Biology Reference
In-Depth Information
However, this holistic view of living organization is at odds with the standard
evolutionary perspective, which sees organisms as the result of changes in genes
that have taken place at the populational level. Modern molecular biology has
grounded this view, presenting a highly hierarchical approach of cellular orga-
nization. According to this view, the extreme precision of cellular organization
relies on the fact that practically all biological reactions are controlled by one
kind of macromolecule: catalytic proteins, i.e., enzymes. If we inquire about
the cause that produces a given protein we will find a rather peculiar situation.
In the first place, we can answer that, as any other component of the cell, a
protein is the result of the action of a set of components (which will constitute,
in Aristotelian terms, the efficient cause of this particular protein). Concretely,
the synthesis of any protein is a direct consequence of the action of tRNAs
and peptidyltransferase protein molecules, both involved in the formation of the
string of amino acids. Another answer to the question is that the cause of a pro-
tein is the smaller molecular aggregates of which it is made of (this constitutes
in Aristotelian terms its material cause). Then, amino acids would be considered
to be the material cause of proteins.
Unlike other components, proteins are highly specific and complex. As is
well known, the specific sequences of amino acids that constitute the proteins
of a particular organism are related ultimately to the specific sequences of the
nucleotides of DNA molecules. DNA (and RNA) acts, then, as an 'informa-
tional' template for the synthesis of proteins, because it contains the necessary
instructions for guiding the construction of primary sequence of proteins. Hence,
we can say, in Aristotelian terms, that DNA molecules are the formal cause
of proteins in biological cells, because their specific sequence of nucleotides
conveys the 'form' of the latter.
If we finally ask which is the cause of the specific form that DNA molecules
carry, the answer would send us to a more encompassing framework than that
of the individual cell. There is a fundamental difference between DNA and
the remaining components of the cell. Although materially speaking, DNA is
made up of building blocks as any other component, the specific order of
the nucleotide sequence of a given DNA is ultimately a consequence of the
evolutionary process, which leads us beyond the level of the cell. DNA represents
a material connection between the evolutionary and the organismic levels, the
collective/historical dimension and the individual organization. This is why DNA
'escapes' in a certain sense the causal closure that characterizes the organization
of individual living beings.
This seems to give the final word to (Darwinian) evolution. But what is
in fact evolution? Biological evolution, as we know it, requires the existence
of certain types of systems: self-reproducing discrete entities based on a full
Geno-Phenotype separation (namely, a code-based organization), which compete
among each other in a noninterbreeding way. Then, if Darwinian evolution does
