B I O T E C H N O L O G Y34 Test-Tube Teeth BY PAUL T. SHARPE A ND CONAN S . YOUNGManufacturing living replacement teeth will blaze a trail for engineering larger organs while leading dentistry into an age of regenerative medicine.P A L E O N T O L O G Y42 The Early Evolution of Animals BY DAVID J. BOT TJERTiny fossils reveal that complex animal life is older than we thought—by at least 50 million years.C O S M O L O G Y48 Is the Universe Out of Tune? BY GLENN D. S TARKMAN A ND DOMINIK J. SCHWARZObservations of the “music” of the cosmos mysteriously differ from theory. Either the measurements are wrong or the universe is stranger than we thought.I N F O RM A T I O N T E C H N O L O G Y56 Morphware BY REINHOLD KOCHMagnetic logic may usher in an era in which computing devices can change instantly from one type of hardware to another.M E D I C I N E64 Beating a Sudden Killer BY JOHN A . ELEFTERIADESNew approaches to care promise to save aneurysm patients from catastrophe.P S Y C H O L O G Y72 Mindful of Symbols BY JUDY S . DELOACHEYoung children often confuse real items with their symbols. These errors show how diffi cult it is to start thinking symbolically.I N N O V A T I O N S78 Nanobodies BY W. WAY T GIBBSTiny “nanobodies” derived from camels may treat a wider range of diseases at lower cost than antibodies can.