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    Do Butterflies Challenge the Meaning of Species?

    Hybridization, it turns out, plays a pivotal role in how life forms evolve. The tree of life may never look the same.Photograph by sezer66 / Shutterstock What is a species? It’s a question that has agonized scientists since well before Darwin. With some exceptions, the thinking has landed on an evidently firm reproductive barrier: Members […]

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    What an Extinct Bird Re-Evolving Says About “Species”

    How could the same species evolve more than once?Photograph by Janos Rautonen / Flickr You may have heard the news of what sounds like a resurrection story on the small island of Aldabra, off the coast of Madagascar. Around 136,000 years ago, the island was submerged in water and a layer of limestone captured the […]