Regional Replacement Model

The Regional Replacement Model suggests that Homo sapiens interbred with early humans as they dispersed across the globe out of Africa. This led to the replacement of these species over time resulting with Homo sapiens becoming the most prominent species. However, there is a multitude of genetic and cultural evidence where modern humans did not entirely replace the other hominin species (i.e. Denisovans and Neanderthals). Through interbreeding, modern humans inherited some traits from other hominin species that helped them adapt and survive in new environments, unfamiliar diseases, climate differences, and altitude changes.

Ancient DNA and Interbreeding

Modern humans did not evolve alone, we share genes and traits with other human species. Neanderthal and Denisovan DNA has been uncovered in modern humans thanks to advanced research in genome mapping. This is clear evidence that Homo sapiens interbred with these species as they migrated out of Africa.

This discovery and continuing research has changed how we view human evolution and shows H. sapiens did not solely replace other hominin species, but interacted with them.

What is a genome?

A genome is a complete set of DNA in one organism, entirely made up of genes. All humans share about 99.9% of their DNA, but small differences make each person unique. These differences are inherited! Some of these differences, or traits, come from immediate ancestors like our grandparents and parents. These include things like eye color, hair color, and even facial features. However, some of these traits come from ancient human relatives like Neanderthals and Denisovans.

Inherited traits

Not all modern humans present with these traits and there is a lot we still don’t understand. Our appearances and our physiology are dependent on multiple factors and not just on one gene in our genome. Some things we did inherit from ancient human relatives include variants in our immune systems, cold climate adaptations, and high altitude adaptations.

Neanderthal genes affect a receptor in our immune systems (Toll-like receptors) which help us fight bacteria and viruses, this is linked to stronger immune responses, but also high allergy risks.
Cold climate adaptations also come from neanderthal genes, which regulate fat storage and metabolism. This helped ancient humans survive colder climates they experienced in Ice Age Europe and Asia.
The EPAS1 gene variant from Denisovans allows better oxygen processing in low oxygenated environments, often found at high altitudes.

Nuclear DNA

Most of these traits are passed down by nuclear DNA (DNA that is inherited from both parents and stored in the nucleus of each cell). This type of DNA controls almost everything, for example: appearance, disease resistance, metabolism, and even physiology. By studying this type of DNA, scientists were able to find clear evidence of Neanderthal and Denisovan ancestry in modern humans. 2 major genome projects were conducted to come to these results.

The Neanderthal Genome Project (2010) was the first to sequence a large portion of the Neanderthal nuclear genome. The results showed 1-2% of DNA in humans not originally from Africa is from Neanderthals. This led to other studies about gene inheritance and affected traits.
The second major genome project was the Denisovan Genome Project, first sequenced from a finger phalange in the Denisova Cave, SIberia and was published in 2010. This revealed that Denisovans were a distinct species, not neanderthals or H. sapiens. This nuclear DNA was further tested and it revealed that populations in Oceania and Southeast Asia have up to 6%. One major find was the EPAS1 gene which is common in people of Tibetan descent.

Cultural Evidence

Art and culture

Chauvet Cave

The Chauvet Cave in France shows sophisticated painting of abstract shapes and animals that are over 30,000 years old. These might have been created by modern humans and Neanderthals. The Venus figurines that were found in Europe also show symbolic thinking.

Venus Figurines

The Venus figurines that were found in Europe also show symbolic thinking.

Tools

In some regions, there is an overlap in tool styles in the Middle to Upper Paleolithic transition (~50,000-40,000 years ago). H. sapiens have started arriving in Europe at this time. Neanderthal groups began to produce tools that looked extremely similar to tools that were made by H. sapiens. The shift from stone-based, flake, scraper, and point tools to long blades, bone tools, and beads and pendants happened suddenly. The exact reason behind this shift is unknown, but there is no doubt that there is a culture blend.

Old neanderthal tools

dull, short, stone based tools

H. sapien tools

sharp, narrow, long

"newer" neanderthal tools

still mostly stone, sharper and pointier

Burial Practices

Similarly, in burial practices, neanderthals seemed to shift to follow H. sapiens, especially during the time they coexisted together in Europe and the Middle East. Neanderthals began following placement, ochre use, and even adding grave goods. This shows another form of cultural blending and other similarities between out ancestor and another relative.

Big picture

The Regional Replacement Model says modern humans evolved in Africa about 200,000 years ago and when they migrated out of Africa into Europe and Asia, they replaced other hominin species. Originally, we assumed there was no interbreeding or sharing of culture between the species, but with modern analysis of DNA and different culture habits, we see long-term gene flow between the populations.

We did not replace all other early humans, we interacted, interbred, and shared culture. Human evolution is not a straight line and without interbreeding, some of the traits we have now wouldn’t exist. These traits, while very limited to have affects on modern humans today which allowed for us to thrive and move around the globe.

References

Content:

Green, R. E., et al. (2010). A draft sequence of the Neandertal genome. Science, 328(5979), 710–722. https://doi.org/10.1126/science.1188021

Sankararaman, S., et al. (2014). The genomic landscape of Neanderthal ancestry in present-day humans. Nature, 507(7492), 354–357. https://doi.org/10.1038/nature12961

Huerta-Sánchez, E., et al. (2014). Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA. Nature, 512(7513), 194–197. https://doi.org/10.1038/nature13408

Brand, C. M., Colbran, L. L., & Capra, J. A. (2022). Predicting archaic hominin phenotypes from genomic data. Annual Review of Genomics and Human Genetics, 23(1), 591–612.

Ko, K. H. (2016). Hominin interbreeding and the evolution of human variation. Journal of Biological Research-Thessaloniki, 23(1), 17.

Pomeroy, E., et al. (2020). Issues of theory and method in the analysis of Paleolithic mortuary behavior: A view from Shanidar Cave. Evolutionary Anthropology, 29(5), 263–279.

Reynolds, N., Dinnis, R., Bessudnov, A. A., Devièse, T., & Higham, T. (2017). The Kostënki 18 child burial and the cultural and funerary landscape of Mid Upper Palaeolithic European Russia. Antiquity, 91(360), 1435–1450.

Zilhão, J. (2006). Neandertals and moderns mixed, and it matters. Evolutionary Anthropology, 15(5), 183–195.

Images:

Douka, K., & O’Reilly, M. (2017). New thoughts on the spread of modern humans. Archaeology Magazine. https://archaeology.org/news/2017/12/08/171208-early-migratory-pathways/

World History Encyclopedia. (2025). Chauvet Cave. https://www.worldhistory.org/Chauvet_Cave/

Smithsonian National Museum of Natural History. (2025). Venus of Willendorf. Smithsonian Institution. https://humanorigins.si.edu/evidence/behavior/art-music/figurines/willendorf-venus

American Museum of Natural History. (2025). Neanderthal Tools. https://www.amnh.org/exhibitions/permanent/human-origins/neanderthal-tools

Max Planck Society. (2020). The oldest Upper Paleolithic Homo sapiens in Europe. https://www.mpg.de/14778668/0505-evan-019609-the-oldest-upper-paleolithic-homo-sapiens-in-europe

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