Human Life Tables and Survivorship Curves

Three questions we are addressing in this lab

• Do females live longer than males on average?• Do the child bearing years lead to greater mortality

among females than males?• Is the life span of people who were buried in newer

cemeteries greater than those who were buried in older cemeteries?

Survivorship curves will help us answer these questions

What are survivorship curves?

• Graphs made from life tables that show the survivorship (log # of survivors) in each age group.

• There are 3 basic types…

Type I (convex)

• Many mammals show this type of survivorship.

• Most individuals will live a long time and die in the largest age groups.

Type I Survivorship

0.00

1.00

2.00

3.00

4.00

5.00

Time

log

# su

rviv

ors

Type II (straight/linear)

• Many song birds and seeds in a soil seed bank show this type of survivorship.

• There is a constant rate of survival, for example, 10% survive each age group.

Type II Survivorship

Age intervals

log

# su

rviv

ors

Type III (concave)

• Many invertebrates and marine fish show this type of survivorship.

• Most individuals die as juveniles.

Type III Survivorship

3.60

3.80

4.00

4.20

4.40

4.60

4.80

Time

log

# su

rviv

ors

Which do we predict to find?Type I Survivorship

0.00

1.00

2.00

3.00

4.00

5.00

Time

log

# s

urv

ivo

rs

Type III Survivorship

3.60

3.80

4.00

4.20

4.40

4.60

4.80

Time

log

# s

urv

ivo

rs

Type II Survivorship

0 to 5

5 to 10

10 to 15

15 to 20

20 to 25

25 to 30

Age intervals

log

# s

urv

ivo

rs

• Why might men live longer than women?

Risks associated with childbirth

• Why might women live longer than men?

Risky behavior

Smoking

Homicide and suicide

Alcohol

War

Toxic effects of testosterone

• Why has human life expectancy increased over the last several decades?

Improvements in medicine, nutrition, and sanitation

Methods

• Work in pairs • Choose a row of headstones, respectfully walk

down the row, and record the data listed on the data sheet (sex, YEAR of death, YEAR of birth).

• Choose headstones by recording the next one you come to. Include infants.

• Record data for 50 males and 50 females.• Be careful of incorrect data. There have been

records of people living 150+ years or less than 0 years.

• Do not overlap with another group.• Return to campus and…

• Each group will enter their data into an Excel spreadsheet and email it to me by tonight at 6:00.

• For full credit for today’s lab, it must be entered in the exact format as on page 76 of your manual. This includes calculating age at death with a formula to proof for (and fix) mistakes.