Challenge Issue In the fall of 2009, a dramatic paleoanthropological find was an-
nounced: a remarkably complete skeleton of a putative human ancestor dated to 4.4
million years ago. Only a half-dozen partially complete fossil skeletons on the human
line older than 1 million years have ever been discovered, and this one is the oldest.
Nicknamed “Ardi,” short for the new species, Ardipithecus ramidus, the fossil remains
themselves were first discovered between 1992 and 1995. All the fine cracks visible
in this close up of Ardi’s lower jaw shows how fragile these ancient bones are. Features
such as the small size of Ardi’s canine tooth led paleoanthropologists to determine
that she is a female. Early analyses of the Ardi remains in the early 1990s also estab-
lished that there were forest rather than savannah dwellers on the human line. For the
following fifteen-plus years, an international team of forty-seven scientists conducted
painstaking excavation, reconstruction, and analysis to create a complete picture of
the lifeways of this new species; through this process Ardi has become “personified.”
A series of research papers in the prestigious journal Science, along with a Discovery
Channel documentary about how the scientists went about their work, reveal not only
the importance of the find but how Ardi has captured our collective imagination. So-
phisticated computer graphics allow scientists to simulate how regulatory genes might
have shaped the development of Ardi’s bones that caused her to move in a more hu-
manlike fashion. Gymnasts were tapped to mimic her gait for scientific analysis, and
advances in physics and chemistry were incorporated in the reconstruction of the an-
cient forested environment she inhabited. In the coming years, as scientists debate
how the Ardi discovery influences theories about the human evolutionary line, these
ancient bones that we know as the individual Ardi challenge us to think about what it
means to be human.
© T. White