Researchers have published a new study in which they claim that inbreeding was a key factor in the extinction of the Neanderthals some 40,000 years ago.
The study published in the ‘Scientific Reports’ was carried out by paleoanthropologists, geneticists, and archaeologists from the Spanish National Museum of Natural Sciences, from the Institute of Evolutionary Biology in Barcelona and the University of Oviedo.
The team used fossil remains from various individuals discovered in the Sidron cave in the municipality of Pilona in the autonomous community of Asturias in northern Spain.
The remains of over 2,500 bones from at least 13 individuals who lived approximately 49,000 years ago were found at the site between 2000 and 2013 and those remains were reportedly key to the study.
The team worked to discover the degree of endogamy in the group. Endogamy is the custom of marrying or maintaining close personal relationships only within the limits of a community, clan, or tribe.
To analyse the degree of the endogamy of the group, the scientists reportedly used the remains of four mandibles (lower jawbones), three maxillas (upper jawbones), teeth, cranial fragments, and different bones from the torso and extremities.
The team reportedly found 17 birth defects in these fossils taken from all over the skeletons.
The bone remains used for the analysis belonged to a family group of 13 individuals: seven adults (four women and three men), three adolescents and three children who shared the same birth defects mainly in the nose, jaw, ribs, foot and wrist.
For Luis Rios, one of the researchers, these discoveries show “high” levels of endogamy which were “maintained over time” and probably intensified in the last groups of Neanderthals who survived in the group.
This genetic verification of endogamy is systematically found in extinct species or those in danger of extinction.
The director of the work and palaeontologist from the National Museum For Natural Sciences, Antonio Rosas, explained that the extinction of the Neanderthals cannot be attributed to only one cause, saying: “It was probably produced by a combination of ecological and demographic factors which include interaction with modern humans.”
However, these humans lived in small, geographically separated groups and were practically isolated which brought them to cross with the members of the same family, according to the study.
As the numbers in the group decreased over time, endogamy within it is believed to have increased.