So when anyone finds a complete skull of a possible human ancestor, paleoanthropologists rejoice. But with new knowledge comes new controversy over a fossil's place in our species' very fuzzy family tree.
In the eastern European nation of Georgia, a group of researchers has excavated a 1.8 million-year-old skull of an ancient human relative, whose only name right now is Skull 5. They report their findings in the journal Science, and say it belongs to our genus, called Homo.
"This is most complete early Homo skull ever found in the world," said lead study author David Lordkipanidze, researcher at the Georgian National Museum in Tbilisi.