Neanderthal Extinction Hypothesis Statement

(Phys.org)—A trio of researchers, two with Stanford University in the U.S. and the third with Meiji University in Japan has created a model that showed that it might be possible that the Neanderthal extinction that occurred in the years after early humans arrived in Europe, was due to the cultural superiority of humans. In their paper published in Proceedings of the National Academy of Sciences, William Gilpin, Marcus Feldman and Kenichi Aoki describe the factors they used to create their model and why they believe it was possible that cultural differences might have been enough to drive the Neanderthal to extinction.

Prior research has shown that populations of Neanderthal were living unfettered in Europe for hundreds of thousands of years, but then, approximately 45 thousand years ago, modern humans arrived in the area after migrating out of Africa—five thousand years later, the Neanderthal were gone. Scientists have offered a variety of ideas regarding what happened—modern humans carried with them diseases that were deadly to Neanderthal, our early ancestors simply killed all the Neanderthals, or Neanderthals were not able to adapt to a changing climate, are the leading explanations that have been offered. In this new effort, the researchers report that a model they built suggests it was possible that Neanderthals went extinct because human cultural advantages were so great that it made survival for the less culturally advanced group impossible.

The researchers used a computer model that had already been built by others to mimic interspecies competition—they added elements that allowed for taking into consideration cultural and technical abilities. The result, they claim, is evidence that a culture that was more culturally advanced could displace one that was less so—even if the less culturally advanced group was initially much larger. The model also showed that such cultural advantages could lead to a feed-back loop—the more advanced one group became the more dominant they became, and the more dominant they became the more their cultural advantage grew. The researchers suggest that cultural advancement goes hand-in-hand with technological innovation which would have allowed early humans to outcompete Neanderthal for natural resources.

What is not clear is why the Neanderthal would not have simply copied the advanced culture or technology developed by early humans once it became clear there was an advantage.

Explore further:Analysis of bones found in Romania offer evidence of human and Neanderthal interbreeding in Europe

More information: William Gilpin et al. An ecocultural model predicts Neanderthal extinction through competition with modern humans, Proceedings of the National Academy of Sciences (2016). DOI: 10.1073/pnas.1524861113

Abstract
Archaeologists argue that the replacement of Neanderthals by modern humans was driven by interspecific competition due to a difference in culture level. To assess the cogency of this argument, we construct and analyze an interspecific cultural competition model based on the Lotka−Volterra model, which is widely used in ecology, but which incorporates the culture level of a species as a variable interacting with population size. We investigate the conditions under which a difference in culture level between cognitively equivalent species, or alternatively a difference in underlying learning ability, may produce competitive exclusion of a comparatively (although not absolutely) large local Neanderthal population by an initially smaller modern human population. We find, in particular, that this competitive exclusion is more likely to occur when population growth occurs on a shorter timescale than cultural change, or when the competition coefficients of the Lotka−Volterra model depend on the difference in the culture levels of the interacting species.

© 2016 Phys.org

The terrestrial civilization has been established with only one human species, but it could have been otherwise. Until about 40,000 years ago, a blink in geologic time, at least one close relative was sharing this planet with us. They were Neanderthals, native Eurasians that today are recovering from their reputation as brutes thanks to scientific findings that have rediscovered them as a species similar to ours in many respects. But there is something that we still don’t know about them, and that is why are they no longer with us.

We have known about the Neanderthals since the nineteenth century, but for decades they were thought of as a primitive species, rightly extinguished when they came up against the intellectual superiority of Homo sapiens. The signs of cannibalism found in 1899 in Krapina (Croatia) reinforced their image as savage barbarians. Since then, much time has passed and a lot of evidence has been unearthed that has spiffed up the image of the Neanderthal people. Like us, they made tools, wore clothes, controlled fire and buried their dead. They also possessed the same variant as us of the FOXP2 gene, essential for language, so they probably spoke. Perhaps they even painted and engraved on the walls of caves. And as for cannibalism, not only did Homo sapiens also practice this, but it’s even possible that some Neanderthals were devoured by our ancestors.

Two reconstructions of the Neanderthal man. Credit: Library of Congress / Wikimedia Commons.

All of which begs the question, if they were so similar to us, why did they disappear? Given that Neanderthals and Homo sapiens only coincided in Europe for about 5,000 years after the arrival of the latter from Africa, the traditional hypothesis assumed that in the competition for resources, there could only be one human species; the Neanderthals were the losers, either by direct conflict or perhaps because of climate change that affected them more due to their more restricted diet and greater energy needs.

Organizational capacity could be key

In recent years, a new theory has been added. Several indications, both anatomical and archaeological, point to the possibility that Neanderthals had less capacity for social organization than Homo sapiens, which would have made them more vulnerable in times of scarcity. In 2014, an analysis of Neanderthal genome led by the Max Planck Institute for Evolutionary Anthropology (Germany) and published in the journal PNAS revealed that our relatives had low genetic diversity and were living in small, isolated groups. Compared to Homo sapiens, Neanderthals had less variety in genes associated with certain behaviours, particularly with features such as hyperactivity and aggressiveness.

Could these genetic differences explain a difference in behaviour that would have hindered the survival of the Neanderthals? The main author of the study, Sergi Castellano, is emphatically cautious: “We don’t know the phenotypic effect of these genetic variants, so they don’t support any theory linked to behaviour,” he tells OpenMind. The difficulty, he adds, is to infer behavioural traits from the genes. According to the researcher, who is currently working on this line by introducing variants of Neanderthals and Homo sapiens separately in mice, “but years of experiments are needed” to reach any conclusion, he stresses.

A Neanderthal man in the Natural History Museum in London. Credit: Paul Hudson.

However, there is someone trying to advance our knowledge using another approach, that of evolutionary psychology. Glenn Geher, of the State University of New York in New Paltz, bases his research on the established fact that most modern humans, except for sub-Saharan Africans, have in our genome around 2% Neanderthal DNA, the result of ancient breeding between the two species. Geher recruits volunteers willing to undergo a genetic analysis of their “Neanderthality” and then subjects them to a comprehensive test of behaviour and personality. Using the classical methodology in psychology, the researcher then correlates the greater or lesser presence of Neanderthal variants with behavioural traits.

Using this approach, Geher has found a “small but statistically significant” correlation between the percentage of Neanderthal genes and facets of personality, according to what he explained to OpenMind. And interestingly, the results are “consistent with this basic theme regarding the sociability of Neanderthals.” Specifically, the psychologist has found that individuals with a higher level of the Neanderthal genome have an aversion to strangers and are more prone to nervousness and anxiety, features possibly associated with lower sociability. Geher considers that his study may open “a brand new avenue to explore the nature of these ancestral cousins of ours – as well as the reasons for their ‘demise’.”

No conclusive evidence

The socialization hypothesis still has a long way to go, if they don’t find new evidence to override it first, that is. Last May, French and Belgian researchers published in Nature magazine news about the discovery in the cave of Bruniquel, in southwest France, of a set of large circles built with pieces of stalagmites. At around 176,000 years old, these stone rings attributed to Neanderthals are among the oldest examples of human construction. The authors of the study wrote: “Our results therefore suggest that the Neanderthal group responsible for these constructions had a level of social organization that was more complex than previously thought for this hominid species.”

The principal co-author of the study, Jacques Jaubert, of the University of Bordeaux (France), tells OpenMind that in his opinion there is no reason to imagine large differences in lifestyle between the Neanderthals and the modern humans who lived in the same period, although both groups changed over time. In any case, Jaubert stresses that the circles of Bruniquel, built 120,000 years before the extinction of the Neanderthals, are too old to shed much light on the issue.

“There is certainly not only one reason which caused demise of the Neanderthals,” concludes Jaubert, and nothing seems to indicate that this prehistoric mystery will be solved any time soon. However, for Geher there is another interpretation of the matter. And, given that billions of humans carry Neanderthal heritage beating in our genes, in some ways our relatives are still present, leading the psychologist to paraphrase Mark Twain: “I’d argue that the news of the extinction of the Neanderthals is greatly exaggerated.”

Javier Yanes for Ventana al Conocimiento (Knowledge Window)

@yanes68

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