Humans
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Like a prehistoric wolf wondering how begging for scraps around a campfire could possibly go wrong, the first Neanderthals to breed with our own species could never have imagined how grave the repercussions would be. And while these ancient hominins avoided the ignominy of being reduced to chihuahuas or pugs, their sexual exploits may ultimately have caused their extinction.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Exactly how Neanderthals fell off the face of the Earth is a hotly debated subject, although one possible explanation is that they didn’t. Instead, their repeated interbreeding with Homo sapiens may have caused them to become genetically diluted by us, to the extent that we basically absorbed them.
Evidence for this sex-fueled demise can be seen in every one of us. On average, all non-Africans alive today carry between two and four percent Neanderthal DNA, yet we don’t all possess the same combinations of archaic genes. In fact, if you add up all the Neanderthal genes in the collective modern human genome, you’d end up with more than half of the Neanderthal genome.
In other words, Neanderthals didn’t disappear, and continue to contribute to the genetic makeup of the human race. But if we kept so many of their genes, why didn’t Neanderthals also survive the inter-hominin love-in by inheriting our DNA?
The answer is that they kind of did – at least for a while. As the two species intermingled, they produced generations of hybrids that not only looked like a cross between humans and Neanderthals, but even created a shared culture. In the Middle East, for instance, these hybrids developed a unified funerary tradition, becoming the first hominins to bury their dead.
The problem for Neanderthals, however, is that there were a lot more of us than there were of them. It’s estimated that as successive waves of Homo sapiens migrated out of Africa and into Eurasia, our numbers began to dwarf theirs by several orders of magnitude.
This meant that as we continued to interbreed, the hybridized gene pool became overwhelmingly stacked with Homo sapiens genes. Neanderthal DNA, on the other hand, became increasingly diluted until the genetic identity of the entire lineage was erased in the offspring population.
Yet this wasn’t the only reason why these Pleistocene hook-ups were laced with regret for our ancient relatives. Some researchers believe that many Homo sapiens genes were actually deleterious for Neanderthals and may have severely hindered their fertility.
For instance, it has been argued that as the modern human Y chromosome replaced the Neanderthal equivalent, Neanderthal males became sterile. Other research suggests that human genes might have messed with the oxygen affinity of Neanderthals’ red blood cells, resulting in pregnancy complications.
Ultimately, we can’t say for certain whether getting into bed with a human was the cause of Neanderthals’ extinction, and it’s highly likely that other factors – including climate change and competition for resources – played a role. But if there’s one lesson from all of this, it’s that when it comes to choosing a mate, you’re always better off finding someone from your own species.
