Clas Blomberg - Physics of life-Elsevier Science (2007)

114 Part III. The general trends and objects
the basic machinery of the organism, which also means that there should be some demarcating
structure, separating the organism from the outside and preventing free exchange of
the constituents, but keeping a controlled flow of energy and suitable compounds in and out
of the organism, a role that is put up by the cell membrane and the cell wall.
But then one can go further. One often makes analogies to computer and mechanical
designs. In a first place I think about a machine that is able to produce exact copies of itself.
It has everything in itself in order to make appropriate building elements, plates, moving
parts, screws and nuts to get everything together and so on. It can be driven by electricity
and the electric current is divided in the machine to perform various tasks. The copies of the
first machine can then make copies of themselves and thus multiply. This has much of the
requirements as life, but its possibilities to evolve are very small. If the machine makes some
error, the copy is generally faulty. It may still work, but its produced copies may be more
faulty and may not work. There may be a possibility that a copy is not exactly like the primary
one but may be more efficient in copying itself. But that is all; the copying of the machines
cannot lead to something completely new.
Instead, if we consider a computer, the possibilities are greater. We can have a computer
program that copies itself and also performs some tasks. One can then add some possibilities
of making variations (errors) in the copying, variations that are propagated and which may
lead to variations of the tasks and even new tasks. Now we get to the possibilities of evolution.
Still, I want more. The program of the computer shall also contain a scheme for its machinery
to build new computers, that is, the whole computer shall be able to make a copy itself
by the instructions of a program that is read by the computer itself. This also includes how
an electric source is utilised to make the details of the computer and get them together, and
to drive the electric circuits for the computing possibilities. In such a machine, variations
of the basic program and the instructions for building lead to variations of the computer,
which may develop new tasks, and improved possibilities, of course, also of faulty computers.
It is also clear that mutations in evolution may lead to more faulty offsprings than improved
ones, but it is also a fact that some offsprings are improved than is relevant and they can
transmit new possibilities. This might be possible by such a computer that copies itself, and
then, I think we can begin to think about a new form of life.
This means that we require some kind of instructions, in the computer the program and in
the living body, i.e. the genes of DNA. Without that, the possibilities of evolution are restricted,
but that kind of instruction that is found on a DNA and in a computer program, in principle,
has almost unlimited possibilities to change. For the machineries of the living organism,
proteins stand for the machinery and they are very good in performing everything that is
needed for a cell. But a protein world without DNA (or RNA) should be restricted as the
simple machine that copies itself. It might be able to do much, but it would not have the
possibilities of evolution.
It is also important to have an appropriate metabolic machinery, and this is usually
accomplished by the proteins of the organism. In this book we find many examples about
how an energy flow is used to drive various relevant processes. Kauffman in his “considerations”
(2000, 2003) puts a strong emphasis on what he calls “Carnot cycles” in his ideas of
“autonomous agents” that represent the simplest forms of life in his description. He refers
to the original model by Carnot, describing a heat machine where a hot mass of gas (air
steam) expands and provides useful work until the gas is cooled to room temperature where