Homo sapiens, the direct ancestor of modern humans, left Africa and coexisted with Neanderthals, who were the first to settle in Eurasia for a while. During this time, they shared blood. So, when did the two species begin to interact, and for how long did they do so? The age of the 'Lapedo Child,' a crucial clue to the answer, has been revealed with cutting-edge technology.
An international research team led by Bethan Linscott, a researcher at the University of Oxford, estimated that the Lapedo Child, a fossil human with mixed blood from Homo sapiens and Neanderthals, lived about 27,780 to 28,850 years ago using advanced carbon isotope dating techniques. The research findings were published on the 8th in the international journal Science Advances.
The Lapedo Child was discovered by chance in 1998 beneath a cliff in Lapedo Valley, central Portugal. During an exploration, students found a small cave under a rock, where the nearly intact skeleton of a child estimated to be about 4 to 5 years old was excavated. This skeleton is significant because it possesses traits of both Neanderthals and modern humans, providing important evidence supporting the hypothesis of genetic exchange between the two groups.
Scientists determine the age of a skeleton through carbon isotope dating. There are carbon isotopes with a mass of 12 and 14. Carbon isotopes occur naturally in a consistent ratio, but the amount of carbon-14 decreases at a steady rate over time. Typically, the age is estimated by extracting a protein called collagen from the bones of the skeleton and measuring the ratio of carbon isotopes.
The research team had previously attempted carbon isotope dating four times; however, the poor preservation state of the skeleton meant that an accurate age could not be determined. Old bones often suffer from deterioration, leading to very little or contaminated collagen.
The research team introduced a more precise 'hydroxyproline dating method.' By extracting solely proline, a specific amino acid that makes up collagen, and analyzing the isotopes of carbon, the influence of contaminants can be minimized. The date obtained from measuring proline extracted from the Lapedo Child's right humerus was found to be between approximately 27,780 and 28,850 years ago.
This research finding is likely to be an important clue in tracking when different human groups started sharing blood in the evolutionary process. Traces of Neanderthals exist within us. Svante Pääbo, a professor at the Max Planck Institute for Evolutionary Anthropology in Germany, discovered that different human ancestors shared blood and received the Nobel Prize in Physiology or Medicine in 2022. By decoding the DNA of Neanderthals and comparing it with modern humans, it was found that today's Asians and Europeans possess 1% to 2% of Neanderthal DNA.
Last year, research teams from the Max Planck Institute for Evolutionary Anthropology and the University of California, Berkeley separately announced in Nature and Science that the first interbreeding period between modern humans and Neanderthals was between 49,000 and 45,000 years ago. It was noted that exchanges between the two species occurred over the following 7,000 years.
If the Lapedo Child lived 28,000 years ago, it is possible that Neanderthals and modern humans interacted for more than 7,000 years. Moreover, even if direct exchanges stopped at 7,000 years, it is conceivable that genetic influences remained for at least 20,000 years afterwards.
The research team also measured the age of the charred wood pieces found around the grave where the Lapedo Child was buried. Previously, there had been opinions that this charcoal was evidence of a burial ceremony carried out before the child was interred. Analysis revealed that the age of the charcoal was older than the time the child was buried, indicating that it is not charcoal formed as a result of a funeral.
This study has demonstrated the potential to more accurately estimate the age of ancient human remains that were difficult to date using previous methods. The research team noted, "The new dating method used through the Lapedo Child can also be applied to fossils that were hard to date with existing methods due to poor preservation" and added that it could be beneficially utilized in Paleolithic sites such as the Mladeč Cave in the Czech Republic or Saint-Césaire in France.
References
Science Advances (2025), DOI: https://doi.org/10.1126/sciadv.adp5769