Download PHIL 481

Addendum to 481 Jan 13 (bring with you!)
1. In E1, in generation n, the distribution of genotypes is:
AA: .25
Aa: .50
aa: .25
This states some initial conditions.
2. [(x) (AAx  tx) & (x) (Aax  tx)] & (x) (aax  ~tx)
Another statement about initial conditions
3. In E1, the relative fitness2 of type t is 1.0.
4. In E1, the relative fitness2 of type not-t is 0.5.
Clauses 3 and 4 indicate the relative fitness2 of types t and not-t in environment E1.
Yet another (apparent) statement of initial conditions; our question: where did these values
come from? Will show you!
5. For any 3 distinct genotypes, X, Y, Z (generated from a single locus), if the proportions of
X, Y, Z in generations n are P, Q, R, respectively, and if the relative fitnesses2 of genotypes X,
Y, and Z are F(Y) and F(Z), respectively, then the propensity of X in generation n + 1 is:
P  F(X)/P F(X) + Q F(Y) + R F(Z).
This is the consequence of the Hardy-Weinberg Law which allows computation of the
expected frequencies in generation n + 1, given information about reproductive rates at
generation n, together with information about initial frequencies of individuals of each
genotype at generation n. Will unpack tomorrow!
6. EC(E)
Like the “ceteris paribus’ clause that is at work in any explanation (“all things being equal”),
this is called the “extremal cause” in evolutionary theory: “natural selection conditions were
present for the environment in question”
7. Given the size of population P, the probability that the obtained frequencies are due to
chance is less than .001.
Here the size of the population matters (to be explained tomorrow…).
In E1 at generation n + 1 the frequency of genotypes is:
AA: .29
Aa: .57
aa: .14 What clauses 1-7 explain.
PHIL 481
Species (Jan 15)
The role of species in evolutionary theory: necessary?
Are species natural kinds? Individuals? Sets (or classes) of individuals?
Alternatively, is the concept (now) empty?
“What are species?”, as considered in philosophy of biology, is an ontological question. That
is, definitions of species in terms of DNA or interbreeding don’t (automatically, at least)
answer it.
Natural kinds:
Chemical elements (H2O)
Galaxies
Electrons, tau neutrinos
And in biology:
Males (make sperm)
Females (make eggs)
Natural kinds and essentialism
Essentialism and species
Phylogeny: evolutionary and for systematics/cladistics
The different goals of engaging in phylogeny and the different concepts of species involved.
Hull
What are the implications of (current) evolutionary theory for the ontological status of …
species?
Thesis: that species are individuals
Individuals vs. classes: historical entities vs. genuine classes
Generally accepted criteria for individuals:
Spatiotemporal continuity
Unity
Location
Reasons for viewing species as individuals rather than as classes
How does the conceptual shift resolve longstanding anomalies within and about biology?
Baum and Donoghe
Phylogeny and systematics/cladistics
What is phylogeny? What different kinds of question does it include?
What is “character-based” phylogeny? What kinds of question does it address?
Are they important “in their own right”? And are they evolutionary in nature?
What is “evolutionary phylogeny”? How is it different from character-based phylogeny?
What is the argument for the claim that a history-based, rather than a character-based,
species concept is more appropriate?