[ExI] Evolution

Ben ben at zaiboc.net
Thu May 21 17:41:00 UTC 2020

On 21/05/2020 17:22, Re Rose wrote:
> DNA repair is my thing, in fact I am about a month away from a 
> publication on this topic which I'd be happy to share (note: saying 
> that here gives me incentive to me complete that damn paper, which is 
> taking a very long time...!). So - I completely disagree, DNA repair 
> systems are amazing. DNA is being replicated constantly, it is under 
> constant siege by radicals and other reactve molecules, it is sitting 
> in an aqueous environment at around 100 degrees depending on the 
> creature, it is subject to constant environmental attack -- and yet 
> its data stays intact for at least 70 years and probably can stay 
> intact for hundreds of years. It is robust to exogenous atttacks such 
> as by mutagens or radiation. There are a number of interacting repair 
> mechanisims which detect any error or damage to the DNA within 
> microseconds, and they quickly recruit the correct repair systems to 
> these lesions. In worst case situations, when data is missing (like 
> over a double strand break), these repair systems can even recreate 
> missing data - a strategy which can fail but it is a last ditch effort 
> and often succeeds.
> So DNA repair is a huge evolutionary sucess which relaibly carries 
> precious biological information forward in time, and the inherent 
> chemical and physical problems evolution solved in order for that 
> relaibility to occur are tremendous. Each type of DNA damage - base 
> adduct, strand scission, oxidation, dimerization, there are many more 
> - all have completely different chemistries, and each DNA repair 
> system deals with each one of these chemistries eparately. It is truly 
> an amazing feat, one which you (or any living organisim) literally 
> could not live without.
> Please. Respect for DNA repair!

First, kudos for studying DNA repair.

Second, you are being blinkered by the existing parameters of life. You 
know about Okazaki fragments, and presumably see it as a clever solution 
to the problem of how to copy a double-stranded molecule where each 
strand has an opposite orientation to the other. And so it is. A clever 
solution in a terrible setup.
My perspective is that this is a horribly inefficient process, and if 
evolution had been able to go back over and undo then re-do things, it 
would have come up with a more efficient and less error-prone (yes, 
error-prone, John Clark is perfectly right about this) method, We are 
looking at the same thing from different perspectives, a bit like a 
neolithic boat-builder and a contemporary aviation engineer both looking 
at a deHavillant Comet and coming to completely opposite conclusions 
about how marvellous it is.

Your very description of the different types of DNA damage, and the need 
for totally different strategies for addressing them, highlights how 
inefficient the process is, and how bad a medium for data-storage DNA 
is. No wonder it's so error-prone.

Respect for DNA repair is like having respect for how quickly and 
perfectly a potter can produce pots.
When you've seen nothing else, it's indeed impressive. When you've seen, 
or can even envisage, a modern pot factory, not so much.

Ben Zaiboc

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