Download Activity 3: What can we learn about human evolution from anatomy

Activity 3: What can we learn about human evolution from anatomy, the fossil record,
and genetic comparisons?
Purpose: The last activity used whales to demonstrate how multiple lines of evidence
support the theory of evolution. But what about people? What evidence is there that
human populations have changed over time?
Initial Ideas
On your own: Examine the tree below which shows the relationships between many
groups of animals based on similarities in their anatomy. Notice that the relationship
between gorillas, chimpanzees, and humans are not drawn in.
Draw a tree that shows your current ideas about the relationships between gorillas (G),
chimpanzees (C), humans (H) and a common ancestor (shown as A).
Exercise 1:Lessons from Anatomy.
Your instructor will put up a slide that shows skulls from chimpanzees, humans, and
gorillas.
Procedure:
Compare the skulls and make notes about their similarities and differences.
What do the human and chimpanzee skulls have in common? What differences do you
see?
What do the human and gorilla skulls have in common? What differences do you see?
Did the evidence from the skulls support your initial ideas? Explain.
Exercise 2: Lessons from our DNA1
You will need:
 Paper clips in 4 colors
In this exercise, you will test your hypothesis about the relationship between humans,
chimps, and gorillas by making model DNA molecules for each species and then
comparing their similarities. The model DNA molecules are based on actual portions of
the genes for hemoglobin proteins in these species.
Procedure:
Each color paper clip represents one of the 4 nucleotides found in DNA. Record the
colors you are using in your model here (Note: each member in your group should use the
same colors):
A_______________ T_____________
1
C_______________ G____________
Adapted from “Teaching about evolution and the nature of science,” National Academy of Science, 1998
Step 1. Working in groups of three or four, "synthesize" strands of DNA according to the
following specifications.

Group member 1
Label this strand "human DNA."

Group member 2Synthesize a strand of DNA that has the following sequence:
Label this strand "chimpanzee DNA."
Group member 3
Label this strand "gorilla DNA."
Step 2. Compare the human DNA to the chimpanzee DNA by matching the strands base
by base (paper clip by paper clip). Count the number of bases that are not the same.
Record the data in the table below.
Step 3. Repeat Step 2 with the human DNA and the gorilla DNA.
Hybridization data for human DNA
Human DNA compared to:
Chimpanzee DNA
Gorilla DNA
Number of matches
Unmatched bases
Questions:
1. How do the gorilla DNA and the chimpanzee DNA compare with the human
DNA?
2. What do these data suggest about the relationship between humans, gorillas, and
chimpanzees?
3. Do the comparisons from the DNA suggest the same relationship as the data from
the skulls?
4. Scientists don’t believe that chimps are the ancestors for humans, or that humans
are the ancestors for chimps. How else might they have come to share common
characteristics?
5. What kinds of data might provide support for answer to #4?
Exercise 3: Meeting our common ancestors
Procedure:
Go to http://www.pbs.org/wgbh/evolution/library/11/2/quicktime/e_s_5_56.html and
watch the video, then answer the questions
1. What percentage of human DNA and chimpanzee DNA is identical?
2. How do scientists think chimpanzees and humans are related?
Exercise 4: Building the fossil record
When Charles Darwin first proposed his theory of evolution by natural selection, very
few fossil hominids had been discovered, so there was very little evidence to support the
idea that humans have changed over time through natural selection. Since Darwin’s time,
many more fossil hominids have been found, and the picture of human evolution
continues to get filled in. In this exercise, you will examine some early fossils in order to
get to know some of our earliest ancestors:2
2
Adapted from Evolution, at pbs.org
You will examine these fossils:




The remains of Lucy, the first Australopithecus afarensis find, discovered in
Hadar, Ethiopia in 1974 by a team of fossil hunters including Don Johanson;
• The skull of a mature male A. afarensis found in 1992 in the Hadar region of
Ethiopia (Hadar Skull) by a team led by Yoel Rak and Bill Kimbel;
The Laetoli Footprints discovered by Mary Leakey in Laetoli, Tanzania in 1978;
• Don Johanson's "First Family," a group of 13 individuals of different ages and
sexes found in Hadar, Ethiopia in 1975.
You will need:

Access to a computer
Procedure:
Go to: http://www.pbs.org/wgbh/evolution/humans/riddle/ed_pop.html
Step 1: Explore the animation and answer the following questions:
1. What evidence from the fossils suggests that A. afarensis walked upright?
2. What characteristics does A. afarensis have in common with chimpanzees?
3. What characteristics does A. afarensis have in common with modern humans?
Summarizing Questions:
1. What is the difference between saying that one species shares a common ancestor with
another species, or saying that one species is descended from another species? Draw a
picture to represent your thinking.
2. Describe how 3 lines of evidence support the theory that humans have evolved over
time.
Comparative anatomy
Fossil record
Molecular evidence
Activity 3 Homework: Solving the mystery of the Neanderthals
Purpose: To use molecular evidence to solve a problem in human evolution.
Background: Ever since skulls of Neanderthals were discovered, people have wondered
about the relationship between modern humans and these ancient hominids. They have
many characteristics in common with us: they had similar anatomy including similar
brain sizes, they used tools, and they even buried their dead. And yet, they are physically
different from us because of their heavy brow ridges and stocky builds. Just what is the
relationship between us and them?
Procedure:
Step 1. Go to http://www.geneticorigins.org/mito/mitoframeset.htm and watch Clip #8 on
the Neanderthal question.
What are the two alternate hypothesis proposed by Dr. Svante Pääbo regarding the
relationship between Neanderthals and modern humans?
Step 2: Go to http://www.geneticorigins.org/mito/mitoframeset.htm and explore the
animation.
Based on mitochondrial DNA comparisons3, how many years have passed since
Neanderthals and modern humans diverged from their common ancestor?
Based on mitochondrial DNA comparisons, what is the relationship between
Neanderthals and modern humans?
3
To learn more about mitochondria and their DNA, check out
http://www.geneticorigins.org/mito/mitoframeset.htm .
Activity 4: (optional) What can evolution tell us about human “races”?
Purpose: In the previous activity, you explored the origins of modern humans. When we
compare humans to chimpanzees or other species, the similarities between all humans
become very obvious. Without that evolutionary perspective, however, humans often
focus on the differences between us – as our war-torn history demonstrates. Human
“race” has been the basis of many of our worst atrocities – slavery, apartheid, genocide in
Rwanda, the extermination of Jews and other non-Aryan’s in the German concentration
camps of World War II, as well as the basis for many less obvious cases of discrimination
and oppression. So, just what is human race anyway? If we look at it through the lens of
evolution, what kinds of differences will we see?
You will need:


Access to a computer
A copy of the article “A fish of a different color”
Procedure:
Step 1: Go to http://video.nytimes.com/video/2007/06/25/science/1194817104756/thescience-of-evolution.html and watch the video
In your own words, what is the field of “evo-devo”?
What evidence does the video present to support that all life on Earth is related?
One argument against the theory of evolution, proposed by people who believe in
Intelligent Design, is that some forms on Earth are too complicated to have evolved
according to natural processes and therefore a supernatural designer is required. How
does scientist Sean B. Carroll argue against Intelligent Design?
Step 2: Read the article A fish of a different color
The human genome is 3 billion base pairs of DNA – in other words, 3 billion letters of
the genetic code of DNA (A, C, T, G) are needed to write the instructions for a human.
How many of those letters are different in the gene of dark and light skinned people?
What percentage difference between dark and light skinned people does this represent?
In your own words, explain how evolution by natural selection led to lighter-skinned
populations of people in Europe.
Which is most evolutionarily “fit” for a human – dark skin or light skin?
Scientists Ideas About Evolution:
Theory of evolution
Homology
Phylogenetic tree
Common ancestor
Descent with modification
Extinction
Speciation