Sometimes, a bone is just a bone. Other times, it’s the earliest modern human-like hand bone, as a group of researchers recently discovered — one that could change how anthropologists see human evolution. After excavating a bone at a Tanzanian dig in 2012, the researchers are reporting that it is a pinkie finger that’s at least 1.84 million years old, writes ScienceNews’ Bruce Bower.

Paleoanthropologists from the University of Madrid published their discovery in Nature Communications. The research is part of a project scouring the Olduvai Gorge in northern Tanzania, where some of history’s most important and ancient fossils have been found.

Homo habilis is the Olduvai Gorge’s most famous resident, but this bone is more humanlike than other fossils that are that old. Hand shape is usually associated with “advanced manipulative skills,” the team writes. They think that the pinkie in question belonged to a creature that could make and use stone tools — and that the hominid it belonged to didn’t live in trees.

This could represent a major breakthrough in the evolutionary timeline, but, as Bower writes, using one bone to define a whole species is controversial. The team tells UPI’s Brooks Hays that their next move is to find the other bones they’ll need to confirm their theory that they’ve landed on a “transitionary species” that fits somewhere between Homo sapiens and Homo habilis.