Epilogue A few years later, 1359mm of rain fell on the Islands: The finches went crazy — the finch population increased by 400%! Lisle Gibbs, a graduate student of the Grants, was there and she measured every finch carefully.

Epilogue continued… When Gibbs returned to Princeton and analyzed his data, he was stunned: Natural selection had reversed course. Large finches were dying: Small seeds were everywhere, but it took too many of them to satiate a large finch with a beak built for big seeds. Small finches were reproducing like crazy.

CQ10: If small birds are selected against in one year and selected for in another, is evolution still taking place? A: Yes. B: No. C: Maybe. D: I don’t know.

Epilogue continued… The cycles weren’t over yet: A year after the heavy rains, 53mm of rain fell. The year after that, the grand total: 4mm. Galapagos weather patterns are cyclical. Let’s look at the finches over a longer time scale…

The graphs on this and the following slides are details from Figure 1 in "Unpredictable Evolution in a 30-Year Study of Darwin's Finches” by Peter R. Grant and B. Rosemary Grant, Science, 26 April 2002, vol. 296, no. 5568, pp. 707–711. Used with permission from AAAS.

CQ11: How has the average body size of these finches changed 1973-2001? A: They are much larger. B: They are a little larger. C: They didn’t change. D: They are a little smaller. E: They are a lot smaller.

CQ12: How has the average beak size of these finches changed? A: They are much larger. B: They are a little larger. C: They didn’t change. D: They are a little smaller. E: They are a lot smaller.

CQ13: How has the beak shape changed? A: They are a lot more pointed. B: They are a little more pointed. C: They didn’t change. D: They are a little more blunt. E: They are a lot more blunt.