Transcript Evolutionary Theory, according to Darwin

Evolutionary Theory, according to Darwin
Definitions and Components of Darwin’s Evolution
• Definition of Biological Change: Differential
Persistence of Variation… Now, what does that
mean? ( AND THIS IS WHAT DARWIN WANTED TO
EXPLAIN)
• Definition of Evolution: Descent with Modification.
– And what does that mean?
– Individuals Vary--- (materialism). Only variation is real!
– Some variation is inheritable, meaning that some observable
variation is inherited from our parents, and some variation is
unique to us.
– Individuals vary in their reproductive success. Some
individuals leave 10 progeny; some individuals leave no
offspring.
• Differences in reproductive success is known as
FITNESS. The Individual who leaves 10 offspring is, in Darwinian
terms “more fit” than individuals who leave only 2 offspring
So what about Adaptation? What is Adaptation?
Adaptation is the consequence (or outcome) of
reproductive success.
If individuals reproduce and their offspring
live to reproduce, the parents are by definition
adapted. Adaptation is a consequence of
reproducing. And adaptation is closely related
to fitness.
Fitness and adaptation are closely related:
If I have 2 children, and you have 10 children
and all of our children live to reproduce, you
are by definition more fit and better adapted
than I am.
What are the causes (mechanisms) in variation
in reproductive success?
• Natural Selection: a concept to Darwin all
the factors in any setting that resulted in
differences in reproduction. There are no
universal selective agents. There are only
agents that affect reproduction in particular
historical settings.
• (after Genetics was discovered, genetic drift
was added as a mechanism of reproductive
success)
SUMMARY
In contemporary evolutionary science, there
are two parts to the differential persistence
of variation:
1) variation at the scale of individuals.
2) Mechanisms of evolution, natural
selection and drift, operate on that variation
so that over time, there is differential
persistence of variation.
Herbert Spencer: Socal
Darwinism
Books:
Principles of Ethics
Principles of Biology
Principles of Psychology
Principles of Sociology
First Principles of the System of Philosophy
Components of Social Darwinism
• Definition of Change: “Transformation” from
relatively incoherent to relative coherent. [analogy
with organic life; higher life forms are more complex
and more coherent than lower life forms]
• With transformation, there is an increase in
coherence and an increase in functional
specialization.
Spencer’s Assumptions
1. All life was a single unbroken chain… all life
connected and transformed [unlinear …one line]
2.Causes of transformation were inherent to life itself.
(Unlike Darwinism, there were no mechanisms that
winnowed variation)
in the 19th Century, this was the “doctrine of
progress”
Inherent directionality to all life that transformed
from simple to complex.
3. The inherent direction was “hard”wired into
organisms. Some organisms could progress
further than other organisms.
Marriage of biology and culture is the third assumption
SPENCER’S CULTURAL EVOLUTION
• Inherent transformation toward greater complexity
charactized humans
• The phrase for that transformation was ”survival of
the fittest” . What he meant by that phrase was a
kind of natural transformation driven by the inherent
nature of humans.
– The phrase was misinterpreted with natural transformation
equated with “good”. Those most capable of
transformation survive.
• Became a justification for the scaling of societies from
simple to complex in the 19th C.
• Darwin liked the phrase and said that in the context of
natural selected it explained adaptation. Survival of the
fittest explains differential persistence of variation
Contrast between Darwin and Spencer
Darwin
Spencer
Evolution
Descent with
Modification
Transformation
Components
Variation
And selection
Mechanism
Internal; hardwired
“natural
Selection”
Cause
Description Bush
of evolution
change
Single line
20th Century Anthropological Evolution:
Neo Evolution
Julian Steward
Leslie White
Leslie White
• Major assumption: human cultural development is
unique. We need unique laws to explain it.
– Evidence of uniqueness: language, symbolism
– Cultural laws must explain cultural evolution
• Influences on his Intellectual framework: Spencer
and Marx
• From Spencer:
– cultural development really is progressive. Human cultures
develops from simple to complex. Progess is a fact!
– The development of culture is unilinear [one large trunk]
• From Marx:
– Fundamental to understanding cultural change is
economics or the modes of production. Modes of
production underlie all other changes.
– Science was the was of understanding and explaining those
changes.
Leslie White (con’t)
• How he modified and used his intellectual guides:
1. Progress was inevitable but no hard wired into the
species. No inherent principle to humans that resulted in
greater complexity. AND no value placed on greater
complexity. It simply is.
2. Causes of development are material. They are to be
found in the material conditions of life, economics,
technology, etc.
White’s Cultural Laws
• Law of Evolutionary Development: [C = E x T]
– C = culture; E= energy capture or efficiency (technology); T=
time. (this is technology)
– Examples: unilineal transformation from Bands to Tribes to
chiefdoms to state
• Law of Cultural Dominance: cultures that exploit
energy more efficiently in one environment will
spread at the expense of the less efficient.
Julian Steward: Multilinear Evolution
• Major premise: Culture change occurs because of the
interaction between environmental setting and people in
that setting. Steward is the beginning of cultural ecology
in Anthroplogy.
– Setting places constraints on the choices that individuals make.
– Environment: a broad definition, including terrain, soils,
resources, and other social groups
AND The same cultural expression can occur in vastly different
settings if the constraints are the same:
development of Bands in the Arctic and in the Great Basin
Steward (con’t)
• Culture Core:
that part of a culture that relates
people to their setting… So, to Steward it was the
culture core that linked people to their setting and was
the basis of the cultural expression.
– "the constellation of features which are most closely related
to subsistence activities and economic arrangements"
(Steward 1955:37).
• Differences from White:
• Culture change is not linear or progressive. Change is
locally determined by the setting and the essential
features that relate folks to that setting.
• Technology does not drive culture change… interaction
between organisms and their setting drive change.
Critique of Neo Evolution from both scienitsts and
post-processualists
•
•
•
•
culture evolution is not unique
lineal sequence does not address the
range of variation in societies
post processualists argue that NE
ignores people and fails to consider the
variation within societies.
Neo evolution does not allow for
contingency
Contemporary Archaeological Evolutionary Ideas
Virginia Butler
Laura Betzig
Selectionism and Evolutionary Ecology
• Commonalities
– Both proceed from a platform of science. Building
knowledge is the goal; answering WHY questions
– Actively building theory. In fact, both have theory,
and that theory is Darwinian Evolution
• Consequently Darwinian principles and
mechanisms apply: individuals vary, heritable
variation, reproduction matters, mechanisms
operate on and winnow variation resulting in
differential persistence
Selection operates on the Phenotype
What is the phenotype?
Menstral Hut
Bower Bird
Male Peacock
DIFFERENCES
• Selectionism: Goal is to explain the
archaeological record… ARTIFACTS in
evolutionary terms
• Human Evolutionary Ecology: explain
human behavior in evolutionary terms.
Use evolutionary principles to account
for human behavior… foraging
strategies, mating systems, birth
spacing
Selectionism ( Robert Dunnell)
• Key Components of his Ideas:
materialism, archaeology as
an historical science and
explanation
• Artifacts are the focus of
explanation: Why new forms,
technologies evolve?
• Artifacts are part of the human
phenotype. Therefore
selection operates on artifacts
• Connect artifacts to two step
evolutionary process
– Produce variation; winnow
variation
Methodology of Selectionism
• Style: those artifact traits that do not contribute to
reproductive success
• Function: artifact traits that contribute to affect
reproductive success
• Mechanisms:
• Selection operates on functional traits, and those
traits show directional changes in frequencies over
time (selection operates on functional traits)
• Drift: random changes in gene frequencies
(drift operates on stylistic traits)
Frequency
Function
Frequency
Style
Time
Shape of Stylistic versus Functional
Trait through time
Time
Shape of selection curves
operating on two alternative
functional traits over time
How Operationalize?
• Select artifact traits to measure…
forms, technology, attributes--like corner and side notching
• Must be able to measure artifact
traits over time… have to have the
temporal dimension
• Count frequencies over time and
construct curves
• Curve shapes tell you whether
• Selection or drift is occurring
– This is an evolutionary
description
• The WHY in evolutionary terms
Critique of Selectionism
We’ll do this together…