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 attempts to describe the ways in which these can vary.
Types of takeover
A diagram of a classical genetic takeover looks something like:
Here, the large, yellow regions represent phenotypes, and G1 and
G2 are the primary and second genetic substrates respectively.
While it is conventional to interpret this diagram as representing organisms
containing a mix of genetic substrates, it is also possible to view it as
This is perhaps better explained with reference to a new diagram:
This diagram shows yellow and red organisms existing within a green ecosystem.
To summarize the difference between the two diagrams, in the second diagram, the
second genetic material is no longer arising directly within the bodies of the
ancestral population - but instead has bodies of its own - reducing the
possibilities for symbiosis.
There are many similarities between the two scenarios - in both:
there is the origin of a new information-storage technology;
this cab be developed by the primary organisms to store inherited information;
there can be a period of co-existence during which information can flow between the genetic substrates.
A naive look at the second diagram might see the creation of a new species,
which wipes out its predecessors. However, there are still excellent reasons
to view the primary organisms as the ancestors of the secondary ones:
Without the primary organisms the secondary organisms would probably
have been effectively incapable of forming from nothing;
There is a period of co-existence - during which the two species can form
symbiotic relationships pass information between the species.
The two diagrams are not really mutually exclusive. Because
the definition of a "body" is vague - and because an
organism's phenotype may extend well beyond what appear to
be its physical boundaries, there is a continuum of
possibilities - from the secondary organisms forming within
the bodies of the primary ones - to the secondary organisms
forming from the waste products of the primary ones.
A sceptic might ask - if a second organism can form from
scratch - what need is there to hypothesize a previous
species of organism whose only role appears to have been
being wiped out by later organisms?
However, it appears that the secondary organisms may have
been incapable of forming without being under the protection
of the primary organisms - and their origin may prove
incomprehensible without their consideration.
As to how the secondary organisms could arise in the
presence of the primary organisms - without being eaten by
them - there are various possibilities:
The secondary organisms might occupy niches
unoccupied by the primary ones - and thus initially avoid
direct competition with them;
The secondary organisms might be deliberately created by
the primary ones - for their utility as slaves, for their
information-storage capabilities, their abilities at
fighting - or possibly for other reasons;
The question of whether there were any genetic takeovers of the second type
around the origin of life appears to be an interesting one.
It appears to me that the most probable candidate for such a takeover appears to
be between the hypothesised "naked gene"-based ecosystem - and one in which the
organisms are surrounded by membrane bubbles.
It seems likely that any "naked gene" ecosystem would have been most likely to
have been based on mineral crystals. These are likely to operate best in an
environment which is maintained in a slightly super-saturated solution by
crystallization processes. This mechanism depends on diffusion between the
medium surrounding the organism and the rest of the environment.
Membranes are useful for holding an organism together so its component parts
don't diffuse away. It also offers physical protection from perturbations in
However crystals hold themselves together with inter-molecular forces - and
rely on perturbations from the environment to reproduce.
Membrane boundaries seem unlikely to have helped crystal-based organisms
directly - it appears that the main function of an enclosing membrane would
have been be to get in the way.
While it may be possible to hypothesize intermediate forms, it seems quite
possible to me that organisms that held themselves together with membranes arose
outside the immediate bodies of the organisms that synthesized their component
parts - from either waste products, as tools or from decaying body parts.
The modern takeover
As was discussed in the essay about genetic takeovers
it appears that a modern genetic takeover is imminent.
There appear to be essentially four possibilities for our form of life in the future:
The human race and its technology are destroyed - perhaps by war,
perhaps by the impact of the earth with a meteorite, or perhaps by the earth
being invaded by an alien ecosystem - and no future descendants of our ecosystem
succeed in establishing themselves.
The humans engineer their own genomes and those of ther companions fast enough that their capacities are not
rapidly dwarfed by those of machines.
We form close symbiotic relationships with machines - which eventually
come to replace our genetic material.
We form more distant symbiotic relationships with machines - and something
like companies producing robots evolve into the dominant form of life.
I have not listed the "Luddite" possibility. Humanity turning its back on
technology is not a realistic evolutionary scenario - the only way something
similar can happen is if warring factions of humanity succeed in completely
wiping the race out.
Option 1) is a possibility - but it is hard to evaluate the probabilities involved.
Option 2) seems to me tremendously unlikely in the long term, due to technical
problems with DNA as a storage medium. I certainly don't think mankind should
aim towards this - since I think limiting our descendants to the use of DNA
would prove to be short-sighted.
I think that options 3) and 4) represent our most probable long-term future.
While it seems likely that we will form close symbiotic relationships with
machines, there do exist scenarios in which significant living systems can form
without much in the say of co-operation or symbiosis with us:
These show an unpleasant glimpse of how self-replicating
entities can arise as a by-product of mankind's waste
products - rather than from a mutually beneficial symbiotic
relationship with us.
Some would dismiss computer viruses as potential forms of
life - since they are isolated in cyber-space and can't gain
access to material phenotypes. However this is a fundamental
misconception - they have material phenotypes - like any
other self-reproducing system - and no-doubt will come to
aspire to occupy a wider range of niches.
I mention computer viruses since - if their
descendants established themselves - they would represent a
modern takeover of the second type - where the new organisms
arise initially largely outside the bodies of the existing
Another candidate for this type of scenario is the nanotechnology "grey goo"
idea - where a very efficient self-replicating agent is manufactured - and
rapidly comes to out-reproduce all existing living systems.
While I think it is probably hubris to think that our technology stands much
chance of developing something so much better than evolution has managed over
billions of years in the short term, in the long term such possibilities
can't be completely discounted.
In the examples I have given, the scenarios with a reduced level of symbiosis
between the two classes of organisms seem to have more potential for conflict -
and less potential for information-transfer between the organisms in question.
It seems likely that future potential genetic substrates will arise outside our
physical bodies - but within our extended phenotype. In order to best avoid
valuable information being lost to our long-term descendants, it appears that it
will be desirable for the modern genetic takeover to be engineered in such a way
that the two systems in question form a close and extended symbiotic relationship.
For a page of references to Cairns-Smith's theories see here.