An upright gait and a relatively sophisticated ability to manipulate objects apparently evolved in tandem among the earliest hominids at least 6 million years ago, said Sergio Almécija of the Autonomous University of Barcelona. That's well before the earliest evidence of stone toolmaking, about 2.6 million years ago, arguing against the idea that fine motor skills for toolmaking drove the evolution of opposable thumbs. Almécija and his colleagues studied a bone from the tip of a thumb belonging to Orrorin tugenensis. At an estimated 6 million years old, Orrorin is the second oldest hominid genus. A more recently identified...