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Unit 1:
Ch. 1
Ch. 2
Ch. 3
Interlude A
Unit 2:
Ch. 4
Ch. 5
Ch. 6
Ch. 7
Ch. 8
Ch. 9
Interlude B
Unit 3:
Ch. 10
Ch. 11
Ch. 12
Ch. 13
Ch. 14
Ch. 15
Interlude C
Unit 4:
Ch. 16
Ch. 17
Ch. 18
Ch. 19
Interlude D
Unit 5:
Ch. 20
Ch. 21
Ch. 22
Ch. 23
Ch. 24
Ch. 25
Ch. 26
Ch. 27
Ch. 28
Ch. 29
Ch. 30
Interlude E
Unit 6:
Ch. 31
Ch. 32
Interlude F
Unit 7:
Ch. 33
Ch. 34
Ch. 35
Ch. 36
Ch. 37
Ch. 38
Interlude G

» Getting Started » A Guide to the Reading » Tying it all together

Getting Started

Below are a few questions to consider prior to reading Interlude D.  These questions will help guide your exploration and assist you in identifying some of the key concepts presented in this chapter.

  1. From what German valley did the Neandertals originate?
  2. What is the scientific name for the earliest known hominid?
  3. What are some of the tools that were developed during the early evolution of the hominids?
  4. What is the multiregional hypothesis?
  5. What has happened to the size of the human brain over the past 75,000 years?
  6. Approximately how much does the development of drug resistant diseases cost society each year?
  7. What do scientists expect to happen to the extinction rate over the next 100 years?
  8. What is eugenics?

A Guide to the Reading

When exploring the content in Interlude D for the first time, the following concepts typically give students the most difficulty.  For each concept, one or more additional references have been identified which may help you gain a better understanding of these potentially problematic areas. 

Multiregional vs Out-of-Africa Hypothesis

The multitude of fossil remains found in Africa, China, and Europe that appear to be intermediate between Homo erectus and Homo sapiens have prompted scientists to develop different hypotheses regarding the origin of modern humans.  The out-of-Africa hypothesis suggests that anatomically modern humans evolved from a single ancestral line in Africa (archaic Homo sapiens) and later spread to other continents, replacing the native hominid populations.  The key to this hypothesis is realizing that there would have been little or no gene flow between the archaic Homo sapiens and native species, maintaining genetic isolation.  In contrast, the multiregional hypothesis provides a more “mixed” view of the origin of modern humans.  In this hypothesis, it is believed that archaic Homo sapiens evolved in parallel from Homo erectus populations that were present in Europe, Africa, and Asia.  As a result, regional differences between human populations in different areas of the world would have developed early in the evolutionary process.  It is also believed that the adaptations that characterize modern humans would have been shared between these populations as a result of gene flow.  Currently, evidence exists to support each hypothesis.  As a result, scientists are not certain which hypothesis is, in fact, correct.

For more information on this concept, be sure to focus on:

  • Interlude D, The Origin and Spread of Modern Humans
  • Figure D.9, The Origin of Anatomically Modern Humans

The Sixth Mass Extinction

As discussed in the interlude, we may currently be in the midst of a sixth mass extinction; a mass extinction caused mostly by mankind.  The environmental impact of human activities is predicted to have the most significant effect in terms of extinction than has ever occurred in the history of the Earth.  Global warming, pollution, and depletion of natural resources and habitat are causing species to go extinct at rates that may soon dwarf the rates seen in previous mass extinction events.  In addition, human activities are also influencing the microevolution of various species that may have a detrimental impact on the health of numerous species as well as our own.  Examples include the evolution of pesticide and antibiotic resistance due to the widespread and indiscriminate application of pesticides and antibiotics.  In addition to the detrimental effects on the health of humans, these developments have also caused (and will continue to cause) widespread economic trouble.

For more information on this concept, be sure to focus on:

  • In Interlude D, People have profound effects on microevolution in other species
  • In Interlude D, People also alter macroevolutionary patterns
  • Figure D.11, Directional Selection for Pesticide Resistance
  • Figure D.12, Human Effect on the Landscape

Tying it all together

Several concepts presented in this chapter build upon concepts presented in previous chapters and may also be revisited and discussed in greater detail in subsequent chapters, including:


  • Chapter 10 – Section 10.2, Gene Mutations: The Source of New Alleles

Mass Extinctions

  • Interlude A – The Beginnings of a Present-Day Mass Extinction
  • Chapter 19 – Section 19.4, Mass Extinctions: Worldwide Losses of Species

Natural Selection

  • Chapter 16 – in Section 16.2, Natural selection and genetic drift are important aspects of evolution
  • Chapter 17 – Section 17.7, Natural Selection: The Effects of Advantageous Alleles

Gene Flow

  • Chapter 17 – Section 17.5, Gene Flow: Exchanging Alleles between Populations

Genetic Drift

  • Chapter 17 – Section 17.6, Genetic Drift: The Effects of Chance


  • Chapter 19 – in Section 19.7, Macroevolution differs from the evolution of populations

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