Neandertals, our close relatives who inhabited Europe and parts of Asia until about 40,000 years ago, have long been a subject of fascination and study. Traditionally viewed as a genetically consistent population, recent discoveries are challenging this notion. A groundbreaking study has revealed that Neandertals may have followed at least two distinct evolutionary paths, suggesting a more complex and fragmented history than previously thought.
The discovery centers around the partial skeleton of an adult male found in France, affectionately nicknamed “Thorin” by the research team. This find is significant because Thorin’s DNA indicates he belonged to a Neandertal lineage that diverged from other European Neandertals around 105,000 years ago. This lineage remained isolated for approximately 50,000 years, almost up to the time when Neandertals as a whole went extinct. This revelation supports the idea that Neandertals likely experienced their own intricate evolutionary history, characterized by local extinctions and migrations, much like modern humans.
Thorin’s remains were discovered at the entrance of the Grotte Mandrin rock shelter in 2015 and are still undergoing excavation. Multiple dating methods, including analyses of teeth from Thorin and nearby animal remains, as well as the position of Thorin’s skeleton within the cave sediments, place his existence between 50,000 and 42,000 years ago. This timeframe coincides with significant climatic changes, including the onset of an ice age in Europe around 50,000 years ago.
Molecular analysis recovered approximately 65% of Thorin’s genome from a molar. When compared to other Neandertal DNA, Thorin’s genetic makeup closely aligns with Neandertals from around 105,000 years ago rather than those from the later periods of 50,000 to 40,000 years ago. Interestingly, Thorin’s DNA does not show evidence of interbreeding with other Neandertal lineages or with Homo sapiens, suggesting a prolonged period of isolation.
Another intriguing aspect of Thorin’s genetic profile is the high percentage of DNA segments containing consecutive pairs of identical gene variants. This pattern is indicative of inbreeding within a small, isolated population—similar to findings in Siberian Neandertals. Such reduced genetic diversity points to mating among closely related individuals, a common trait in small, isolated groups.
The study posits that Thorin was part of a Neandertal population spread across parts of southwestern Europe, as evidenced by similarities between his DNA and that of a Neandertal individual from Gibraltar. This suggests that the lineage Thorin belonged to extended across a broader geographic area, potentially spanning from France to Spain’s southern tip. However, the exact age of the Gibraltar fossil remains uncertain, leaving some questions about the full extent and timeline of this lineage.
The implications of this discovery are profound. It suggests that Neandertal populations were not monolithic but rather consisted of multiple, genetically distinct groups that may have adapted to their local environments in different ways. This diversity within Neandertals could explain variations in their morphology, behavior, and interactions with early Homo sapiens.
Paleogeneticist Carles Lalueza-Fox of the Institute of Evolutionary Biology in Barcelona, who was not part of the study, highlights the significance of this finding: “The possibility of a long-lasting, isolated Neandertal population in southwestern Europe supports the idea that these hominids very likely had their own, complex evolutionary history, with local extinctions and migrations, just like us.”
While Thorin currently represents the only source of DNA from his lineage, ongoing excavations and future discoveries may uncover more individuals, providing a clearer picture of the genetic landscape of Neandertals. Understanding these isolated lineages can offer deeper insights into the factors that led to the extinction of Neandertals and how they interacted with contemporary Homo sapiens.
In conclusion, the discovery of Thorin’s partial skeleton and the genetic evidence it carries reveal that Neandertals were more diverse and followed more complex evolutionary paths than previously understood. This finding not only enriches our knowledge of our ancient relatives but also underscores the intricate tapestry of human evolution, marked by multiple lineages and interactions that shaped the course of history.