The Origin of Life

Enumerating genetic gakeovers

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This essay is about genetic takeovers - an idea proposed by A. G. Cairns-Smith.

[If you are not sure what these are, I recommend you follow this link before reading further]

It discusses how many genetic takeovers have happened in the past - and how many are likely to happen in the future.

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Past takeovers
Essentially, it is an open question how many genetic takeovers have occurred in the past.

I think that we can state with some confidence that at least one such takeover happened - however whether the figure is larger - or much larger than this is difficult to say.

Much the same is true of the date of the last takeover. It lies somewhere between the origin of life and when the last common ancestor lived - but it is not clear when it happened.

It might be that evolving a decent genetic substrate from scratch was one of the most difficult problems evolution has faced - and consequently the modern system might have taken quite a while to arise.

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Future takeovers
The signs that a modern takeover is underway suggest that there will be at least one more genetic takeover in the future.

However, it seems likely that there will be very many future forms of genetic storage - and it may be that future genetic takeovers will become much more common and much less traumatic.

In the past it might have been difficult to imagine a piece of machinery being developed by natural selection which read information from one source - and wrote it to a completely different one - but now that sort of thing happens all the time - there are no great problems involved in transferring information between different media.

Such technology decreases the loss of information that can happen during a genetic takeover - and makes them less painful events.

The other development which might act in the same direction is the development of a "phenotype abstraction layer".

While amino-acid chains have proved to be very flexible in acting as general purpose machinery - it seems likely that future organisms will want a more flexible set of basic construction materials than is provided by proteins.

There is already something of a divide between the genetic substrate and the phenotype technology - represented by the genetic code. However there are also still links between them - i.e. both are rather fundamentally one-dimensional.

I expect future organisms will complete the divorce - making it more practical to change phenotype technology without changing the storage medium used - and similarly to swap in a replacement storage medium without affecting too many other aspects of the system.

If the storage medium can be turned into a component in this way, then it should become much easier to swap it out and replace it - when new technology comes along.

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The combination of:

  • A layer of abstraction between the genotype and the phenotype it specifies;
  • The ability to copy existing information from one medium into another;

...seems likely to eventually make genetic takeovers easier, less painful - and more commonplace.

If a proper, modular architecture for storing heritable information is developed we may see phenomena such as:

  • Caching information from one media in another one - when faster read access is required;
  • Hot-swapping the genetic storage medium dynamically - in existing organisms;
  • The performing of regular backups into more stable, long-term storage media;
  • Relatives adopting different storage media if they are placed in environments with differing resource costs;


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For a page of references to Cairns-Smith's theories see here. |