Evolution
A Brief and Idiosyncratic
History of the Concept of
Evolution
or why we think we know how we
got here
Pre-scientific World View
•Understanding of the universe was based on
the interpretation of supernatural concepts
•There were two long-standing notions that
impeded the development of the concept of
evolution:
–Fixity of species: stasis or lack of change through
time
–Relatively short duration since the creation of the
earth
•The concept of evolution is used widely
across subdisciplines in anthropology
•Most broadly construed, evolution simply
means change
•Archaeologists, ethnohistorians focus on
social and cultural evolution
•Physical anthropologists borrow the central
paradigm of modern biology, organic
evolution by natural selection, as an
organizing principle
Archbishop James Ussher
(1581-1656)
•A scholar in the pre-scientific tradition,
Ussher used a literal interpretation of the
bible to estimate the time of creation
–By evaluating how many years individuals
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estimate that the earth was created in 4,004
B.C.
•Refined by other scholars: 9:00 a.m., October 23,
4,0004 B.C.
–I.e., the earth was less than 6,000 years old
Scientific Revolution
•Science provided a framework to
attempt to discover the Natural Laws or
fundamental principles that govern the
universe
•The procedure includes
–The formulation of testable hypotheses
–The application of empiricism, the
collection of data to test the hypotheses
Carolus Linnaeus
(1707-1778)
•Proposed a basis for taxonomy--a
hierarchical classification of organisms
into multiple levels
–Attempted to discover the grand design of
the Scale of Being
–Accepted fixity of species, as created
•Binomial Nomenclature: Genus and
species
–Homo sapiens for man
1
Jean Baptiste Lamarck
(1744 - 1829)
•Evolution of species according to fixed laws
–Species adapt to changing environment by
use/disuse of organs
–Systems develop according to wants & needs of
organism
•e.g., fish in drying lake develop lungs as needed for
oxygen
–Proposed mechanism: Inheritance of acquired
characteristics
Charles Lyell
(1797 - 1875)
•Uniformitarianism
–Geological processes same in past as
they are today
–Slow, gradual process of earth's
formation
–Earth vastly older than estimated by
clerics
Charles Darwin
(1809-1882)
•During the 5 year cruise of the Beagle,
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Principles of Geology, and became
convinced of the transmutability of
species
•After returning home, a reading of
Malthus finally triggered the notion of
natural selection as the mechanism
driving evolution
Georges Cuvier
(1769-1832)
•Pope of Bones--Father of
Paleontology
•Believed in the fixity of species
•Proposed Catastrophism from
natural causes as a mechanism to
produce fossils
Thomas Malthus
(1766-1834)
•English clergyman and economist
•An Essay on the Principle of Population
(1798):
–Population growth potentially exceeds increases in
food resources
–In nature, overpopulation is checked by a struggle
for existence between members of a species
–Not all organisms secure adequate food every
generation
–Most individuals die, leaving only a few who
survive to perpetuate the species
Alfred Russel Wallace
(1823-1913)
•Came to the same conclusions about
evolution by natural selection as a result
of his work in the Malayan Archipelago
•Wallace became a fervent selectionist,
ending up not believing in human
evolution because he could not envision
the adaptive purpose for the human
mind
2
Thomas Huxley
(1825 - 1895)
Principles of Natural Selection
•Acquainted with both Darwin and Wallace
•Uponr
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proponent of evolution by natural selection in
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•Offspring produced faster than food supply
increases
•All living organisms vary (especially to be
noted between members of the same
species)
•Because more individuals are born than
survive, there is a struggle for existence
•Those individuals with favorable adaptations
are most likely to survive and leave offspring,
sometimes known as survival of the fittest
Principles of Natural Selection
Principles of Natural Selection
•The environment determines which traits are
beneficial and which are not
•As a result, individuals with favorable
adaptations increase in relative number from
generation to generation
–Traits that are favorable in one setting may be
harmful in another
–Greater and greater numbers and proportions
within the species have the adaptation
•Traits are inherited and passed on in a
relatively stable way to the next generation
•Over long periods of time, such successful
variations (favorable adaptations) produce
differences that result in the formation of new
species
–That is, offspring tend to resemble their parents
and reflect the variations possessed by their
parents
Darwinian Evolution
Darwin's Evidence
Species A
Environmental
Change
Species B
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•The way that changes are bred into
domesticated organisms, especially pigeons
•Geographic distribution of species such as
the finches of the Galapagos Islands
•The geological and paleontological record
•Comparative anatomy (e.g., the resemblance
between apes and man)
•Embryology (e.g., the possession of gills by
mammalian embryos)
Species A
3
Darwin's Failures
•Never understood the source of the
variation that is so important for the
operation of natural selection
–Mutation
•Never understood the nature of
inheritance, in spite of having a reprint
ofMendel
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Theodosius Dobzhansky
–Particulate Inheritance
Simultaneous Rediscovery of
Mendel (1900)
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evolutionary terms is not to
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•Hugo de Vries, Holland
•Erich von Tschermak, Austria
•Carl Correns, Germany
Sir Peter Medawar
Basis of population genetics-equilibrium model
•William E. Castle, 1903, American
animal breeder
•Godfrey H. Hardy, 1908, British
mathematician
•Wilhelm Weinberg, 1908, German
physician
Development of Population
Genetics from H-W Model
•R.A. Fisher, 1930, The Genetical
Theory of Natural Selection
•J.B.S. Haldane, 1932, The Causes of
Evolution
•Sewall Wright, 1931, Evolution in
Mendelian Populations
4
Synthesis of genetics and
Darwinism
•Theodosius Dobzhansky, 1937,
Genetics and the Origin of Species
•Julian S. Huxley, 1942, Evolution. The
Modern Synthesis
•Ernst Mayr, 1942, Systematics and the
Origin of Species
Biological Species Concept
•Shortcomings of concept:
–Restricted to sexually reproducing organisms, so
does not apply to single cell organisms that
reproduce by simple cell division (mitosis)
–No clear application to the fossil record, since
reproductive isolation does not show up in
fossilized materials
Biological Species Concept
•Species are groups of interbreeding
natural populations that are
reproductively isolated from other
such groups (Mayr, 1963)
–Defines species in terms of the gene pool,
isolated from other similar gene pools
Paleospecies
•A paleospecies or chronospecies is a
morphologically or anatomically defined
fossil species
–Since interbreeding is not determinable for
extinct species, species boundaries are
determined by similarity of form
•Still most useful concept to understand the
evolution of species
Speciation
•The process by which new species are
produced from earlier ones. This is the
central process of macroevolution, or
evolution at the level of the species or
above
–Microevolution involves evolutionary
change at the level of the population, and
is defined by changes in allele frequencies
within the population
Origin of Species
•Speciation occurs when populations of
a species become reproductively
isolated so that they can no longer
interbreed with full fertility
–Geographic isolation of populations usually
initiates the process
–Selection operates to produce isolating
mechanisms of anatomy, behavior, etc.
5
Modes of Evolution
•Cladogenesis is branching evolution,
the production of two or more daughter
species from a single ancestral species
•Anagenesis is linear evolution, the
production of a single daughter species
from a single ancestral species
Tempo of Evolution
•Gradualism views evolutionary change as
occurring at a slow, steady rate over time
•Punctuated Equilibrium views the tempo of
evolution as consisting of long periods of
stability (equilibrium), followed by relatively
short periods of rapid evolutionary change
(punctuations)
Tempo of Evolution
a. Gradual change through time
b. Increasing rate of change through time
c. Punctuated equilibrium: stasis and bursts of
change
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