On 16 Feb 2011, at 15:20, Lux, Jim (337C) wrote: > Aside from how brains are "programmed" (a fascinating question) > > One big difference between biological systems and non-bio is the handling of > errors and faults. Biological systems tend to assume that (many) failures > occur and use a strategy of massive redundancy with fuzzy collective action.
<biologist mode on> Actually, I'd quibble with that statement about redundancy. On the system level, there's very little redundancy in most [animal] organisms. You only have one heart. You only have one aorta, stomach, oesophagus and so on. Even when some things are paired, the loss of either one (such as severing a carotid or femoral artery) can in many cases result in total organism failure. :-) Biological systems tend to be plastic and self-healing rather than redundant, I would have said. At the sub-cellular level, redundancy is much more widespread of course, with various protein families able to cover for each other, resulting in redundant biochemical pathways in many cases, although again not all. Consider the DNA repair disorder xeroderma pigmentosum; it's a failure of one particular DNA repair mechanism, and there are seven genetic complementation groups for the disease - in other words there are seven distinct genes involved in the process, and the failure of any one of them results in the failure of the entire process. There's redundancy in the fact that you have two copies of most chromosomes, of course, although you and I, being male, are a bit buggered if there's anything wrong with our X chromosome. Ask any haemophiliac. Plants of course do much better, and do tend to be massively redundant, both at the structural level of the whole organism, and also at the genetic level (they often have much larger genomes than us, and massively redundant). Ever tried eradicating bindweed from your garden? That stuff is just impossible to kill. But as to mental processing, I think one only has to look at what happens in brain injury cases like strokes to see that the processing is not redundant; a stroke can remove some particular processing ability. The brain however, has a lot of plasticity, especially when young, and other parts of the brain can learn to take over the functions. But I don't think that's quite the same as true redundancy; it's like re-programming another set of flash chips to take over. Having said all that, I haven't been actively doing any biology research for 15 years, so I'm a bit out of touch. Regards, Tim -- The Wellcome Trust Sanger Institute is operated by Genome Research Limited, a charity registered in England with number 1021457 and a company registered in England with number 2742969, whose registered office is 215 Euston Road, London, NW1 2BE. _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
