Key
concepts. The human mind is designed to
function within human time scales and in a purposeful manner. Human thought needs
to structure its understanding of the important evolutionary processes. To balance
our tendency to short term and overly purposeful thought: 1) scientific
theories will be contrasted to folk theories and scientific history with folk
history, 2) phylogenetics will be contrasted to orthogenetics, 3) chaos theory
will be contrasted to the “purpose-chance dichotomy”, and 4) neutral traits
will be contrasted to selectively advantageous or disadvantageous ones.
Overview. The study of evolutionary history relies on
genealogical theory, which assumes that all alleles, genes, individuals, populations,
and higher taxa (species, genera, etc.) that have ever existed were born from
pre-existing alleles, genes, individuals, populations, and higher taxa,
respectively. The forces shaping genealogies are mutation, drift, and selection.
The first two are stochastic and the last is deterministic. Four main areas
will be covered during the last half of the semester. 1) recent population
divergence, which is studied with population genetic approaches including
calculating Fst values from which phylogenies can be reconstructed; 2) old
population divergence including speciation, which includes the study of DNA
sequence information and sometimes morphology and the reconstruction of
phylogenies using such methods as cladistic; 3) the application of phylogenetic
knowledge to the study of such areas as epidemiology and adaptation, and 4)
human evolution, about which modern evolutionary theory and evidence has much
to say, including why it might be good to know something about our innate
tendencies.
1.
Scientific theory. Folk histories are
creation myths that give purpose to a particular people, place and time. The
origin of American
baseball is an excellent example of a folk history. Abner Doubleday, a
civil war hero, invented American baseball during 1839 in Cooperstown, New
York. The Baseball Hall of Fame and the Doubleday Field in Cooperstown honor
this event. Baseball, however, evolved over 200 years from stick-and-ball games
played by the lower class in at least England. Regardless, the myth of baseball
serves to distinguish American culture from others (e.g., British). In folk
theories or histories, facts fit the purpose of distinguishing a particular
people, place, and time (i.e., culture).
Scientific
theory bearing on history (geology, cosmology, and evolutionary biology)
provides no evidence of purpose for particular peoples, places, and times. In
the historical sciences, like all of science, theories explain the factual
state of the world. For example, the theory of natural selection explains the
balance of cooperation and selfishness in social animals (pp. 471-477), and why
in human societies true communism is not predicted to endure whereas fascism
and racism unfortunately are, or why “transparency” during social interactions should
be promoted because it will bring out the better part of human behavior.
2.
Phylogenetics is the study of
relationships among alleles, genes, populations, species, and higher taxa
(genealogy in popular parlance focuses on the relationships among individuals).
Phylogenetics helps counter the tendency for an orthogenetic view.
Orthogenetics, one of the components of Lamarckian evolution and an overly
purposeful way of thinking about evolutionary history, is directed evolution from
primitive to advanced forms (i.e., unperfected to perfected, inferior to
superior, or lower to higher). The concept of phylogeny suggests that all
living beings, from alleles to higher taxa, are related to varying degrees and each
is specialized to a particular environment.
3.
Chaos Theory. Chaos theory (e.g., J.
Gleick, 1987. Chaos: making a new science. Viking, Penguin) describes
evolutionary history well: the interaction of deterministic (purposeful) and
stochastic (chance within bounds) processes that gives rise to complexity often
with fractal symmetry. Genealogies are shaped by the interaction of deterministic
(adaptation via natural section) and stochastic processes (mutation and genetic
drift). Scientific theories, in contrast to folk histories, are not strictly purposeful.
Fractal geometry is also part of chaos theory and relates to evolutionary
biology in that the allele, gene, individual, population, and higher taxon phylogenies
are superimposed on each other are subject to the same deterministic and
stochastic processes.
4.
Neutral traits. Neutral variants have a
fitness of 1 or nearly so (i.e., selectively equivalent). Neutral variation is
most informative historically because it comprises similarity not due to
functional constraint. Neutral variation is analogous to surname variation
– it is arbitrary and needs no purposeful explanation. Shared similarity
in neutral variation can thus be explained only by inheritance from a common
ancestor (i.e., homology).