Transition phase —from ageing to senescence
Some plants and fungi never seem to become old. These species make continuous copies of their own cells and tissues without the need for female and male mating and the production of new generations of offspring. This is asexual reproduction. Sexually reproducing organisms grow old and die. Aging is part of the entire human life cycle. Before birth, some cells must die so that others can live, grow, and develop. The creation of reproductive cells (eggs and sperm) and the bio-behavioral system for mating, fertilization, and care of offspring come at great cost to the other parts of the individual. In sexually reproducing organisms these costs are so great that a limited lifespan and death of the individual are inevitable.
Aging is the visible process of becoming older and is related with time —for humans time may be measured in calendar years. Senescence is a biological process of loss of cellular, tissue, and organ function that reduces the ability of an individual to respond favorably to intrinsic and extrinsic stressors. These stressors, including disease and emotional trauma, push the senescent person out of a healthy equilibrium and toward an increasing probability of death. Senescence is measured in biological time and the pace of senescence is variable in terms of its progression and the timing (calendar age) of transition towards degeneration and death. The transition to senescence depends on prior levels of physical and cognitive reserves of the individual which accumulated during the infancy, childhood, juvenile, and adolescent stages of development. Greater reserves accumulate in those people who benefited from higher quality investment in biocultural reproduction from family, community, and society. People with poor physical and cognitive reserves may show signs of senescence after age 35 while people with better reserves maintain prime adult capacities to age 50 years and beyond. Despite all efforts to maintain body and mind, there is eventually a decline in the function and repair ability of many body tissues or systems. Notable signs of early senescence are a decrease of muscle and bone tissue, often with an increase of relative or absolute percentage of body fat. Decline in cognitive functions also takes place. These changes lead to an ever-faster decrease of physical and cognitive working ability. During the early and middle phases of the transition toward senescence it is usually possible to adopt biobehavioral strategies for compensation, such as stronger lighting for reading, a slower pace at physical labor, and multiple revisions of mental tasks to avoid errors. In the later phase of the transition compensation strategies become less and less effective.
The images above present two men in the later phase of the senescence transition. The man on the left was photographed in the marketplace of the city of Merida, Yucatan, Mexico. The man on the right is Mr Birkha Bhadhur Muringla, a scholar of the Limboo language (also spelled Limbu) who helped to restore the language to its modern form. The Limboo people are native to the Himalayan regions of India, including Sikkim, Eastern Nepal, and Western Bhutan. Limbu is one of the few languages of the Central Himalayas to possess its own pre-20th century written alphabet and grammar. Limboo writing was repressed in the late 19th and early 20th centuries by the dominant political groups and Limbu language monuments were destroyed or the writing obliterated. After political changes in the 1920s there was some revival of written Limboo, but the major restoration of the written language took place in the 1960s and especially after 1975 when Sikkim became part of India. In 2018 Mr Bhadhur Muringla was effectively blind, a cruel outcome of aging to a man of letters and language. [Barry Bogin]