Neanderthals and Humans Interbred

Superfact 114: Early humans (early Homo sapiens) lived at the same time as many other homo species including Neanderthals (Homo Neanderthalensis) and Humans and Neanderthals Interbred.

Two skulls facing each other. Art Study - Old Textured Paper Vintage Antique Poster style (Vintage Version). | Neanderthals and Humans Interbred
Neanderthals Archaic Extinct Human Skull Vs Modern Human Skull Comparison. Shutterstock Asset id: 2238778267 by Winters860

It’s been known for more than a decade that ancient members of our species, Homo sapiens, met and mated with our evolutionary cousins, Neanderthals. If you have read the Savage Land trilogy by Jacqui Murray, or you have taken a DNA test from, for example, 23AndMe, then you already knew that. Today, up to 2% of the genomes of people outside sub-Saharan Africa originated from Neanderthals. The Neanderthal genome was successfully sequenced in 2010. You can read more about it here. More recently, an analysis of Neanderthal X chromosomes found that most cross-species couplings involved Neanderthal males and modern human females.

Photo of a reconstruction of a Neanderthal man
Reconstruction of a Neanderthal by Natural History Museum. Werner Ustorf, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons

My wife and I took a DNA test with 23AndMe to find out about inherited diseases as well as our ancestry. I found out that my ancestry was 99.8% Northwestern European, 85.3% Scandinavian/Sweden/Norway, 14.4% Finnish, 0.1% other Northwestern European, and 0.2% Siberian. I also found out that I had strong Neanderthal ancestry. The report said that I have more Neanderthal variants than 99% of customers. Even though this kind of information is fun, it is risky to have some of this information exposed, so I deleted it.

Man geneticist. Doctor sits at table in genetic laboratory. Chains of DNA or RNA. Sequencing human genome. Doctor studies DNA. Geneticist conducts scientific experiments Geneticist looks at test tubes
Geneticist sequencing human genome Asset id: 2479929725 by FOTOGRIN

Anyway, I consider this a super fact because it comes as a surprise to many that humans and Neanderthals interbred, and that many of us therefore have traces of neanderthal DNA. It is also an important fact that we know is true.

This map of Europe and West Asia shows the region where Neanderthals have been found. | Neanderthals and Humans Interbred
Known Neanderthal range in Europe (blue), Southwest Asia (orange), Uzbekistan (green), and the Altai mountains (violet), as inferred by their skeletal remains (not stone tools). There were 165 such places by 2017. Nilenbert, N. Perrault, auteur du guide complet du canotageI, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/&gt;, via Wikimedia Commons

Early Homo Sapiens lived at the same time as many other human species

Early humans, early homo sapiens, lived at the same time as many other human species, not just Neanderthals. Early Homo sapiens lived at the same time as Denisovans, Homo floresiensis, Homo naledi, Homo luzonensis. Homo heidelbergensis, Homo erectus, and maybe other species as well.  Neanderthals interbred with homo sapiens and died out around 40,000 years ago. The Denisovans also interbred with homo sapiens and died out around 30,000 to 50,000 years ago. Moreover, Homo Neanderthalensis interbred with Homo Denisova. You can read more here and here.

The map shows the movement of Homo heidelbergensis originating in Africa and moving into Europe and Asia with Neanderthals (in yellow) emerging in Europe and moving into Asia. The Denisovans emerged in Asia and spread further east.
The evolution and geographic spread of Denisovans as compared with Neanderthals, Homo heidelbergensis and Homo erectus. John D. Croft at English Wikipedia, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons.

Speciation is considered relative

Homo Neanderthalensis and Homo Sapiens were different species, so it may seem strange that they could interbreed. However, species is a complex non-static concept, and it is considered relative.

It is often said that two animals belong to the same species if they can interbreed in nature and produce viable, fertile offspring. However, it is not that simple. An animal A may be able to successfully interbreed with an animal B, and that animal B may be able to successfully interbreed with an animal C, but animal A and C cannot interbreed. Animal A could be said to be a different species relative to animal C, but animal B could be said to be the same species as both animal A & C using the definition above. A great geography related example of this is ring species. In a ring species, gene flow occurs between neighboring populations of a species, but at the ends of the ring the populations don’t interbreed.

The picture depicts different subspecies as little colored circles centered around a big lake. The color changes a little bit at the time. All the circles next to each other can interbreed. | Neanderthals and Humans Interbred
Illustration of ring species, an example of how speciation can be relative. All the circles next to each other can interbreed but at the end it no longer works. Andrew Z. Colvin, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons

For the case of Neanderthals and Homo sapiens (and Denisovans); at certain points in history, you could consider Homo Neanderthalensis and Homo Sapiens to be different subspecies rather than different species. That is why you sometimes hear the terms Homo Sapiens Neanderthalensis and Homo Sapiens Sapiens. I can add that Homo sapiens certainly got around, as you can see on the map below.

A world map showing portions of Africa being yellow and red, and portions of Asia being yellow and dark yellow with red arrows representing migrating Homo Sapiens. The map features several time markers representing the arrival of Homo Sapiens. | Neanderthals and Humans Interbred
The spread of Homo Erectus (yellow), Homo Sapiens (red) and Homo Neanderthalensis (dark yellow). NordNordWest, Public domain, via Wikimedia Commons

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Author: thomasstigwikman

My name is Thomas Wikman. I am a software/robotics engineer with a background in physics. I am currently retired. I took early retirement. I am a dog lover, and especially a Leonberger lover, a home brewer, craft beer enthusiast, I’m learning French, and I am an avid reader. I live in Dallas, Texas, but I am originally from Sweden. I am married to Claudia, and we have three children. I have two blogs. The first feature the crazy adventures of our Leonberger Le Bronco von der Löwenhöhle as well as information on Leonbergers. The second blog, superfactful, feature information and facts I think are very interesting. With this blog I would like to create a list of facts that are accepted as true among the experts of the field and yet disputed amongst the public or highly surprising. These facts are special and in lieu of a better word I call them super-facts.

58 thoughts on “Neanderthals and Humans Interbred”

    2. Thank you so much Maggie. I’ve read some of Jean Auel’s books too, a long time ago. Jacqui Murray’s books and Jean M. Auel’s books have similarities but Jacqui’s books are based on more recent discoveries and research and often include information about the time period. They are very exciting, a lot of fun and interesting.

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        1. No don’t worry, but if you liked Jean Auel’s book I’ll bet you will like Jacqui’s books. I can add that Jacqui also cover a larger time span and several homo species, which gives you a wider perspective.

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  2. How intriguing, Thomas! I’m fascinated that you and your wife took a DNA test (kind of wish me and my husband could also do this!). I see what you mean about Homo Neanderthalensis and Homo Sapiens being a different subspecies and it’s cool that Homo Sapiens got around, as shown by the map.

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    1. Thank you Ada. I agree it is fascinating information that many do not know. I believe you can still take DNA tests with 23AndMe but their bankruptcy spooked me. The problem is that there are a lot of health related information in the DNA and you don’t want insurance companies to get their hands on that.

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      1. Wow, I never thought of that! Yes, if insurance companies got their hands on it, that would be a gamechanger! I’m a bit torn with the whole thing, to be honest, as I think it would’ve helped me at certain points to know things in the test (I have an autoimmune condition triggered by childbirth and didn’t realize or get a diagnosis for it until years later) but keeping this data safe is another issue entirely.

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        1. Unfortuntaly, as long as health inusrance companies can reject people for any pre-existing condition, this information is dangerous for us and a goldmine for them. Otherwise this information could be very useful for detecting problems long before they occur. It is a complicated situation but I decided to delete it.

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  3. This was a great read. I have actually started a similar post, but from a slightly different angle: do we really know where we come from?

    Whenever I hear someone yell, “Go back where you came from,” in some news clip or online argument, I can’t help but think, “Okay, if we go back far enough, we all came from Africa.”

    Modern humans, Homo sapiens, originated in Africa before migrating across the globe. Along the way, they encountered and interbred with other human species, including Neanderthals. As a result, many people today carry a small percentage of Neanderthal DNA.

    What fascinates me most is not the differences between us, but the similarities. Despite all the lines we draw between countries, cultures, races, and religions, we are all branches of the same family tree. The evidence suggests that Homo sapiens were the last surviving human species, likely due to a combination of adaptability, cooperation, communication, and social organization.

    I was not aware that Neanderthal ancestry is a sensitive topic for some people. Personally, I find it fascinating. Rather than diminishing our humanity, it adds another chapter to the story of who we are and how we got here.

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    2. That sounds very interesting. I am looking forward to your post Kevin. I should say that what spooked me about 23AndMe was not the Neanderthal finding but the fact that they went bankruptcy and the DNA analysis include a large amount of health related information that you don’t want health insurance companies to get their hands on.

      I joined an online Neanderthal club that required you to be in 98 percentile or above for membership (I have 99%). However, some people in the club said weird things like we in the club should demand reparations because homo sapiens were responsible for the demise of neanderthals. I thought it was joke and laughed at first. Then when I realized that many took this seriously I decided it was time to leave the club.

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      1. Yea that is very odd! reparations. Good move getting out, I think it is kind of cool. I read that they did not have a chance, lack of any communication type skills, organization skills and their heads were to big consuming a lot of energy. That is not a sapiens thing and it is kind of nuts that is even a discussion topic.

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  6. Thank you for the shout out. You have touched on a piece of Neanderthal-H. sapiens admix I don’t understand, maybe you can help me with: Neanderthals and Homo sapiens interbred but I am reading that the Neanderthal Y chromosome–for males–didn’t survive, only females. Can you explain that? According to med.stanford.edu: There is no trace of the Neanderthal Y found in any modern human male. I’m assuming that had to contribute to their extinction? Or am I wrong?

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    1. I don’t know the details but this article from Science (it is a reputable science publication) is stating that it likely was sexual preference (consensual or not). That is certainly an interesting topic to explore. Thank you so much Jacqui for the visit and I am looking forward to your upcoming books.

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    1. That is a good question. I’ve been told that the title needs to be short and I just used “human” to refer to Homo Sapiens or Homo Sapiens Sapiens, and human is not precise. Homo is the genus to which both Homo Sapiens and Homo neanderthalensis belong but Homo Sapiens and Homo neanderthalensis are two different species. However, as mentioned above – (ring species) species is a fluid concept and at times they were rather subspecies Homo Sapiens Sapiens and Homo Sapiens neanderthalensis and during those times they could interbreed. I would say that if you with human mean modern humans, like anyone alive today, then Neanderthals were not human. If you with human mean anyone in the homo genus, then Neanderthals were human.

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    1. I did not explain, but what happened was that the DNA from 23AndMe included a lot of health related information (hundreds of items/genes) and 23AndMe went bankruptcy. I was afraid that health insurance companies could get a hold of our health related DNA and misuse it. Ancestry and Neanderthal stuff is just fun info but the health related information could be dangerous if it gets in the wrong hands. For example, if you have a gene that makes you pre-disposed for let say a certain type of cancer the health insurance company could use that to deny you health insurance.

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    1. Ha ha maybe you are right Cindy. If I read one more of Jacqui’s books maybe I will walk into the grocery store wearing a reindeer hide and a spear and the police come and arrest me. Anyway, I agree with you, Jacqui’s books are great. Thank you so much Cindy.

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  12. Although this Superfact is not new to me, I still find it interesting. I remember in the 1970s going to the natural history museum in Seattle and seeing their reconstruction of a Neanderthal. It looked just like the country singer, Buck Owens. At the time, before we knew that Neanderthals and Homo Sapiens interbred, my dad and I speculated that Owens must have been at least part Neanderthal. Now we know that might actually be possible!

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  14. It’s interesting that I’ve assumed the definition of species I learned in high school about the viable offspring, was correct, though I know things are often more complex than we once believed. Thank you for clarifying.

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    1. Well, that definition is not wrong. It is a simple one that is often used. However, it is often the case that A can breed with B (viable offspring) and B can breed with C but A can’t breed with C. Despite being a useful definition it is fuzzy, fluent and relative. Real life is complicated. Thank you JoAnna.

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  15. Java Bean: “Ayyy, our Dada has done one of those DNA tests, but not the one that tells you if you have any Neanderthal DNA, so that remains a mystery. Given that he has ancestors in France and Italy, though, it seems like he might!”Lulu: “That’s funny, you and I know how ‘wolfy’ we are, but Dada doesn’t know how ‘Neanderthal’ he is …”

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