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Futurists, scientists, and scammers periodically make the headlines with speculation that humans will achieve lifespans of 200, 300, 500 years and more. There is a reason that's impossible. But it's still possible to live a very long time.

The Hayflick limit tells us that we aren't ever going to find medical methods for becoming immortal. We are all going to die. But the mere fact that our DNA is not capable of being copied indefinitely really is not the problem. The problem is that all our cells do not age at the same rate, and some cells wear out before others.

For example, cells in the localized regions of arteries that are lesioned by calcified, cholesterol-laden plaques are typically filled with non-replicating, senescent (old), or dead cells. The artery wall on either side of them may be in good shape. The linings of the veins may not be affected at all. But that one region of just a few millimeters (usually), just a fraction of an inch, may be the "clog" that stops circulation and causes death--frequently without any warning that death was imminent.

The problem isn't that all of our cells won't ever live past 120 years. The problem is that some of our cells won't even live to 100, or 90, or 80, or 70 or 60 years.

 Our cells can be damaged by:

  • Pressure. High blood pressure is a killer, but it kills localized cells that accumulate into lesions that cause the problems we recognize as disease.
  • Toxins. Not all cells all over the body are affected in the same way by toxins. Nerve tissue, because neurons are "stretched out" over large parts of the body, one part of the nerve cell up to a meter (several feet) from the protective organelles of the nerve cell that could rejuvenated, is especially vulnerable to certain toxins.
  • Radiation. Whole-body radiation affects all of the tissues of the body at the same time. Therapeutic radiation, and certain kinds of accidental radiation, may cause certain cells to age rapidly and have no effects on others at all.
  • Telomeres. Every strand of DNA has some "junk" DNA, which really is not junk at all, which protects the active DNA it its middle. These protective telomeres can grow shorter with age. When the telomere is too short, the cell won't "risk" replicating itself and getting the sequence of DNA out of order, so it will not become cancerous.

For a large part of our lives, our immune systems simply come along and take out the senescent cells, leaving healthy, young cells to do their tasks in tissues. When something compromises the health of the immune system, however, or when they number of aging and dysfunctional cells in a tissue simply becomes too great, the tissue ceases to function. There may be a mass of calcified dead cells, as there is inside atherosclerotic plaques, or there may be a mass of protein the cells that make them simply could no longer regulate, as there is inside cataracts.

Either way, parts of our bodies age and cause us serious illness long before our entire bodies reach their aging limits. And if we really want to live as long as we can, Haylflick tells us, we do not need to try to make all our cells immortal, we need to avoid localized problems commonly lead to disease and death, especially heart disease and cancer.

  • Hayflick L. The illusion of cell immortality. Br J Cancer. 2000 Oct. 83(7):841-6.
  • Sills ES, Takeuchi T, Rosenwaks Z, Palermo GD. Reprogramming somatic cell differentiation and the Hayflick Limit: contrasting two modern molecular bioengineering aims and their impact on the future of mankind. J Assist Reprod Genet. 2001 Aug. 18(8):468-70.
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