Download 2011 Essay 2

Biology 14
Second Essay Assignment, due Thursday, March 24 at 11:30 AM
Spring, 2011
Four typewritten, double spaced pages. Minimize introductory remarks and summary, get right to
the point, assume your reader understands what you are writing about, and use all four pages.
Take the time to make your writing clear, pithy and succinct.
The extensions of the theory of natural selection that explain the evolution of social behaviors are
kin selection, reciprocal altruism, parent-offspring conflict, and sexual selection.. State what these
mechanisms are and why, in the light of the kinds and frequency of social behaviors we find in animals
and humans (aggressive, cooperative, conflict, selfishness, altruistic, spite, etc), these mechanisms do or
do not provide adequate explanations for social behaviors. Include discussion of the possible levels at
which natural selection acts and why these four kinds of natural selection must be thought of as acting
proximately (during an individual’s lifetime) on an individual’s phenotype, but ultimately (from one
generation to the next) on the individual genes/alleles that an organism passes on to its offspring. Is group
selection a likely mechanism of social evolution?
Writing this essay requires an understanding of the lectures, reading and handouts in sections (a)
through (f) of the section of the course on “Natural Selection and Social Theory” and chapter 6 of the text
(G&Z, Biology, Evolution and Human Nature); so see the syllabus for what these are. One article from
the previous section of the course, Dawkins’ “God’s Utility Function” is also relevant. The handouts that
are particularly pertinent include those on kin selection in social Hymenoptera/ bees, the summary of
evolutionary social theories and the handout on level of natural selection; a lot of what is in these
handouts repeats what is/ was in the text and lectures, but they include summaries, re-phrasings and
explications of the ideas that should be helpful, The handout on “levels of natural selection” should
definitely be understood for your thinking about the essay topic.
It should help your thinking about the evidence for/ against group selection to know that Darwin
thought that the evolution of sterile reproductive castes (female worker) in social insects (bees, ants,
wasps) was a fatal objection to his theory of natural selection because he could not imagine how an
individual (female worker) could evolve to be sterile!!! So he argued that it was the reproductive success
of the colony as a whole---the queen, the workers and the drones together as unit---that was the cause of
their social evolution. In other words, he invoked group selection: those bee colonies that out-reproduced
other bee colonies (by having a sterile caste, the female workers who do all the work, and a single
reproducer, the queen) left more descendant bee colonies than others that did not have reproductive
“division of labor” by sterile castes. Note that Hamilton’s theory of kin selection seems to account for the
evolution of sterile castes (reproductive altruism) AS WELL AS for the other highly non-altruistic
behaviors in bee hives (see handout) that are wasteful and thus bad for the colony as a whole. You
might also consider lots of behaviors (conflict, infanticide, siblicide, dominance fighting, territory
defense, mating competition, mate choice, etc) and encumbering structures (horns, antlers, male lion
manes, peacock tails, etc) in the same way---good for the genes underlying them but bad/ wasteful/
inefficient for the perpetuation of the group (population, species) as a whole. By the way Darwin also
thought that human moral “instincts” ---which he thought of (as a good Victorian Englishman and son of
a doctor!!) only as indiscriminate altruism for the good of everyone in the group---evolved by group
selection. That is, he argued, human groups with more, highly moral people in them were more successful
in competing with other human groups over time.