Epistemic values and an introduction to Evolutionary
From Michael Ruse Mystery of Mysteries (1999):
a contrast to cultural values
Promote the "truth-seeking" nature of science
Epistemic values: a good theory should show
- Predictive accuracy - the power to make forecasts
about what one will find.
- Internal coherance - the parts must fit together
- External consistency - must fit with other
- Unifying power - unites previously unrelated
material under "a single explanatory roof"
- Fertility - makes predictions beyond the original
- Simplicity - Ockham's razor: the simpler of
two competing hypotheses is more likely to be true. Is this too close to nonepistemic
values? An aesthetic preference?
What are we trying to explain?
- Why are there so many species (plants, animals, etc.)?
- How are species related to each other?
- By what process are species formed?
Theory must accommodate these observations
- the earth is very old
- there are fossils of extinct forms
- diversity and complexity increase with time
- organisms show "homologous" structure and
biochemical similarities (DNA)
Natural selection as the mechanism
- similar theories were developed independently by Charles
Darwin and Alfred Russell Wallace
- population a group of interbreeding individuals
of the same species, in a more-or-less definable area.
- fitness the total number of offspring that
an individual leaves behind when it dies
- adaptation a genetically-determined trait that
helps an organism to survive and reproduce in a particular environment; the
process by which such traits evolve.
Evolution by natural selection is a consequence of these
- potential for rapid reproduction most organisms
can produce more offspring than the environment is capable of supporting
- because of condition 1, the availability of resources
(food, water, space, light, etc.) will limit the size of the population
- where there is heritable variation in traits that
influence reproductive success, individuals with those traits should become
increasingly predominant in the population.
As a consequence of the three conditions listed above,
over a long period of time, the frequency of alleles that result in higher fitness
should increase over time.
Note that neither Darwin nor Wallace knew anything about
the mechanisms of inheritance.
The precise definition of evolution, according to the
modern "Neodarwinian synthesis" is: Change in the relative frequencies
of alleles in a population over time. (This definition will make more sense
after the third evolution talk.)
If over a long time, populations become so different
that they are no longer capable of interbreeding, they are then considered to
be different species. This outcome of the evolutionary process is called speciation.