Scientists studying human evolution have uncovered remarkable evidence that Denisovans, an ancient hominin group, interbred with early modern humans through multiple interbreeding events. These genetic exchanges have left traces of Denisovan DNA in modern populations, influencing traits that helped early humans adapt to diverse environments.
The discovery of Denisovans as a distinct hominin group came in 2010 when genetic analysis of a finger bone, found in Denisova Cave in the Altai mountains of Siberia, revealed a unique genome, unlike any known at the time. This finding followed the sequencing of the Neanderthal genome, which had already confirmed that Neanderthals and early modern humans had interbred. These discoveries transformed scientists’ understanding of human evolution, revealing a complex picture of interbreeding among multiple hominin groups.
Dr. Linda Ongaro, a postdoctoral researcher at Trinity College Dublin and lead author of a new review published in Nature Genetics, highlights that human evolution is not the neat, linear process it was once thought to be. Instead, our evolutionary history includes interbreeding events with different hominin groups, such as Denisovans, which have contributed to the genetic diversity seen in modern humans today.
While Denisovan fossil evidence is sparse—a finger bone, a jawbone, a few teeth, and some skull fragments—their genetic legacy lives on in certain populations, particularly in parts of Asia and Oceania. By examining surviving Denisovan DNA segments within modern human genomes, scientists have found evidence of at least three separate interbreeding events with Denisovan populations, each event contributing distinct Denisovan genetic material into the human gene pool. This points to a complex and ongoing relationship between Denisovans and early humans over thousands of years.
In their review, Dr. Ongaro and her colleague, Professor Emilia Huerta-Sánchez, discuss evidence suggesting that Denisovans were highly adaptable, living across diverse environments from Siberia to Southeast Asia, and potentially even influencing populations as far as Oceania and the Americas. The Denisovan genes passed to modern humans may have conferred specific advantages, helping ancient humans survive in challenging climates and conditions.
One of the most notable Denisovan genetic traits is a variant that enhances tolerance to hypoxia, or low oxygen levels, a trait beneficial for populations living at high altitudes, such as the Tibetan people. This genetic adaptation likely improved their capacity to survive in mountainous regions with thin air. Denisovan genes have also been linked to enhanced immune responses, which could have helped early humans resist diseases in new environments, and a gene affecting lipid metabolism, which aids in generating body heat under cold conditions—a trait advantageous for Arctic populations like the Inuit.
Future research could uncover even more about the Denisovan contribution to modern humans. Dr. Ongaro notes that analyzing the genomes of understudied populations may reveal hidden traces of Denisovan ancestry, shedding light on how these ancient humans impacted the evolutionary path of humans across the globe. Moreover, if more Denisovan fossils are discovered, integrating this genetic data with archaeological findings could provide a more detailed account of Denisovan lifestyles, migration patterns, and interactions with other hominins.
The Denisovans’ genetic influence on modern humans underscores the complexity of human evolution, with interbreeding and adaptation playing crucial roles. Far from a simple lineage, the history of humankind reflects a web of interactions with other hominin species, whose genetic legacies continue to shape us today. This expanding research opens new possibilities for understanding how ancient genetic exchanges helped our ancestors survive and thrive in a world filled with diverse climates and environments.
Source: Trinity College Dublin