Early modern humans originated in Africa around 80,000 years ago. They began spreading across the globe, encountering other ancient human species like Neanderthals who had already established themselves in Europe and parts of Asia. As they interacted, they sometimes had intimate encounters that led to the mixing of their DNA. Remarkably, traces of this prehistoric interbreeding still echo in the genetic makeup of contemporary humans.
The revelation of Homo sapiens interbreeding with Neanderthals emerged in 2010, thanks to the pioneering work of Swedish geneticist Svante Pääbo. He developed innovative techniques for extracting, sequencing, and analyzing ancient DNA from Neanderthal remains. Pääbo’s groundbreaking effort involved mapping the entire Neanderthal genome. This monumental achievement enabled scientists to compare Neanderthal genomes with the genetic records of present-day humans.
Today, most people carry a small fraction of Neanderthal DNA in their genetic code, even Africans who were previously believed to have no genetic ties to Neanderthals.
Researchers have since been exploring the significance of this genetic legacy. They’ve discovered links between Neanderthal DNA and various aspects of human physiology and traits, such as fertility, pain perception, and immune system function. Neanderthal genes may also influence characteristics like skin tone, hair colour, height, sleeping patterns, mood, and even susceptibility to addiction among contemporary Europeans.
Surprisingly, recent research has even suggested a possible connection between Neanderthal DNA and the course of COVID-19 infection, adding a new layer of relevance to this ancient genetic legacy.
Svante Pääbo, who has dedicated three decades to the study of Neanderthal DNA, expressed his excitement at how these ancient genes continue to impact us, even 50,000 years after Neanderthals went extinct. Pääbo and his team have turned their attention to addressing one of the most pressing concerns in medical science: the coronavirus pandemic. They aim to determine if Neanderthal DNA can offer insights into COVID-19.
In their research, scientists examined a specific DNA strand associated with severe cases of COVID-19. They compared this strand to genetic sequences known to have been inherited from Neanderthal ancestors by present-day Europeans and Asians. Notably, they found that certain variations in this sequence were linked to an increased risk of severe illness from COVID-19.
Moreover, the study uncovered notable disparities in the prevalence of this genetic risk variant across different parts of the world. It is particularly common in South Asia, where roughly half of the population carries this Neanderthal risk variant. In Europe, about one in six individuals possesses this risk variant, while in Africa and East Asia, it is almost nonexistent.
However, it’s important to stress that Neanderthals are not to blame for COVID-19 or other diseases. The genetic links to these ancient humans are intriguing but ultimately have modest effects.
Tony Capra, a geneticist at the University of California, emphasized the importance of recognizing that social and environmental factors are the primary drivers of health issues. While there are associations between Neanderthal DNA and certain conditions like depression and addiction, these associations are not causative.
To explore these links, scientists rely on large biobanks containing genetic information from living humans and their medical records. These extensive studies have made it easier to investigate the impact of Neanderthal DNA on contemporary populations.
While many of the links between Neanderthal DNA and specific traits remain largely of academic interest, some may have medical implications. For example, recent research found that women carrying a Neanderthal-inherited gene variant were less likely to experience miscarriages and pregnancy-related bleeding. This was attributed to increased progesterone receptors in their cells.
The story of Neanderthal DNA is a fascinating one. Although the popular image of Neanderthals often depicts them as primitive cave dwellers, they had a sophisticated existence. They survived in diverse climates, crafted tools, created art, and interacted with early modern humans for tens of thousands of years. The extent of their interactions and interbreeding remains unclear, but it is evident that these encounters influenced the genetic makeup of modern humans.
Neanderthal genes could have conferred an advantage on early modern humans as they migrated to new regions. These genes influence their immune systems and traits such as skin colour, hair type, and immune response. This adaptability was crucial for survival in different environments and withstanding new challenges.
Over time, some Neanderthal genes evolved or disappeared, but those that remain are believed to offer certain benefits to contemporary humans.
However, it’s essential to understand that these effects are generally modest, accounting for a small percentage of the variation in traits across the human population. Identifying individuals with Neanderthal DNA is not as simple as observing their physical characteristics.
The field of research is limited by the lack of ethnically diverse biobanks, with most genetic data focused on Western Europeans. Scientists are also exploring the genetic contributions of other ancient human groups, such as Denisovans. These mysterious humans left limited fossils, but genetic data suggests they had an impact on modern humans, particularly in adapting to high-altitude environments.
Understanding the history of our species and how various ancient humans have shaped our genetic diversity is a source of enduring fascination for researchers.