The theory that Eurasian Neanderthals subjected Skhul-Qafzeh humans to continual multidimensional predation generates three major predictions that can be used to test the hypothesis:
• Neanderthal sexual predation would gradually result in a proliferation of hybrids—mutants—displaying a mix of both Neanderthal and human traits;
• Neanderthal predation would gradually deplete the prey population—as occurs in animal populations in the wild. This would push the Levantine Skhul-Qafzeh population to the brink of extinction; and
• the few humans that survived would be those born with physical and/or behavioural traits that would allow them to withstand Neanderthal predation. These ‘Neanderthal proof ’ survivors would become the founders of modern humanity.
According to NP theory, each of these predictions corresponds to a major phase in the transformation of archaic humans into fully modern humans. These predictions are the holy trinity of NP theory and there- fore need to be tested against reliable palaeontological, archaeological and genetic datasets.
Because both species were descended from the same common ancestors, sexual encounters between Eurasian Neanderthals and Skhul-Qafzeh females would likely result in fertile offspring. This predicts that the period of predation resulted in numbers of hybridised half-Neanderthal/half humans.
In theory, these hybrids would have features from both species, and eventually this would affect the appearance of each population. Physically, the Eurasian Neanderthals would begin to look less like classic European Neanderthals, and the Skhul-Qafzeh humans would start to show some Neanderthal features. Eventually, we would expect to see two highly variable ‘mutant’ populations (sharing common features) appearing in the Levant.
In practical terms, this means the Eurasian Neanderthal specimens from the Levant (represented by skeletal material from Tabun, Amud, Kebara and Shanidar sites) should display some human features, while the early human skeletons from the Levant, represented by the Skhul and Qafzeh fossils, should display a number of Neanderthal features.
So, is there any evidence of hybridisation in the Levant?
The first place we would normally look to answer this question is the DNA evidence—and geneticists have tried hard to extract DNA from at least two Eurasian Neanderthals (Amud from Israel and Dederiyeh from Syria)360 to test for hybridisation. Unfortunately, extracting ancient DNA is a complex and difficult task, not only because the DNA in bones deteriorates over time, but also because the process of amplifying what little DNA exists is prone to contamination by modern DNA from the researchers and archaeologists themselves. Despite the best efforts, the world’s foremost authority on Neanderthal DNA Svante Pääbo informed me he had been unable to extract enough viable DNA from Levantine specimens to conduct hybridisation tests (personal correspondence, November, 2007). The main reason for this is that the DNA in fossils is destroyed over time by heat, and usually survives only in cold dry climates like permafrost or high altitude caves. In warm humid environments like the Levant, it quickly deteriorates, making it unlikely we will ever get useable DNA from Levant fossils.361
In the absence of viable DNA from Eurasian Neanderthals, or from the Skhul or Qafzeh skeletons, testing the Levant hybridisation hypothesis has to rely on other methodologies, and the most obvious is archaeological evidence from occupied sites.
The researchers involved in examining the Levantine fossils have noted the skeletal similarities between Eurasian Neanderthals and early human assemblages from Levantine contexts and many of them have interpreted this as evidence of interbreeding between the species.362 The mosaic nature of both the Skhul-Qafzeh humans and Eurasian Neanderthals led to the view (still maintained by a minority of researchers) that all these Levantine assemblages form part of a single highly variable population.363,364
Certainly, the Skhul early human fossils from Mt Carmel (among the earliest representatives of modern humans) share many skeletal features with Eurasian Neanderthals.365 Although Skhul 4 and Skhul 9 are generally thought to be early human, cranial features like the forward projection of the skull and the thick brow ridges, are considered by anthropologist Robert Corruccini, from Southern Illinois University, to be more Neanderthal-like than modern human.366
Even though the Tabun C2 specimen from Mugharet-et-Tabun, Israel is considered a Neanderthal,367 Rolf Quam and Fred Smith claim it is so similar to the Qafzeh and Skhul mandibles (jaw bones) as to suggest they are related. They conclude that the possibility of interbreeding between Levantine humans and Eurasian Neanderthals cannot be ruled out.368
Another team of anthropologists, led by Baruch Arensburg and Anna Belfer-Cohen, undertook an extensive re-evaluation and comparison of Neanderthal specimens from Israel (Tabun, Amud, Kebara), and Iraq (Shanidar) with the early modern humans from Skhul and Qafzeh. They too found a distinct resemblance between the groups:
...both groups display a similar pattern of marked morphological variability. In both groups, specimens display numerous plesiomorphic traits as well as many that are common to both archaic and modern Homo sapiens.369 [‘Plesiomorphic’ describes a trait that species share because it is inherited from a common ancestor.]
Their conclusions reveal, “numerous incongruencies, such as assumed ‘Neandertals’ lacking specific Neandertal traits and AMHS [anatomically modern Homo sapiens] manifesting Neanderthaloid features.”370
Originally, it was thought there was only one species of Neanderthals— those that inhabited Europe. But as excavations in the Levant increasingly dug up Neanderthals who looked noticeably different from their European cousins, a distinction had to be drawn to separate them. While the term Neanderthal is still widely used in the media, the term classic Neanderthal or European Neanderthal is now commonly used by anthropologists to describe the original population, while the atypical Levantine Neanderthals are known as Eurasian Neanderthals. The emergence of the Eurasian sub- species is consistent with the argument that a degree of hybridisation occurred in the Levant as a result of Neanderthals forcibly interbreeding with local humans.
In The Neandertals, Erik Trinkaus and Pat Shipman discuss admixture, quoting the findings of anthropologist F Clark Howell, whose comparison of Eurasian Neanderthal specimens suggests that, over time, they gradually became more human looking:
...instead of neandertalizing through time, the western Asian Neandertals undergo “sapiensation”. The more modern looking Neanderthals from Tabun and Teshik-Tash turn, not into something like La Chapelle-aux-Saints, [classic European Neanderthals] but into the even more humanlike populations whose remains were found at Skhul.371
In 2008, anthropologists Philipp Gunz and Ekaterina Bulygina re-exam- ined the infant Neanderthal skull from Teshik-Tash because “some have considered the morphology of the Teshik-Tash cranium to be more simi- lar to modern humans such as those represented at Skhul and Qafzeh”. At a meeting of the American Association of Physical Anthropologists, they reported that, “the Teshik-Tash frontal bone morphology is intermediate between classical Neanderthals and early modern humans.”372
Still, while these various lines of evidence support my theory of coercive interbreeding in the Levant, until DNA can be extracted from Levantine samples, it will not be possible to resolve the issue.