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4 days ago · Adulthood, the period in the human lifespan in which full physical and intellectual maturity have been attained. Adulthood is commonly thought of as beginning at age 20 or 21 years. Middle age, commencing at about 40 years, is followed by old age at about 60 years.
- Maturation
Other articles where maturation is discussed: animal...
- Human Aging
human aging, physiological changes that take place in the...
- Middle Age
middle age, period of human adulthood that immediately...
- Biological Development
Biological development, the progressive changes in size,...
- Maturation
- Overview
- The scope of development
biological development, the progressive changes in size, shape, and function during the life of an organism by which its genetic potentials (genotype) are translated into functioning mature systems (phenotype). Most modern philosophical outlooks would consider that development of some kind or other characterizes all things, in both the physical and biological worlds. Such points of view go back to the very earliest days of philosophy.
Among the pre-Socratic philosophers of Greek Ionia, half a millennium before Christ, some, like Heracleitus, believed that all natural things are constantly changing. In contrast, others, of whom Democritus is perhaps the prime example, suggested that the world is made up by the changing combinations of atoms, which themselves remain unaltered, not subject to change or development. The early period of post-Renaissance European science may be regarded as dominated by this latter atomistic view, which reached its fullest development in the period between Newton’s laws of physics and Dalton’s atomic theory of chemistry in the early 19th century. This outlook was never easily reconciled with the observations of biologists, and in the last hundred years a series of discoveries in the physical sciences have combined to swing opinion back toward the Heracleitan emphasis on the importance of process and development. The atom, which seemed so unalterable to Dalton, has proved to be divisible after all, and to maintain its identity only by processes of interaction between a number of component subatomic particles, which themselves must in certain aspects be regarded as processes rather than matter. Albert Einstein’s theory of relativity showed that time and space are united in continuum, which implies that all things are involved in time; that is to say, in development.
The philosophers who charted the transition from the nondevelopmental view, for which time was an accidental and inessential element, were Henri Bergson and, in particular, Alfred North Whitehead. Karl Marx and Friedrich Engels, with their insistence on the difference between dialectical and mechanical materialism, may be regarded as other important innovators of this trend, although the generality of their philosophy was somewhat compromised by the political context in which it was placed and the rigidity with which their later followers have interpreted it.
Philosophies of the Heracleitan type, which emphasize process and development, provide much more appropriate frameworks for biology than do philosophies of the atomistic kind. Living organisms confront biologists with changes of various kinds, all of which could be regarded as in some sense developmental; however, biologists have found it convenient to distinguish the changes and to use the word development for only one of them. Biological development can be defined as the series of progressive, nonrepetitive changes that occur during the life history of an organism. The kernel of this definition is to contrast development with, on the one hand, the essentially repetitive chemical changes involved in the maintenance of the body, which constitute “metabolism,” and on the other hand, with the longer term changes, which, while nonrepetitive, involve the sequence of several or many life histories, and which constitute evolution.
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All organisms, including the very simplest, consist of two components, distinguished by a German biologist, August Weismann, at the end of the 19th century, as the “germ plasm” and the “soma.” The germ plasm consists of the essential elements, or genes, passed on from one generation to the next, and the soma consists of the body that may be produced as the organism develops. In more modern terms, Weismann’s germ plasm is identified with DNA (deoxyribonucleic acid), which carries, encoded in the complex structure of its molecule, the instructions necessary for the synthesis of the other compounds of the organism and their assembly into the appropriate structures. It is this whole collection of other compounds (proteins, fats, carbohydrates, and others) and their arrangement as a metabolically functioning organism that constitutes the soma. Biological development encompasses, therefore, all the processes concerned with implementing the instructions contained in the DNA. Those instructions can only be carried out by an appropriate executive machinery, the first phase of which is provided by the cell that carries the DNA into the next generation: in animals and plants by the fertilized egg cell; in viruses by the cell infected. In life histories that have more than a minimal degree of complexity, the executive machinery itself becomes modified as the genetic instructions are gradually put into operation, and new mechanisms of protein synthesis are brought into functional condition. The fundamental problem of developmental biology is to understand the interplay between the genetic instructions and the mechanisms by which those instructions are carried out.
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In the language of genetics the word genotype is used to indicate the hereditary instructions passed on from one generation to another in the genes, while phenotype is the term given to the functioning organisms produced by those instructions. Biological development, therefore, consists of the production of phenotypes. The point made in the last paragraph is that the formation of the phenotype of one generation depends on the functioning of part of the phenotype of the previous generation (e.g., egg cell), as the mechanism that begins the interpretation of the instructions contained in the new organism’s genotype.
- Conrad H. Waddington
Adulthood is the life stage between adolescence and death, but assigning exact ages to the beginning and end of adulthood is not easy. The event that marks the end of adulthood (death) is clear cut, but the age at which it occurs varies considerably.
The notion that the adult stage is the target of development is unacceptable, both because it implicitly gives development a purpose, and because it does not apply to the biology of many organisms. In the common use of the term adult, two different notions are confused: adult as reproductively mature stage and as a stage that maintains its ...
- Early adulthood (20s to early 40s) Early adulthood is the stage most of us associate with the biggest life changes. This period is characterised by exploration and establishing independence.
- Midlife (40s to 60s) Welcome to midlife, the stage where reflection becomes vital. After establishing oneself in early adulthood, the focus often shifts to evaluating one’s life choices.
- Late adulthood (60s to 80s) The late adulthood stage is often associated with retirement, but it is so much more than that. It’s a time for reflection, for looking back on life with pride or regret.
- Elderhood (80s and beyond) The final stage, elderhood, is marked by a profound sense of perspective. Elders, often retired, have a unique understanding of life.
From Birth to Adulthood. For the first year after birth, a baby is called an infant. Childhood begins at age two and continues until adolescence. Adolescence is the last stage of life before adulthood.
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Development of the human body is the process of growth to maturity. The process begins with fertilization, where an egg released from the ovary of a female is penetrated by a sperm cell from a male.
