testing biological ideas on evolution, aging and longevity with demographic and genealogical data

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Testing Biological Ideas on Evolution, Aging and Longevity with Demographic and Genealogical Data. Leonid A. Gavrilov Natalia S. Gavrilova Center on Aging, NORC/University of Chicago, 1155 East 60th Street, Chicago, IL 60637. - PowerPoint PPT Presentation

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  • Testing Biological Ideas on Evolution, Aging and Longevity with Demographic and Genealogical Data Leonid A. GavrilovNatalia S. Gavrilova Center on Aging, NORC/University of Chicago, 1155 East 60th Street, Chicago, IL 60637

  • What are the data and the predictions of the evolutionary theory onLinks between human longevity and fertility

    Lifespan heritability in humans

    Quality of offspring conceived to older parents

  • Founding FathersBeeton, M., Yule, G.U., Pearson, K. 1900. Data for the problem of evolution in man. V. On the correlation between duration of life and the number of offspring. Proc. R. Soc. London, 67: 159-179.Data used: English Quaker records and Whitney Family of Connectucut records for females and American Whitney family and Burkes Landed Gentry for males.

  • Findings and Conclusions by Beeton et al., 1900They tested predictions of the Darwinian evolutionary theory that the fittest individuals should leave more offspring.Findings: Slightly positive relationship between postreproductive lifespan (50+) of both mothers and fathers and the number of offspring.Conclusion: fertility is correlated with longevity even after the fecund period is passed and selective mortality reduces the numbers of the offspring of the less fit relatively to the fitter.

  • Other Studies, Which Found Positive Correlation Between Reproduction and Postreproductive LongevityTelephone inventor Alexander Graham Bell (1918): The longer lived parents were the most fertile.

    Bettie Freeman (1935): Weak positive correlations between the duration of postreproductive life in women and the number of offspring borne. Human Biology, 7: 392-418.Bideau A. (1986): Duration of life in women after age 45 was longer for those women who borne 12 or more children. Population 41: 59-72.

  • Studies that Found no Relationship Between Postreproductive Longevity and ReproductionHenry L. 1956. Travaux et Documents.Gauter, E. and Henry L. 1958. Travaux et Documents, 26.Knodel, J. 1988. Demographic Behavior in the Past. Le Bourg et al., 1993. Experimental Gerontology, 28: 217-232.

  • Study that Found a Trade-Off Between Reproductive Success and Postreproductive LongevityWestendorp RGJ, Kirkwood TBL. 1998. Human longevity at the cost of reproductive success. Nature 396: 743-746.

    Extensive media coverage including BBC and over 100 citations in scientific literature as an established scientific fact. Previous studies were not quoted and discussed in this article.

  • Point estimates of progeny number for married aristocratic women from different birth cohorts as a function of age at death. The estimates of progeny number are adjusted for trends over calendar time using multiple regression.Source: Westendorp, Kirkwood, Human longevity at the cost of reproductive success. Nature, 1998, 396, pp 743-746

  • Number of progeny and age at first childbirth dependent on the age at death of married aristocratic women

    Source: Westendorp, R. G. J., Kirkwood, T. B. L. Human longevity at the cost of reproductive success. Nature, 1998, 396, pp 743-746

  • it is not a matter of reduced fertility, but a case of 'to have or have not'.Source: ToonLigtenberg & HenkBrand. Longevity does family size matter? Nature, 1998, 396, pp 743-746

    Table 1 Relationship between age at death and number of children for married aristocratic women

    Age at death

    Proportion childless

    Number of children

    (years)

    mean for all women

    mean for women having children

    90

    0.49

    1.80

    3.53

  • Source: Westendorp, R. G. J., Kirkwood, T. B. L. Human longevity at the cost of reproductive success. Nature, 1998, 396, pp 743-746

  • Do longevous women have impaired fertility ?Why is this question so important and interesting? Scientific Significance

    This is a testable prediction of some evolutionary theories of aging - disposable soma theory of aging (Kirkwood)

    "The disposable soma theory on the evolution of ageing states that longevity requires investments in somatic maintenance that reduce the resources available for reproduction (Westendorp, Kirkwood, Nature, 1998).

  • Do longevous women have impaired fertility ?

    Practical Importance. Do we really wish to live a long life at the cost of infertility?: the next generations of Homo sapiens will have even longer life spans but at the cost of impaired fertility Rudi Westendorp Are we becoming less disposable? EMBO Reports, 2004, 5: 2-6. "... increasing longevity through genetic manipulation of the mechanisms of aging raises deep biological and moral questions. These questions should give us pause before we embark on the enterprise of extending our lives Walter Glennon "Extending the Human Life Span", Journal of Medicine and Philosophy, 2002, Vol. 27, No. 3, pp. 339-354.

  • Educational Significance Do we teach our students right? Impaired fertility of longevous women is often presented in scientific literature and mass media as already established fact (Brandt et al., 2005; Fessler et al., 2005; Schrempf et al., 2005; Tavecchia et al., 2005; Kirkwood, 2002; Westendorp, 2002, 2004; Glennon, 2002; Perls et al., 2002 etc.). This "fact" is now included in teaching curriculums in biology, ecology and anthropology world-wide (USA, UK, Denmark). Is it a fact or artifact ?

  • General Methodological Principle:

    Before making strong conclusions, consider all other possible explanations, including potential flaws in data quality and analysis

    Previous analysis by Westendorp and Kirkwood was made on the assumption of data completeness: Number of children born = Number of children recorded

    Potential concerns: data incompleteness, under-reporting of short-lived children, women (because of patrilineal structure of genealogical records), persons who did not marry or did not have children. Number of children born >> Number of children recorded

  • Test for Data Completeness

    Direct Test: Cross-checking of the initial dataset with other data sources We examined 335 claims of childlessness in the dataset used by Westendorp and Kirkwood. When we cross-checked these claims with other professional sources of data, we found that at least 107 allegedly childless women (32%) did have children! At least 32% of childlessness claims proved to be wrong ("false negative claims") !

    Some illustrative examples: Henrietta Kerr (16531741) was apparently childless in the dataset used by Westendorp and Kirkwood and lived 88 years. Our cross-checking revealed that she did have at least one child, Sir William Scott (2nd Baronet of Thirlstane, died on October 8, 1725). Charlotte Primrose (17761864) was also considered childless in the initial dataset and lived 88 years. Our cross-checking of the data revealed that in fact she had as many as five children:Charlotte (18031886), Henry (18061889), Charles (18071882), Arabella (1809-1884), and William (18151881). Wilhelmina Louise von Anhalt-Bernburg (17991882), apparently childless, lived 83 years. In reality, however, she had at least two children, Alexander (18201896) and Georg (18261902).

  • Point estimates of progeny number for married aristocratic women from different birth cohorts as a function of age at death. The estimates of progeny number are adjusted for trends over calendar time using multiple regression.Source: Westendorp, R. G. J., Kirkwood, T. B. L. Human longevity at the cost of reproductive success. Nature, 1998, 396, pp 743-746

  • Antoinette de Bourbon(1493-1583)Lived almost 90 yearsShe was claimed to have only one child in the dataset used by Westendorp and Kirkwood: Marie (1515-1560), who became a mother of famous Queen of Scotland, Mary Stuart. Our data cross-checking revealed that in fact Antoinette had 12 children!Marie 1515-1560 Francois Ier 1519-1563 Louise 1521-1542 Renee 1522-1602 Charles 1524-1574 Claude 1526-1573 Louis 1527-1579 Philippe 1529-1529 Pierre 1529 Antoinette 1531-1561 Francois 1534-1563Rene 1536-1566

  • Characteristics of Our Data Sample for Reproduction-Longevity Studies3,723 married women born in 1500-1875 and belonging to the upper European nobility.

    Women with two or more marriages (5%) were excluded from the analysis in order to facilitate the interpretation of results (continuity of exposure to childbearing).

    Every case of childlessness has been checked using at least two different genealogical sources.

  • Typical Mistakes in Biological Studies of Human LongevityUsing lifespan data for non-extinct birth cohorts (cemetery effect)Failure to control for birth cohort spurious correlations may be found if variables have temporal dynamicsFailure to take into account social events and factors e.g., failure to control for age at marriage in longevity-reproduction studies

  • Childlessness is better outcome than number of children for testing evolutionary theories of aging on human dataApplicable even for population practicing birth control (few couple are voluntarily childless)Lifespan is not affected by physiological load of multiple pregnanciesLifespan is not affected by economic hardship experienced by large families

  • Source: Gavrilova et al. Does exceptional human longevity come with high cost of infertility? Testing the evolutionary theories of aging. Annals of the New York Academy of Sciences, 2004, 1019: 513-517.

  • Source: Gavrilova, Gavrilov. Human longevity and reproduction: An evolutionary perspective. In: Grandmotherhood - The Evolutionary Significance of the Second Half of Female Life. Rutgers University Press, 2005 (in press).

  • Short Conclu

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