Science news this week: An enigmatic human relative, dark matter discovery and mysterious lights in the sky during nuclear weapons tests Live ScienceEarly hominin Australopithecus afarensis may not be our human ancestor after all Natural History MuseumMystery owner of 3-million-year-old foot found in Africa identified, scientists say CBS NewsMystery foot suggests a second early human relative lived alongside Lucy NBC NewsTwo Australopithecus Species Co-Existed in Ethiopia 3.4 Million Years Ago Sci.News