Stage 4 population is large low birth and death rates

This preview shows page 33 - 35 out of 40 pages.

stage 4: population is large, low birth and death rates as life expectancy increases, probability of death decreases as life expectancy goes up, total fertility rate decreases total fertility rate has been falling worldwide since the 1950s or prior, birth rate decreases in 1850s as a result of access to contraceptives. as populations go through demographic transitions, life expectancy increases, total fertility rate decreases more aged countries as total fertility rate decreases when people are living longer U.S. total fertility rate in 2010: 1.9 million cultural phenonmenon? parents feel need for more investment in each child. overtime,
social norms change biological phenomenon? matches predictions from life history theory disposable soma theory of aging: senescence is not inevitable, but maintenance requires energy! species evolve to optimize the balance between energy spent on maintenance vs. reproduction. This balance determines their lifespan why not live forever? senescence: age-related decline in function oxidative stress and aging cell: mitochondria, produce energy for the cell (ATP) —> Reactive oxygen species (ROS) byproduct of energy production —> most ROS are neutralized by antioxidants —> any ROS that escapes can cause damage (ex: heart disease, cancer) as number of offspring goes up, percent of parents surviving goes down number of offspring and survivorship of parents are inversely proportional as primates get bigger, they live longer humans have long post-reproductive life (for women) (an evolved trait) humans have exceptionally long lives, as body mass increases, life span increases aging is complex trait! genes x environment having a sibling live to 100 increases your chances of living to 100 by 5-10 times macaque calorie restriction study: 20 years severe 25% reduction in calories eaten (80% survive) control group: eat as much as they want (50% survive: increased rates of diabetes, cancer, heart disease, brain atrophy) being calorically restricted allows organisms to live a lot longer As GDP per capita (wealth of a country) increases (per person), life expectancy increases, access to medicine and hygiene is better, but life expectancy levels off as you get to 30,000 GDP wealthy countries have higher expectancies evidence for a limit to human lifespan: 120 very little change in life expectancy for those over 100 since 1900, improvement in maintaining health in quantity but not quality Anthp 105 5/5 Review: life history trade-offs, reproduction vs. maintenance, why not live forever? Disposable Soma Theory of Aging Human Energetics Paradox: fast reproduction and long lives evolution of human metabolic rate and body fat and sharing aging as a complex trait aging in hunter-gatherer populations evidence for aging in the human fossil record menopause grandmother hypothesis statistics = median is better than average for age (judges for standard deviation, skews, etc) fast vs. slow life history: fast life history: grow up fast, reproduce often, die young slow life history: grow up slow, reproduce slowly, die old

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture