Thursday, November 21, 2019

Evolutionary Theories of Aging and Longevity Research Paper

Evolutionary Theories of Aging and Longevity - Research Paper Example This paper analyses some of the major evolutionary theories with respect to aging and longevity. Mutation accumulation theory was formulated by Sir Peter Medawar, a noted British professor of zoology and anatomy at the University of London who won the Nobel Prize in medicine (1960) for his work on acquired immunological tolerances† (Mutation Accumulation Theory of Aging). According to mutation accumulation theory; Aging is an inevitable result of the declining force of natural selection with age. For example, a mutant gene that kills young children will be strongly selected against (will not be passed to the next generation) while a lethal mutation with effects confined to people over the age of 80 will experience no selection because people with this mutation will have already passed it to their offspring by that age. Over successive generations, late-acting deleterious mutations will accumulate, leading to an increase in mortality rates late in life (Gavrilov and Gavrilova, p .341). Mutation accumulation theory argues that the negative effects or adverse events originated at the time of evolution may decline as time goes on. In other words, living things acquire more and more abilities to counter the adverse effects of evolution since the transfer of genes which causing adverse events may decline as reproduction goes on. For example, the epidemic diseases in the past are no more a threat to the current generation. This is because of the reduction in the transfer rate of genes responsible for such epidemic diseases to the upcoming generation from the generations in the past. Mutation accumulation theory believes that aging is caused by defective genes which may become hyperactive during the later stages of life. For example, genetic diseases such as Huntington’s chorea may appear in the life of a person only at the final stages of his life. It should be noted that the genes which are causing this disease was present in the body of that person even at the time of his birth. However, such genes may not be active during early parts of his life and aging is the process which helps the activities of such genes. Antagonistic pleiotropy theory was formualted by George C Williams in 1957. Pleiotropic According to Antagonistic pleiotropy theory, â€Å"Late-acting deleterious genes may even be favoured by selection and be actively accumulated in populations if they have any beneficial effects early in life†(Gavrilov and Gavrilova, p.341). In normal circumstances, each gene may have only a single trait. However, in certain circumstances, it may have more than one trait which usually refers as pleiotropy. Antagonistic pleiotropy theory believes that the same gene which is responsible for increased reproduction during the early parts of one’s life may cause aging during the later parts of his life. For example females loss fertility during later parts of their life even though they may have high rate of fertility during the early parts of their life. It should be noted that the same gene is responsible for both fertility and non-fertility. The postulates of mutation accumulation theory and that of the Antagonistic pleiotropy theory are almost similar even though some differences are there. Antagonistic pleiotropy theory argues that the defective genes are kept in the gene pool whereas mutation accumulation theory point out that the defective genes will be accumulated as time goes on. If aging is a side effect of genes that have a

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