The idea that two different human species, Homo sapiens (us) and the Neanderthals, who coexisted in western Eurasia 50 to 40,000 years ago, have long captured the imagination of academics and the public alike.
It is therefore not surprising that this period – the transition from the Middle to Upper Paleolithic – has been a focus of research for many archaeologists, physical anthropologists and, more recently, geneticists.
Over the years, various scenarios have been explored, from those that assume tens of thousands of years of coexistence between the two groups of humans, to those that suggest a much more rapid replacement of the Neanderthals by H. sapiens – either through the active or accidental displacement of our cousins, or by outcompeting them for resources.
Both positions allow for incidental interbreeding that has led to a little bit of Neanderthal being present in many of us, especially those of European and East Asian descent.
However, there are many challenges in exploring this distant time. Human skeletal remains are relatively rare; many of the best-known fossils were unearthed under less than ideal conditions in the 19th and early 20th centuries.
When skeletal remains are found, there are often questions about their precise relationship to other archaeological remains at the same site, such as stone and bone tools, animal remains and other finds. It is often assumed that there is a connection between a certain human species and finds from excavations, but this later turns out to be false in a number of cases.
Major revisions
The transition period of 50–40,000 years ago is within the lower limits of radiocarbon dating – a technique that only works on organic remains up to about 50,000 years old. This means that the smallest amounts of more recent contamination from the cemetery or from museum conservation materials can make dating finds at these locations extremely difficult.
This has resulted in major revisions to the chronology of early human occupation in the past decade, shifting some dates of Neanderthal and modern human remains by many thousands of years.
This is of course crucial to the debate, as it is impossible to speak of overlap or substitution without a robust chronology. There is also the issue of spatial scale. For example, does the survival of the Neanderthals after 40,000 years ago in southern Iberia mean a long period of overlap and coexistence, or a ‘last stand’ on the edge of the continent, expressly avoiding contact with the newcomers ?
The latest entry into the battle comes from the Ilsenhöhle cave in Ranis, in east-central Germany, beautifully situated at the foot of a 16th-century Renaissance castle with earlier medieval origins.
An international, multidisciplinary team has human (H. sapiens) remains from both early 20th-century and more recent excavations in the cave, which date them to about 45,000 years ago. The authors say that, combined with early data from H. sapiens in France and a variety of dates for the presence of Neanderthals at 45,000 years across Europe, this allows for a potential period of overlap between the two species that could last some 10,000 years.
In an accompanying paper, the researchers reported the results of their analysis of stable oxygen isotopes (different chemical forms of an element) taken from teeth of mammals in the equine family. These teeth came from the same sediment levels as the human remains. The results place humans in a particularly cold snap about 45 to 43,000 years ago.
The H. sapiens remains are associated with what was previously considered an ambiguous stone tool industry (a specific way of making tools), called the Lincombian-Ranisian-Jerzmanowician (LRJ). But it is unclear whether these were made by Neanderthals or modern humans.
Mystery tool makers
Other Middle-Upper Paleolithic stone tool industries have a long history of the same problem; we’re not sure who made them. Most notable is the Châtelperronian from southern France and northern Spain: do the remains of Neanderthals accompanying some of these ‘modern-looking’ tool industries mean that they were the tool makers, or is the association coincidental?
This debate continues apace, with a possible H. sapiens the ilium of a newborn child has recently been identified in a Châtelperronian assemblage in the Grotte du Renne in Arcy-sur-Cure, central France. Only Neanderthal remains had previously been identified here.
Most caves with Paleolithic deposits were occupied intermittently, often by both Neanderthals and H. sapiens, over millennia. Materials can easily become mixed together and therefore, short of finding tools buried in a modern human grave, it is difficult to say who made them. However, Ranis appears to have an advantage in this regard, as the levels containing the human remains and the LRJ tools were sealed together by a falling rock.
But even here a warning must be sounded. The dates for the levels in question still span several millennia, during which there may have been brief visits by both camps.
New archaeological techniques
Ranis’s results not only contribute important new data to our understanding of the Middle-Upper Paleolithic transition, but also highlight the contributions of recent developments in archaeological science.
Far from unearthing a complete skeleton or skull that would traditionally have heralded an important new hominid fossil, Ranis yielded only a few small bone fragments recognizable as human. Some other small bone fragments were identified as belonging to hominins (the broader human family) using a technique known as proteomics – the study of protein structures unique to genera and sometimes species. This technique was also applied to the site’s fauna in another companion article.
Relatively accurate radiocarbon dates were then obtained for both the sediment level and the human remains themselves. The accuracy of this data was further improved using statistical models.
But most importantly for the question at hand, ancient DNA analysis – in this case mitochondrial DNA (mtDNA) – confirmed the identification as H. sapiens. The mtDNA results link Ranis to other human remains from the First Paleolithic at Zlatý kůň in the Czech Republic and the Grotta di Fumane in Italy.
As the authors of the Ranis study note, an intriguing twist to the story is that recent genetic studies suggest that H. sapiens It appears that the conduct of these early forays into Europe itself has been replaced by others H. sapiens populations later in the Upper Paleolithic.
Thus, the focus on the Middle-Upper Palaeolithic transition and its replacement of one hominin population by another may need to be extended to similar subsequent events that have remained much less visible because they were all related. H. sapiens.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Rick Schulting does not work for, consult with, own stock in, or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond his academic appointment.