Darwin's Reasoning About Common Ancestry

Elliott Sober will discuss three of Darwin's guiding assumptions about common ancestry:

(1) Similarity is evidence for common ancestry.

(2) Adaptive similarities provide meager evidence for common ancestry while nonadaptive similarities provide stronger evidence.

(3) The fact of common ancestry can be used to infer characteristics of ancestors and thereby test hypotheses about natural selection.

Elliot Sober will use the Law of Likelihood (so named by Ian Hacking) to analyze these assumptions.