London: Early humans who lived around 34,000 years ago recognised the dangers of inbreeding and developed social and mating networks to avoid it, new research has found.
The study, published in the journal Science, suggests that the early development of more complex mating systems may at least partly explain why anatomically modern humans thrived while other species, such as Neanderthals, did not.
Small family bands likely had interconnected with larger networks, facilitating the exchange of people between groups in order to maintain diversity, said Martin Sikora, Professor at the University of Copenhagen, Denmark.
The researchers examined genetic information from the remains of anatomically modern humans who lived during the Upper Palaeolithic, a period when modern humans from Africa first colonised western Eurasia.
The results suggest that people deliberately sought partners beyond their immediate family, and that they were probably connected to a wider network of groups from within which mates were chosen, in order to avoid becoming inbred.
The research was carried out by an international team of academics, led by the University of Cambridge in Britain and the University of Copenhagen.
They sequenced the genomes of four individuals from Sunghir, a famous Upper Palaeolithic site in Russia, which is believed to have been inhabited about 34,000 years ago.
The human fossils buried at Sunghir represent a rare and highly valuable source of information because very unusually for finds from this period, the people buried there appear to have lived at the same time and were buried together.
To the researchers' surprise, however, these individuals were not closely related in genetic terms; at the very most, they were second cousins.
This is true even in the case of two children who were buried head-to-head in the same grave.
What this means is that even people in the Upper Palaeolithic, who were living in tiny groups, understood the importance of avoiding inbreeding, said Eske Willerslev from the University of Copenhagen.
The data suggests that it was being purposely avoided.