18 December 2009
Vol 326, Issue 5960

About The Cover

Cover image expansion

COVER Ardipithecus ramidus, a possible human ancestor, inhabited then-wooded regions of Ethiopia 4.4 million years ago. This year, studies of the fossilized skeleton of a member of the species raised surprising questions about how key human traits evolved. See the Breakthrough of the Year special section beginning on page 1598) and at Image: © 2009, Jay Matternes