If Neanderthals Went Extinct, Why Do Some Humans Still Have Their DNA? — Scientists Finally Explain

Neanderthals were believed to have been extinct for nearly 40,000 years. But surprisingly, their DNA still persists in people who did not descend from Africa. So, most individuals who have European and Asian ancestry typically have 1 to 2% of their genome from Neanderthals.

This is simply due to interbreeding between the two species, which allowed the Neanderthals to pass on their genes despite being extinct now. However, how was this all possible? And are Neanderthals really extinct, or did we just slowly mix with them?

Interbreeding Left a Lasting Legacy

Around 60,000 to 50,000 years ago, groups of early homo sapiens encountered another human species after migrating from Africa into Eurasia. Genetic analysis of their offspring’s remains from around that era showcases that they reproduced together with modern humans’ ancestors.

Scientists have pinpointed that most of the interbreeding occurred about 47,000 years ago, lasting nearly 7,000 years before stopping. This is also around the same time Neanderthals were believed to have gone extinct.

Some of the reasons are thought to be climate change, the reproductive and resource competition against homo sapiens, and potential transmission of disease they are not immune to.

Read more: Smithsonian Magazine

Who Has Neanderthal DNA—and How Much?

A Neanderthal Perspective on Human Origins - 2014

The estimate of people’s genes to have been from Neanderthal DNA is about 1 to 4%; however, the most common range is about 1 to 2%. Keep in mind that these numbers usually are only from homo sapiens who have originated from outside of Africa.

It is because the humans who did not venture out to Europe and Asia most likely did not encounter Neanderthals. However, they have met some other human species, such as the Denisovan. In fact, some African populations, like the Melanesians, have 4 to 6% of their DNA from them.

Why Some Neanderthal Genes Persist

Most of the neanderthal genes present in some individuals are actually non-coding, which means that they do not directly affect visible traits. Scientists believe that they will gradually disappear due to negative selection. However, they still persisted because some of these genes provided useful adaptations.

For example, researchers have found out that they affect our immune system, skin pigmentation, and even some human behaviors, like our sleeping cycle. These genes could have made some individuals morning people, and they also contributed to both lighter and darker skin tones, suggesting that Neanderthals are diverse themselves.

Read more: Wikipedia

Why Neanderthals Gone—But Their DNA Remains

Homo sapiens, or modern humans, before even migrating out of Africa, were already surviving in multiple different types of environments. Archaeologists found them living in forests, dry lands, and mountain areas, which is a key factor in their global expansion and eventual domination.

Neanderthals, on the other hand, are low in population, making them have reduced genetic diversity, which exposes them to more risks and diseases. In other words, if a disease emerges, let’s say from homo sapiens, their population would not have enough genetic diversity that could create beneficial mutations for resisting said disease.

This is one of the theories of scientists as to why they have vanished, along with the intense competition with a growing number of Homo sapiens who are more adept at surviving different types of environments and genetic challenges. However, before they became extinct, they were able to pass on some of their genes to their mixed-species offspring, who passed them on to their own, and so on.

What If the Neanderthals Had Not Gone Extinct?

Author's Final Thoughts

Neanderthals may have been extinct as a species, but their legacy still lives on today, about 40,000 years since they last walked on the Earth. Interbreeding during early human migration inserted their DNA into our own, which led to some neutral and some beneficial traits. So, while they are gone now, pieces of who they were will continue to shape who we are.

Read next: If Evolution Is Real, Why Aren’t Apes Turning Into Humans? — Here’s How Scientists Explain the Confusion

References & Further Reading

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

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

Vernot, B., & Akey, J. M. (2014). Resurrecting surviving Neandertal lineages from modern human genomes. Science. https://doi.org/10.1126/science.1245938

Prüfer, K., et al. (2014). The complete genome sequence of a Neanderthal from the Altai Mountains. Nature. https://doi.org/10.1038/nature12886

Browning, S. R., et al. (2018). Analysis of human sequence data reveals two pulses of archaic Denisovan admixture. Cell. https://doi.org/10.1016/j.cell.2018.02.031