Inthis lesson, students will be introduced to Darwin’s theory of evolution and how it applies to humandevelopment throughout earth’s history.In the Introductory Activity, students learn about Charles Darwin andthe foundation for the theory of evolution.In the Learning Activities, students explore the specifics of humanevolution, through our earliest primate ancestors to the present day, throughweb interactives and videos from The Human Spark. For the Culminating Activity, studentsdiscover humans’ evolutionary similarities and differences with the rest of theanimal kingdom.
Students will be able to:
- Explain Charles Darwin’s significance in the science of evolution;
- Explain what natural selection means;
- Identify characteristics of early hominid ancestors;
- Discuss behavioral similarities between humans and primates;
- Explain ways that we can tell that humans and otheranimals share a common ancestor.
6 – 8
(3)45-minute class periods
Human Nature Video
Part I: Introductory Activity
1. Askstudents if they have ever heard of Charles Darwin, and what they know abouthim. Tell students that Charles Darwinwas a British scientist who traveled around the world from 1831 to 1836 on aship called the HMS Beagle. Darwin was originally asked to join the ship’s crew simplyas a dining companion for the captain, but quickly fell into the role of ship’snaturalist, and took the position very seriously. During his time on the Beagle, Darwin observed plants, animals, and geological features inand around South Americaand Australia, and recorded his observations in a diary, which waslater published as a book titled Voyage of the Beagle.
2. Tell students that you are going to have them read an excerpt from Charles Darwin’s diary. You may ask students to visit Excerptsfrom Charles Darwin’s Voyage of the Beagle, or you may wish to distribute hard copies of the excerpts to each student. Ask half of the class to read the excerpt titled Buenos Aires, Argentina: 34ºS, 59ºW August 24, 1833 and half to read the excerpt titled Galapagos Islands, Ecuador: 0ºS, 90ºW September 15, 1835. Encourage students to ask about or look upany unfamiliar words in a dictionary.(If the language or vocabulary in the excerpts is too complicated oradvanced for your students, you may wish to read the excerpts together as aclass.) Ask students to underline orhighlight any text that refers to the number or quantity of different species,or the physical structure or appearance of individuals within species. Give students 10 – 15 minutes to read their excerpts.
3. Ask each group to present a brief summary of itsassigned excerpt, and ask students to share what they underlined/highlighted. Make sure the following concepts areaddressed:
- Manyanimals, both in the same location and in different locations, shared similarcharacteristics.
- Animalsthat seemed to be different shared some characteristics.
- Anygiven location seemed to be home to many species.
- Animalson the mainland were similar but not identical to animals on the surroundingislands.
- Several species were perfectly suited to theirunique environments.Ask students if, at this point, they have any of theirown theories that might link these observations together.
4. For Darwin, these observations led to his curiosity about therelationships between species and the origins of new species. He developed the idea that many species couldemerge from one original species. Hethought that species could change—or adapt—over time, and that all specieswere related to a common ancestor. Theseideas were the foundation of Darwin’s famous theory of evolution.
5. Eventually Darwin came to the idea that the key to evolution wasvariation, or different characteristics within a species. He observed that within a species individualshad varying characteristics, such as eye color in people. Individuals with traits useful in theirenvironments, such as finches whose beaks can crack a specific nut, have abetter chance of surviving to reproduce and pass along those traits. Conversely, individuals with harmful traits, likean inability to digest a nut that is the only food source, would not survive,and would not pass those traits to future generations. Darwin called this process “natural selection.” It is also sometimes know as “survival of thefittest,” but Darwin himself did not use that term.
6. Darwin started writing about his new theory almost immediately after returningto England after the Beagle voyage, but did not publishhis famous work On the Origin of Species by Means of Natural Selectionuntil 1859. By the time of his death in1882, his theory of evolution was widely, but not universally, accepted. In later works Darwin discussed how natural selection applied to theprocess of human evolution. He was facedwith skepticism and controversy when he suggested that humans shared commonancestors with primates like apes or monkeys, but today it is a commonlyaccepted theory. Ask students how theythink natural selection has factored into human evolution.
Part II: Learning Activity
The Human Spark
1. Askstudents to think about their family trees.How far back can they trace their ancestors – 3, 5, maybe even 10generations? According to Darwin’s theory that all life on earth evolved from a commonancestor, a person’s family tree actually goes back thousands, maybe millionsof generations! Tell students that thehuman “family tree” does not look at individual branches (like uncles orcousins) but presents a broader view of the early species that are directly andindirectly related to modern human beings.Modern humans – known scientifically as Homo sapiens–evolvedover millions of years through the process of natural selection, like all otherspecies on earth.
2. Explainto students that the path of human evolution is not a straight line. On the human family tree, some branches keptgrowing from the beginning, some split into two or three different branches,and some stopped growing altogether. Eachof these branches played a role in human evolution, but only one grew directlyinto Homo sapiens. Tell studentsthat you are going to show them a video that explores some of thesebranches of our family tree. Givestudents a focus for watching the video by asking them to observe and notespecific characteristics and abilities possessed by our ancestors. Play Links in the Evolutionary Chain. When the video has finished, askstudents if they noticed any specific characteristics or abilities, like skulland brain size, or new tools and inventions.Ask students why they think those characteristics and abilities changedover time. Why did some things changewhile others remained the same? Why diddifferent groups have different characteristics and abilities?
3. Inpairs or small groups, have students log on to Who’sWho in Human Evolution. Assign each group or pairs one of the foursubgroups presented in the interactive: early hominins, Australopithecus,paranthropus, Homo. (Depending on howmany students are in your class, some or all of the subgroups may be assignedto more than one pair or group of students.) Have students click on the fossils in theirgroup, read the text, and write in their notebooks which characteristics theythink are similar to humans today and which are different. Give students 5 – 10 minutes to complete theactivity. When finished, project theinteractive on a screen for the class.Ask students to share their noted observations, and click on the fossilsbeing described for all students to see. Ask the class which characteristics madeit all the way from early hominins to Homo sapiens. Which were lost? Which were picked up along the way? Why do they think that happened?
1. Pointout to students that the human family tree featured in the interactive stopped7.6 million years ago. Ask studentswhat, if anything, they think came before that in the history of humanevolution. Explain that the human familytree does go back even further, as Darwin speculated, to primates including gorillas, monkeys,and our closest living relatives, chimpanzees.
2. Projector distribute copies of A timeline of life on earth (if projecting, cover the top half so only “From primitive primates to people” shows).Explain that this timeline represents when different species branchedoff from their ancestors and became a new distinct species. Project/distribute HowIda fits into the primate family tree for a more detailed representationof the different branches. Make surestudents understand that as part of the evolution process new species branchedoff to form new ones but the original species still existed in some form forsome period of time. This image depictsprimate ancestors that still exist today, but potentially several primateancestors species (like humans) branched off and then became extinct.
3. As students may have observed, all branches of the hominin family tree have died off except for Homo sapiens.However, many of our earlier ancestors still populate the earth. Explain to students that this access to ourearly ancestors can give scientists unique insight into the origins of humanbehavior. Tell students that you aregoing to show them a video relating to our primate ancestry. Ask students to observe the evolutionarydistance between modern humans and the primates mentioned in the video. Play Human Nature.Follow up by reviewing the focus question. Point out that we can see that the sharedtraits between humans and primates go beyond physical characteristics – theyapply to behavior patterns as well. Whatbehavioral characteristics did students observe that are similar to modernhumans behavior patterns? What isdifferent? What makes us distinctlyhuman?
4. Explainthat some scientists feel that the evolutionary gap between humans and apes isstill too wide and they are looking for what they call “the missing link” – anancestor that clearly ties the two branches of the family tree. “Ida,” shown on the two timelines, was arecent fossil discovery that some scientists believed to be a crucial link inthe chain of human evolution. Others arenot so sure. What traits would youexpect this creature to have? Would itbe classified as an early hominin or a primate?What would its body look like? Howwould it act around others? Whatcharacteristics would it need to possess in order to be a direct ancestor of Homosapiens?
Part III: Culminating Activity
1. Remindstudents that according to Darwin’s theory, all species evolved from a common ancestor,even further back than the earliest primate 55 million years ago. Reveal the top half of A timeline of life on earth to show that before primates, our family tree included early mammals,reptiles, even fish and worm.
2. Howcan we tell? Just as we can observesimilar traits among humans and primate ancestors, we can perceive sharedtraits with other species. In pairs orsmall groups have students log on to The Zoo of You. Have students click through the interactiveand ask them to make a note of any “Oops” characteristics. Give students 10 – 15 minutes to complete theinteractive. Ask students if they foundanything particularly surprising or interesting.
3. Returnto Darwin’s theory of natural selection, where beneficialvariants allow individuals to survive and reproduce. Ask students how they think the “oops”characteristics fit into this theory?Why have our modern human bodies evolved to include them?