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12.1 Is molecular evolution contrary to the second law of
thermodynamics?
12.1.1 Thermodynamics and the creation of "order" by evolution
Thermodynamics and the theory of evolution by natural selection
are among the great scientific theories of the nineteenth century.
Yet almost immediately after the introduction of these two great
theories they were pitted against each other. The opinion that
evolution was contrary to the second law of thermodynamics was
pushed by scientists who did not accept evolution. In the twentieth
century this alleged conflict has been a favorite theme of the
Biblical creationists and of the creation-science advocates
(Wilder-Smith, 1981; Gish, 1989).
An isolated system is one which _does not_ exchange heat or work
with another system. The second law of thermodynamics states that
the Maxwell-Boltzmann-Gibbs entropy of an isolated system does not
decrease; it is, in general, not a conservation law since entropy
is conserved only in reversible processes. Entropy is regarded as
a measure of 'order', sometimes without bothering to define 'order'.
Thermodynamics, as it was viewed in the nineteenth century,
predicted a 'heat death' of the universe in which all bodies in
the universe will be at the same temperature in a state of complete
'randomness' or 'disorder'. (Think of it as the death of heat
exchange, not a death by heat.) Evolution, on the other hand, so
it was thought, predicted an increase in 'order' in the sense that
more highly evolved organisms were considered to be more 'orderly'.
Thus the reason for the conflict between the evolutionists and
the creationists is that the second law was perceived to predict
increasing 'disorder' while the theory of evolution was perceived
to predict increasing 'order'. The notion that a paradox exists
between biological evolution and the second law of thermodynamics
persists today and is perceived to require resolution (Waldrop,
1990).
As I shall show, a proper understanding of both evolution and
the second law of thermodynamics demonstrates that they are not
in conflict and that the supposed paradox is merely a play on
words.
[...]
Scientists who defend evolution have been caught, much as
Br'er Rabbit by the Tar Baby, in a word-trap implying that
evolution leads to organisms that are increasingly more 'orderly'.
As I have mentioned in this book several times, it is perilous
for the scientist to use words in their everyday meaning to express
scientific concepts. One should remember that in science these
words are merely names for mathematical functions and have no
other meaning in themselves.
[...]
Kitcher(1982) believes that there is a dilemma and that the way
out is to declare that life is an open system receiving work and
heat and that in such systems entropy _decreases_ over time. This
is true but inapplicable. Although organisms use energy, as I have
pointed out (Yockey, 1974, 1977c), the entropy that is pertinent
in the genetic system is the Shannon entropy or the Kolmogorov-
Chaitin algorithmic entropy. Kitcher(1982), along with many others,
is unaware that each probability space has its own peculiar entropy.
Two probability spaces that are not isomorphic have no relation
except in those cases where such a relation is established by a
code. Patterson (1983) also makes the mistake of confusing order
with complexity; he cites some references in which the Biblical
creationists claim that evolution is impossible based on the false
notion that evolution violates the second law. He believes that
highly organized molecular assemblies have a low entropy. He
thereby falls into the word-trap set by the creationists of using
words like 'order' and 'complexity' without defining them
mathematically. His explanation in other words is rather lame.
[...] Even a scientist as eminent as Eddington (1931a) believed
there is a conflict between the second law of thermodynamics and
evolution:'We must of course drop the theory of evolution, or at
least set alongside it a theory of anti-evolution as equally
significant'. As usual, Eddington could put his finger on the
problem even if a solution was not available at the time. Later in
that article he pointed out that it is _organization_ that increases
in evolution. But he had no mathematical definition of organization.
This had to await the definition given by algorithmic entropy as
discussed in section 2.4.1.
As has already been discussed in this book (section 2.2.2),
the entropy to which the second law of thermodynamics applies
is the Maxwell-Boltzmann-Gibbs entropy. This entropy addresses
the energy efficiency of heat engines, the directions of chemical
reactions and, in biology, the energy economy of the cell. Thus
it is the 'orderliness' of energy that is addressed by the second
law of thermodynamics. Organisms cannot defy the second law: there
has never been any question in sober minds that organisms are not
perpetual motion machines (although small children may seem to be).
One should remember that classical thermodynamics deals only with
energy and the Maxwell-Boltzmann-Gibbs entropy. It is even
independent of the existence of atoms.
All probability spaces have an entropy peculiar to them (section
2.2.1). The entropy that is applicable to the case of the evolution
of the genetic message is, as I believe the reader should now be
convinced, the Shannon entropy of information theory or the
Kolmogorov-Chaitin algorithmic entropy. In thermodynamics one has
two invariants of the system, namely the mass of the system and
the conservation of energy as expressed in the first law of
thermodynamics. In communication systems one has only the
conservation of the number of letters. There is no invariant
corresponding to energy in the case of communication systems and
consequently no analogue of temperature. Furthermore, the Shannon
entropy and the Maxwell-Boltzmann-Gibbs entropy are based on
probability spaces that are not isomorphic to each other.
Consequently, for this reason also, as I have pointed out before
(Yockey, 1977c), they have nothing to do with each other.
Therefore it is easy to see that thermodynamics has nothing to
do with Darwin's theory of evolution.
12.1.2 The increase in genetic algorithmic entropy during evolution
The Kolmogorov-Chaitin genetic algorithmic entropy is increased
in evolution due to the duplications that occurred in DNA. [...]
Thus the genetic algorithmic entropy increases with time just
as the Maxwell-Boltzmann-Gibbs entropy does. Therefore creationists,
who are fond of citing evolution as being in violation of the
second law of thermodynamics (Wilder-Smith, 1981; Gish, 1989),
are hoist by their own petard: evolution is not based on increasing
_order_, it is based on increasing _complexity_. In fact, evolution
requires an increase in the Kolmogorov-Chaitin algorithmic entropy
of the genome in order to generate the complexity necessary for the
higher organisms. Let us recall from section 2.4.3 that _highly
organized_ sequences, by the same token, have a large Shannon
entropy and are embedded in the portion of the Shannon entropy
scale also occupied by _random sequences_.Evolution is not in
violation of the second law of thermodynamics. This is what any
reasonable scientist believes; nevertheless, it is important to
avoid word-traps and to reach the correct conclusion for the correct
reasons.
-- Hubert Yockey,_Information Theory and Molecular Biology_,
Cambridge University Press, 1992, p. 310-313.
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Brian Harper |
Associate Professor | "It is not certain that all is uncertain,
Applied Mechanics | to the glory of skepticism" -- Pascal
Ohio State University |
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