Changing how we see aging

Dying to Live Longer (2)

The weird and wonderful attempts at prolonging life Science

Leonard Hayflick

A public perception exists that is at odds with our knowledge of aging. The first misunderstanding is the difference between lifespan and life expectancy. While lifespan is the maximum number of years humans have ever reached, life expectancy is the age before which half of the population is expected to die. Not one single study exists that shows the extension of lifespan in humans. And as for the much-touted increase in life expectancy, this is due to reduced child mortality and has virtually little to do with advances in treatment of older adults. In the last century life expectancy at 65 has increased by only 5.7 years, which tells us that medicine exerts little influence on population aging. Despite the lack of evidence of prolongation of human life, folklore themes pervade commonly-held beliefs, which then seep into the science of aging.

The complex science of aging can be succinctly summarized under four basic inclusive themes. These are 1) a slowing down of metabolic rate; 2) an accumulation of toxins; 3) a wearing down of the body; and 4) entropy--randomness and disorder within the body. In some contexts all of these themes play a role in death. The umbrella concept is that of entropy.

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Entropy is the second law of thermodynamics and explains the loss of energy. Only recently have we considered accepting this concept to explain aging. In folklore it was assumed that humans did something wrong to deserve death—such as eating from the forbidden tree; or the Taoist’s loss of Ching; or with Aristotle’s loss of innate moisture. All of these imply that we are immortal except that we are doing something wrong. This was epitomized by Nobel prize winner Alexis Carrel who stated “that all cells explanted in culture are immortal . . . .”

It was Leonard Hayflick who broke this established dogma. Unable to reproduce Carrel's results, Hayflick exposed the error in Carrel's experiment, which consisted of daily addition of chicken embryonic stem cells to the cell culture. Carrel was in fact replacing the cells not just feeding them, and hence why they never died. In his own experiments, Hayflick found that a normal human fetal cell divides between 40 and 60 times. It then enters a phase where it dies—The Hayflick Limit. Each replication shortens the life of the cell.

We now know, thanks to Alexey Matveyevich Olovnikov, that with each replication the cell losses a part of its DNA called telomeres. When the telomeres become too short, the cell dies. Shortened telomeres are found in atherosclerosis, heart disease, hepatitis, and cirrhosis. It is of no surprise that the bio-tech industry in San Diego, working on cancer research, is intricately associated with aging research. Cancer cells are immortal.

The science of aging is still a long way from advancing from staying healthy to assuring the prolongation of life. Eating good quality food, moderate consumption of (red) wine, and enjoying the company of friends is not only good for longevity, it is one of life’s great pleasures. We do not need science to tell us that. We have a lease on life. If we use it wisely and cultivate quality, it will eventually contribute to the quantity of life as well.

© USA Copyrighted 2013 Mario D. Garrett

Mario Garrett, Ph.D., is a professor at the school of social work, San Diego State University.


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