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

350 Part VIII. Applications
oscillatory processes, there is a kind of “stable manifold” of states that turn to the unstable
periodic process (which has a kind of saddle point character, there is some manifold going
to it, but another that diverges away from it). Some event close to the stable manifold may
approach the unstable oscillatory state but later go away from it. The detection of such
behaviour makes a possibility to find and stabilise a regular oscillation pattern. This works
well if the states that proceed towards the oscillation comprise a sufficiently broad group,
so that a chaotic time process may appear in such a state with a sufficiently large probability.
It seems that there, in the studied chaotic processes, are only a few really approachable
unstable periodic orbits of a meaningful type in this context. Although there are an unlimited
number of such orbits, only a few can really be approached.
We can add here that the kinds of complex behaviour which have been studied and classified
in relatively simple terms are quite limited. When one gets to dynamics of large networks
with varying connections between the centre points, one may think about possibilities
far exceeding possibilities that hitherto have been characterised in strict terms. One may,
for instance imagine a kind of process that from a kind of original input approaches a first
kind of relatively well-defined structure, that corresponds to some retrieved memory.
However, from that the process may spread out in a new direction, reaches some kind of
associations and also later cross between various momentarily seemingly regular patterns.
§33 ORIGIN OF LIFE
33A
Ideas about early molecular evolution
It is natural for a physicist with an interest in basic principles and an ambition to look for
the simplest representatives to wonder about the start, the big question on how life started
on earth and developed without all the biological machinery that is present today. The dominating
question for a physicist is how? There are many threads here and much that is not in
line with our general trends. These parts will be dealt with more briefly, and we put the
main emphasis on questions which were the most important steps towards life. What can
be said from a physicist’s point of view about what must have taken place and can we say
anything about the basic steps? A good review of the field is by Orgel (1988).
First, we must admit, no one can tell how life appeared. No one was there and there are
few actual evidences about the actual start. At present, there is no agreement about the first
traces of actual life, and there is an uncertainty of about a billion years. We can thus not
give a satisfactory answer about whether life appeared quite early during the history of the
earth or if it appeared after a very long time. It is often claimed that life started very early
and thus, that the conditions for life were there at the beginning and the development of life
followed a relatively clear and general path. A general opinion is that the probability to
develop life is relatively large if the conditions are appropriate, which one usually believes
were valid on earth. But this view is difficult to hold when it is not clear whether life
appeared early or first about a fourth of the time the earth had existed (earth has been there
for a billion years). Can we assert the view that the probability of appearance of life is large