Ageing (original) (raw)
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Dream 2047, 2023
Modern biology is revolutionising our ideas about ageing.
Age and ageing: What do they mean?
Ratio, 2021
This article provides a philosophical overview of different approaches to age and ageing. It is often assumed that our age is determined by the amount of time we have been alive. Here, I challenge this belief. I argue that there are at least three plausible, yet unsatisfactory, accounts to age and ageing: the chronological account, the biological account, and the experiential account. I show that all of them fall short of fully determining what it means to age. Addressing these problems, I suggest the Two-tier principle of age: whenever the three accounts of age contradict, combine the two accounts that differ the least, and reject the third. However, while this principle does solve some difficulties, it is itself vulnerable to problems; therefore I propose we should jettison it. I conclude that there are no accounts to ageing that are satisfactory; they all come with a bullet to bite.
From gerontology to geroscience: a synopsis on ageing
Anthropological Review, 2021
Biological ageing can be tentatively defined as an intrinsic and inevitable degradation of biological function that accumulates over time at every level of biological organisation from molecules to populations. Senescence is characterised by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. With advancing age, all components of the human body undergo these cumulative, universal, progressive, intrinsic and deleterious (CUPID) changes. Although ageing is not a disease per se, age is the main risk factor for the development of a panoply of age-related diseases. From a mechanistic perspective, a myriad of molecular processes and components of ageing can be studied. Some of them seem especially important and they are referred to as the hallmarks of ageing. There is compelling evidence that senescence has evolved as an emergent metaphenomenon that originates in the difficulty in maintaining homeodynamics in biological systems. From an evolutionary perspective, senescence is the inevitable outcome of an evolutionarily derived equilibrium between the amount of resources devoted to somatic maintenance and the amount of resources devoted to sexual reproduction. Single-target , single-molecule and disease-oriented approaches to ageing are severely limited because they neglect the dynamic, interactive and networking nature of life. These limitations notwithstanding, many authors promote single-target and disease-oriented approaches to senescence, e.g. repurposed drugs, claiming that these methods can enhance human health and longevity. Senescence is neither a disease nor a monolithic process. In this review, the limitations of these methods are discussed. The current state of biogerontology is also summarised.
My aim, in this essay, is twofold. Firstly, I want to characterise ageing as a normative biological process, rather than a purely physical one. This, in effect, means that “ageing” is not a pure wear-and-tear mechanism. In fact, it isn’t even a mechanism, and I’ll explain why I’m critical of the use of that word in biology. It is therefore not accurate, in my view, to define ageing either as a mere imbalance between exergonic and endergonic reactions in the metabolism, as “the free radical theory of ageing” does, or as an imbalance between the excessive formation of reactive oxygen species and the limited amount of antioxidant defences. As we’ll see, ageing is a process, but it is also a constraint, or a set of biological constraints, values, functions, and norms. More specifically, it is a repulsive constraint (1). This means that ageing is not so much a norm, or function, as a normative property. [I will focus on the example of the mammal, and will give an illustration of this point through the example of vicious molecular circles in connective tissues and in mitochondria.] With the expression “normative property,” I mean that ageing is not simply a regulative property. It is a property through which the structure and constraints of a living being are actually transformed. Ageing is not destruction or degradation, but self-destruction. Ageing indicates that biological systems have a tendency to lose their normative power, that is, their ability to change their norms and generate new ones, and to do so in a way that’s regulated. I suggest we refer to ageing thus understood as a process of alteration. Secondly, I want to analyse the relations between ageing and longevity. Not all organisms age, as everybody knows. In worms, yeast, and other organisms, ageing is opposed to longevity, which counteracts the process of self-destruction. If the dynamic of ageing is also self-regulated, how are we to understand the claim, often found in the found in the literature, that longevity “counteracts” ageing (23)?
A Review on Theories Regarding Ageing
2016
Ageing and resulting senescence has been fascinating for scientists as well as common people. Ageing is an extremely complex multi-factorial process. Different types of morphological, physiological, biochemical, endocrinological and cellular changes are responsible for ageing. In this review, several theories are identified only briefly and a few (evolutionary, gene regulation, cellular senescence, free radical, and neuro-endocrine-immuno theories) are discussed in more detail. The multiplicities of mechanisms are examined also at the molecular, cellular and systemic levels to explore the possibility of interactions at these three levels. However, in spite of recent advances in molecular biology and genetics, the mysteries that control human life span are yet to be unraveled.