Finding the Way

WIKIMEDIA COMMONSManhattanhenge was a bust last month, ruined by rain-filled clouds. This beautiful alignment of the setting sun along the east-west grid of Manhattan’s numbered streets received its Stonehenge-derived moniker from the personable astrophysicist Neil deGrasse Tyson, who knows how to get people excited about all things planetary. I know we’re still deep in the heat of summer, but even so, the potential of seeing the sunset perfectly framed between New York’s skyscrapers reminded me that the sunsets will occur earlier and earlier each night as the days grow shorter. When this issue is published, on August 1, some 2 minutes of daylight are already gone since the June solstice. Shortening days are a reminder that in the coming months dozens of species—from birds to sea turtles to monarch butterflies—will begin to migrate, some over thousands of kilometers, making a beeline to their favored overwintering sites. How do they pull off such incredible feats? In this issue’s cover story, “A Sense of Mystery,” Associate Editor Dan Cossins reports on the latest research into how animals use the Earth’s magnetic field to navigate to their migratory destinations. The story is complicated by contradictory evidence of where magnetism-sensing cells reside—the inner ear, the beak or nose, or the eye—and how they do their thing. Despite the many challenges of studying this enigmatic sixth sense, of which humans have no experience, Cossins writes that “there is a palpable sense of momentum” in the field. Pathogens also migrate in mysterious ways. In a Thought Experiment essay that throws some light on how this happens, Andrew Dobson describes the cross-country spread of a bacterium that infects the eyes of house finches, its virulence level rapidly evolving to facilitate its dissemination. His take-home message is that pathogens can evolve “thousands of times more rapidly” than their hosts, but that such evolution is “very dependent upon whether the pathogen is competing in a local population or spreading and colonizing new areas.” Both insights obviously have important epidemiological implications. The discipline of synthetic biology also seems to have evolved fairly rapidly. In “Engineering Life” (here), Ahmad Khalil, Caleb Bashor, and Timothy Lu, all veterans of the Boston University laboratory headed by Jim Collins, one of the field’s founders, describe synthetic biology’s present status as “preindustrial” and offer advice about how it can become a full-fledged engineering discipline. To get there, the authors maintain, synthetic biologists must explore life in its full context, in addition to building it, and take a few lessons from nature. “Evolution has shaped the design of natural systems through iterative ‘tuning,’ whereby biological parts have been introduced, modified, and assembled over and over again to arrive at systems that are optimized for both function and context,” they write. “In considering how to engineer functions in living cells, the only unifying design rules may be those gleaned from the blueprints provided by nature.” The success of synthetic biology may depend on a careful reading and editing of nature’s handbook, but Dorion Sagan thinks that too closely identifying with nature as we know it is the reason earthlings have such problems envisioning “aliens who are truly aliens”—rather, we simply see slightly warped reflections of ourselves. You can read his thoughts on the issue in a Reading Frames essay, “Intelligent Life: The Search Continues” here. Which will be the perfect prelude to selecting one of the fun-to-read summer fiction books reviewed here. Enjoy the long summer evenings while they last. And as you look to the skies, watch for migratory passersby guided by forces we can’t feel, and perhaps even allow yourself to imagine life-forms we’ve not yet seen. Mary-Beth Aberlin Editor-in-Chief eic@the-scientist.com