The discovery of a 4,600-year-old grave containing a mother, father, and two sons in Germany provides the first evidence that the nuclear family existed in the Stone Age, a rather happy discovery except for one thing: They were murdered. The family, whose members were buried in each other's arms, is believed to have died in a massacre along with nine other bodies found nearby. One female skeleton had a stone projectile in her spine, another a fractured skull, and others had cuts on their hands and forearms, indicating self-defense. DNA testing confirms the relations in the four-person family, but this does not mean the nuclear family was the dominant social model at the time. Other evidence points to polygamous unions.