First Family's last stand. (African Ancestors).

Nearly 30 years ago, excavations at Ethiopia's Hadar site yielded the 3.2-million-year-old hominid remains of nine adults and four children who apparently met a sudden, collective demise. Researchers have since speculated that this group, unearthed in a shallow channel and dubbed the First Family by its discoverers, either drowned during a flood or died after sinking into a mucky pit.

All the fossils belong to Australopithecus afarensis, the same species as the famous partial skeleton from Hadar called Lucy.

Renewed work at Hadar over the past decade has produced additional First Family fossils and inspired a revised theory of how these ancient folk perished. It now appears that at least 17 individuals, including three adolescents and five children, were killed in an attack by large predators, such as saber-tooth cats, say Anna K. Behrensmeyer of the Smithsonian Institution in Washington, D.C., and Elizabeth H. Harmon of Arizona State University in Tempe.

Behrensmeyer and Harmon first determined that the channel in which the First Family perished carried only a shallow stream of water, so they probably didn't drown. Next, the researchers determined that the First Family died in an isolated area that contains few remains of other creatures.

Finally, the First Family's fossils display a cardinal sign of carnivore consumption. Remains from below the head come primarily from the arms and legs, with virtually no rib or vertebral bones. Carcasses fed on first by large predators and then by smaller, scavenging animals commonly exhibit this pattern of bone loss, the researchers say.