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  • In 1997, a French woman named Jeanne Calment

  • passed away after 122 years and 164 days on this Earth,

  • making her the oldest known person in history.

  • Her age was so astounding

  • that a millionaire pledged $1 million to anyone who could break her record.

  • But in reality, living to this age or beyond

  • is a feat that very few, maybe even no humans,

  • are likely to accomplish.

  • Human bodies just aren't built for extreme aging.

  • Our capacity is set at about 90 years.

  • But what does aging really mean

  • and how does it counteract the body's efforts to stay alive?

  • We know intuitively what it means to age.

  • For some, it means growing up,

  • while for others, it's growing old.

  • Yet finding a strict scientific definition of aging is a challenge.

  • What we can say is that aging occurs when intrinsic processes

  • and interactions with the environment, like sunlight,

  • and toxins in the air, water, and our diets,

  • cause changes in the structure

  • and function of the body's molecules and cells.

  • Those changes in turn drive their decline,

  • and subsequently, the failure of the whole organism.

  • The exact mechanisms of aging are poorly understood.

  • But recently, scientists have identified nine physiological traits,

  • ranging from genetic changes

  • to alterations in a cell's regenerative ability

  • that play a central role.

  • Firstly, as the years pass, our bodies accumulate genetic damage

  • in the form of DNA lesions.

  • These occur naturally when the body's DNA replicates,

  • but also in non-dividing cells.

  • Organelles called mitochondria are especially prone to this damage.

  • Mitochondria produce adenosine triphosphate,

  • or ATP,

  • the main energy source for all cellular processes,

  • plus mitochondria regulate many different cell activities

  • and play an important role in programmed cell death.

  • If mitochondrial function declines,

  • then cells and, later on, whole organs, deteriorate, too.

  • Other changes are known to occur in the expression patterns of genes,

  • also known as epigenetic alterations,

  • that affect the body's tissues and cells.

  • Genes silenced or expressed only at low levels in newborns

  • become prominent in older people,

  • leading to the development of degenerative diseases,

  • like Alzheimer's, which accelerate aging.

  • Even if we could avoid all these harmful genetic alterations,

  • not even our own cells could save us.

  • The fact remains that cellular regeneration,

  • the very stuff of life,

  • declines as we age.

  • The DNA in our cells is packaged within chromosomes,

  • each of which has two protective regions at the extremities called telomeres.

  • Those shorten every time cells replicate.

  • When telomeres become too short,

  • cells stop replicating and die,

  • slowing the body's ability to renew itself.

  • With age, cells increasingly grow senescent, too,

  • a process that halts the cell cycle in times of risk,

  • like when cancer cells are proliferating.

  • But the response also kicks in more as we age,

  • halting cell growth and cutting short their ability to replicate.

  • Aging also involves stem cells that reside in many tissues

  • and have the property of dividing without limits to replenish other cells.

  • As we get older, stem cells decrease in number

  • and tend to lose their regenerative potential,

  • affecting tissue renewal and maintenance of our organs original functions.

  • Other changes revolve around cells' ability to function properly.

  • As they age, they stop being able to do quality control on proteins,

  • causing the accumulation of damaged and potentially toxic nutrients,

  • leading to excessive metabolic activity that could be fatal for them.

  • Intercellular communication also slows,

  • ultimately undermining the body's functional ability.

  • There's a lot we don't yet understand about aging.

  • Ultimately, does longer life as we know it come down to diet,

  • exercise,

  • medicine,

  • or something else?

  • Will future technologies, like cell-repairing nanobots,

  • or gene therapy,

  • artificially extend our years?

  • And do we want to live longer than we already do?

  • Starting with 122 years as inspiration,

  • there's no telling where our curiosity might take us.

In 1997, a French woman named Jeanne Calment

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TED-ED】なぜ私たちの体は老化するのか?- モニカ・メネシーニ (【TED-Ed】Why do our bodies age? - Monica Menesini)

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    Jamie Wei に公開 2021 年 01 月 14 日
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