Contents

04 September 2009
Vol 325, Issue 5945

About The Cover

Cover image expansion

COVER Ants live together in highly complex societies, often sacrificing individual gain to achieve common goals such as forming a living bridge. Such cooperation makes evolutionary sense because the ants are all related, as detailed in this month's Origins essay on page 1196. The essay and two Reports on pages 1269 and 1272 address how cooperation evolves in unrelated individuals and even between species. Photo credit: iStockphoto.com/Anders Boman