The extinction of Homo neanderthalensis (the official name of the Neanderthal man) is an issue that is being addressed and has been extensively studied since the discovery of what was considered the first Neanderthal sample. In 1856, in the Neander Valley of Germany, some fossils were found; other Neanderthal fossils had been discovered earlier, but their true nature and significance had not been recognized, and therefore no separate species name were assigned. When more findings came to light, the world was unprepared for the discovery of a new kind, which is beyond the anatomically modern man. Even after publication of On the Origin of Species by Charles Darwin, the scientific community (for the most part) was not ready to accept the idea of another human species, other than Homo sapiens, existing. When, with the identification of anthropological remains, the Neanderthal species was separated from the Sapiens, then researchers began to wonder why Homo neanderthalensins became extinct.
In 19th century, researchers were mainly concerned with the origin of Homo sapiens. Initially, all interpretations of Neanderthals were placed in the context of linear theory of evolution (Smith et al.,1989). According to this theory, Neanderthals belong to the same species as modern man, and thus can be characterized as their ancestors. For most of the first half of the 19th century, the scientific community believed that humans had suddenly appeared a few thousand years ago, although geology had shown that Earth and life were much older. However, a series of archaeological discoveries in the 1840s and 1850s brought to light stone tools associated with the remains of extinct animals. In the early 1860s, as summarized in Charles Lyell's book, Geological Evidences of the Antiquity of Man (1863), it was widely accepted that humans had existed during a prehistoric period. This view of human history was more compatible with the evolutionary origins of mankind than ever before. On the other hand, at that time there was no evidence of fossils showing human evolution. The only fossils found, before the discovery of the Java Man (the oldest hominid fossils ever found) in 1890, were either Homo sapiens or Neanderthals. Homo neanderthalensis was considered the link between modern man and primates. This would explain, without a second thought, the causes of Neanderthal extinction; since according to the first theories, they did not disappear but rather they evolved into Homo sapiens.
However, research brought to light skeletal findings which did not appear to support this model. Such were the anthropological remains of Homo heidelbergensis, Homo erectus and, later the biggest prank of palaeolithic archaeology and palaeontology, the Piltdown man. Research in the first half of the 20th century led to the birth of a new theory (the pre-sapiens hypothesis). This theory holds that there was a species of pre-sapiens that bridged the gap between Homo erectus and Homo sapiens. Neanderthals and Homo sapiens had a common ancestor in Europe, from which they latter evolved, while the former remained stagnant and disappeared. This means that Neanderthals and Homo sapiens are not the same species, but could be considered "cousins". Keith, in his work “the antiquity of man”, concluded that these two species do not present the same characteristics. The discovery of Piltdown man (Dawson & Woodward, 1913) came to confirm the theories of the proponents of the pre-sapiens hypothesis. He looked like a humanoid who presented similar characteristics, which led to the conclusion that he was the ancestor of Homo sapiens. Only when it was discovered that this finding was a fraud did the narrative of pre-sapiens hypothesis collapse and the linear theory of evolution came to the fore again (Weimer et al., 1953).
In 1978, Santa Luca rejected the pre-sapiens hypothesis by studying anthropological specimens that had been characterized as transient, and recognizing specific features, which are observed only in Neanderthals. Also, he recognized the possibility of differentiation of their skeletal characteristics. Neanderthals, that had been discovered in Syria and Palestine compared to those that had discovered in Europe, led him to reject the theories of eastern development for these species. Beyond that, the theory of local continuation of human species was not supported by research as it became apparent that Neanderthals were a separate extinct human species. Following the definitive rejection of linear theory by Santa Luca, two new approaches to the origins of modern man came to the surface; one is called "Multiregional" and the other, "Out of Africa".
The "Multiregional Evolution" theory claims that Homo erectus gave genus in Homo sapiens throughout its dispersal (1 million years ago: Africa, China, Indonesia and possibly Europe) (Stringer & Andrews, 2012).It is a scientific model proposed by Milford H. Wolpoff in 1984. This theory maintains that human evolution, took place within a single human species, whose different populations would have evolved in parallel throughout the world to Homo sapiens. This unique species encompasses all archaic human forms. The theory is based on the systematic cline mechanism, with a balance between genetic drift, gene flow and natural selection throughout the Pleistocene (a geological time period that began about 2.6 million years ago and ended 11,700 years ago, according to the International Commission on Stratigraphy). The model of multiregional evolution is based on the observation of features deemed to be common between fossils from different periods in the same region. When Homo erectus scattered in the Old World, they began to develop modern features and local differences. Modern proponents of this view emphasized the importance of genetic material flow (mixing) beyond geographical limits, which prevented divergence and speciation. New features were allowed to spread throughout the inhabited world. The space-time continuity, between various forms of Homo erectus and its local offspring, were so complete that they could be represented as one species: Homo sapiens.
Opposite diametrically is the model "Out of Africa"; according to this theory (which is prevalent nowadays), Homo sapiens has a space-time origin (Stringer & Andrews, 2012). The proponents of the theory focus on Africa as a key locus. The later stages of human evolution, like the earlier ones, are characterized by divisible events and coexistence of different species. It recognizes Homo heidelbergensis as an intermediate species between Homo erectus and Homo sapiens. According to this view around 600 Kya (thousand years ago), Homo erectus populations in Africa and Europe showed a satisfactory change in the skull, and so it was recognized as a new species named Homo heidelbergensis (spreading to Africa, Europe, possibly China).
In the case of "Out of Africa", this species led to two new species after 400 thousand years: Homo sapiens and Homo neaderthalensis. The first species evolved in Africa and the second in Europe and Western Asia. Around 100 Kya, the early modern anatomical humans spread across from the African continent to Europe, and were the first to reach Australia and the Americas (before 40 Kya, 60 Kya and 15 Kya respectively). The regional (racial) diversity was therefore developed by the dispersal of modern anatomically people onwards, resulting in no continuity of local characteristics between Homo erectus and the current inhabitants of the same areas.
Essentially the populations from Africa were crossed with the local archaic populations where they arrived, for example with the Neanderthals in Europe or with the descendants of Homo erectus in Java. Like the "Multiregional Model", this theory accepts that Homo erectus evolved outside the Africa, but argues that non-African evolutionary lines have disappeared without a trace, while some archaic populations were replaced, such as the Neanderthals in their areas (Stringer & Andrews, 2012).
The separation of the two species, Homo sapiens and Homo neanderthalensis, is very important in the research of the causes of Neanderthal extinction. This is because there are paleoanthropological findings that show characteristics of both species. If the "Out of Africa" theory is prevalent today, then research needs to be done more intensively on why Neanderthals and Homo sapiens share common features in their genetic code. Whether this question is related to the disappearance of Neanderthals will be discussed in the next chapters.
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