For a long time we thought that the confrontation with modern man cost the Neanderthals the head. However, no archaeological evidence for this has ever been found. New research shows their extinction was likely a natural phenomenon.
“The fact that Neanderthals are said to have died out because they have lost is pure discrimination,” says archaeologist and computer modeller Fulko Scherjon (Leiden University). Together with Krist Vaesen of Eindhoven University of Technology, among others, he made two simulation models that followed the population growth of the Neanderthal for ten thousand years. The calculations show that Neanderthals had a high chance of dying out anyway, even without interference from or confrontation with Homo sapiens.
"This finding is an important addition to the evidence that Neanderthals were no different from Homo sapiens," Scherjon said. “We still often think that Neanderthals were inferior to modern humans. Less smart, fast, creative or he could use the landscape less well, while there is no archaeological evidence for this. In fact, recent studies show that there is no archaeological difference between Neanderthals and Homo sapiens at the time of the Neanderthals.”
Simulation population growth
This study confirms that no difference between the two species was needed to explain why Neanderthals disappeared. Krist Vaesen also emphasizes that the extinction of species is a natural phenomenon. “Homo erectus for example, which roamed the earth between 1.9 million and 140,000 years ago, also lived in small groups and became extinct at some point.”
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Why it goes well for so long, and then the point of extinction is reached, we see reflected in the models. The Neanderthals have been followed by the computer simulation for ten thousand years, during which the researchers looked at the effect of inbreeding, Allee effects (the relationship between population size and reproductive rates) and stochasticity (random demographic fluctuations).
The computer simulated the lives of various numbers of initial populations:groups of fifty to five thousand individuals that were born, reproduced, and died. The effect of fluctuating birth and death rates, for example due to extreme weather, was also included. This showed that the Allee effects had the most influence on the extinction of the species.
Vaesen:“Small groups that work closely together in hunting and raising the children are more affected by a shrinking population than large groups. Working together with few congeners becomes increasingly difficult, as does finding a partner. External fluctuations that depress birth rates also have a more adverse effect on a small population. And so the groups get smaller and smaller until they die out.”
Extensive habitat
It is generally assumed that Neanderthals lived in small groups, based on archaeological finds and research into Neanderthal genes. Estimates of the total number of Neanderthals on Earth at the same time range from 10,000 to 70,000 individuals. The fact that the researchers' model, which assumes a maximum group size of 5000 men and women, is plausible is due to the enormously extensive habitat of the Neanderthals, Vaesen says.
Neanderthals lived in Europe and the Levant from 400,000 to 45,000 ago. These small groups came into contact with each other through migration routes and could choose mates outside their own group to avoid inbreeding. However, in the last 10,000 years before their extinction, inbreeding became more common, according to archaeological finds. “Probably the migration routes were blocked – perhaps because modern humans migrated from Africa to Europe at that time – making partner choice more difficult. The groups then became smaller and less fit due to inbreeding, and the number of groups also decreased, until the Neanderthals came to an abrupt end about 45,000 years ago,” says Vaesen.
Pure happiness
To be sure, the researchers also ran a mathematical model on a population of 70,000, looking at birth and death rates, and the number of children women have. That model also shows that it is plausible that the Neanderthal would become extinct after 10,000 years, without the intervention of Homo sapiens.
Homo sapiens may therefore have played a role in the extinction, but the model shows that they do not have to be the cause. They could only have sped up the process. Modern man himself once started with small groups and you can apply the same calculations to them. “But they have been more fortunate,” Vaesen explains.
“For example, the migrated group of modern humans from 45,000 years ago did not survive in Europe. Genetically, they are hardly related to the group that came to Europe from Africa 25,000 years later.” We also think that the probably oldest Homo sapiens in Europe, of which a 210,000-year-old skull fragment has recently been found, are extinct.
Scherjon confirms that modern man has gone through the eye of a needle several times in terms of extinction. "The fact that Homo sapiens finally made it in Europe is due to the already larger population in Africa, which indeed resulted in new growth several times."
Additional handicap
With this model, there is now a null hypothesis for the extinction of Neanderthals. If you want to know whether there were reasons other than natural attrition, for example by losing the competition with Homo sapiens, additional evidence is needed.
Scherjon. “This is very important because until now the Neanderthal has been modeled in archeology with a disability compared to Homo sapiens, for example as a slower runner. When you then simulate the course of the population, the outcome is certain:logically, the handicapped species always disappears, with the handicap being the reason. This is circular reasoning. It is methodologically wrong and also not proven archaeologically that the Neanderthal was 'disabled' compared to modern humans."
Neanderthal lovers
When asked, archaeologist at Leiden University Gerrit Dusseldorp looks at the new research, in which he was not involved. “Computer models of these kinds of scenarios have been made for some time, and in some of them it takes only a very small 'disability' to lead to the extinction of Neanderthals. This research shows that Neanderthals could very well be extinct without a disability.”
These kinds of computer models do not prove exactly how it happened, Dusseldorp emphasizes. “They show how things could have gone if the input from the models was correct. I think that input is realistic:based on genetics and archaeology, we know that Neanderthals lived in small groups and probably very low population densities for most of their existence.”
Vaesen and Scherjon's research shows that there is no difference between Homo sapiens and Neanderthals. Decreasing populations simply have a greater chance of extinction and that has become fatal for the Neanderthal. “I think these kinds of models are very important, because they force us to make our assumptions explicit,” says Dusseldorp. “Many of the 'analog' interpretations of Neanderthal archaeology have similar basic assumptions under the carpet. So you roughly put Neanderthal bashers, and Neanderthal lovers. I belong to the second group:I think archeology shows that Neanderthals were probably as smart as modern humans. And I think it's very valuable to build computer models based on that assumption.”