HW 5 Migration Aging and Carrying Capacity (1)

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Anthropology

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Jan 9, 2024

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Anth 145 – Summer 2023 – Homework #5 Teen Pregnancy, Migration, Aging and Carrying Capacity 1. Teenage pregnancy is associated with poor birth outcomes in the United States but early pregnancy has a less of a detrimental effect in traditional societies or in developing countries. [4 pts] a. What are some reasons why teen mothers in traditional small-scale societies suffer less in terms of maternal mortality, child survival compared to developed nations with modern medical care? [1 pt] Teen mothers may suffer less because as a teen, the mothers’ bodies can more easily repair themselves and may be healthier/more fit than at older ages. Because they are healthy, they are also properly fit to care for their children. b. What are some reasons why teen mothers in traditional small-scale societies suffer lower social and economic costs of teen pregnancy, compared to developed nations with integrated market economies and established social and educational institutions? [1 pt] Traditional small-scale societies suffer lower in terms of teen pregnancy because it is socially acceptable to bear children early and young mothers receive support from their family and community which minimizes economic cost. c. What are some advantages to early motherhood? [1 pt] Some advantages include better birth outcomes, being healthy while caring for children, and more opportunities to reproduce. d. Why is teen pregnancy negatively correlated with educational enrollment? [1 pt] Teen pregnancy is higher in nations where education enrollment is lower and teen pregnancy prevents mothers from investing into their education because they are investing in caring for their children. 2. Table E9-1 is a matrix showing U.S. regions of residence for those who migrated between 2011 and 2012, according to the Census Bureau’s Current Population Survey. Define as an interregional migrant anyone who had a different U.S. region of residence in 2012 than she or he reported for 2011. Answer the following questions [7 pts] : a. If someone was moving out of the South in 2012, what region were they most likely to move to? [1 pt] They might move to the West, judging frome the migration pattern between 2011 and 2012 where the West was the most popular region for Southerners to migrate. b. The migration stream from the Northeast to the South had 362,000 people. How many were in the migration stream from South to Northeast? [1 pt] The migration stream from the South to the Northeast was approximately 178,000 people. c. The volume of (gross) migration between the South and the Northeast was 540,000 people. What was the (gross) volume of migration between the Midwest and the South? [1 pt] The gross volume of migration between the Midwest and South was 677,000 people. d. The net migration from the Northeast to the South was plus 184,000. What was the net migration from the South to the Northeast? [1 pt] The net migration from the South to the Northeast was -184,000. e. What was the net migration from the Midwest to the South? [1 pt]

The net migration from the Midwest to the South was plus 69,000. f. More people moved to the South than anywhere else between 2011 and 2012. What was the total net migration to the South in this period? [1 pt] Total net migration to the South was 164,000 people. g. Which region lost the most people during this period? What was net migration from this region? [1 pt] Most people also migrated out of the South, with the net migration from the South being 901,000 people. 3. Given what you know about the contribution of migration to population growth and the relative roles of natural rate of increase ( B t – D t ) vs. net migration ( M in – M out ), which do you think will contribute more to US population growth over the next decade and why? [1 pt] I think migration will contribute more to the population growth in the United States over the next decade because the net migration is higher than the natural rate of increase. 4. For demographers, the term senescence generally refers to actuarial senescence, which is observed when mortality increases with age across later life. Theories for the evolution of senescence try to explain why increased mortality at older ages could be favored by natural selection. [3 pts] a. Antagonistic pleiotropy is one such explanation, which says that if two genes are inherited together but one has beneficial effects and the other has detrimental effects, natural selection may favor individuals with both these genes, given what crucial element in their expression? [1 pt] Natural selection favors the genes if the protective allele increases health in early life and allows survival to reproduce and if the deleterious gene affects health later in life after reproduction. b. Another theory for the evolution of senescence is mutation accumulation, which predicts that deleterious alleles that are expressed late in life may not be reduced by natural selection. What does this theory have in common with antagonistic pleiotropy? [1 pt] Both of these theories state that natural selection considers the timing of when the genes express themselves and that natural selection does not protect against genes that may have harmful effects later in life. c. Disposable Soma theory also predicts increases in late-life mortality, but depends on zero-sum allocation constraints favoring maintenance allocation insufficient for complete repair of damage. What would an organism’s limited energy be allocated to instead? [1 pt] An organism’s energy may be allocated towards growth and reproduction instead because investment in

future health is not as valuable for reproduction and natural selection. 5. The global human carrying capacity reflects the ability of the environment to support human life and depends on many interrelated factors. Given what we have discussed about the factors determining the global carrying capacity for humanity, give at least two reasons why oil prices are linked to food prices worldwide? [1 pt] One reason why oil prices are linked to food prices is because the use of oil is involved in the production and distribution of food, therefore greater production and distribution consumes more oil, which drives prices. Additionally, since oil prices may increase due to increased scarcity, that means that there are more costs in food production and distribution which would in turn drive up food prices as well. 6. Below, the graph and embedded equation on the left describe logistic population growth, which predicts rapid growth when populations are small followed by a reduction of population growth rates as population size approaches the carrying capacity ( K ). The carrying capacity is theorized as the maximum population size that is sustainable for a given environment and when populations exceed this threshold, survival and fertility are expected to suffer due to density-dependent competition for limited resources. The graph on the right shows the global population trend between 500 CE and 2150 CE based on 2004 United Nations projections (assuming low, medium or high fertility). [4 pts] a. Does the graph on the right show the world population approaching the global carrying capacity? Give at least one reason why it might and one reason why it might not. [1 pt] The world population may be approaching global carrying capacity because carrying capacity is reached after rapid growth, which is shown on the graph, based on the population growth model. However estimates for the carrying capacity of the human population are widely varied and not agreed upon b. If the graph on the right does show the global population approaching its carrying capacity, would we expect mortality to be increasing or decreasing? [1 pt] We would expect mortality to be increasing because of resources becoming more limited, however in actuality the global population is likely to decline due to declining birth rates rather than increasing mortality. c. Global population is predicted to peak between 2060 and 2100 and at 9-11 Billion people. If we assume that 11 Billion is the global carrying capacity ( K ) and the current world population ( P ) is 7.9 Billion, and the current rate of natural increase (d P /d t ) is 1%, so the annual change in population is 790 Million/year (d P /d t = 0.01* P ), what does the logistic growth rate predict the intrinsic growth rate ( r ) would be in the absence of density-dependence? [1 pt] The intrinsic growth rate in the absence of density-dependence or the global carrying capacity is r=0.1 per year. d. Given observed fertility declines across much of the world, does this support or undermine the argument that we are approaching the global carrying capacity? [1 pt] The fertility declines do not necessarily support the argument that the human population is approaching the global carrying capacity. Rather than increasing competition for resources, the fertility declines are attributed more to the changes in society and culture such as economic development, urbanization, and access to family planning to favor having smaller families.

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HW 5 Migration Aging and Carrying Capacity (1)

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