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Posted by Pierre on August 27, 1999 at 04:40:17:
If we agree that selection optimizes global functions of multicellular
organisms (immunity, intelligence), we must define the initial steps of
multicellularity (see JJ Kupiec work), before organisms with such emergent
global functions appears. When we think, what is a neuron doing ? At a single
cell level, there is no thought. Is the neuron just obeying the genetic program
of thinking ? What kind of selective advantages is the neuron obtaining from
obeying such a program ?
I am not an expert, but it looks like a classical "initial step"
evolutionary problem. The selection cannot create a global physiological
function. The structure that will be able to support the function must exist
before, for reasons that are not the obtention of the global function.
For example, neuron associations that will be able to think cannot appear
randomly, or TO think. Neurons probably grouped to obtain some other advantages
and when grouped, will be able to be optimized for thinking.
Even for simple neural function, performed by a single cell : the specialized
structure of a neuron cannot appear by chance, or with the purpose to be a
neuron. It was optimized by selection, in the advantage of the neuron, for
other reasons. I think the reasons are food related. The neuron emitted roots
for food. This is the selective advantage obtained at the one cell level. These
roots where used as axons and dendrites later.
In the same manner, the clonal selection theory
of antibody formation considers that cells are selected by a signal from the
organism, designed by the required defense from infections as a selective
advantage. This is a strange multi selected unit conception of darwinism. The
cell is the selected unit, but the selective advantage is at the organism level
!
This is a terrible mistake. We do not say that the tree is selected to maintain
the oxygen balance of earth. It does, but this is not the reason it was
selected for.
This is why the clonal selection theory in immunology, as well as many modern
physiological interpretations are wrong. Rethinking physiology requires
rethinking the mechanics of embryonic development. For this, we
have to forget our anthropocentrism, and just consider cells as independant
animals obeying not a program that represent ourselves, but the rules of
evolution.