How is evolutionary (genetic) change measured, and how is the cause determined?
- Deviation from the proportions of gene frequencies and genotype frequencies as defined by the Hardy– Weinberg law of equilibrium is used to measure evolu- tionary change.
- There is no apparent evolution of a gene in a popula- tion if there is no change in frequency over time.
- If gene frequency is changing, then evolution is likely occurring owing to one or more forces of evolution, but the Hardy–Weinberg law does not indicate which particular force (or forces) is the cause. The scientist examines the context for change, such as change in climate, migration of populations across territorial or geographic boundaries, introduction of new diseases, and change in diet.