Control Systems in the Living World - Building the Most Complex Structure on Earth - page 21

operational in multicellular animals ( Cabej, 2005, 2008, 2012, pp. 9-32 ). Such sys-
tems are better known in higher vertebrates, including humans. The picture of the
control system in unicellulars is still blurred (see later in this chapter), while in
plants, only separate controls are known (see later in this chapter), which can pos-
sibly be subordinate to a still-unknown integrated control system.
A prerequisite of an integrated control system is that it has to be able to monitor
all parts of the organism by continuously receiving information on their state. This
implies that the control system must have a pervasive presence throughout the liv-
ing organism. A second imperative is that it has to compute in order to compare the
actual state with the normal state, which is inscribed in the form of set points for
various variables. This implies that the control system knows the normal structure
of the system. Third, it needs to problem-solve; that is, to generate and send instruc-
tions throughout the animal's body for restoring the normal state.
While most of us may agree that coordination of the development of all the
parts of organism is a necessity, the prevailing gene-centric view attributes this
function to a genome rather than to a specialized center. Despite attempts to prove
that a genetic program could account for the control of development, no model,
however loose, has ever been presented on how this may happen. Even if one
takes for granted that the genome is the control center in unicellulars, the question
would naturally arise: which billions or trillions of cells of a multicellular animal
would have the privilege of playing the role of the “genomic” integrated control
system? How will this empowered genome receive information on the state of the
system and send back instructions to restore the normal state in any parts of the
organism?
There is absolutely no evidence, no hint, or even any hypothesis of a genome
somehow controlling any systemic parameter in multicellulars. There is no evidence
that the genome might control and regulate homeostasis in unicellulars. On the con-
trary, empirical evidence shows that genome (including its duplication and gene
expression) is itself regulated rather than the regulator of homeostasis (see Section
“The Control System in Unicellulars,” later in this chapter).
We know where the crucial control center is in most metazoans (see later in this
chapter, section "The Control System in Plants"). Beginning in the second half of the
nineteenth century, experimental evidence progressively showed that in metazoans,
a central system that controls and regulates vital functions (blood circulation, blood
pressure, breath rate, and function of organs and organ systems) is operative and
essential for their existence and evolution. Indeed, the study of the central mecha-
nisms of control of animal functions is one of the main objects of animal physiology,
and it is textbook knowledge that the maintenance of homeostasis and behavior in
metazoans are functions of the nervous system. Through afferent pathways, sensory
nerves send to the CNS sensory information about various parameters, which are
compared to the corresponding set points; if deviations are detected, the brain sends
chemical instructions via effectors to restore the normal level of the parameter.
In contrast with the clear picture of the control system in multicellular animals,
the evidence on the control system in unicellular organisms and plants is still limited,
poorly systematized, and awaiting scientific formulation and elaboration.