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The question, “when does development end and aging begin?” has been widely-debated over the last century, and is continually being researched today by individuals in the fields of gerontology, sociology, and psychology. To answer this question, one must look at many factors, including time, a multitude of environments, and everyone’s individualized capacity to age and grow (class discussion). I stand by the belief that development can be considered “complete” around the age of 25 (Wallis, ) and that aging, despite it being observed as an ongoing process, formally starts once there is evidence of loss of function in biological processes and various phenotypic changes (Arking 11).
Development can be defined in many ways, but I feel that the simplest and most direct way is to describe it is by considering it as the stage of life in which individuals are gaining function, both in biological and social terms (PPT 1/24/18). It is important to understand that all organisms develop in some way or another, but that when it comes to aging, each individual ages at their own pace (the process is not uniform) (Arking, 16). Women, for example, have their peak developmental experience around when menstruation occurs (class discussion, 1/22/18). However, it can be noted that in today’s world, the first appearance of a girl’s reproductive ability has become increasingly earlier, which is due to different hormonal levels, toxin exposures, medical advances, etc. (1/22, class discussion). Additionally, it has been discovered by researchers that the human skeleton in most individuals seems to cease growing around the age of 20, and that in many athletes, their average peak performance ages range from anywhere between 20-30 years old (Zhav 4). This makes it clear that despite thinking that development ends at an early adolescent age, it continues into young adulthood.
Therefore, development can be considered to formally end around the age of 25 due to different hormonal levels, and the level of prefrontal cortex development that has been observed (Wallis, ).
The definition of interspecific plasticity sums up my strong beliefs about development and aging: “After a developmental period that culminates in sexual maturity, adults maintain physical vigor for a relatively long time before beginning to manifest progressive dysfunctions in various physiological systems over a relatively extended period of time” (Arking 22). In this sense, it appears that aging may not happen directly after reaching maturation, but it might occur over a longer period of time.
Aging, therefore, begins at an undefined time after an individual achieves maturity (Woodruff 7). Often, the terms “aging” and “senescence” are used interchangeably, but senescence refers specifically to the period of functional decline that occurs as aging progresses (Arking 11). Senescent changes, since they are often found to occur later in life, also have an impact on the mortality characteristics that are displayed by individuals (Arking 12). Additionally, research has concluded that biological aging brings about issues such as the loss of neurons or the presence of anomalous chemicals at high concentrations in the brain (Woodruff 14). So, based on this information, the time of aging in each organism and species is not uniform- we see that do to intrinsic or extrinsic factors, aging can occur at different times and display many different characteristics in different organisms. We can measure biological age by using various biomarkers, and if it appears that changes in the organisms are heading in a direction of decline, then it is aging a specific rate compared to another organism (Arking 11).