Biological Anthropology Lab

Human Population

Michelle Y. Merrill, Ph.D.

Ernst Mayr Summarizes

Darwin’s Argument forEvolution via Natural Selection

• Fact #1: organisms reproduce exponentially

• Fact #2: population size generally constant

• Fact #3: resources limited• Inference #1: The Struggle

for Existence• Fact #4: organisms vary • Fact #5: variation heritable• Inference #2: non-random

survival and reproduction• Inference #3: accumulation

of favorable characteristics adaptation

How to be a human?

Fact #1: All organisms could increase population exponentially.

“The greatest shortcoming of the human race is our inability to understand the exponential function.”

-Albert A. Bartlett, Physicist

7% annual growth = doubles every decade!

Growth rateGrowth rate’’95-’00 = 1.37%95-’00 = 1.37%’’00-’05 = 1.24%00-’05 = 1.24%’’05-’10 = 1.17%05-’10 = 1.17%

(~198,000 years)

Which would you rather?

• $1,000,000.00 right now OR• A penny today, that would double every day

for a month• Day 2: $0.02• Day 3: $0.04• Day 4: $0.08• Day 5: $0.16 …

• Day 30: $5,368,709.12That’s the POWER of That’s the POWER of exponential growth!exponential growth!

Exponential Population Growth

19 Children361 Grandchildren6,859 Great-grandchildren130,321 Great-great-grandchildren2,476,099 – 5th generation47,045,881 – 6th generation893,871,739 – 7th generation16,983,563,041 – 8th generation

Duggar Family, Arkansas

“19 Kids and Counting”At the Duggar’s reproductive rate, how many generations would it take for the Duggar population to exceed Earth’s present population?

The Lily Pond ParableThe Lily Pond Parable• If a pond lily doubles every If a pond lily doubles every

day, and it takes 30 days to day, and it takes 30 days to completely cover a pondcompletely cover a pond…

• At what point would preventative action At what point would preventative action become necessary to prevent unpleasant become necessary to prevent unpleasant events?events?

• On what day will the pond be 1/2 covered? On what day will the pond be 1/2 covered?

• 1/4 covered? 1/4 covered?

• How much would it help if we could double How much would it help if we could double the size of the pond? the size of the pond?

• With respect to human population and With respect to human population and environmental degradation, what environmental degradation, what corresponding day is it for the world?corresponding day is it for the world?

Adapted from http://www.ecofuture.org/pop/facts/exponential70.html

http://youtu.be/8x98KFcMJeo

Population Growth Rates by country, 2006

Population Growth Explained with Ikea Boxes

http://www.gapminder.org/videos/population-growth-explained-with-ikea-boxes/