Download 23 Human Evolution

PART VII
HUMAN EVOLUTION AND ECOLOGY
23 Human Evolution
24 Ecosystems and Human Interferences
25 Conservation of Biodiversity
Chapter 23 – Human Evolution
BEHAVIORAL OBJECTIVES
1. Give a sequence of events by which life may have originally arisen from non-life. [23.1, p.462, Fig. 23.1]
2. Give a sequence of events by which the first cell may have evolved from a protocell and how life thereafter
diversified. [23.1, pp.462-463]
3. Cite categories of evidence for the evolutionary process. [23.2, pp.464-465, Fig. 23.2 & 23.3]
4. Explain five statements that outline the process of natural selection as developed by Darwin. [23.2, p.465]
5. Name the classification categories in sequence, and be able to recognize a binomial name. [23.3, p.466, Table
23.1]
6. Tell what characteristics distinguish primates from other mammals. [23.3, pp.466-467, Fig. 23.4]
7. Describe the line of descent that includes the australopithecines. [23.4, p. 468, Fig. 23.5]
8. Trace the evolution (including relevant geography) of humans from the hominids to Cro-Magnons. [23.5,
pp.469-472, Fig. 23.6-23.10]
9. Contrast the multiregional continuity hypothesis with the out-of-Africa hypothesis. [23.5, p.471, Fig. 23.8]
10. Compare the skills of Neaderthals with those of the Cro-Magnons. [23.5, p. 472, Figs. 23.9 & 23.10]
11. Explain how human “races” represent phenotypes of the same species and that molecular data do not support
use of the term “race”. [23.5, p. 474]
12. Understand and use the bold-faced and italicized terms included in this chapter. [Understanding Key Terms,
p.475]
EXTENDED LECTURE OUTLINE
23.1 Origin of Life
The Primitive Earth
The sun and planets formed from aggregates of dust and debris 4.6 billion years ago. The primitive atmosphere on
earth was produced by outgassing from the earth’s interior and contained very little free oxygen. As the earth cooled
over millions of yeas, water vapor condensed and produced the earth’s oceans.
Small Organic Molecules
As the earth cooled, clouds of water vapor condensed and rained down on the earth, bringing with them atmospheric
gases. Energy from lightning and volcanic heat triggered the gases to react, producing simple organic compounds.
Macromolecules
Small molecules reacted and formed larger ones, and RNA likely formed. RNA can act both as a substrate and an
enzyme, which supports this RNA-first hypothesis.
The protein-first hypothesis suggests that dry heat, such as on a rocky shore, caused proteins to form from amino
acids. This led to DNA genes, which today need protein enzymes for replication.
The Protocell
A protocell with a lipid-protein membrane must have evolved first. It might have contained RNA, which served both
as genetic material and as enzymes. Small organic molecules would have served as food for this heterotroph.
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The True Cell
A true cell carries on protein synthesis to produce enzymes that allow DNA to replicate. If the first cell had RNA
genes, they could have directed protein synthesis. A reverse transcriptase would have produced DNA in multiple
copies,
If the cell began with proteins, they could function as enzymes, guiding the synthesis of nucleotides, and eventually,
nucleic acids.
Mader VRL CD-ROM
Image 0442l.jpg (Fig. 23.1)
Life Science Animations VRL 2.0
Mader ESP Modules Online
Evolution/Origin and History of Life/Chemical Evolution in the
Atmosphere
Evolution/History of Life/Origin of Life
Transparencies
332 (Fig. 23.1)
23.2 Biological Evolution
The first true cells were most likely prokaryotes. Eukaryotic cells, with nuclei, evolved later. All living things can
trace their biological evolution back to the first cells. Differences among living things can be attributed to adaptation
to the environment.
Common Descent
Charles Darwin was one of the first scientists to accumulate data that supported the idea of common descent.
Fossil Evidence
The fossil record shows gradual change in certain lineages and a general increase in complexity over time,
supporting evolutionary theory. The age of fossils can be determined using isotopes.
Biogeographical Evidence
Biogeography is the study of the distribution of plants and animals throughout the world. Darwin noted that
South America had no rabbits although the environment could have supported them. He concluded that
rabbits evolved elsewhere.
Anatomical Evidence
Many diverse organisms show anatomical similarities, such as vertebrate forelimbs. Similar structures that
were inherited from a common ancestor are called homologous structures. The unity of plan seen in all
vertebrates is evident in their common stages of embryological development. Analogous structures have the
same function but do not share a common ancestry.
Biochemical Evidence
Nearly all organisms on earth use the same biochemical molecules (DNA, ATP), all use the same triplet
code for amino acids, and many share similar gene sequences. The degree of relatedness between
organisms is reflected in the similarity of their DNA base sequences.
Natural Selection
Charles Darwin’s theory of evolution through natural selection was based on the idea that a species becomes adapted
to its environment over time. The environment selects the individuals that are best adapted. This idea contrasts with
the teleological notion of Lamarck that organisms acquired characteristics throughout their life spans.
Darwin’s ideas on natural selection are based on variations within the population, an inherent struggle for existence,
survival of the fittest, and adaptation.
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Image 0443l.jpg (Fig. 23.2)
Image 0444l.jpg (Fig. 23.3)
Life Science Animations VRL 2.0
Evolution/Origin and History of Life/Continental Drift
Evolution/Origin and History of Life/ Formation of Sedimentary
Rock
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Evolution/History/Evidence for Evolution
Evolution/History/Before Darwin
Evolution/History/Voyage of the Beagle
Evolution/History/Natural Selection
Evolution/Processes/Natural Selection
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333 (Fig. 23.3)
23.3 Humans Are Primates
Biologists classify organisms based on evolutionary relationships. Categories used for classification include
kingdom, phylum, class, order, family, genus, and species. Organisms are named using their genus and species, a
binomial system of classification.
Characteristics of Primates
Primates have an opposable thumb, a shortened snout, stereoscopic vision, extended parental care of offspring, and
an emphasis on learned behavior during a lengthy juvenile dependency period.
Relationships Among Primates
Our evolutionary tree indicates that humans evolved from primates, most of which live in trees. Humans are most
closely related to the apes. Molecular data suggests that chimpanzees are our closest relatives. Humans can be
distinguished from apes by bipedalism, which evolved about 6 MYA, and by various other traits.
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Image 0445l.jpg (Fig. 23.4)
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Evolution/Origin and History of Life/ Modern Human Skeletal
Features and Those of a Gorilla
Evolution/Origin and History of Life/ Binocular Vision
Evolution/Human Evolution/Primates
Transparencies
334 (Fig. 23.4)
23.4 Evolution of Australopithecines
The hominid line led directly to modern humans and began with the australopithecines in Africa. both gracule and
robust australopithecines may have existed simultaneously.
Southern Africa
Australopithecus africanus, a gracile type, and A. robustus, a more robust form are both believed to have walked
upright but had apelike limbs.
Eastern Africa
Australopithecus afarensis, or “Lucy,” was small but walked upright and had a heavy jaw and smaller brain than
modern humans. Several species of hominids may have existed 2 MYA, descending from Lucy’s species. All human
characteristics did not evolve at the same time but instead exhibited mosaic evolution.
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Image 0446al.jpg (Fig. 23.5a)
Image 0446bl.jpg (Fig. 23.5b)
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Evolution/Human Evolution/Hominid History
23.5 Evolution of Humans
Early Homo
Homo habilis (“handy man”) made stone tools. Stone flakes were used to clean hides and remove meat from bones.
Speech was likely in this group, which also probably possessed attributes of culture and cooperation. Brain size,
posture, and dentition cause H. habilis to be classified as a Homo.
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Homo erectus
Homo erectus had an even larger brain and traveled extensively throughout Europe, Africa, and Asia. It probably
first appeared in Africa. It was the first hominid to use fire and to make axes and cleavers. It was a good hunter.
Evidence indicates the use of “home bases” and social interaction. Language and culture were likely.
Evolution of Modern Humans
The multiregional continuity hypothesis suggests that modern humans arose simultaneously in several different
places. The out-of-Africa hypothesis suggests that Homo sapiens arose from H. erectus in Africa and then migrated
to other areas of the world about 100,000 years ago.
Neanderthals
The Neanderthals (H. neanderthalensis) from 200,000 years ago had massive brow ridges and protruding facial
features, and were, perhaps, an archaic H. sapiens. They were heavily muscled and had larger brains than modern
humans. They were culturally advanced and buried their dead with flowers, indicating a possible religion.
Cro-Magnons
Cro-Magnons (H. sapiens), from 100,000 years ago, had a modern appearance, were accomplished hunters, and
likely caused the extinction of many large mammals. They painted and sculpted, and lived in small groups.
We Are One Species
All humans on earth today belong to one species, Homo sapiens, even though differences occur. Such phenotypic
differences like skin color are most likely due to climatic differences. Differences in stature could reflect climatic
temperature differences. Molecular data do not support the notion of separate “races” of people.
Mader VRL CD-ROM
Image 0447l.jpg (Fig. 23.6)
Image 0448l.jpg (Fig. 23.7)
Image 0449al.jpg (Fig. 23.8)
Image 0449bl.jpg (Fig. 23.8)
Image 0450l.jpg (Fig. 23.9)
Image 0451l.jpg (Fig. 23.10)
Image 0452l.jpg (Fig. 23A)
Image 0453l.jpg (Fig. TA23.1)
Life Science Animations VRL 2.0
Evolution/Origin and History of Life/ Origin of Modern
Humans
Mader ESP Modules Online
Evolution/Human Evolution/Hominid History
Transparencies
335 (Fig. 23.6)
336 (Fig. 23.8)
337 (Fig. TA23.1)
SEVENTH EDITION CHANGES
New/Revised Text:
This was chapter 22, Evolution, in the previous edition. The entire chapter has been completely rewritten
and expanded to include more detailed information on the origin of life and human evolutionary events. This
chapter contains many new, interesting, and helpful illustrations and photographs. The chapter has a new
introductory story.
23.1 Origin of Life (previously 22.3 Organic Evolution). This section has been rewritten in more detail and
Miller’s experiment is explained. Taxonomy has been moved to 23.3 Humans are Primates. Only the classification
of humans is examined.
23.2 Biological Evolution includes evidences of evolution – common descent and natural selection. The
entire section has been rewritten. Each topic goes into more detail than previously.
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23.3 Humans are Primates. This section has been completely rewritten. Characteristics of primates and the
primate evolutionary tree are examined.
23.4 Evolution of Australopithecines. This new section gives details about the discoveries of
australopithecine fossils in Southern and Eastern Africa.
23.5 Evolution of Humans. This entire section has been rewritten and has much more information and
detail than in the previous edition.
New Bioethical Focus: The Theory of Evolution.
New/Revised Figures:
23.1 Chemical evolution; 23.2 Fossils; 23.3 Mechanism of evolution; 23.4 Primate evolutionary tree; 23.5
Australopithecus africanus; 23.6 Human evolution; 23.7 Homo erectus; 23.8 Origin of modern humans; 23.9
Neanderthals; 23.10 Cro-Magnons; 23A Australopithecus africanus skull
New/Revised Tables:
23.1 Evolution and Classification of Humans
STUDENT ACTIVITIES
Recent Find: Rafting Lizards
1. The Washington Post and The Salt Lake Tribune recently reported that biologists have documented that a
floating raft of trees uprooted by hurricanes in 1995 carried 15 green iguanas from Barbados to the island of
Anguilla. This confirms theories of how one species could be transported from one land mass to another. Ask
your students to read the Oct. 8, 1998 Nature article or find a suitable popular magazine article. Ask students to
discuss how this supports part of our theory of evolution.
The Lives of Neanderthals
2. Have your students read Rick Gore’s article on Neanderthal behavior in National Geographic, January 1996,
pages 2-35. Ask your students to comment on items they found especially interesting in this article. For
example, the injuries that many Neanderthals suffered were consistent with those often seen in rodeo riders. The
conclusion? Neanderthals jumped on the backs of and stabbed the large animals they killed for food, evidently
never conceptualizing of throwing a spear. Their dangerous hunting methods, burial behavior, and possible
instances of cannibalism are described in this fascinating article.
Differentiating Between Ape and Human Fossils
3. Students often wonder how scientists discern between humanlike fossils and ape fossils. Share with your
students the following list of how paleontologists and anthropologists differentiate the two:
Apelike feature
Hominid feature
Jaw shape
Rectangular dental arcade
U-shaped dental arcade
Shape of spine
Straight spine
S-shaped spine
Posture
Knuckle-walked
Erect, bipedal locomotion
Pelvis
Elongated
Short
Supraorbital ridges
Pronounced
Not pronounced
Plane of face
Projected forward
Flat-faced
Teeth
Larger; large canines
Smaller; small canines
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