Lecture 4 - Introduction to Theoretical Evolutionary Biology
I. VERY brief historical background:
See article by Betty Smocovitis
- The view of biological species (and the Universe) from antiquity was that species were
fixed entities, stems from Aristotle and especially Plato, consistent with biblical account
- 1809: Lamarck proposes first formal, coherent theory of evolution.
Salient features are
origins of living forms, life evolves from the simple to the complex, traits change
by use and disuse (e.g., giraffe's neck), and acquired characters are heritable.
- 1858: Darwin and Wallace present their papers on Evolution by Nat Seln to Linnean
Society of London; each inspired by geographic variation, and read Malthus; Darwin
particularly inspired by plant and animal breeding.
- 1859 Origin published; Evolution
("transmutation") quickly accepted, NS as the
- Objections to Evol by NS: Fossil record, lack of intermediate forms; "utility of form",
i.e., highly adapted and complex structures, e.g., the vertebrate eye; age of the Earth
(calculated at ~25,000 yrs by Lord Kelvin); especially the putative mechanism of
heredity, i.e., blending inheritance, as argued by Jenkin.
Non-Darwinian theories of evolution
; inheritance of acquired modifications.
proposed inheritance of acquired characters; prevalent form of evolutionism in the late
Weismann (1893); embryologist, selectionist, proposed separate germ-
line and soma, proposed chromosomes as the "seat of heredity", refuted inheritance of
(popular among paleontologists): variation directed toward fixed
goals, species evolves in a pre-determined direction, some argued that trends need not
be adaptive, and the ultimate goal was extinction.
No mechanism ever proposed.
: Mendel rediscovered ca. 1900, clearly establishing the discrete
nature of heredity.
From that first principle, the Ms argued that mutations with discrete,
large effects drove evolution, small continuous variation unimportant.
In the early 20th
century selectionists were represented by the "Biometricians", who were (as it happens)
the fathers of modern statistics.
They focused on continuously distributed variation in
the population and made statistical arguments for natural selection as the mechanism of
The geneticists were experimentalists, among them De Vries (