Even when they were first discovered, in 2005, the four graves near Eulau, Germany, made scientists sit up and take notice: at 4,600 years old, they were unusually ancient and well preserved. But now, having performed genetic and isotopic tests on the remains, scientists have realized they have something even more momentous: one group of adults and children buried facing each other is the oldest nuclear family identified with molecular genetic evidence, Australian scientists are reporting today in the online edition of Proceedings of the National Academy of Sciences. And analyses of strontium isotopes in tooth enamel, which reveal where people came from, indicate that the males and children came from around the area where they died, while females came from far away: in this Late Stone Age society, it seems, males found mates from outside the clan and brought them home, the first evidence of a practice that was to become widespread during human prehistory.

This region of Germany is already known in archaeological circles as the discovery site of the Nebra sky disk, a Bronze Age (1600 B.C.) disc that suggests that these ancient Europeans knew a little astronomy . Four graves were discovered in 2005: one with a woman (35–50 years old at death), a man (40–60), and two children (4 to 5 and 8 to 9); a second grave with a woman (30–38) and three children (an infant, a 4-to-5 year old, and 7-to-9-year old); a third with a man (25–40) and two children (4 to 5 and 5 to 6), and the final grave with a woman (25 to 35) and a child (4 to 5).

“Intriguingly,” write the scientists, “the arrangement of the dead seems to mirror their relations in life. The latter is reflected by the face-to-face arrangement of several pairs of individuals and the positioning of their arms and hands, which are interlinked,” suggesting that the dead in each grave constituted a family of some kind. In addition, each grave contained funerary offerings: stone axes for the men and boys, flint tools or animal tooth pendants for the women and girls, and butchered animal bones in each of four graves, reportscientists led by Wolfgang Haak of the Australian Centre for Ancient DNA at the University of Adelaide.

And how did they die, and come to be interred together? The radiocarbon dates for the four graves are identical, the scientists note, strongly suggesting that all four occurred at the same time. A strong clue to what happened is the age of the dead: children no older than 10 and adults 30 or older, but no adolescents or young adults. In addition, five of the dead were victims of violence: a stone projectile point is embedded in a vertebra of one, two others have skull fractures, two men have defensive injuries on the forearm—all of which paints a picture of a violent raid by a rival clan that killed all 13 individuals, conclude the scientists, and the survivors--probably young people old enough to go out hunting or gathering—to bury the dead.

Genetic analysis of the ancient DNA shows that the man, woman and two children facing each other were a nuclear family (the woman is the children’s biological mother, the man, their father). The two children in the second grave are siblings or half-siblings (they had the same mother), but the woman buried with them was not she (she was, instead, either a paternal aunt or perhaps a step-mother). What is remarkable is that the survivors recognized the primacy of the nuclear family, choosing to keep it intact in death as in life.