Biology Reference
In-Depth Information
differentiated state. Interactions between cells play an important
role, but they do not involve signals inducing changes of state, as the
theory of genetic programming supposes. Rather, they stabilise
genetic expression when a viable combination of differentiated cells
has been produced by the genes functioning randomly (Kupiec,
1983). The genetic expression is then frozen and the cells can no
longer change their state. If a cell does not adapt to its microenvi-
ronment through this random process, it ceases to multiply and dies
or becomes pathological. The conceptual structure of this model is
therefore a mixture of chance and selection, analogous to the theory
of natural selection but transposed to the level of cell behaviour.
However, the analogy with Charles Darwin's theory (1809-1882)
goes further. According to cellular Darwinism, embryogenesis is a
real extension of natural selection within organisms. Ontogenesis
and phylogenesis are the two inseparable sides of a single reality
produced by a unique process: ontophylogenesis. Organisms develop
and evolve at the same time. Both phenomena are the result of a
single mechanism (Kupiec, 1986), so for this reason, the usual def-
initions of the genome and the environment are not apt. Since it
functions randomly, not only is the genome not the bearer of a
genetic programme of rigid instructions in which the adult organ-
ism is inscribed in advance, but the conception that we have of the
environment is equally incorrect. It comprises not only an external
environment from which the organism is separated by a hermetic
barrier, but it continues inside the organism forming the selective
microenvironment of the cell, to which the latter must adapt. This
conception of the cell microenvironment corresponds to Claude
Bernard's 'internal environment' (1813-1878). For him, organs and
cells lead an autonomous life in this internal environment (Bernard,
1878). Cellular Darwinism borrows, therefore, both from Darwin's
and Bernard's theories, and consists of applying natural selection to
the cells which live in the internal environment. A similarly inspired
theory was put forward by Wilhelm Roux (1850-1924) in the 19th
century, but it was eclipsed by the expansion of genetic conceptions
(Roux, 1881).
