Introduction / John Edward Terrell and John P. Hart -- Adaptation / Todd L. VanPool -- Biological constraints / James Steele -- Cause / Michael J. O'Brien and R. Lee Lyman -- Classification / R. Lee Lyman and Michael J. O'Brien -- Complexity / John Kantner -- Culture / Paul Roscoe -- Descent / Scott MacEachern -- History / Sibel Barut Kusimba and Chapurukha M. Kusimba -- Individuals / Dean R. Snow -- Learning / Stephen J. Shennan -- Models / Bruce Winterhalder -- Natural selection / Robert D. Leonard and George T. Jones -- Population / Kevin M. Kelly.