In this lecture, we review the four forces of evolution -- mutation, migration/gene flow, genetic drift, and natural selection -- and the contribution that each one makes to either increasing or decreasing variance in a population over time. So a more complete picture of evolution is a tense combination of these forces, each of them leading to different kinds of effects on the distribution of alleles (strategies) in a population. We discuss how the tendency for natural selection to produce higher quality solutions is ultimately limited by genetic drift that dominates when populations have low fitness diversity (low selective pressure), and we discuss how this sets up a speed–accuracy tradeoff between mutation (which counteracts drift in a way that does not require more time for convergence but makes it impossible to fine tune solutions) and population size (which can fine tune solutions but requires a longer time to converge to a good solution). Selection operators and evolutionary hyper-parameters should be chosen with these pressures and tradeoffs in mind.
Whiteboard notes for this lecture are archived at:
https://www.dropbox.com/scl/fi/09u3vd7l3m9h68pc5uyr9/IEE598-Lecture1D-2024-01-28-The_Four_Forces_of_Evolution_and_The_Drift_Barrier-Notes.pdf?rlkey=u4id8rcd9ou45og4eqxx5fu38&dl=0
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