Reading focus
Syllabus: How Does Evolution Help Explain Behavior?
Separate immediate developmental responses, heritable variation in those responses, and evolutionary change in their regulation.
Why you’re reading it. Add the origin of variation to the earlier questions about function and comparative history.
A question to consider. A new foraging opportunity changes behavior within a generation: what observations would distinguish repeated learning from genetic accommodation across generations?
Why this reading
Selection requires variation, but explaining its origin is a separate task. West-Eberhard argues that development can reorganize existing capacities into new forms that subsequently undergo genetic change. The paper links environmental responsiveness to evolutionary hypotheses.
Before you read
Plasticity is the capacity to develop differently under different conditions. Developmental recombination reorganizes an existing phenotype. Genetic accommodation changes the inherited regulation or form of a trait through selection. A change within one organism is not itself evidence of change across generations.
Read for
- Use the stickleback example to distinguish a developmental possibility from evidence establishing the history of species differences.
- Identify where heritable variation and selection enter the argument, and which observations would test the proposed order of events.
Consider afterwards
- A changed diet alters a fish's form and behavior. What further evidence would establish genetic accommodation?
- Could selection favor maintaining plasticity rather than fixing one form?
Editorial context
This is a theoretical synthesis, with examples of differing evidential strength. It does not establish that environmental induction always precedes genetic change. Sommer's later review develops mechanistic and comparative tests while retaining open questions about genetic assimilation. Plasticity can contribute to evolutionary explanation without replacing selection.