Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
The US biochemist Gerald Edelman explains location-dependent development of body cells (e.g., how a cell knows where in the body it is supposed to grow in order to generate the shape and function of the animal) by assuming that development is based on topo-biological events which are regulated by cell-adhesion and substrate-adhesion molecules on the surface of the cell. In other words, a cell's competence is due essentially to its location.
In detail, the story reads like this. Living systems exhibit three properties that allow them to exist: heredity, variation in their hereditary material, and competition as the environment changes. Living systems are self-replicating systems, whose genome undergoes mutation and whose variant individuals undergo natural selection. Characteristic of living systems is development, in particular morphogenesis, the emergence of form during embryonic development. Roughly the same cell types appear in different parts of the body. The difference in position and shape results from the interaction of a number of driving forces (namely cell division, cell motion and cell death), which determine the number of cells in a particular region, and regulatory processes (namely cell adhesion and cell differentiation), which determine the interaction among cells.
Pattern, and not mere cell differentiation, is the evolutionary basis of morphogenesis.
The cell surface, not its core, plays the fundamental role in this process, because it mediates signals from other cells and links with other surfaces to form tissues. A sequence of interactions between certain special types of genes via epigenetic signal paths provides the basis of pattern by controlling temporal sequences of mitosis, movement, death and further signaling.
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