Â鶹ÒùÔº

Malaria is one of the world's most widespread and deadliest parasitic diseases. But some people may have natural protection thanks to DNA inherited from an extinct group of archaic humans known as the Denisovans. New research has looked at specific Denisovan-derived genes that may protect against this and other tropical diseases.

The Denisovans emerged roughly 370,000 years ago and spread across parts of Asia before disappearing around 30,000 years ago. As more of their fossils and genetic material are discovered, we're learning more about them and the diverse environments they inhabited. They were likely exposed to a wide range of illnesses carried by disease vectors such as mosquitoes and ticks. Over time, some Denisovans probably developed natural ways of resisting these pathogens.

To see if the diseases Denisovans were exposed to influenced the genes they passed down to us, Attila Trájer from the University of Pannonia in Hungary used computer models to reconstruct the ancient climates and environments of three Denisovan fossil sites in Siberia, on the Tibetan Plateau, and in Laos.

He then compared this data with the known habitats of various diseases and disease-carrying insects to determine which ones could have survived in those areas. This information was then cross-referenced with Denisovan DNA found in people today to see if the ancient environments shaped our ability to fight diseases.

The results, in the Journal of Human Evolution, confirmed that the Denisovans lived in a wide variety of environments, including cold, subarctic forests and temperate monsoon regions. The sites in Siberia and Tibet were suitable for a type of tick that carries Lyme disease, but not for tropical diseases like malaria. In contrast, the Cobra Cave site in Laos would have had an environment suitable for tropical diseases, suggesting some Denisovans were exposed to them.

Disease and Denisovan DNA

The study also found that people with a high amount of Denisovan DNA, particularly those in Melanesia (a region in the southwestern Pacific Ocean), are more likely to carry specific immune-related genes, such as HLA-H*02:07, from these ancient ancestors. This is significant because the same regions with the most Denisovan DNA do not have Lyme disease. It suggests that the protective genes were passed down from Denisovans living in warm, humid areas, such as the Cobra Cave, rather than their relatives from colder climates in the north.

"The extensive Denisovan genetic legacy related to pathogen resistance in modern humans appears less surprising. Denisovans inhabited highly diverse environments, as reflected in the environmental reconstructions of even the relatively few known sites," wrote Trájer in his study. "Denisovan habitats shaped modern human disease resistance"

The research highlights how our evolutionary history affects our health today. Understanding more about this connection, could help inform the development of new treatments and preventative strategies in regions with high rates of infectious diseases.