Darwin's finches played a key part in the formulation of his theory of evolution by natural selection. They have since become an iconic model for adaptive radiation — 14 species evolved from a common ancestor to occupy different niches on the Galapagos Islands, with 1 species living on Cocos Island. On page 371 of this issue, Lamichhaney et al. present the genome sequences of 120 individuals from among all 15 species and 2 close relatives (S. Lamichhaney et al. Nature 518, 371–375; 2015).

The work marks the first extensive genomic characterization of these birds. Unexpectedly, the analysis reveals that breeding between species has continued throughout their adaptation, contributing to their evolution.

Credit: P. R. Grant

The morphology of Darwin's finches has been extensively studied, with a particular focus on the diverse shapes of their beaks (pictured: Geospiza magnirostris). The authors use their rich data set to probe the genetic basis of beak shape, and identify six genomic regions that have a role in craniofacial morphology.

One region, which encodes the protein ALX1, is a major player in the rapid beak-shape evolution seen both across Darwin's finches and within one species, the medium ground finch (Geospiza fortis). The function of ALX1 is evolutionarily conserved — mutations in this gene also affect craniofacial development in humans and zebrafish.Footnote 1