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Reduced costs of reproduction in females mediate a shift from a male-biased to a female-biased lifespan in humans.

Bolund E, Lummaa V, Smith KR, Hanson HA, Maklakov AA - Sci Rep (2016)

Bottom Line: Life-history theory suggests that reduced reproduction should benefit female lifespan when females pay higher costs of reproduction than males.Only women paid a cost of reproduction in terms of shortened post-reproductive lifespan at high parities.Further, our results have important implications for demographic forecasts in human populations and advance our understanding of lifespan evolution.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Uppsala SE-752 36, Sweden.

ABSTRACT
The causes underlying sex differences in lifespan are strongly debated. While females commonly outlive males in humans, this is generally less pronounced in societies before the demographic transition to low mortality and fertility rates. Life-history theory suggests that reduced reproduction should benefit female lifespan when females pay higher costs of reproduction than males. Using unique longitudinal demographic records on 140,600 reproducing individuals from the Utah Population Database, we demonstrate a shift from male-biased to female-biased adult lifespans in individuals born before versus during the demographic transition. Only women paid a cost of reproduction in terms of shortened post-reproductive lifespan at high parities. Therefore, as fertility decreased over time, female lifespan increased, while male lifespan remained largely stable, supporting the theory that differential costs of reproduction in the two sexes result in the shifting patterns of sex differences in lifespan across human populations. Further, our results have important implications for demographic forecasts in human populations and advance our understanding of lifespan evolution.

No MeSH data available.


Age-specific survival after the onset of reproduction in four 25-year birth cohorts that cover the demographic transition in Utah.Survival curves represent females (red) and males (blue) that reproduced and had full known reproductive history. Shown in each figure are the birth years contained in that cohort (Yr), the sample size (n), the average ± SD number of children born to females (CHf), the χ2 and p-values indicating differences in the survivor function between the two sexes from the Peto and Peto modification of the Gehan-Wilcoxon test (GW, this test weights differences in survivorship that occur early more heavily than differences at later survival times) and from a log-rank test (LR, this test weights differences at later survival times more heavily). Dotted vertical lines indicate the average lifespan of each sex in each cohort.
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f1: Age-specific survival after the onset of reproduction in four 25-year birth cohorts that cover the demographic transition in Utah.Survival curves represent females (red) and males (blue) that reproduced and had full known reproductive history. Shown in each figure are the birth years contained in that cohort (Yr), the sample size (n), the average ± SD number of children born to females (CHf), the χ2 and p-values indicating differences in the survivor function between the two sexes from the Peto and Peto modification of the Gehan-Wilcoxon test (GW, this test weights differences in survivorship that occur early more heavily than differences at later survival times) and from a log-rank test (LR, this test weights differences at later survival times more heavily). Dotted vertical lines indicate the average lifespan of each sex in each cohort.

Mentions: Here, we use a unique resource to study the patterns of survival and reproduction in the two sexes in a single population before, during and after the demographic transition. This allows us to document changes in the sexual dimorphism in lifespan over time in a population that is going through dramatic demographic changes and relate this to the costs of reproduction in the two sexes. The Utah Population Database (UPDB) is one of the world’s largest existing multigenerational research demographic datasets. The full UPDB now contains data on over 8 million individuals from the late 18th century to the present. The multigenerational pedigrees representing Utah’s founders and their descendants were constructed based on data provided by the Genealogical Society of Utah (GSU). Pedigrees spanning the past 80 years have been expanded extensively based on vital records and, together with the GSU data, form the basis of the deep genealogical structure of the UPDB. We use a subset of 140,600 reproducing individuals that had full information on their reproductive history as well as a number of demographic variables that can influence life-history patterns, such as birth place, birth order, being in a polygamous union and the identity of the birth mother. In historic Utah, fertility rates were very high, with average reproductive rates reaching nine children (Fig. 1) and this decreased dramatically over the demographic transition, which started around 1870–188048. Specifically, we first quantify how sexual dimorphism in lifespan changed over time as the population went through the demographic transition. Second, we examine whether either sex payed a cost of reproduction in terms of a shortened post-reproductive lifespan. We predict that sexual dimorphism in adult lifespan should change over time if fertility patterns change.


Reduced costs of reproduction in females mediate a shift from a male-biased to a female-biased lifespan in humans.

Bolund E, Lummaa V, Smith KR, Hanson HA, Maklakov AA - Sci Rep (2016)

Age-specific survival after the onset of reproduction in four 25-year birth cohorts that cover the demographic transition in Utah.Survival curves represent females (red) and males (blue) that reproduced and had full known reproductive history. Shown in each figure are the birth years contained in that cohort (Yr), the sample size (n), the average ± SD number of children born to females (CHf), the χ2 and p-values indicating differences in the survivor function between the two sexes from the Peto and Peto modification of the Gehan-Wilcoxon test (GW, this test weights differences in survivorship that occur early more heavily than differences at later survival times) and from a log-rank test (LR, this test weights differences at later survival times more heavily). Dotted vertical lines indicate the average lifespan of each sex in each cohort.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834564&req=5

f1: Age-specific survival after the onset of reproduction in four 25-year birth cohorts that cover the demographic transition in Utah.Survival curves represent females (red) and males (blue) that reproduced and had full known reproductive history. Shown in each figure are the birth years contained in that cohort (Yr), the sample size (n), the average ± SD number of children born to females (CHf), the χ2 and p-values indicating differences in the survivor function between the two sexes from the Peto and Peto modification of the Gehan-Wilcoxon test (GW, this test weights differences in survivorship that occur early more heavily than differences at later survival times) and from a log-rank test (LR, this test weights differences at later survival times more heavily). Dotted vertical lines indicate the average lifespan of each sex in each cohort.
Mentions: Here, we use a unique resource to study the patterns of survival and reproduction in the two sexes in a single population before, during and after the demographic transition. This allows us to document changes in the sexual dimorphism in lifespan over time in a population that is going through dramatic demographic changes and relate this to the costs of reproduction in the two sexes. The Utah Population Database (UPDB) is one of the world’s largest existing multigenerational research demographic datasets. The full UPDB now contains data on over 8 million individuals from the late 18th century to the present. The multigenerational pedigrees representing Utah’s founders and their descendants were constructed based on data provided by the Genealogical Society of Utah (GSU). Pedigrees spanning the past 80 years have been expanded extensively based on vital records and, together with the GSU data, form the basis of the deep genealogical structure of the UPDB. We use a subset of 140,600 reproducing individuals that had full information on their reproductive history as well as a number of demographic variables that can influence life-history patterns, such as birth place, birth order, being in a polygamous union and the identity of the birth mother. In historic Utah, fertility rates were very high, with average reproductive rates reaching nine children (Fig. 1) and this decreased dramatically over the demographic transition, which started around 1870–188048. Specifically, we first quantify how sexual dimorphism in lifespan changed over time as the population went through the demographic transition. Second, we examine whether either sex payed a cost of reproduction in terms of a shortened post-reproductive lifespan. We predict that sexual dimorphism in adult lifespan should change over time if fertility patterns change.

Bottom Line: Life-history theory suggests that reduced reproduction should benefit female lifespan when females pay higher costs of reproduction than males.Only women paid a cost of reproduction in terms of shortened post-reproductive lifespan at high parities.Further, our results have important implications for demographic forecasts in human populations and advance our understanding of lifespan evolution.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Uppsala SE-752 36, Sweden.

ABSTRACT
The causes underlying sex differences in lifespan are strongly debated. While females commonly outlive males in humans, this is generally less pronounced in societies before the demographic transition to low mortality and fertility rates. Life-history theory suggests that reduced reproduction should benefit female lifespan when females pay higher costs of reproduction than males. Using unique longitudinal demographic records on 140,600 reproducing individuals from the Utah Population Database, we demonstrate a shift from male-biased to female-biased adult lifespans in individuals born before versus during the demographic transition. Only women paid a cost of reproduction in terms of shortened post-reproductive lifespan at high parities. Therefore, as fertility decreased over time, female lifespan increased, while male lifespan remained largely stable, supporting the theory that differential costs of reproduction in the two sexes result in the shifting patterns of sex differences in lifespan across human populations. Further, our results have important implications for demographic forecasts in human populations and advance our understanding of lifespan evolution.

No MeSH data available.