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Reading Comprehension Assignment #05 – Human Evolution
All Reading assignments are worth one quiz grade. Read the following article and answer all of the
questions that follow in complete sentences for full credit.
Glossary
1. Homo erectus - an extinct species of hominin; the earliest first fossil evidence dating to around 1.9 million
years ago and the most recent to around 143,000 years ago
2. Clade – a group of organisms believed to have evolved from a common ancestor
3. Cladogram - a branching diagram showing the cladistic relationship between a number of species
4. Primates - diverse group of between 190 and 350 living species; They range in size from the 2-ounce
pygmy mouse lemur to the 440-pound wild gorilla; most have five digits on these appendages, including
opposable thumbs; brains are one of the most distinguishable characteristics from other types of mammals
or animals
5. Lineage - a sequence of species each of which is considered to have evolved from its predecessor.
6. hominid – a primate of a family ( Hominidae ) that includes humans and their fossil ancestors
7. Homo sapiens - Modern humans
8. Australopithecus anamensis - a pre-human species that lived approximately four million years ago
9. Australopithecus afarensis - an extinct hominid that lived between 3.9 and 2.9 million years ago
10.
Homo neanderthalensis – an extinct species of human in the genus Homo; lived 200,000 - 40,000
years ago; they are closely related to modern humans, differing in DNA by just 0.12%
11.
Morphological - branch of biology dealing with the study of the form and structure of organisms and
their specific structural features
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Human Evolution
Evolutionary biologists are interested in understanding how humans fit into the history of life and how the
processes of evolution have shaped us. Much scientific effort goes into studying human evolution, and as a
result, our understanding of this area is moving forward rapidly, as new evidence emerges and hypotheses are
tested, confirmed, discarded, or modified.
The location of our very own twig: Humans on the tree of life
This tree is based on morphological and genetic data. Chimpanzees and humans form
a clade with DNA sequences that differ by only 1%1.
This genetic similarity made it hard to figure out exactly how these two primates are related, but recent genetic
studies have strongly suggested that chimpanzees and humans are each other’s closest living relative.2
How did humans evolve?
About six million years ago in Africa3, the chimpanzee lineage and our own split.
What happened to us after that split? The hominid lineage did not march in a straight line to Homo sapiens.
Instead, the early hominid lineage gave rise to many other (now extinct) hominids. Examining the fossils, the
artifacts, and even the DNA of these relatives has helped us understand how this complex hominid tree
evolved, and how modern humans came to exist.
Here are some of the important events in human history, with approximate dates, which reflect the evidence
currently available:
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1) Before 5 mya: In Africa, our ancestral lineage and the chimpanzee lineage split.
2) Before 4 mya: Fossil evidence reveals bone structures suggesting the hominid Australopithecus
anamensis walked around what is now Kenya on its hind legs.
3) >3 mya: Australopithecus afarensis (“Lucy”) lived in Africa.
4) 2.5 mya: Some hominids made tools by chipping stones to form a cutting edge. There were perhaps four
or more species of hominid living in Africa.
5) 2 mya: The first members of the Homo clade, with their relatively large brains, lived in Africa.
6) 1.5 mya: Hand axes were used. Also, hominids had spread out of Africa and into much of Asia and
Europe. These hominids included the ancestors of Neanderthals (Homo neanderthalensis) in Europe and Homo
erectus in Asia.
7) 100,000 years ago: Human brains reached more or less the current range of sizes. Early Homo
sapiens lived in Africa. At the same time, Homo neanderthalensis and Homo erectus lived in other parts of the Old
World.
8) 50,000 years ago: Human cultures produced cave paintings and body adornment, and constructed
elaborate burials. Also, some groups of modern humans extended their range beyond Africa.
9) 25,000 years ago: Other Homo species had gone extinct, leaving only modern humans, Homo sapiens,
spread throughout the Old World.
Pennisi, E. 2002. Jumbled DNA separates chimps and humans. Science298(5594):719–721.
Ruvolo, M. 1997. Molecular phylogeny of the Hominoids: Inferences from multiple independent DNA sequence data sets. Molecular Biology and
Evolution 14:248–265.
3 Gibbons, A. 2002. In search of the first hominids. Science 295(5558):1214–1219.
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Analysis Questions
1. By what percentage do chimps and humans differ with regards to DNA?
2. Think of 10 differences between chimps and humans and list them below.
3. What is the title of the article that states the difference in DNA?
4. What is the name of the journal that published the article, “Molecular phylogeny of the Hominoids:
Inferences from multiple independent DNA sequence data sets. Molecular Biology and Evolution”?
5. According to the cladogram, which modern-day organism is not considered a primate?
6. The reading lists chimps as our closest relative. According to the cladogram, which primate do we share a
common ancestor with all of the other primates?
7. All the organisms listed at the top of the cladogram exist(ed) when?
8. On the cladogram, circle the split for the place where the lineage for humans and chimps split.
9. Researchers don’t just study the fossils of extinct human ancestors. What two other forms of evidence
does the reading list as evidence?
10. In what year did A. Gibbons publish his/her article, “In search of the first hominids”?
11. How many human ancestors does the graph show? Don’t just count the skulls.
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12. According to the chart, how long ago did the first human ancestor Homo appear? How long did it last before
it went extinct?
13. When did our human ancestors begin walking on two legs?
14. How many hominid species were living in Africa about 2.5 million years ago? What other event occurred
around that time?
15. Which human ancestors were thought to be living in Asia and Europe around 1.5 million years ago?
16. Roughly when Homo sapiens become the only living human species?
17. Why do you think human evolution is studied so much?
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