Thursday, March 07, 2013

Testing Evolutionary Theories of Aging and Longevity

 Greetings,

We are pleased to share with you the abstract of our invited lecture 'Testing Evolutionary Theories of Aging and Longevity',  given at the Seminar of the University of Southern California (USC) Longevity Institute, on Friday, March 1, 2013  in Los Angeles (see below).

Comments and suggestions are most welcome!  We would be delighted to present our new  research findings at your organization too, if you like.  Fell free to contact us, if you are interested.

Kind regards,

-- Leonid  and  Natalia

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-- Leonid Gavrilov, Ph.D., GSA Fellow
-- Natalia Gavrilova, Ph.D., GSA Fellow
Center on Aging, NORC at the University of Chicago
Website: http://longevity-science.org/
Blog: http://longevity-science.blogspot.com/

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Seminar at the University of Southern California Longevity Institute, Friday, March 1, 2013 at 3 pm, Conference Room 'Gerontology 224', 3715 McClintock Ave, Los Angeles, CA 90089  

Testing Evolutionary Theories of Aging and Longevity

Leonid Gavrilov, Ph.D., GSA Fellow, and Natalia Gavrilova, Ph.D., GSA Fellow
Center on Aging, NORC at the University of Chicago, e-mail: gavrilov@longevity-science.org

This talk will focus on testing the predictions of evolutionary theories of aging and longevity with human population data.  The presentation will discuss the following ideas and findings:

       (1)  Opponents of programmed aging often argue that there is a too high variation in timing of aging-related outcomes, compared to much smaller variation in timing of programmed developmental outcomes (such as age of sexual maturation).  In other words, aging just does not have an expected clock-wise accuracy, which is anticipated for programmed events.
       To test the validity of this argument we compared relative variability (coefficient of variation) for parameters that are believed to be determined by the developmental program (age at sexual maturity) with variability of characteristic related to aging (age at menopause).  We used information on the ages at sexual maturation (menarche) and menopause from the nationally representative survey of the adult population of the United States (MIDUS study) as well as published data for 14 countries. We found that coefficients of variation are in the range of 8-13% for age at menarche, 7-11% for age at menopause. Thus, the relative variability for the age at menopause is surprisingly the same as for the age at menarche [1].

         (2)  Many evolutionary biologists believe that aging can be readily understood in terms of the declining force of selection pressure with age.  At extremely old postreproductive ages when the force of natural selection reaches a zero plateau, some evolutionary biologists ( i.e. Michael Rose) believe that the mortality plateau should also be observed (no further increase in mortality rates with age).  To test the validity of this argument we analyzed the data for humans, rats and mice.  We found that mortality rates increase exponentially with age (the Gompertz law), and no expected late-life mortality plateaus are observed [2]. 
         Late-life mortality deceleration and mortality plateau reported in some earlier studies may be related to problems with data quality and biased estimates of hazard rates at extreme old ages.  It seems unreasonable to explain aging (Gompertz law of mortality) by declining force of natural selection, because aging continues at the same pace at extremely old postreproductive ages when the force of natural selection already reaches a zero plateau.

         (3) One of the predictions of the disposable soma theory and the antagonistic pleiotropy theory is that exceptional longevity should come with the price of impaired fertility (longevity-fertility trade-off ).  This prediction seemed to be confirmed by a high profile study published by Nature by Westendorp and Kirkwood (1998), which claimed that almost half of long lived women were childless.  However our careful re-evaluation of the study found that it used very incomplete genealogical data, so that many allegedly childless women in fact did have children.  After data cleaning, we found that there is no expected increase in childlessness of longer-lived women [3-5].

To summarize, we found that some predictions of evolutionary theories of aging are not confirmed with existing data, however these theories, including the theory of programmed aging suggest fruitful avenues for biological and perhaps even medical research


References

1. Gavrilova NS, Gavrilov LA, Severin FF, Skulachev VP. Testing predictions of the programmed and stochastic theories of aging: comparison of variation in age at death, menopause, and sexual maturation. Biochemistry (Moscow). 2012 Jul;77(7):754-60. doi: 10.1134/S0006297912070085.  http://www.ncbi.nlm.nih.gov/pubmed/22817539

2. Gavrilov L.A., Gavrilova N.S. Mortality measurement at advanced ages: A study of the Social Security Administration Death Master File. North American Actuarial Journal, 2011, 15(3): 432-447.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3269912/

3. Gavrilova, N.S., Gavrilov, L.A. Human longevity and reproduction: An evolutionary perspective. In: Voland, E.; Chasiotis, A. & Schiefenhoevel, W. (eds.). Grandmotherhood - The Evolutionary Significance of the Second Half of Female Life. New Brunswick, NJ: Rutgers University Press, 2005, 59-80.  http://longevity-science.org/Reproduction-2005.pdf

4. Gavrilova NS, Gavrilov LA, Semyonova VG, Evdokushkina GN. Does exceptional human longevity come with high cost of infertility? Testing the evolutionary theories of agingAnnals of the New York Academy of Sciences, 2004, 1019: 513-517.  http://longevity-science.org/Evolution-ANYAS-2004.pdf

5. Gavrilov, L.A., Gavrilova, N.S. Evolutionary theories of aging and longevityThe Scientific World JOURNAL, 2002, 2: 339-356. http://longevity-science.org/Evolution.htm and http://longevity-science.org/Evolution.pdf

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