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Copyright © 2013 Pearson Education, Inc. All rights reserved.
Exploring Biological Anthropology:
The Essentials, 3rd Edition
CRAIG STANFORDJOHN S. ALLEN
SUSAN C. ANTÓN
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Chapter 5 The Forces of Evolution And The
Formation of Species
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How Evolution Works
• Where Does Variation Come From?
–Mutations• Point mutation• Chromosomal mutation
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How Evolution Works (cont’d)
• How Natural Selection Works
– Phenotypes in environments– Changes in gene frequencies– Directional Selection/ Stabilizing Selection
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How Evolution Works (cont’d)
• Other Ways By Which Evolution Happens
– Gene Flow: movement of genes between populations
– Genetic Drift: random changes in gene frequency in a population
– Founder Effect: genetic bottleneck
– Sexual Selection: Differential reproductive success within one sex of any species
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Classification and Evolution
• Taxonomy and Speciation– Systematics: branch of biology that describes
organismal variation (what used to be called taxonomy)
– Homology: the notion that similar features in two related organisms look alike because of a shared evolutionary history• Convergent (parallel) evolution
– Cladistics• Cladograms
– Phenetics: numerical taxonomy
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Classification and Evolution (cont’d)
What is a Species?• An interbreeding group of animals or plants
that are reproductively isolated through anatomy, ecology, behavior, or geographic distribution from all other such groups (Mayr, 1942)– Biological species concept– Evolutionary species concept– Ecological species concept– Recognition species concept
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Classification and Evolution (cont’d)
Species Concepts• Biological species concept• Evolutionary species concept• Ecological species concept• Recognition species concept
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Classification and Evolution (cont’d)
• Reproductive Isolating Mechanisms (RIMs)– Any factor that prevents a male and female of two
different species from hybridizing
• Premating RIMs• Postmating RIMs
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Classification and Evolution (cont’d)
• Premating RIMs• Habitat isolation• Temporal isolation• Behavioral isolation• Mechanical incompatibility
• Postmating RIMs• Sperm-egg incompatibility• Zygote inviability• Embryonic or fetal inviability• Offspring inviability• Offspring sterility
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Classification and Evolution (cont’d)
• The Origin of Species: how species are formed– Anagenesis– Cladogenesis– Allopatric speciation– Parapatric speciation– Sympatric speciation
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Classification and Evolution (cont’d)
• The Tempo of Speciation– Gradualism• Darwinian• Gaps?
• Macroevolution– Punctuated equilibrium
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Classification and Evolution (cont’d)
• Adaptation
Adaptations are evolved phenotypic traits that
increase an organism’s reproductive success
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Classification and Evolution (cont’d)
Adaptations are evolved phenotypic traits that
increase an organism’s reproductive success
adaptionism reductionism
• Is Everything Adaptive?
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Classification and Evolution (cont’d)
(p + q)2 = p2 + 2pq + q2 = 1
Hardy-Weinberg Equilibrium
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Levels of Selection
• Group selection• Inclusive Fitness – Behavioral ecology• Kin selection• Coefficient of relatedness rb > c
– Hamilton’s Rule
