Copyright © 2013 Pearson Education, Inc. All rights reserved. Exploring Biological Anthropology: The Essentials, 3rd Edition CRAIG STANFORD JOHN S. ALLEN SUSAN C. ANTÓN * As you work through this set of chapter slides, keep in mind the notations that are included from your instructor. Open, read carefully, download if necessary, and use in conjunction with your reading and video lesson study. All these components supplement each other. The wise student will keep this in mind. Copyright © 2013 Pearson Education, Inc. All rights reserved. Chapter 5 The Forces of Evolution And The Formation of Species * Consider the following and keep it in mind: a. Earth 4.5 billion years; b. Life on earth appears around 3.5 billion years ago c. Evolves from simple to compound to complex forms Copyright © 2013 Pearson Education, Inc. All rights reserved. How Evolution WorksWhere Does Variation Come From? Mutations Point mutationChromosomal mutation * Genetic (allele) mutation & variation is the basis of all evolution. Without this evolution will not happen. Nature influences the frequency of alleles in a population. Nature RESHUFFLES THE GENETIC DECK OF CARDS. Copyright © 2013 Pearson Education, Inc. All rights reserved. How Evolution Works (cont’d) How Natural Selection Works Phenotypes in environmentsChanges in gene frequenciesDirectional Selection/ Stabilizing Selection * Genotype + environment leads to phenotype or overall anatomical characteristics, both visible and invisible Three types of natural selection to remember: Directional selection = a move toward a particular feature, such as from a narrow to a broad beak in the Galapagos finches. Or vice versa! Stabilizing selection--natural selection favors the center (e.g., large---->medium<----small); those individuals near the mean have a higher fertility rate. Disruptive selection--natural selection favors both extremes; individuals near the mean have lower fertility rate. Small<--------->large; favors both ends of spectrum. Copyright © 2013 Pearson Education, Inc. All rights reserved. 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 * a. Gene flow: New alleles are introduced to a population. b. Genetic Drift: With “genetic drift”, by chance, all alleles in a population will NOT be represented proportionally in the next generation. c. Founder Effect: A segment of a population migrates to another area (e.g., the AMISH) and may become the founding population for a later group that will result. Due to the very small genetic pool, down drastically from original larger pool, there is a tendency toward “bottlenecking.” No, silly, not hugging a bottle! What was originally a big pond of genetic possibili.

1. Copyright © 2013 Pearson Education, Inc. All rights reserved.
Exploring Biological Anthropology:
The Essentials, 3rd Edition
CRAIG STANFORD
JOHN S. ALLEN
SUSAN C. ANTÓN
*
As you work through this set of chapter slides, keep in mind the
notations that are included from your instructor. Open, read
carefully, download if necessary, and use in conjunction with
your reading and video lesson study. All these components
supplement each other. The wise student will keep this in mind.
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Chapter 5
The Forces of Evolution And The Formation of Species
*
Consider the following and keep it in mind:
a. Earth 4.5 billion years;

2. b. Life on earth appears around 3.5 billion years ago
c. Evolves from simple to compound to complex forms
Copyright © 2013 Pearson Education, Inc. All rights reserved.
How Evolution WorksWhere Does Variation Come From?
Mutations Point mutationChromosomal mutation
*
Genetic (allele) mutation & variation is the basis of all
evolution. Without this evolution will not happen.
Nature influences the frequency of alleles in a population.
Nature RESHUFFLES THE GENETIC DECK OF CARDS.
Copyright © 2013 Pearson Education, Inc. All rights reserved.
How Evolution Works (cont’d)
How Natural Selection Works
Phenotypes in environmentsChanges in gene
frequenciesDirectional Selection/ Stabilizing Selection
*
Genotype + environment leads to phenotype or overall
anatomical characteristics, both visible and invisible
Three types of natural selection to remember:
Directional selection = a move toward a particular feature, such

3. as from a narrow to a broad beak in the Galapagos finches. Or
vice versa!
Stabilizing selection--natural selection favors the center (e.g.,
large---->medium<----small); those individuals near the mean
have a higher fertility rate.
Disruptive selection--natural selection favors both extremes;
individuals near the mean have lower fertility rate. Small<------
--->large; favors both ends of spectrum.
Copyright © 2013 Pearson Education, Inc. All rights reserved.
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
*
a. Gene flow: New alleles are introduced to a population.
b. Genetic Drift: With “genetic drift”, by chance, all
alleles in a population will NOT be represented proportionally
in the next generation.
c. Founder Effect: A segment of a population migrates to
another area (e.g., the AMISH) and may become the founding
population for a later group that will result. Due to the very
small genetic pool, down drastically from original larger pool,
there is a tendency toward “bottlenecking.” No, silly, not

4. hugging a bottle! What was originally a big pond of genetic
possibilities is now a much narrower one. Guess what the
danger is here? Check the book on it.
d. sexual selection leads to changes in gene frequencies
from generation to generation. Individuals consciously choose
mates: cute, wealthy, stable, smart, etc.
Types of nonrandom mating are CONSANGUINOUS
mating, CROSS-COUSIN Preferential marriage,
ASSORTATIVE mating.
Consanguineous mating (Inbreeding)
Cross-cousin preferential marriage -- you marry at the
outer fringes of your available cousins. (See textbook on this
one.)
Assortative mating: We pick from an assortment of
possibilities out in the general population.
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Classification and EvolutionTaxonomy and
SpeciationSystematics: 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
historyConvergent (parallel)
evolutionCladisticsCladogramsPhenetics: numerical taxonomy
*
Central to the scientific study of the diversity of life is the
science of classifying organisms into different categories is

5. known as taxonomy.
Linnaeus published the 10th edition of his classification of
the living world in 1758. He developed or elaborated on the
binomial system of genus & species
TERMINOLOGY: homology, analogy, convergent &
parallel evolution
Anagenesis = evolution of a trait or a species in a
“straight” line of development.
Cladogram (branching diagram showing evolutionary
relationships) No time scales are involved.
Phylum. See Linnaeus’s Classification System: The
hierarchy goes like this….
Kingdom-->Phylum-->Class-->Order-->Family--
>Genus-->Species
[Look up “phenetics” and just be aware of its meaning.]
Copyright © 2013 Pearson Education, Inc. All rights reserved.
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 conceptEvolutionary species
conceptEcological species conceptRecognition species concept
*

6. *** WHAT IS A SPECIES? (p.92) It is “an interbreeding group
of animals or plants that are reproductively isolated through
anatomy, ecology, behavior, or geographical distribution from
all other such groups.” (p.92) [Page numbers may vary; check
your book.]
*** SPECIES CONCEPTS (see Box 5.1 p.93) Consider the
difficulties with just how the species concept is applied.
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Classification and Evolution (cont’d)
Species ConceptsBiological species conceptEvolutionary
species conceptEcological species conceptRecognition species
concept
*
Refer to textbook here. This material is important to grasp as
we move forward. See especially pp. 90-92.
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Classification and Evolution (cont’d)Reproductive Isolating
Mechanisms (RIMs)Any factor that prevents a male and female
of two different species from hybridizing
Premating RIMsPostmating RIMs
*
*** REPRODUCTIVE ISOLATING MECHANISMS: (see
table 9.2 p.94) The elimination of gene flow between demes,
usually the result of some type of geographical barrier, allows

7. for the accumulation of different mutations within a deme.
(p.105-6) See also next slide on all of this.
Reproductive isolating mechanisms may be external or
internal:
A. External Factors: (all pre-mating) Ecological
isolation, seasonal isolation, sexual isolation (can’t attract),
mechanical isolation.
B. Internal Factors: Gametic mortality (sperm
immobilized); zygotic mortality--developing egg “dies”
C. At or After Birth: (Post-mating) hybrid inviability
(offspring die), and hybrid sterility.
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Classification and Evolution (cont’d)Premating RIMsHabitat
isolationTemporal isolationBehavioral isolationMechanical
incompatibility
Postmating RIMsSperm-egg incompatibilityZygote
inviabilityEmbryonic or fetal inviabilityOffspring
inviabilityOffspring sterility
*
Read in conjunction with previous slide.
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Classification and Evolution (cont’d)The Origin of Species:
how species are formedAnagenesisCladogenesisAllopatric
speciationParapatric speciationSympatric speciation

8. *
*** HOW SPECIES ARE GENERATED OR FORMED:
Allopatric species arise due to geographical isolation (fig
5.11 p.95)
Parapatric species results when two populations or
communities (of same species) live near or next to each other
over a wide territory.
[See textbook for Anagenesis, Cladogenesis, and Sympatric
Speciation.]
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Classification and Evolution (cont’d)The Tempo of
SpeciationGradualismDarwinianGaps?
MacroevolutionPunctuated equilibrium
*
*** TEMPO OF EVOLUTION: (p.96) There are two views
of the usual tempo of evolutionary change:
Phyletic gradualism and Punctuated equilibrium.
Phyletic (phylum) gradualism: slow & gradual
transformation. (Darwin’s view)
Punctuated gradualism/equilibrium: The normally gradual
pace of evolutionary change is interrupted by shifts in tempo;
evolutionary “bursts” occur.

9. Copyright © 2013 Pearson Education, Inc. All rights reserved.
Classification and Evolution (cont’d)
Adaptation
Adaptations are evolved phenotypic traits that
increase an organism’s reproductive success
*
*** ADAPTATION (adaptive radiation) The movement
of species into a new ecological niche. Four Factors are
required:
1. No barriers
2. There is a variety of niches
3. The newcomers are pre-adapted
4. Either the new niche is unoccupied or the
newcomers are able to compete successfully for resources.
* Extinction: (This is NOT an unusual event.)
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Classification and Evolution (cont’d)
Adaptations are evolved phenotypic traits that
increase an organism’s reproductive success
adaptionism
reductionism
Is Everything Adaptive?

10. *
Adaptationism: The entire organism changes and not just
one element or trait.
Reductionism (e.g., Gould p.97): only specific traits
evolve.
Example: Is it just the Hummingbird’s beak or all of
the Hummer that will adapt?
Copyright © 2013 Pearson Education, Inc. All rights reserved.
Classification and Evolution (cont’d)
(p + q)2 = p2 + 2pq + q2 = 1
Hardy-Weinberg Equilibrium
*
“Evolution” A population is evolving IF the frequencies of its
alleles are changing. No change, no evolution = Genetic
equilibrium.
However, because the forces of evolution are always present,
genetic equilibrium can only be “a hypothetical” state. Why
have the H-W Equilibrium formula?
The Hardy-Weinberg formula allows us to measure the strength
of evolutionary forces by making comparisons between the
hypothetical situation of no change and change that is observed
in real life situations. Godfrey Hardy and Wilhelm Weinberg
developed the formula in 1908. And NO, you will not be
expected to use it; just understand it’s reason for being.

11. Copyright © 2013 Pearson Education, Inc. All rights reserved.
Levels of SelectionGroup selectionInclusive Fitness Behavioral
ecologyKin selectionCoefficient of relatedness rb > cHamilton’s
Rule
*
INCLUSIVE FITNESS: (p.100) The individual’s own
fitness plus his or her effect on the fitness of any relative.
With kin selection, the individual contributes to
his or her reproductive success either by:
1. Actually picking a partner, or
2. Acting in an altruistic manner that allows his or
her kin to be reproductively successful. [Wolves in the wild;
humans, too.]
The Coefficient of relatedness: The number of shared
alleles decreases as our relationship becomes more and more
removed from a common point of origin. Grandparents will
differ markedly from their distant grandchildren (e.g., several
generations removed the chance of like alleles being present
will become less and less.)