National Geographic : 2013 Mar
photo: M. FriedMan. graphic: Álvaro valiÑo NEXT Weight of the World At seven billion plus, the global population isn’t the only thing expanding; our waistlines are too. A team of U.K. scientists calculated that the people of Earth are now 3.9 million tons overweight. Russia and Egypt are among the top contributors. So is Mexico, which represents just a sliver of the world population. Who’s carrying around the most excess fat? Americans. Indeed, if all countries mimicked the U.S., the collective hike in world- wide heft would equal the weight of another billion people. —Catherine Zuckerman Wandering Eyes Flatfish such as flounder and halibut look like regular fish when they hatch. then it takes about two weeks for one eye to drift over the head to the other side. the anatomy is so peculiar, critics of charles darwin once argued that flatfish couldn’t have evolved gradually because an intermediate fish—semiflat, with a partially migrated eye—would be maladap- tive. one biologist advocated that modern flatfish arose instead from a sudden anatomical change. Until 2008 no fossils showing an evolutionary transition from symmetric to asymmetric fish had been identified. then paleobiologist Matt Fried- man came across records of a 50-million-year-old fossil with one eye socket shifted upward but not migrated fully to the other side. When he studied the fossil along with a similar one (above) that he spotted in a vienna museum, he found a “smoking gun”: the first evidence of an intermediate flatfish. Friedman, who last year published more detailed research on his initial study, hopes the discovery encourages a greater focus on fish fossils. as he notes, “they can illuminate how weird specializa- tions arise.” — Luna Shyr Average weight 110 lb 120 130 140 150 160 170 180 World North America Oceania U.S . Latin America and Caribbean Africa Asia Europe HEAVIER LIGHTER a missing link in the flatfish fossil record, Heteronectes chaneti had a partially migrated left eye.