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About The Cover

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COVER Lingering questions about the evolutionary history of baleen whales are finding answers, thanks to a new genomics study. To date, baleen whales' evolutionary history has been difficult to decipher, in part because of conflicting evidence from genes and morphology. Ulfur Arnason et al. conducted whole genome sequencing of six baleen whale species, several of which had not been sequenced before. The researchers then produced a phylogenetic tree and analyzed "conflicts" in it; formation of new baleen species, they conclude, occurred not via classical Darwinian patterns but instead by a more gradual process. It involved new species evolving from a single ancestral species while still inhabiting the same geographic region. [CREDIT: MEGAN WHITTAKER/ALAMY STOCK PHOTO]