'Intellectually inferior' humans caused Neanderthals to go extinct, a new book claims

• What drove Neanderthals to extinction is one of the biggest mysteries in human history.
• A new book “The Naked Neanderthal” says humans were the main cause thanks to their superior weapons.

“Who the hell was this Neanderthal?”

That's the question archaeologist Ludovic Slimak asks in his new book "The Naked Neanderthal."

Neanderthals were humans' closest relatives. But something happened millennia ago that wiped them out.

Today, there are 8.1 billion modern humans on Earth and 0 Neanderthals.

"Why are they no longer here?" It's one of the big questions researchers always ask about Neanderthals, University of Victoria archaeologist April Nowell told Business Insider.

In the past, scientists depicted Neanderthals as less intelligent than humans. But, according to Slimak, an ancient Homo sapien was, in terms of creativity, “probably no match for Neanderthal populations and was in all likelihood intellectually inferior,” he wrote.

Many scientists suggest a combination of factors, including climate change and low fertility rates, wiped out Neanderthals. But Slimak thinks that, despite being intellectually inferior, early humans are to blame.

In other words, if it weren't for us, Neanderthals might still be here.

Who were the Neanderthals?

Humans and Neanderthals share a common ancestor dating back to between 550,000 and 750,000 years ago. Compared to early humans, Neanderthals were muscular with a prominent brow and less pronounced chin.

Neanderthals spread into northwestern Europe, the Middle East, Central Asia, and Southern Siberia long before Homo sapiens. They lived in some of these regions for hundreds of thousands of years until around 40,000 years ago, when they went extinct.

Did humans kill off Neanderthals?

Slimak suspects humans are to blame because of what he discovered in a cave in Southern France in 2008.

By dating the soot where various artifacts were located, he determined that humans and Neanderthals overlapped there around 54,000 years ago.

It was the first time, he wrote, there was evidence of an encounter between humans and Neanderthals.

There isn’t direct proof of conflict between the two species, Slimak noted.

"To find archaeological traces of a Neanderthal–Sapiens war we would need to uncover many more archaeological sites from this key period," he wrote.

At this particular cave, however, Neanderthals did return, followed by humans around 44,000 years ago. Since humans were the final species to occupy the cave, Slimak argues it's because they'd replaced those Neanderthals by wiping them out.

Nowell said that while direct competition or conflict between the two species may have caused humans to take over the site Slimak studied, "it may not be the case everywhere."

Humans' superior weapons

Scientists have found relatively few weapons belonging to Neanderthals, Slimak wrote. However, Neanderthals were “excellent artisans,” making tools with “a creativity that is beyond us.”

But this creativity was not enough to outwit humans’ regimented weapon making, which ultimately led to Neanderthals' extinction, according to Slimak.

That's because the “modern humans who colonized Europe produced weapons that were both more numerous and more effective,” he wrote.

Humans’ insistence on standardization led to uniform flints, and Neanderthals’ originality couldn’t compete.

The Neanderthals in our genes

Archaeologists haven't found much direct evidence of the two species living among one another, but genetic sequencing shows humans and Neanderthals interbred.

In some populations, the data suggests the two species mated multiple times over thousands of years.

Yet genes can't tell us much about the nature of these interactions or how closely or amicably humans and Neanderthals lived. For that, archaeologists need more evidence like Slimak's French cave.

Even with existing sites, it's tough.

The difficulty with linking the first appearance of humans and the last appearance of Neanderthals in Europe is that it relies on radiocarbon dating, Nowell said.

Scientists use the technique to measure the amount of carbon remaining in a substance and calculate the age based on carbon isotopes’ rate of decay.

It’s most accurate until around 50,000 years ago, Nowell said.

“The disappearance of Neanderthals is right at the edge” of Carbon-14 dating, Nowell said. “And that's exactly the time period that we're interested in.”

There are areas in France and Spain where humans do appear to replace Neanderthals. With the current technology, though, it's difficult to tell whether they cohabitated for 1,000 years or 5,000 years first.

If humans and Neanderthals coexisted for several millennia, their interactions might be more complex than the "fully-fledged conquest" that Slimak described.

Neanderthals may have already been in decline

Nowell thinks many archaeologists view creativity differently than Slimak. “Usually the argument is made that Homo sapiens are more creative,” she said. They were able to move into new environments and adapt.

Moving into new spaces could have caused conflict, but human colonization is far from the only explanation for Neanderthals’ extinction, according to Nowell.

“I think there's as many theories about what happened to them as there are paleoanthropologists,” Nowell said. “Most people would see it as a more nuanced model.”

She noted that Neanderthals’ numbers were already dwindling when humans arrived, and there was a lack of genetic variation. Humans may have added to the stress, on top of a changing climate.

“There's a whole bunch of things going on, for sure,” Nowell said.

To Slimak, these other stresses simply don't matter as much as humans. "We can argue endlessly about dates, climate, or this or that other factor, but we have to accept that we are faced with a clear and radical replacement of population," he wrote.

"When Sapiens made an appearance, Neanderthal disappeared from the archaeological record."