Results and Discussion

1. 1 Abstract 3 Results and Discussion Figure 3. (+ 1 S. E.) Figure 4. (+ 1 S. E.) Figure 5. 2 Introduction (+ 1 S. E.) Demography is the study of the composition of a population over time, and the effects of that population in terms of growth (Neher 2004). Human population compositions can be studied by constructing survivorship curves, which are graphical representations of the probability a certain person will survive from birth to a particular age (Neher 2004). To assemble survivorship curves, we collected headstone data (birth, death, age) from eleven populations to try to infer… If there is a significant difference between the population’s ability to survive to a certain age before 1900 and after 1900? If the survivorship of urban and rural populations differ significantly? If there is a significant difference in the ability to survive to a certain age between genders? We collected headstone data from 5 urban populations (Corvallis, Monmouth, Hillsboro, McMinnville, and Newberg) and 6 rural populations (Vernonia, Banks, Willamina, Sheridan, Falls City, and Dallas) (Figures 1 and 2). We grouped each population into males born before 1900, males born after 1900, females born before 1900, and females after 1900. By comparing survivorship curves of different time periods, historical trends in the demography of each population could be inferred and link changes to historical events and/or cultural differences, each population’s environment. We constructed survivorship curves following Hedrick (1984). Specifically, we plotted qx , the probability of surviving to a specific age class, against time t, where: qx is the probability of surviving to a certain age:  px is age-specific mortality:  lx is the proportion alive at the beginning of each age class (standardized to populations of 1,000 individuals). Figure 6. (+ 1 S. E.) 4 Conclusions • Males, both urban and rural, born before 1900 expressed reduced survivorship through midlife [age classes 3 to 18 (15 to 90yrs)] when compared to males born after 1900. • Males and Females born before 1900 lived significantly longer than those individuals born after 1900 despite medical advancement. • In urban and rural communities, females lived significantly longer than their male counterparts for both before and after 1900. Literature Cited 5 Gender Differences in Age-Specific Survivorship Between Rural and Urban Communities in Central Willamette Valley, OR Grabow, Jessica A., and Scott P. Oeffner Department of Biology, Western Oregon University Monmouth, Oregon 97361 We collected demographic data from 3,543 headstones (n = 1,642 rural headstones, n = 1,901 urban headstones) between urban and rural communities in the Northern Willamette Valley, Oregon (Table 1). We hypothesized no differences in survivorship between genders, and those born before and after 1900. Males, both in urban and rural communities, exhibited significantly lower survivorship than females. Analyses also revealed differences in (qx), the probability of surviving to a certain age, between urban and males born both before and after 1900. Most significant differences were found during mid-life (ages 30 to 50). We conclude that significant industrial, sociological, and global events during the early 20th Century equally affected both community types. We found a significant difference between the survivorship curves (age class 14 to 21 (ages 70 to 105)) of males and females (Figure 3). This pattern was true for all comparisons; urban males versus urban females, rural males versus rural males, and both before and after 1900. Biological/physiological differences between males and females are likely the reason for this difference. There was a significant difference between males born before 1900 and males born after 1900 (Figure 4). Although we did not show the comparison of survivorship curves between females born before 1900 and females born after 1900, this comparison showed a significant difference during the age classes 13 to 18 (ages 65 to 90). This was surprising because advances in technology and medicine would likely have led to increases in survivorship, not decreases. Military conflicts throughout the 1900’s (WWI and WWII, Korean War, etc.) may have significantly decreased the ability to survive to greater age classes for those individuals born after 1900. Our future research will investigate this hypothesis. There was no significant difference between the survivorship curves comparing rural males and urban males as well as comparing rural females to urban females (Figures 5 and 6). However, many of the communities sampled had less demographic differences than previously assumed. Specifically, both communities were equally affected by the events (industrial, sociological, and global) that altered the ability to survive to greater age classes for those individuals born after 1900. Figure 2. Scott P. Oeffner collecting tombstone data from the Vernonia community cemetery. Figure 1. Satellite map of the Willamette Valley, Oregon showing the 11 sampled communities in relation to the cities of Portland and Eugene (Urban indicated by redpins and Rural indicated by bluepins). Hendrick, Philip W. 1984. Population Biology: The Evolution and Ecology of Populations. 206-213pp. Jones and Bartlett Publishers Inc. Portola Valley, California. Neher, Deborah. 2004. Human Demography. 56-67pp. http//www.uvm.edu/~dneher/ biodiversity/10_Demography.pdf. Accessed 19 November 2008