1
The Evidence for Evolution
I. THEORIES and THE SCIENTIFIC APPROACH
A. What is a Hypothesis?
1) A hypothesis is an informed statement of what might be true.
B. What is a Theory?
1) A theory is a mature, coherent body of interconnected statements, based on reasoning and evidence, that
explain a variety of observations.
C. The Theory of Special Creation.
1) Scientific theories have two components:
a. A statement of a pattern that exists, and
b. A process that explains that pattern.
2) For the Theory of Special Creation, the statement of pattern, or facts were:
a. Species were created independently of one another.
b. They do not change through time.
c. They were created recently.
3) For the Theory of Special Creation, the statement of process was:
a. All of the species on act were created by a special, supernatural process – an act of creation by God.
D. Evolutionary Theory.
1) In the Origin of Species, Darwin proposed two large hypotheses.
a. One of these was a statement of pattern – descent with modification, from common ancestors (the
hypothesis of descent with modification.)
b. The cause of this process was: that natural selection sorts among hereditary variations.
II. EVIDENCE FOR DESCENT WITH MODIFICATION
A. Distinguishing among three possible theories of the history of life.
1) So we might want to consider the following three theories.
a. Evolution
b. Transformism, in which species change, but the number of origins of species matches the number of
species present.
c. Separate creation, in which species originate separately and remain fixed.
B. Species were created independently of one another vs. the relatedness of life forms –
Evidence for Common Ancestry.
1) Homology through Comparative Anatomy.
2) Richard Owen (1804-1892) –homology - Organs (or anatomical features) that share fundamental similarities,
yet belonging to different species
a. Idealistic morphology – in which organisms were assumed to have been created according to certain
“archetypes” or “plans”.
b. This is reminiscent of Plato’s philosophy of essentialism.
c. Homologous structures in two species (e.g. the leg of a lizard and the leg of a mammal) as
corresponding parts of the same “plan”.
d. In contrast, Darwin gave homology a historical meaning: organs of two organisms are homologous if
they have been inherited (and perhaps modified) from an equivalent organ in the common ancestor.
3) A character may be homologous among species (e.g. toes), but a given character state may not be (e.g., a
certain number of toes).
4) Darwin concluded that the similarity of structures was not very good evidence that they were created
independently, but were related by common ancestry.
Docsity.com
