Galaxies stop producing stars at a relatively young age. Until now, astronomers thought the shutdown was due to peaking of the activity of the supermassive black hole at each galaxy's center. But an analysis of 177 galaxies by postdoctoral researcher Kevin Schawinski and his colleagues showed that stars stopped forming well before the high point of galactic nuclei activity. The work appeared in the February 10 Astrophysical Journal Letters.

A four-inch, 390-million-year-old fossil is the missing link in the evolution of the front claws of horseshoe crabs and scorpions. Schinderhannes bartelsi, named in part to honor a late-eighteenth-century German bandit, was described by paleontologist and Peabody Museum director Derek Briggs and his colleagues in the February 6 issue of Science. It was discovered in a slate quarry in Germany.

Only a tiny number of animal species undergo a natural sex change. But the biological costs of "sequential hermaphroditism," though significant, are not sufficient to account for its rarity, report evolutionary biologist Suzanne Alonzo and graduate student Erem Kazancioglu in the March issue of the American Naturalist. They are exploring whether factors such as mating and parental care are at work.

In 2007, the U.S. Supreme Court ruled that a Georgia policeman was justified in engaging in a high-speed chase captured on videotape. "No reasonable person" who viewed the tape could have thought otherwise, the justices wrote. Law School professor Dan Kahan showed the tape to 1,350 people of differing culture, politics, economic circumstances, race, gender, and age. Kahan and his colleagues found that among certain subgroups, as many as 65 percent of these reasonable people disagreed with the court majority. The study appeared in the January Harvard Law Review. 

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