Improbable Big Birds

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Science  12 Jan 2018:
Vol. 359, Issue 6372, pp. 157-159
DOI: 10.1126/science.aar4796

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Darwin's finches, a group of 18 species endemic to the Galápagos archipelago, are a classic example of adaptive radiation—the process whereby a single ancestral species multiplies in number to produce divergent species, often in rapid succession (1). These birds are evolutionary biologists' most celebrated example of natural selection in action. On page 224 of this issue, Lamichhaney et al. (2) have succeeded in observing a process even more elusive than natural selection—the formation of a new species (speciation). Because speciation typically takes place on time scales that are too long for direct human observation, before now it was only in organisms with very fast generation times, such as viruses and bacteria, that scientists had directly observed this process [for example, (3)]. Lamichhaney et al. show through direct observation and DNA sequencing that new species can form very rapidly: within three generations. The key, in this case, is hybridization between different species.