Researchers say new examinations of arm and leg fossils support existing evidence that an identified species could be our earliest known ancestor.The fossil bones were found near a skull that was discovered in 2001 in the African nation of Chad.The scientists who found the skull have suggested that it belonged to a being who walked upright and could be our earliest known ancestor.Now, researchers say a study involving the arm and leg fossils strengthens that argument.The team looked for signs that the species walked on two feet instead of four.The move toward upright walking is a main division between human and ape development.The fossil species, called Sahelanthropus tchadensis, walked upright while still being able to climb and move around in trees, the team said.The species dates back to around seven million years ago, which makes it by far the oldest known human ancestor.
