Study
Unpredictable evolution in a 30-year study of Darwin’s finches
Grant, Peter R.; Grant, B. Rosemary
Science, 2002
Measured beak and body dimensions in every individual of two finch populations on Daphne Major across three decades, through droughts, floods and a strong El Niño, tracking survival and reproduction against measured traits.
- Studied in
- Geospiza fortis, Geospiza scandens
- Sample size
- 30 years of continuous measurement on one island
Beak dimensions shifted measurably within a few generations in response to changes in the available seeds, and shifted back and sideways as conditions changed. The direction of change over thirty years was not predictable from any one episode.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Natural selection is measurable in real time in a wild population, and it is episodic and reversing rather than steadily directional.
How NatureHQ reads it
The record NatureHQ uses to show what adaptation in the strict sense actually looks like when somebody watches it happen: it is a population statistic, it takes generations, no individual bird changed its beak, and the direction reversed. Every part of that contrasts with acclimatisation.
- Two species on one small island; the tractability that makes the system work also makes it unusual.
- Beak dimensions are unusually easy to measure and unusually tightly coupled to a measurable resource, which is not the general case.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: American Association for the Advancement of SciencePublished in Science or Science Advances (AAAS).
doi.org/10.1126/science.1070315
Checked against Crossref on 2026-09-28, and they agree on the title, the authors and the year.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-09-03.