Codes and Macroevolution

The role of the organic codes in the history of life can be appreciated by underlining that their origins are closely associated with the great events of macroevolution.

Any time that a new organic code came into being, something totally new appeared in Nature, something that had never existed before.

The origin of the genetic code, for example, made it possible to produce proteins with specific sequences and to pass them on indefinitely to other systems. That gave origin to biological specificity and to heredity, the most fundamental of life's properties. The origin of the genetic code, in short, was also the origin of protein-based life, i.e. of life-as-we-know-it.

Similar considerations apply to the other organic codes. The signal transduction codes, for example, allowed primitive systems to produce their own signals and therefore to separate their internal space from the outside environment. That was a precondition for the origin of individuality, and in particular for the origin of the cell.

Another great innovation was brought about by the codes of splicing, because the appearance of a complete set of splicing rules brought something unprecedented into being. Splicing requires a separation in time between transcription and translation and that was a precondition for their separation in space, i.e. for the origin of the nucleus. The defining feature of the eukaryotes, in other words, was made possible by the origin of the splicing codes.

Many other eukaryotic innovations were brought into existence by a whole stream of organic codes. The cytoskeleton codes, for example, allowed the cells to build their own scaffoldings, to change their own shapes and to perform their own movements. The origin of embryos was also associated with organic codes because typical embryonic processes like cell determination, cell adhesion, cell migration, and cell death have all the qualifying characteristics of codified phenomena (Barbieri, 1998, 2003).

In the case of embryonic development, furthermore, we have entirely new codes before us. The correspondence is no longer between two types of molecules, like genes and proteins or first and second messengers, but between molecules and cell states. The determination of the body axes, for example, is obtained by a link between molecules and cell memory. The body axes are the same in all triploblasts, but their molecular determinants are of countless different types, which show that there is no necessary correspondence between molecules and cell states. This means that the link between molecular determinants and cell states can only be realized by codes that we can refer to as body pattern codes.

The major events in the history of life, in short, went hand in hand with the appearance of new organic codes, from the first cells all the way up to multicellular life, and this suggests a very deep link between codes and evolution. It suggests that the great events of macroevolution were made possible by the appearance of new organic codes (Barbieri, 1998, 2003).

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