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