A recent study published in Cell has uncovered the ancient origins of a genetic mutation known as CCR5 delta 32, which provides resistance to HIV. This mutation first appeared in an individual near the Black Sea between 6,700 and 9,000 years ago. By disabling a key immune protein that most strains of HIV use to enter human cells, individuals who inherit two copies of this mutation are essentially shielded from the virus.
Ancient Mutation Meets Modern Virus
HIV is a relatively modern disease, identified only in the last century, whereas the protective mutation against it has existed for millennia. Led by Professor Simon Rasmussen and researcher Kirstine Ravn from the Novo Nordisk Foundation’s Metabolic Research Center at the University of Copenhagen, the international research team analyzed over 3,000 ancient and modern human genomes. Utilizing a novel AI-based method, they successfully detected the mutation in the often degraded DNA of ancient bones.
The analysis included DNA from over 900 individuals spanning from the early Mesolithic period to the Viking Age. The team found that the CCR5 delta 32 mutation emerged suddenly and spread rapidly among human populations, particularly as societies transitioned from a nomadic hunter-gatherer lifestyle to denser agricultural communities. This shift presumably exposed people to new pathogens, creating an evolutionary pressure that favored carriers of the mutation.
Leonardo Cobuccio, a co-author and postdoctoral researcher, explained that individuals with this mutation had higher survival chances, likely because it modulated immune responses during a time when people confronted new diseases. While it may seem detrimental for an immune system gene to be altered, the mutation likely conferred advantages. An overly aggressive immune system can lead to serious complications, much like severe allergic reactions or even severe viral infections where the immune response can cause the most damage.
CCR5: The Key to Blocking HIV Infection
The CCR5 protein guides immune cells to areas of inflammation in the body. When the delta 32 mutation is present, the HIV virus has a much harder time infecting these cells. This discovery has had significant medical applications, with scientists leveraging the protective features of the mutation to successfully treat a small number of HIV patients.
Surprising Genetic Legacy from the Black Sea
One of the study’s most compelling findings is that all modern carriers of the CCR5 delta 32 mutation—estimated to represent between 10% and 16% of Europeans and up to 25% of Danes—likely trace back to a single ancestor who lived near the Black Sea thousands of years ago. Previous theories suggested that the mutation spread due to more recent historical events, such as the Black Death or Viking-era pandemics. However, new genetic evidence contradicts these hypotheses, demonstrating that the mutation proliferated more widely between 8,000 and 2,000 years ago, well before these events.
A New Chapter in Human Evolution
This research alters our understanding of human adaptation to disease and highlights the remarkable synergy of ancient DNA analysis and modern technology in unveiling hidden chapters of human history. The findings shed light on the evolutionary dynamics of populations and the complex interplay between genetics and environmental pressures over millennia.
By identifying how this ancient mutation has persisted and spread, the study opens avenues for further research into genetic resistance to diseases and the evolution of immune responses through time. The implications could extend beyond HIV, potentially offering insights into other diseases influenced by genetic factors.
