pretty much the same inside, but at some point, we start to suffer from a lack of velocity. As we gradually improve medical methodologies, our life expectancy increases, if and only if, we can still move fast enough to cross the road before the faster and faster cars catch us.
A question we could ask, but never do, of course, is how old are we supposed to get? If you are a cat or a dog 15 to 20 is pretty much all you can expect. If a macaw, maybe 70, but if a giant tortoise you could be looking at 150 to 200 years of silly politics. So where do we fit in?
Back to our closest animal relative, the chimpanzee, 50 years old is about it, and they don’t have to put up with the stress of studying stock market fluctuations. Sherwood et al in the current issue of the Proceedings of the National Academy have attacked this question of comparisons by using MRI scans of chimpanzee and our brains (1).
Looking at almost a hundred chimpanzees of a range of age from young to old, they found that their brain volumes were pretty constant. Well perhaps that’s a slight overstatement if one looks at the data, but there wasn’t a trend for loss of their little grey cells with age.
Not so with us humans though. With almost as many humans from 22 to 88, the brain scan showed that we were losing cells on the way to become small-minded with age. The authors point out that we are unusual in this rather careless habit (and another recent paper has shown that its not due to the demon drink) as other species don’t appear to do this and have their hippocampus and frontal lobes shrink.
Interestingly, their conclusion is that, maybe, we have reached our sell by date when our brain starts to shrink. Evolutionwise, we should have popped off by then and our extended lifespan is to blame. Philosophically, this seems to me to be a very scary thought to follow down its rabbit hole. Should monitoring changes in our brain volume become as routine as measuring our changes in cholesterol or blood glucose? Would that information be useful to health insurance providers?
