When Barack Obama moves into the White House in January, he'll bring his wife and children with him. The nuclear family is not only as American as apple pie but also the cultural norm in most societies across the world. New genetic and chemical analyses of 4600-year-old burials in Germany suggests that family togetherness has deep roots, going back at least as far the beginnings of agriculture in Europe.
Before humans settled down and began to farm, they lived as nomadic hunters and gatherers. Many anthropologists have assumed, based on observations of sometimes polygamous modern-day hunter-gatherers, that the basic social unit of early humans was the band or tribe rather than the family. Figuring out when the nuclear family became central to human social organization has been difficult. Archaeologists have dug up thousands of skeletons at early farming sites across the Near East and Europe, and many of them are buried together in ways that might suggest family ties. For example, at the 9500-year-old early farming site of Çatalhöyük in Turkey, excavators have uncovered two skulls with their foreheads touching and the skull of a man cradled in the arms of a woman. But without DNA evidence, researchers are reluctant to ascribe modern-day interpretations to ancient burials.
Now, a team led by Wolfgang Haak, a geneticist at the Australian Centre for Ancient DNA in Adelaide, claims to have worked out some family relationships in a remarkable series of burials uncovered in central Germany in 2005. At the early farming site of Eulau, German archaeologists found four graves containing 13 individuals who had apparently met a violent death. Two graves were particularly well-preserved: In one, an adult male and female had been placed on their sides, face to face and arms intertwined with two boys; in the other, an adult woman was buried facing away from two girls and a boy. Working with the German team, Haak and colleagues were able to extract enough mitochondrial and nuclear DNA from the skeletons in the first grave to conclude that the two adults were the parents of the two boys. In the second grave, the team concluded that the three children were probably brothers and sisters, although the adult female was not their mother. Rather, the researchers suggest, she might have been an aunt or a step-mother.
"We have established the presence of the classic nuclear family in a prehistoric context," Haak and his co-workers declare online today in the Proceedings of the National Academy of Sciences. In further work, the team analyzed the strontium isotope content of the 13 skeletons' teeth, which varies according to the chemistry of the soil where an individual spends his or her childhood. The researchers found that the children and the adult men grew up in the Eulau area, whereas the adult women came from at least 60 kilometers away--an indication that nuclear families in this region were organized around local men who mated with outside women.
"This is a great piece of work," says Alexander Bentley, an anthropologist at Durham University in the U.K. Bentley adds that the new findings, including the signs of violence on the skeletons--such as multiple skull fractures--are consistent with other archaeological evidence from Central Europe that men raided outside communities and captured their women. Still, Marek Zvelebil, an archaeologist at the University of Sheffield in the U.K., says that the authors' claims to have worked out the biological relationships between the skeletons may be a stretch. The genetic markers the team used are "very widespread in Europe," he notes, meaning that they cannot be used to work out exact family relations without a broader study of prehistoric skeletons from the region.