(Source: https://www.sciencenews.org/article/ancient-dna-unveils-unknown-neandertals)
Relevance – Archaeology Paper 1&2 and Physical Anthropology – 1.6 Human Fossils
Introduction
For decades, Neandertals have been considered a genetically homogenous population, following a single evolutionary path until their extinction around 40,000 years ago. However, a groundbreaking study challenges this notion, revealing that European Neandertals consisted of at least two distinct populations. A newly discovered Neandertal lineage, identified through ancient DNA analysis, suggests a long period of isolation and independent evolution
Discovery of Thorin: A Unique Neandertal
Unearthing a Hidden Lineage
In 2015, archaeologists discovered the partial skeleton of an adult male Neandertal at the Grotte Mandrin rock shelter in France. This individual, nicknamed Thorin—after a character in The Hobbit—was found in a natural depression on the cave floor.
Dating and Genetic Analysis
Through various dating methods, including the analysis of teeth and animal remains buried nearby, researchers estimated that Thorin lived between 50,000 and 42,000 years ago. A crucial finding came from his molar, which preserved about 65% of his genome. This allowed scientists to compare his DNA with that of other Neandertals, ancient Homo sapiens, and present-day humans.
Genetic Insights: A Separate Evolutionary Path
A 50,000-Year-Old Isolated Lineage
Thorin’s genetic structure closely resembles that of Neandertals who lived around 105,000 years ago, rather than those from 50,000 to 40,000 years ago. This indicates that his lineage had remained genetically distinct for nearly 50,000 years, likely due to long-term isolation.
Lack of Interbreeding
Unlike many other Neandertals, whose DNA shows signs of interbreeding with both Homo sapiens and other Neandertal groups, Thorin’s genome lacks genetic input from outside populations. This suggests that his lineage may have deliberately avoided interbreeding with other Neandertals, potentially due to cultural, linguistic, or geographical barriers.
Inbreeding and Small Population Size
Thorin inherited an unusually high number of identical gene pairs, a trait commonly associated with mating among close relatives. This pattern has been observed in other isolated Neandertal populations, such as those in Siberia. It indicates that Thorin’s lineage likely consisted of small, closely related communities that exchanged mates within a restricted group.
Implications for Neandertal Evolution
Neandertal Migration and Isolation
This discovery challenges the traditional view that Neandertals were a single, unified population. Instead, it supports the idea that they experienced local extinctions, migrations, and regional variations, much like modern human populations.
Connections to Gibraltar Neandertals
Thorin’s DNA shows similarities to a Neandertal fossil found in Gibraltar in 1848. This suggests that his lineage may have once spread across southwestern Europe, possibly forming isolated clusters in different regions. However, without a confirmed age for the Gibraltar fossil, further research is needed to determine the extent of this population.
A Complex Evolutionary History
If Thorin truly lived 50,000 years ago, it would mean that late Neandertals had a far more complex genetic structure than previously assumed. His lineage may have survived in isolation while other Neandertals interbred with different populations. However, if Thorin’s remains turn out to be older, it could indicate that his group disappeared earlier than expected.
Future Research and Unanswered Questions
Further Excavations at Grotte Mandrin
Thorin’s remains are still being excavated, and researchers hope to uncover more fossils from his lineage. This could help confirm the exact timeline of this population and determine whether Thorin’s body was deposited in older sediment.
Clarifying Population Dynamics
One key question remains: Why did Thorin’s lineage remain isolated for so long? Possible explanations include:
- Geographical barriers that prevented contact with other groups.
- Cultural or linguistic differences that discouraged interbreeding.
- Deliberate avoidance of outsiders due to social or survival strategies.
Extracting More DNA
Currently, Thorin’s DNA is the only genetic evidence of his lineage. Isolating more DNA from his remains or discovering additional fossils from this group could further clarify their evolutionary history.