Human evolution is a fascinating thing and every discovery we make brings us closer to our ancient ancestors. Some of these discoveries have also shown us that some of those ancestors weren’t so different from us as we once believed.
Take Neanderthals, close cousins to Homo sapiens. Modern breakthroughs in examining their genome and our own has shown the existence of Neanderthal genes in the modern human population.
As Homo sapiens and Neanderthals once coexisted, interbreeding left an undeniable mark on our genetic makeup. Our Neanderthal cousins have influenced everything from the color of our hair to what makes us ill.
The Science
Scientists first began to suspect that we, Homo sapiens, share DNA with Neanderthals back in the late 20th century. Advancements in genetics and paleontology, as well as the clues that came from the examination of anatomical similarities between Homo sapiens and Neanderthal remains made it clear that our two species had once been closer than previously suspected.
The breakthrough, however, came in the late 1990s and early 2000s when researchers finally managed to extract and analyze ancient DNA from Neanderthal remains. Svante Pääbo and his team at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany played a pivotal role in this endeavor, particularly with the successful extraction of Neanderthal mitochondrial DNA in 1997. This provided the first tangible evidence of a genetic link between Neanderthals and modern humans.
In 2010 this same team sequenced the Neanderthal genome, a landmark achievement that revealed the extent of genetic overlap between modern humans and Neanderthals and provided a roadmap for understanding the interbreeding between Homo sapiens and Neanderthals. By comparing their data to that of the Human Genome Project and its 2000 sequencing of the human genome they estimated that non-African populations share about 1-2% of their DNA with Neanderthals.
Pääbo’s team isn’t alone. Subsequent research has delved into that 1-2% to explore the regions of our genome influenced by Neanderthal genes. Numerous studies, like those conducted by the Max Planck Institute for Evolutionary Anthropology, have managed to pinpoint specific genetic markers associated with traits like immunity and pigmentations. It’s hoped this research won’t just educate us on our shared ancestry but perhaps impact the medical field as we begin to understand our genes in more detail.
This research has also revolutionized our understanding of human-Neanderthal interbreeding, which is now substantiated by a wealth of genetic and archaeological evidence. The research into our shared genes has made it clear that our ancient history saw multiple interbreeding events between modern humans and Neanderthals. We even have specific examples.
Notably, the Altai Neanderthal, discovered in the Denisova Cave in Siberia, represents a hybrid individual with a mix of Neanderthal and Denisovan ancestry, highlighting the complex interactions between different hominin groups. Fossil evidence backs up the genetic record. Skeletal remains from sites like Oase Cave in Romania and Bacho Kiro Cave in Bulgaria exhibit a blend of modern human and Neanderthal features, dating to around 40,000-45,000 years ago.
Our Neanderthal Traits
On its own, the fact that we share DNA with Neanderthals isn’t that surprising. Evolution is a complex, messy thing and we share DNA with everything from gorillas and chimps to mice and even zebrafish. One of the reasons fruit flies are extensively used in genetic research is that many genes that are crucial for development and disease in humans have counterparts in fruit flies.
However, what makes the Neanderthal research so interesting is it has revealed just how closely related we are. We’ve been able to pinpoint specific shared genes and what they do. Everyone has a little bit of Neanderthal in them and some of these genes are really important.
For a start, Neanderthal genes have a considerable effect on the diversity of hair and skin colors. Specific genetic variants, such as those found in the MC1R gene, contribute to traits like red hair and fair skin. These characteristics, inherited from Neanderthals, served as adaptive responses to different climates and environments encountered by early humans.
Even more importantly, Neanderthal genetic contributions to the modern human immune system are discernible in genes like HLA (human leukocyte antigen). These genes play a pivotal role in recognizing and responding to pathogens. The diversity in HLA genes inherited from Neanderthals has contributed to a more robust immune system in humans and defense against various infectious agents.
Unfortunately, it’s not all positive. While some Neanderthal genes bolstered the immune system, others are associated with an increased susceptibility to certain diseases.
Specific Neanderthal genetic variants are known to elevate the risk of autoimmune disorders like Crohn’s disease and lupus. This dual nature of Neanderthal genetic legacy underscores the intricate trade-offs involved in genetic inheritance. The upside is that it’s hoped research into the Neanderthal genome could offer breakthroughs in the treatment of these illnesses or help to identify those at risk before symptoms show themselves.
It isn’t just our physical traits that our Neanderthal genes affect. It’s been found they impact aspects of our behavior and metabolism. Genetic variants associated with circadian rhythm regulation, like the CLOCK gene, affect sleep patterns and responses to daylight cycles.
Neanderthal genes have also been implicated in shaping metabolic traits and influencing body fat distribution. Variants associated with adipose tissue (body fat) development and energy metabolism may have been inherited from our Neanderthal relatives. Neanderthal genes have also been found to cause or affect all types of human behavior.
What kinds of behavior? Well, research has implicated our ancestors’ DNA in influencing behaviors such as susceptibility to nicotine addiction. Genetic variants related to nicotine metabolism, including those in the CHRNA3 and CHRNB4 genes, find their origins in Neanderthal heritage.
Neanderthal genetic contributions extend to sensory perception, influencing both vision and olfaction (sense of smell) in modern humans. Specific genetic variants associated with Neanderthal genes suggest adaptations to diverse environments.
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These variations in sensory functions, such as enhanced color perception and olfactory acuity, may have provided advantages in activities like hunting, foraging, and navigating different landscapes. Bad eyesight? Maybe you need more Neanderthal DNA in your genome!
Researching Your Genes
One of the results of all this research is that now anyone interested can pay a private company to analyze specific markers in their DNA. These firms claim to be able to then do everything from estimating peoples’ percentage of Neanderthal DNA to ancestry estimates, matching relatives, and even potential health insights.
Over the last few years, quite a few companies have cropped up offering these kinds of services. They usually work by sending out customers a designated kit and asking them to provide a DNA sample, usually through a saliva sample or cheek swab.
The DNA is then extracted from these samples, genotyped, and analyzed. The data is then compared to reference populations and databases to determine the geographic regions and populations that share genetic similarities with the individual, amongst other things.
It can be extremely exciting, but anyone interested in such services has to be careful. There are major privacy concerns as to what these companies do with your genetic data. At least one already has been found handing over data to law enforcement agencies in the US.
They also tend to overpromise. The results are estimates based on available data and ongoing research and can be overgeneralized. There have been allegations of companies pretty much making up results or copy-pasting them. If research shows you have 1-2% Neanderthal DNA why pay a company to tell you the same thing?
More than Human?
From pigmentation variations to immune system enhancements and behavioral traits, our Neanderthal relatives have left an enduring mark on our genetic landscape. Physical and genetic evidence paint a vivid picture of a dynamic past, where Homo sapiens and Neanderthals exchanged not just genetic material but the very essence of what makes us human.
Beyond the laboratory, this shared heritage resonates in the mosaic of human traits, offering a glimpse into the profound interconnections that define the intricate tapestry of our evolutionary journey. Human evolution and our shared genetic legacy bring us all together showing that deep down none of us are that different from one another.
Top Image: Neanderthal genes have had a profound influence on many of the physical traits of Homo sapiens. Source: ImagineRbc / Adobe Stock.
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