AGE OF LIFE. — From the stage of the fertilized egg cell to extreme old age, the individual passes through a gradual and interconnected series of transformations. While the unchanging identity of the spirit that animates him remains constant, phenomenally the individual varies, adapting in organic structures, functional attitudes, and the unfolding of psychic activities, following a curve of evolution from the beginning of life to full maturity and of involution from that point to whatever degree of old age he may reach; this occurs regularly according to well-determined "auxological laws."
Viola’s law of autogamy shows how, in its growth, the organism is subject to two opposing tendencies: one promotes the growth of mass (ponderal development), the other morphological differentiation; Godin’s law of alternation illustrates how these two tendencies unfold in regular alternation during successive developmental periods, so that a phase of mass increase in width (turgor phase) is followed by one of lengthening and morphological refinement (procariety phase), and so on; only through the harmonious succession and interplay of these two drives can a regular normotypic development be achieved (v. NORMOTIPO), balanced both in ponderal and morphological terms.
Considering that the fertilized egg cell arises from the union of two sexual elements of opposite structural and functional characteristics, it is suggested that the laws of antagonism and alternation, according to which the individual develops, are linked to the periodic alternation of ontogenetic dominance between the brevilinear, vegetative, mass-related characteristics of the ovum and the longilinear, relational, morphologically differentiated traits of the spermatozoon.
In the succession of ages of life, as the organism now increases its mass—almost concentrating raw material to be processed—now refines its organic differentiation, the phenomenal manifestation of Viola’s and Godin’s laws is clearly discerned. Their intimate mechanism operates in relation to the predominant endocrine balance (v. ENDOCRINE, GLANDOLE, GLANDS) at each phase of the individual’s life—that is, the behavior of groups of endocrine associations with anabolic or catabolic action, stimulating vegetative or relational activity (law of the rhythmic and balanced activity of the two hormonal constellations that govern morphogenesis, or Fende’s law). From this, in relation to the periodic balanced predominance of one hormonal constellation (thyroid, pituitary, adrenal medulla, sexual endocrine gland) over the other (thymus, adrenal cortex, parathyroids, pancreatic islets, etc.), arise the morphological, functional, and neuropsychic characteristics of the various ages of life; the definitive harmonious balance in the adult as a normotype, or as a megalosplanchnic brevilineal hypervegetative etiotype, or a microsplanchnic longilinear hypovegetative one.
The ages of life unfold through a prenatal and a postnatal period. The first includes the phase of the fertilized egg, the first two weeks of life with predominant mass development (intror); the embryonic phase, from the third to the ninth week inclusive, marked by intense organogenesis and morphological differentiation (procariety); the fetal phase, from the tenth week of life until birth, with further organic refinement and full mass development (turgor).
The postnatal period encompasses the entire extrauterine life of the individual; in it, the organism traverses the entire vital parabola, up to the final stage granted to it by its particular hereditary biological essence, in interplay with the contrast of environmental factors capable of either allowing the full development of its biological destiny or cutting it short prematurely.
First comes the neonatal phase (newborn), in which, over the course of two weeks, the new organism adapts to its new extrauterine state, regains the weight lost in the first days, perfects the suckling instinct, and its thermoregulatory mechanisms. This is followed by childhood (v.), divided into three periods that bring the individual, around the seventh year, to boyhood (v.) or puerility; then adolescence (v.) or prepubescent age, which, between the 13th–15th year in females and the 15th–18th in males, reaches a new organic equilibrium in puberty (v.). In the post-pubescent or interpubertal phase characteristic of youth (v.), it can be said that the organism, between the ages of 20 and 23 (according to N. Fende, not before 25–30), has completed and perfected its physical structures and achieved the full rational development of its intelligence. From this point onward, life in virility (v.) or maturity undergoes a slowing of its evolutionary momentum, then a halt, and finally, around 48–50 years in women and 50–55 in men, a progressive decline that, through old age (v.) and decrepitude, culminates in death.
Such is the course of life in its entirety, depicted as a parabola in which an ascending evolutionary phase is followed by an involutional one, affecting organic and vegetative functions, relational activities, and the highest manifestations of intelligence. While the substance of the phenomenon remains the same, the attributes of nomenclature and, within certain limits, the milestone points of each stage may vary. Thus, some designate infancy and the period from the third week of life to the end of the first year as "fanciullezza," and the span from the second to the tenth year as boyhood, divided into early and late boyhood, with a division around the sixth year. The Romans (Varro) divided life into five stages of fifteen years each (pueri, adolescentes, juniores, seniores, senes).
The ages of life, marked as they are by the alternation of turgor and procariety phases, of increments in vegetative and relational life, are punctuated by the appearance of particular biological, somatic, and psychic characteristics. Among the former, for example, the successive emergence or replacement of different types of teeth—long, sharp, or pointed (incisors, canines) or broad and crushing (molars), of milk and permanent dentition; among the latter, the predominant development of instinctive-affective faculties or intellective-volitional ones, the prevalence of mental development in sensory, animistic, evasive, or imitative, finalistic, extroverted, or intuitive, individualistic, introverted forms, or more fully rational ones.
It is considered impossible for an educator to perform truly intelligent work without knowledge of the somatic, functional, and mental characteristics proper to each age of life.
From a purely ethical standpoint, the influence exerted by age on human acts is especially significant in the so-called critical ages. For related observations, V. FANCIULLEZZA; PUREZZA; VECCHIAIA; VIRILITÀ.