Communication, one of the most important
functions of life, occurs at any spatial scale from the
molecular one up to that of populations and ecosystems,
and any time scale from that of fast chemical reactions
up to that of geological ages. Information theory, a
mathematical science of communication initiated by
Shannon in 1948, has been very successful in
engineering, but biologists ignore it. This book aims
at bridging this gap. It proposes an abstract definition
of information based on the engineers' experience which
makes it usable in life sciences. It expounds
information theory and error-correcting codes, its
by-products, as simply as possible. Then, the
fundamental biological problem of heredity is examined.
It is shown that biology does not adequately account for
the conservation of genomes during geological ages,
which can be understood only if it is assumed that
genomes are made resilient to casual errors by proper
coding. Moreover, the good conservation of very old
parts of genomes, like the HOX genes, implies
that the assumed genomic codes have a nested structure
which makes an information the more resilient to errors,
the older it is. The consequences that information
theory draws from these hypotheses meet very basic but
yet unexplained biological facts, e.g., the existence of
successive generations, that of discrete species and the
trend of evolution towards complexity. Being necessarily
inscribed on physical media, information appears as a
bridge between the abstract and the concrete. Recording,
communicating and using information exclusively occur in
the living world. Information is thus coextensive with
life and delineates the border between the living and
the inanimate.
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