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Morphological trajectories of adult Geospiza fortis (A to C) and G. scandens (D to F). In the absence of change, mean trait values should have remained within the 95% confidence intervals (horizontal broken lines) of the estimates from the 1973 samples (body size: G. fortis, n = 115, G. scandens, n = 37; beak traits: G. fortis, n = 173, G. scandens, n = 62). Sample sizes varied from 45 (1997) to 976 (1991) for G. fortis and from 30 (1999) to 336 (1983) for G. scandens. The 1972 sample is composed of the adults (=1 year old) in 1973. (From [ Peter R. Grant and B. Rosemary Grant, 2002, "Unpredictable Evolution in a 30-Year Study of Darwin's Finches," Science 296(5568):707-711].