A Means to an End: The Molecular Basis of Aging

By Clark, William R. | The World and I, June 1998 | Go to article overview

A Means to an End: The Molecular Basis of Aging


Clark, William R., The World and I


The phenomenon of aging is not a consequence of the evolutionary accumulation of "bad" genes but appears to be driven by molecular mechanisms that have been in place for billions of years.

The awareness that we are growing old may be uniquely human. Perhaps other animals, particularly higher mammals with rudimentary cognitive function, may be aware that they are slowing down with time, unable to keep up with others in their group, not as quick to find food, capture prey, or escape from danger. But we doubt they understand the full implications of the process. Humans, on the other hand, know only too well that the end point of aging is death. This knowledge drives in us a concern about the aging process--senescence--a concern that is lacking in other species.

Where did aging come from? Like other biological phenomena, aging may be assumed to have arisen through the processes of genetic variation and natural selection--mechanisms of evolution. When a new gene variant arises by modification of an existing gene, a decision has to be made to keep it or discard it. According to evolutionary theory, that decision is made on the basis of whether the variant raises the reproductive success of the corresponding organism. If it does, the variant gene will spread through the individual's offspring and, over time, to the rest of the species. If not, it will likely disappear in short order.

It is easy to see how this process of natural selection can work for traits like increased physical vigor, better eyesight, or brighter plumage for attracting mates. But how do we explain the inheritance of genes related to aging and death? As individuals get older, their ability to find mates, reproduce, and care for offspring is seriously impaired. How, then, could a trait so clearly contrary to the interests of the individual organism have been selected?

This issue is complicated by another factor: Most animals do not live long enough to experience serious aging. They die from disease or predation long before they become noticeably old. For most species, elderly individuals can be found only in zoos or laboratories, or as pets. In other words, the very trait that natural selection is supposed to act upon rarely shows up in nature. Yet, if kept in zoos or labs, animals do age. If the genes responsible for aging weren't picked up by natural selection, where did they come from?

One proposal is that aging may be triggered by genes such as the one responsible for Huntington's disease. We do not know what the normal Huntington's gene does, but inheritance of a single "bad" copy of this gene results in the development of a disorder that is uniformly lethal. This disorder, however, usually sets in only after the person is about 35--40 years of age--ample time for the patient to have passed on the gene to offspring. Some of the genes involved in Alzheimer's disease, and genes that predispose a person toward certain cancers, could also fall in this category. This proposal has become embedded in what is commonly called the "evolutionary theory of aging," which asserts that aging-related traits are the result of random accumulation of such genes over evolutionary time in different species.

Challenging a theory

Recent advances in molecular biology, however, suggest that this aspect of the evolutionary theory of aging is wrong. A study of the genes underlying aging and consequent "programmed" death in the simplest unicellular eukaryotes, such as paramecia and yeast, all the way through human beings, shows that these genes are remarkably similar in every species. Prof. Joan Valentine and her colleagues at the University of California, Los Angeles, have shown that genes involved in certain forms of cellular aging in humans continue to function when replacing equivalent aging genes in yeast, and vice versa.

This startling observation would not have been predictable from the evolutionary theory of aging. …

The rest of this article is only available to active members of Questia

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this article

This article has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this article

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited article

A Means to an End: The Molecular Basis of Aging
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Author Advanced search

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.