The evolutionary history of our species is closely linked to the existence and interaction with other human species such as Neanderthals and Denisovans. These connections, occurring thousands of years ago, have left a significant mark on our health, appearance, and physiology today, thanks to advancements in ancient DNA research.
Heritage from Neanderthals and Denisovans
When Homo sapiens migrated out of Africa tens of thousands of years ago, they encountered and interbred with Neanderthals across various regions of Eurasia. This led to modern human populations inheriting an average of about 2% DNA from Neanderthals. Similarly, recent studies have discovered that Denisovans, another branch of prehistoric humans, also contributed 2-5% DNA to the gene pool of some indigenous groups in Oceania.
This mixing has created a “patchwork” genetic landscape in modern populations, with ancient genes carrying distinctive traits. Research shows that Neanderthal DNA may influence our nose size, while Denisovan DNA relates to lip width. These findings not only help reconstruct the morphological traits of our ancestors but also provide insights into how ancient genes affect adaptation to the environment.
The immune system of modern humans is a result of ancient genetic intermingling.
Impact on Health and Immune System
One of the most significant legacies of this genetic intermingling is the immune system of modern humans. Since Neanderthals and Denisovans lived in Eurasia for hundreds of thousands of years, they developed resistance to pathogens endemic to the region. When Homo sapiens settled here, they inherited immune-related genes through interbreeding.
These genes brought substantial benefits, helping our ancestors combat new bacteria and viruses. For example, a cluster of Neanderthal genes on chromosome 12 has been shown to protect modern humans from severe Covid-19 symptoms. However, not all of these legacies are positive; another cluster of Neanderthal genes on chromosome 3 is believed to increase the risk of contracting Covid-19.
Research in Japan has also indicated that Denisovan DNA is linked to several health conditions, including Type II diabetes and coronary artery disease. This suggests that genetic variants that were advantageous in primitive environments sometimes become risk factors in modern medical contexts.
Unanswered Questions
While research has provided many important insights, there remain significant gaps in understanding the genetic influences of prehistoric human species. In particular, the genetic flow between these species and modern Homo sapiens in Africa is still not well understood. Some scholars suggest that there may be genetic traces from an unidentified hominin species in the genes of African people.
There are still many gaps in exploring the genetic influences of prehistoric human species.
Researchers emphasize that the genetic contributions from Neanderthals and Denisovans are not only biological legacies but also evidence of the evolution of modern humans. “The mixing has significant implications for function, phenotype, and evolution,” the research group asserts in a report published in Current Opinion in Genetics & Development.
These discoveries remind us that Homo sapiens did not evolve in isolation but rather as a result of complex intermingling among multiple species. This contributes not only to the diversity of humanity today but also opens new research directions regarding the relationship between genetics, evolutionary history, and public health.
