The logic of embryonic development

The discovery of genes that control embryonic development has started a true revolution in biology, both from an experimental and from a theoretical point of view. On the experimental side, it has opened fields of research that previously seemed unapproachable. 

From a theoretical point of view, it has inspired the conclusion that embryonic development is the execution of a genetic program, in the sense that all processes of ontogenesis depend, more or less indirectly, on the transcription of genes. Unfortunately, many have also concluded that the central problem of development - the problem of form - has been, in principle, resolved. Many details are still to be worked out, it is said, but the logic is now clear because the form of an organism depends on its genes. 

In his book The Problems of Biology (1986), John Maynard Smith has lucidly sounded a note of caution against this attitude  

Maynard Smith s point can also be expressed in another way embryonic development is a process that increases the complexity of a living system, but we do not know how to build machines that increase their own complexity, and we cannot therefore understand the logic of development. We can also leave aside the physical construction of machines and concern ourselves only with their planning. If we could prove, with a mathematical model, that it is possible to increase the complexity of a system, we already would have taken a major step forward. The search for the logic of development begins therefore with the search of a mathematical model for systems which are capable of increasing their own complexity. 

At this point, however, a formal distinction between two very different cases is called for. An increase in complexity took place even during the history of life, but in this case new structures arose by chance mutations, and the increase was a divergent process. In embryonic development, on the contrary, new structures are never formed by chance, and we are dealing with a convergent increase of 

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At this point we are left with the problem of discovering yet more memory matrices, and here we have plenty of suggestions. It is plausible, for example, that a memory of boundaries, or more generally a memory of discontinuities, could be built, but we can leave these developments to the future. We have seen that the memory matrix method can indeed perform reconstructions from incomplete information, and therefore we already have what we were looking for a model that may help us understand the logic of embryonic development. 

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