Changes in Survival
Objectives:
1. Understand differences in human mortality and survivorship between historic and modern times.
2. Understand how changes in human mortality and survivorship influence population growth.
Introduction:
Human survival in North America has changed significantly in the past 100 years. Improved nutrition, preventative medicine, life-style changes, and new technologies are a few of the reasons for this life span increase. Increased survival rates influence population size—there are more of us (increased survival of very young) and we are living longer (increased survival of elderly). Life expectancy in North America today is approximately 75 years, with women living, on average, a few more years than men. The decline of infant and youth mortality in the last 100 years is particularly significant in the growth of human population.
Hypothesis: What differences do you expect to observe when comparing human survival between people that died before the year 1900 and people that have died recently?
Methods:
1. Data were gathered from a local cemetery (Livingston, AL) to compile information about human survival before the year 1900. Each data set consists of 104 males and 104 females (Tables 1 and 2).
2. Consult the obituary pages from an ONLINE newspaper and record the age at death for males and females that died recently. Each data set must consist of approximately 100 individuals (100 females and 100 males). Students without access to obituary pages may gather data in a library or through on-line newspapers.
3. Work through each of the 4 data sets, and count the number of people that died within each age bracket in tables 1-4 (This has been done for you for the Pre 1900 data set). We will assume that every person in the data set was born alive, so the first entry in the “Number Dead” column of tables 1-4 will be zero, as nobody was dead at birth (see example).
4. Next complete the “Number Surviving” column of tables 1-4, starting with the sample size for each data set as the number surviving at birth (again, we are assuming that everybody was born alive). As you progress down the table, subtract the number dying within each age bracket from the total number of individuals left alive in the previous age bracket to get the number of individuals left alive (see example).
5. The last step in to the data-gathering process is to calculate the “Percent Survival” column for each data set. Take the Number Surviving within each age bracket and divide that by the total number of individuals in each data set. Multiply that number by 100 to get Percent Survival (see example).
6. Enter your Percent Survival data into the provided excel data sheet (human survival worksheet.xls) and view the graph. You will get a line graph for this data and your graph will have 4 lines, one for each data set.