Our two-legged life may have originated in the trees, say researchers who spotted numerous instances of wild Sumatran orangutans walking in the trees. In some 90 percent of those instances, the apes walked with straight legs while using their hands to maintain balance. This simian sauntering suggests that, contrary to previous thinking, bipedalism could have begun before our ancestors descended from the canopy, which would explain fossil evidence of upright behavior dating back from before chimpanzees and humans split. —JR Minkel
Soaking the Mantle
Water under the earth's crust helps to generate volcanic activity and lubricate rock, possibly triggering large earthquakes, but how water made it under the crust was uncertain. Scientists at the University of Tokyo used a seismic array to investigate the Japan Trench. Water exists in the oceanic crust as hydrated minerals, which are expected to expel their water at the pressures and temperatures found 50 to 150 kilometers deep. Instead of floating upward, this freed water could fuse with mantle rock to form greenish serpentinite and get subducted downward below the crust. The researchers found what appears to be a channel of such hydrated rock flowing down farther into the mantle on top of a descending plate, confirming how the mantle gets wet. The findings are slipped into the June 8 Science. —Charles Q. Choi
Parlez-Vous English, Baby?
Visual cues alone seem to enable infants to recognize when a multilingual person switches dialects. Researchers at the University of British Columbia assert that without hearing a word, a four-month-old child can detect a language shift simply by observing shapes made by the speaker's mouth and other facial changes. Cultural mannerisms such as rhythmic head bobbing can also cue the babies. Infants in a monolingual family seem to lose this innate capacity by the age of eight months. —Nikhil Swaminathan