An international team of researchers, including experts from the University of Bristol, have discovered a burial site containing a number of closely related adults and children that is more than 4,600 years old - making it the oldest example of a "family" ever found.
The graves contained groups of men, women and children buried facing each other, which was an unusual practice in Neolithic culture.
One of the graves contained a female, a male and two children, which the researchers, using DNA analysis, established were a mother, father and their two sons aged around eight or nine and four or five years old.
They say this is the oldest evidence of a nuclear family in the world.
The skeletons, discovered and excavated at Eulau, in central Germany, were also unusual for the way in which they were buried.
The remains of 13 individuals were found in total and all had been buried simultaneously.
Several pairs of individuals were buried face-to-face with arms and hands interlinked and all the burials contained children ranging from new-borns up to 10 years of age and adults of around 30 years or older. Many showed injuries that indicated they were the victims of a violent raid.
One female had a stone projectile point embedded in one of her vertebra and another had skull fractures.
Several bodies also had defence injuries to the forearms and hands.
The researchers used state-of-the-art genetics and isotope techniques to determine the relationships of the dead.
In an article published this week in Proceedings of the National Academy of Sciences lead author Dr Wolfgang Haak of the University of Adelaide said: "By establishing the genetic links between the two adults and two children buried together in one grave, we have established the presence of the classic nuclear family in a prehistoric context in Central Europe - to our knowledge the oldest authentic molecular genetic evidence so far.
"Their unity in death suggests a unity in life. However, this does not establish the elemental family to be a universal model or the most ancient institution of human communities."
As well as establishing the biological relationships of the people buried, the researchers were also able to shed light on their social organisation using strontium isotope analysis.
Hylke de Jong, a PhD student at the University of Bristol, said: "We measured strontium isotopes in their teeth to give us an indication of where these people spent their childhood.
"Strontium from the food you eat is incorporated into your teeth as they grow. We can relate the proportion of different strontium isotopes back to regions with different geology and identify the area where a person grew up."
This revealed that females spent their childhoods in a different region from the males and children in the group.
Dr Alistair Pike, Head of Archaeology at the University of Bristol and co-Director of the project, said this is an indication that marrying out of society and that the women were expected to move to where the men were.
"Such traditions would have been important to avoid inbreeding and to forge kinship networks with other communities," he said.