Information Theory in Biology
Control Systems Laboratory, U. Illinois, 1952
One of the basic tools in natural science is the energy concept.
In recent years, another concept has begun to attain comparable dignity.
It is something more subtle and elusive than energy; it is
derived from a desire for dealing methodically with problems of complexity,
order, organization, specificity.... It is known as entropy
or amount of
information, and plays a prominent role in the
new fields of information theory, communication theory, and cybernetics.
The "new movement" is based on evaluative concepts (R. A. Fisher,' s
experimental design, A. Wald's statistical decision function,
J. von
Neumann's theory of games), on the development of a measure of information
(R. Hartley, D. Gabor, N. Wiener,
C. Shannon), on studies
of control mechanisms, and the analysis and design of large systems
(W. S. McCulloch and W. Pitt's "neurons," J. von Neumann's theory of
complicated automata,
N. Wiener's cybernetics).
It has become increasingly evident that the principles of information
theory are applicable to the "higher" functions of living
organisms. They can also be used to advantage in analyzing basic
functions such as metabolism, growth, and differentiation. There
are remarks to that effect in Wiener's
Cybernetics; in
E. Schrödinger's
What is Life? there is a provocative discussion on how organisms
feed on
negative entropy." In the present volume, the
formalism of information theory and cybernetics has been applied to
some basic biological problems, with some degree of success.
Theoretical biology should consist of the application of information theory to explain the control and communication systems that we call "information processing," which is unique to biology, and the creation of abstract information (ideas), unique to the mind of man?
The amount of control and communication involved in the basic
biological processes is very great. Indeed, it appears that there
is little difference between the exercise of the basic biological
activities, and the exercise of the most sophisticated skills in the
most highly differentiated organisms. We do not claim that the
absolute difference between basic and highly specialized activities
is small; after all, this difference is the result of the order of a
billion years of organic evolution. The claim is only that the gap
between simple and complicated living organisms is small in comparison
to the gap which separates the simplest living things from the
most complicated non-living systems, say, between a bacterium and a
giant electronic brain. Thus, when we say that the functional
complexities of man and bacterium are closely comparable, we do so,
not because of a low estimate of the functional complexity of man,
but because we are very much impressed by the complexity of bacterial
life.
The cybernetics of biological functions should ultimately contribute
to the understanding of the nature of biological control
systems. The first stage in the analysis is quantification: a
count of control elements, a measure of the amount of control exercised.
Most papers in this volume deal with counts and measures;
only on a few occasions have steps beyond this stage been attempted.
It is in the nature of cybernetics that it cuts across traditional
boundaries between various fields of science. Because of this,
symposia have played a major part in its development--in particular,
the British symposia ('50, 52), the series of Macy conferences,- the
French symposium ('52). The present volume, too, is the result of a
cooperative effort; it stems largely from lectures and discussions
arranged, in the summer of 1952, under the auspices of the Control
Systems Laboratory at the University of Illinois.
("Introduction," Essays on the use of INFORMATION THEORY IN BIOLOGY, Ed. University of Illinois Press, Urbana,, 1953)
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