Last week, scientists published a study of five 1.8 million-year-old hominid fossils. They may reveal profound lessons about a crucial chapter in our evolution: how our ancestors changed from bipedal apes to a more human-like lineage–in other words, the emergence of our genus, Homo. So what name do we give these skulls? What species do they belong to? It’s no simple matter naming our hominid ancestors, and that difficulty tells us something intriguing about their biology. And that’s the subject of my “Matter” column this week in the New York Times. Check it out.