Visualizing evolution as it happens

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Science  09 Sep 2016:
Vol. 353, Issue 6304, pp. 1096-1097
DOI: 10.1126/science.aah5641

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One of the greatest symbols of the birth of evolutionary biology is Darwin's first sketch of an evolutionary tree, above which he wrote: “I think.” Not only are evolutionary trees central to how scientists conceptualize evolutionary processes, Darwin's words also capture a key aspect of evolutionary science: It is difficult to observe, forcing researchers to rely heavily on inference. In recent decades, studies of fast-growing microorganisms have allowed hypotheses about evolutionary processes to be tested experimentally (1). On page 1147 of this issue, Baym et al. (2) report a device for visualizing evolutionary branching as bacteria grow across a meter-scale agar slab. The results offer important insights into evolutionary dynamics in spatially extended systems.