Lucy, that starlet among ancient human relatives, may have shared the stage with a hominin very different from herself, a newly discovered fossil suggests.

Out of the Ethiopian desert, researchers have unearthed a rare, 3.4-million-year-old partial foot that resembles those belonging to Ardipithecus ramidus, a species thought to have roamed East Africa a million years before Lucy and other members of her species, Australopithecus afarensis.

The findings, published in Thursday’s edition of the journal Nature, provide the first good evidence that another bipedal human relative was still climbing trees at the same time that Lucy and her kind had their feet planted on the ground.

Foot bones are seldom found intact because they’re usually too delicate to survive in harsh environments, said Bruce Latimer, a paleoanthropologist at Case Western Reserve University in Cleveland who worked on the study. This makes the new fossil, made up of eight bones from the front part of a right foot, a valuable find - particularly since it has several toes intact, allowing scientists to get a better sense of how the foot operated as a whole.

Lucy’s foot shares many fundamental qualities with those of modern humans. Our big toes are large and parallel with the other four, […]