Understanding Our Inner Neanderthal: What Neanderthal DNA Reveals About Modern Humans

Nancy Deng | January 11th, 2024

The rising trend in commercial ancestry testing and at-home DNA tests is evident with the popularity of companies like Ancestry and 23andMe. The company Ancestry focuses primarily on genealogy and ancestry exploration, while 23andMe offers a broader range of services encompassing both ancestry testing and health-related insights.

One particularly interesting feature of 23andMe is its Neanderthal ancestry report. This report details the percentage of Neanderthal DNA a user possesses and how this genetic inheritance might impact specific traits. Although most individuals have a relatively small percentage of Neanderthal DNA, the lasting genetic legacy of Neanderthals holds significance for both the health and history of modern humans.

What have we learned from Neanderthals?

The sequencing of the Neanderthal genome in 2010 by Nobel Prize winner Svante Paabo has provided scientists with valuable insights into the genetic legacy of Neanderthals. Subsequent studies have used ancient DNA to shed light on human migration, genetic adaptations to environmental changes, and implications for health. 

Neanderthals diverged from modern humans approximately 500,000 years ago and likely evolved outside of Africa. Meanwhile, most early modern humans remained in Africa until around 60,000 years ago when they migrated outwards. 

Approximately 50,000 years ago, early modern humans (EMH) and Neanderthals interbred, leading to the presence of Neanderthal DNA in modern humans. Research suggests that people of European or Asian ancestry have about 1-2% Neanderthal DNA, and a recent study indicates that people of African ancestry have an even smaller fraction of Neanderthal DNA. This genetic inheritance, though seemingly small, has been found to have real effects on modern humans such as variants associated with present-day diseases. Scientists are still studying the full effects of this genetic legacy but have discovered that it can be both beneficial and harmful.

What does Neanderthal DNA tell us about modern humans?

Prior to the migration out-of-Africa, EMH had little to no immunity to diseases in Europe and Asia while Neanderthals in that time evolved to have many unique adaptations to help survive in their environments. The interbreeding between EMH and Neanderthals helped address this issue in the past. However, research has indicated that this inbreeding may also be the reason why people today have differences in their immune response. Research has linked Neanderthal DNA to various health-related traits in modern humans. Tony Capra, an evolutionary geneticist and associate professor at the University of California, San Francisco—also formerly an associate professor at Vanderbilt University, along with collaborators in their Science paper, discovered associations between Neanderthal DNA and a range of dermatological, immunological, and psychiatric traits. A finding in the paper proposed that Neanderthal DNA has been found to influence keratin production, which affects hair, skin, and nail characteristics.  This helps protect the skin from environmental damages like sun-exposure in modern humans. Conversely, this genetic legacy may also have harmful effects, as Neanderthal DNA is also associated with type 2 diabetes, addiction, and response to pain. 

The genetic legacy of Neanderthals

The study of Neanderthal DNA has provided valuable insights into human history, evolution, health, and our understanding of how humans interact with the world. While popular genetic testing services like 23andMe offer users information about the associations between Neanderthal DNA and quirky human traits such as sneezing after eating dark chocolate, sense of direction, and dandruff, there is deeper and richer information that Neanderthal DNA offers. So, let’s take a moment to appreciate the Neanderthal within us. 

Works Cited

Corinne N. Simonti et al., “The phenotypic legacy of admixture between modern humans and Neandertals.” Science, 351, pp. 737-741, 12 Feb. 2016,  https://www.science.org/doi/10.1126/science.aad2149. 

Dannemann, M, et al. “Neandertal introgression partitions the genetic landscape of neuropsychiatric disorders and associated behavioral phenotypes”. Transl Psychiatry, 12, 433, 2022, https://doi.org/10.1038/s41398-022-02196-2.

Lu Chen, et al., “Identifying and Interpreting Apparent Neanderthal Ancestry in African Individuals.” Cell, Vol. 180, Issue. 4, pp. 677-687.e16, 20 Feb. 2020,  https://doi.org/10.1016/j.cell.2020.01.012.

Michael Dannemann. “The Population-Specific Impact of Neandertal Introgression on Human Disease.” Genome Biology and Evolution, Vol. 13, Issue 1, January 2021, https://doi.org/10.1093/gbe/evaa250. 

“Neanderthal DNA has subtle but significant impact on human traits.” Vanderbilt University, 11 Feb. 2023, https://news.vanderbilt.edu/2016/02/11/neanderthal-dna-has-subtle-but-significant-impact-on-human-traits/. Accessed 30 Nov. 2023. 

Reardon, Sara. “Neanderthal DNA affects ethnic differences in immune response.” Nature, 20 Oct. 2016, https://doi.org/10.1038/nature.2016.20854. Accessed 30 Nov. 2023.