In this issue:
"How Homo sapiens Became the Ultimate Invasive Species": Many human species have inhabited Earth. But ours is the only one that colonized the entire planet. A new hypothesis explains why.
"In Search of Alien Jupiters": Two rival teams of astronomers are racing to capture unprecedented images of giant planets around other stars. What they find could change the future of planet hunting.
"Hidden Hearing Loss from Everyday Noise": Jackhammers, concerts and other common noisemakers may cause irreparable damage to our ears in unexpected ways.
"Researchers Find That Frequent Tests Can Boost Learning": Too often school assessments heighten anxiety and hinder learning. New research shows how to reverse the trend.
©2015 Scientific American