Before the early 2010s, scientists were conflicted on the question of Homo sapiens interbreeding with Neanderthals, but since then, multiple studies have shown the incredible overlap between Neanderthal and human DNA - enough that approximately 1%-4% of modern human DNA traces directly back to Neanderthal ancestry.
Neanderthals coexisted with modern humans for tens of thousands of years, and the two groups certainly met. Evidence shows that Homo sapiens not only procreated with Neanderthals - they also slew and ate them.
It's not surprising that prehistoric humans mated with Neanderthals since prehistoric people were notoriously promiscuous. But while science proves humans mated with Neanderthals, the evidence still leaves some questions open. When did they begin to interbreed? Was it consensual? And were there human-Neanderthal relationships?
- Photo: Service communication du Conseil général des Alpes de Haute-Provence / Wikimedia Commons / CC BY-SA 3.0
Homo Sapiens Outnumbered Neanderthals
Why did Neanderthals go extinct while Homo sapiens flourished? Part of the answer has to do with the small size of the Neanderthal population. Between 38,000 and 70,000 years ago, the Neanderthal population in Europe was small, perhaps as few as 1,500 female Neanderthals of reproductive age. In the twilight of the Neanderthal era, they were simply outnumbered by Homo sapiens.
Researcher Adrian Briggs explains, "Because there never really were millions of them, they probably were more susceptible to some event that made them go extinct, which to me, suspiciously coincides with the emergence of modern humans."
- Photo: Daniela Hitzemann (left photograph), Stefan Scheer (right photograph) / Wikimedia Commons / CC BY-SA 4.0
Neanderthals And Homo Sapiens Weren't That Different
While Neanderthals and Homo sapiens diverged evolutionarily around 500,000 years ago, the two groups weren't that different. Homo sapiens edged out the Neanderthal slightly in height, while the Neanderthal boasted bigger and stronger bones. Neanderthals had larger brow ridges and bigger noses.
Another similarity anthropologists commonly refer to is the genitalia. Neanderthal penises probably looked a lot like human ones. Anthropologist John Hawks explains that most primates have "horny papillae" or spines on their penises, but both humans and Neanderthals were missing the genes for these spines.
- Photo: Xavier-ROSSI/Gamma-Rapho / Getty Images
Homo Sapiens Likely Interbred With Other Early Hominid Species
Neanderthals weren't the only hominids that Homo sapiens interbred with. New research shows that Homo sapiens also mated with Homo erectus and Homo habilis, as well as with Denisovans, who populated much of Asia. Modern people from Oceania and East Asia still carry fragments of Denisovan DNA.
Dr. Michael Hammer says, "We think there were probably thousands of interbreeding events. It happened relatively extensively and regularly." Although prehistoric Homo sapiens interbred with other hominid species, Homo sapiens outlived their competition.
- Photo: State Office for Heritage Management and Archaeology Saxony-Anhalt / State Museum of Prehistory Halle / Wikimedia Commons / CC BY 3.0
There Are Still Questions As To Whether Or Not Neanderthals And Homo Sapiens Co-Existed
Some scholars question the recent studies showing Neanderthal-human interbreeding. In a 2012 study, researchers precisely dated Neanderthal bones from southern Spain, discovering they predated the arrival of Homo sapiens in the area by as much as 10,000 years. However, it's possible Homo sapiens arrived in the area sooner than previously known.
Others argue that the genetic similarities trace back to a common ancestor rather than coming from interbreeding. Yet with modern humans showing up to 4% Neanderthal DNA, and the lack of Neanderthal DNA in Africans, interbreeding remains the current scientific consensus.