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Male Mortality (male + mortality)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

HAPLODIPLOIDY AS AN OUTCOME OF COEVOLUTION BETWEEN MALE-KILLING CYTOPLASMIC ELEMENTS AND THEIR HOSTS

EVOLUTION, Issue 4 2004
Benjamin B. Normark
Abstract Haplodiploidy (encompassing both arrhenotoky and paternal genome elimination) could have originated from coevolution between male-killing endosymbiotic bacteria and their hosts. In insects, haplodiploidy tends to arise in lineages that rely on maternally transmitted bacteria for nutrition and that have gregarious broods in which competition between siblings may occur. When siblings compete, there is strong selection on maternally transmitted elements to kill males. I consider a hypothetical bacterial phenotype that renders male zygotes effectively haploid by preventing chromosome decondensation in male-determining sperm nuclei. By causing high male mortality, such a phenotype can be advantageous to the bacterial lineage. By eliminating paternal genes, it can also be advantageous to the host female. A simple model shows that the host female will benefit under a wide range of values for the efficiency of resource re-allocation, the efficiency of transmission, and the viability of haploid males. This hypothesis helps to explain the ecological correlates of the origins of haplodiploidy, as well as such otherwise puzzling phenomena as obligate cannibalism by male Micromalthus beetles, reversion to diploidy by aposymbiotic male stictococcid scale insects, and the bizarre genomic constitution of scale insect bacteriomes. [source]

The sex ratio and age-specific male mortality: Evidence for culling in utero

AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 6 2007
Tim Bruckner
While adverse conditions early in life reportedly predispose individuals to increased mortality in adulthood, controversy remains as to whether exogenous insults in utero, especially among male fetuses, induce similar cohort "damage" in populations. A rival theory postulates that exogenous stressors in gestation may "cull" frail male members of the cohort before birth, leaving a smaller but hardier cohort with improved survival. Recent tests, which use the sex ratio (i.e., the odds of a male live birth) as a gauge of insults inflicted upon cohorts in gestation, support the culled cohort argument. These tests, however, examined only aggregate male lifespan, thereby obscuring potential heterogeneity of both damaged and culled cohorts at specific ages over the life course. Using time-series methods, we explore associations between the sex ratio and cohort male mortality in infancy (before age 1), childhood (1,4 years), youth (5,19 years), adulthood (20,54 years), and old-age (55,79 years). We examine males born in Sweden (1751,1913), Denmark (1835,1913), and England and Wales (1841,1912). Our findings generally support culled cohorts in that male mortality across all ages fell below its expected value among cohorts in which the sex ratio dropped below its expected level. These findings suggest that exogenous shocks to gestation, as measured by a lower than expected sex ratio, may cull males in utero, leaving behind a less frail cohort over the entire life course. Am. J. Hum. Biol., 2007. © 2007 Wiley-Liss, Inc. [source]

Beyond Material Explanations: Family Solidarity and Mortality, a Small Area-level Analysis

POPULATION AND DEVELOPMENT REVIEW, Issue 1 2010
Jon Anson
Social solidarity, being embedded in a network of binding social relationships, tends to extend human longevity. Yet while average incomes in the Western world, and with them, life expectancies, have risen dramatically, the second demographic transition has occasioned a breakdown in traditional family forms. This article considers whether these trends in family life may have slowed the rise in life expectancy. I present a cross-sectional analysis of Israeli statistical areas (SAs), for which I construct indexes of Standard of Living (SOL), Traditional Family Structure (TFS), and Religiosity (R). I show that (1) increases in all three of these indexes are associated with lower levels of mortality, (2) male mortality is more sensitive to differences in SOL and TFS than is female mortality, and (3) net of differences in SOL and TFS, there is no difference in the mortality levels of Arab and Jewish populations. [source]