Out on a Limb
The science of body development may make kindling out of evolutionary trees
By Bruce Bower
Over the past 25 years, paleoanthropologists have nurtured one evolutionary tree after another, hoping to reap ever sturdier portrayals of humanity’s descent. Each of these trees sprouts out of an approximately 5-million-year-old presumed common ancestor and then branches along lines for various australopithecine and Homo species, ending at Homo sapiens. Recently, investigators have become fond of assigning new fossil finds to unique rather than established species, so evolutionary trees have gotten downright bushy.