Are Humans The Cause Of Neanderthals Extinction ?
It is possible that our ancestors may have contributed to Neanderthals extinction, but the extent of our role remains to be determined.
After 400,000 years of roaming Europe and Asia, Neanderthals disappeared. Why this happened is a contentious topic amongst experts. It is possible that our ancestors may have directly or indirectly contributed to Neanderthals extinction, but the extent of our role remains to be determined.
Our distant cousins, the Neanderthals, lived for around 400,000 years in Europe and some parts of Asia. From 80,000 years ago, their populations began to decrease, and, eventually, they disappeared 50,000 years later.
Our species, Homo sapiens, evolved in Africa around 200,000 years ago. Around the time that the Neanderthal populations were decreasing, H. sapiens began leaving the African continent and populating Asia and Europe.
Did our ancestors simply move into the territories Neanderthals had left behind, or was their movement north the reason for the Neanderthals’ downfall? We asked 16 experts in paleoanthropology whether H. sapiens drove Neanderthals to extinction – the consensus was ‘uncertain’ with a score of 50 percent. Here is what we found.
Is there any evidence that Homo sapiens and Neanderthals fought each other?
Due to the classic portrayal of ‘cave man’ being violent in nature, supported by fossils showing that both H. sapiens and Neanderthals frequently suffered traumatic injuries, we might infer that our ancestors brutally killed all the Neanderthals.
There was an overlap of at least 100,000 years between the two species, but archaeological evidence suggests that, in most areas, modern humans only arrived after Neanderthals had died out.
Genetic evidence, on the other hand, shows that some gene exchange occurred between the two species, meaning that they bred together. As a result of this, about 2 percent of the DNA of non-African descendants is Neanderthal. Expert Paul Pettitt from Durham University thinks this close contact “was probably at the edges of their ranges, i.e., in western and central Asia, and not in their European core”.
He adds that “while contact obviously did occur from time to time, and that such contact could have been violent, if this did occur it was exceptional, and certainly nowhere near enough to cause, or probably even contribute in a minor way, to Neanderthal extinction.”
Professor Chris Hunt believes that more data is required to confidently answer this question. He believes “we have to concentrate effort on sites where it looks as if there was no gap between Neanderthals and H. sapiens.
“It then requires very high-resolution dating to demonstrate that the gap between one and the other was very short, and a careful exploration of the evidence about what Neanderthals and H. sapiens were doing on the site, how they lived, the ecology and climate of the time and so forth.”
Such investigation is currently taking place at Shanidar Cave in Iraq.
Is there any evidence that Homo sapiens competed with Neanderthals for resources and territories?
Neanderthals shared a lot of similarities with our ancestors. Like the ancient H. sapiens, they made fires, hunted large animals, and even cared for the injured.
These similarities suggest that the two species would have thrived in similar territories. Dr Andrew Sorensen from Leiden University says the “inflow of peoples from Africa would have increased competition for food resources”.
This theory assumes that H. sapiens had certain advantages over Neanderthals, such as superior intelligence, adaptability, or strength.
Although the exact nature of this advantage is not clear, archaeological evidence suggests that our ancestors’ population increased tenfold as they replaced Neanderthals in Europe.
Could the Neanderthals have been wiped out by climate change?
“Neanderthals went extinct at a time when a lot of other ecological things were happening. There were extinctions of a number of large mammals during this general time including the cave bear and the cave hyena,” says Dr John Stewart from Bournemouth University.
This means that other factors, such as climate, may have played a role in the disappearance of Neanderthals.
Professor John Shea notes that the timing of Neanderthal extinction coincides with “the Heinrich H5 Event, a several thousand-years long shift from already very cold conditions to even colder conditions … the H5 event probably wiped out most of them, and swiftly, for such events happen fast. The survivors might have lived on in pockets along the Mediterranean, where their numbers dwindled.”
Are there any other explanations for the extinction of Neanderthals?
A recent publication asked 216 paleoanthropologists what they thought drove the extinction of Neanderthals. The most popular reasons were demographic factors.
This means statistical factors that influence populations, such as initial population size, inbreeding, and stochasticity. The Neanderthal population was likely very small, making it vulnerable to extinction as a result of even small environmental changes.
Interestingly, a 2017 publication used a computer model to show that Neanderthal extinction could occur without the need for competition from H. sapiens or climate change. Another model made in 2019 could simulate the extinction of Neanderthals simply through natural shifts in the population birth and death rates.
When the migration of H. sapiens was included in this model, our ancestors only needed to migrate into territories in such a way that the already small Neanderthal population became fragmented – no competition was needed.
In conclusion, there is no clear consensus on what caused the extinction of Neanderthals, and whether our ancestors are to blame.
Most researchers in the field agree with Professor Joshua Akey that “a number of reasons likely explain why the Neanderthal lineage ended ~30,000 years ago.”
Dr Oren Kolodny adds that, “the majority of living humans carry in their genes some 1-2 percent of DNA sequence that originates in Neanderthals, so in some sense, they never went extinct at all.”
Originally published at Science Alert