A comprehensive re-analysis of a skull fragment found in a Greek cave back in the late 1970s suggests early modern humans were present in Eurasia some 210,000 years ago. It’s the earliest indication of our species on the continent, but the lack of supporting archaeological evidence raises some questions.
New research published today in Nature describes two fossilised skull fragments found in Apidima Cave in Southern Greece in 1978. A team led by palaeoanthropologist Katerina Harvati from Eberhard Karls University of Tübingen identified the remnants as belonging to two individuals, an early modern human (Homo sapiens) and a Neanderthal.
The human fragment, dubbed Apidima 1, is just the back of the skull and was dated to 210,000 years ago, making it the oldest evidence of modern humans in Eurasia. The Neanderthal fragment, called Apidima 2, was dated to 170,000 years ago and is considerably more complete than the human skull, but it was found without the lower jaw or teeth.
Unfortunately, no other archaeological or palaeontological evidence was uncovered at the site, and neither fragment was found in its original depositional layer. These and other limitations aside, the notion that early modern humans were present in Greece some 210,000 years ago is wholly plausible, and even expected.
Our species emerged in Africa around 100,000 years prior, with the earliest evidence of our species dating back to the Jebel Irhoud site in Morocco and the remarkable discovery of 315,000-year-old human fossils. Moreover, the earliest prior evidence of modern humans outside of Africa was discovered in Israel’s Misliya Cave – a partial jawbone dated to between 175,000 and 200,000 years ago. That’s not too far off in terms of the timeframe, but the new study does suggest an earlier dispersal date from Africa.
As an important aside, other species of humans had already ventured throughout much of Eurasia by this time, including Homo erectus, which left Africa some 2 million years ago, and the yet-to-be-identified ancestral species of Neanderthals, which made its way into Europe somewhere between 800,000 to 600,000 years ago. So yeah, we were kinda late to the show.
The Apidima 2 skull fragment (right) and its reconstruction (left). This specimen was identified as Neanderthal. Image: Katerina Harvati, Eberhard Karls University of Tübingen
That said, Harvati doesn’t believe the Apidima humans survived. Speaking at a press conference on Monday, she said the presence of the Neanderthal skull suggests these humans were eventually “replaced” by Neanderthals in the region. As to why these early humans died out, Harvati said it remains an “important question.” It’s possible, she said, that these small pockets of humans faced climatic pressures, or even pressures from the Neanderthals. Regardless, this interpretation suggests a complicated migration scenario for early modern humans, as this is potential evidence of multiple dispersals from Africa, rather than one major exodus.
“These results suggest that two late Middle Pleistocene human groups were present at this site – an early Homo sapiens population, followed by a Neanderthal population,” wrote the authors in the new study. “Our findings support multiple dispersals of early modern humans out of Africa, and highlight the complex demographic processes that characterised Pleistocene human evolution and modern human presence in southeast Europe.”
As noted, these skull fragments were discovered back in the 1970s. Though analysed and dated previously, the new study involved “more comprehensive analyses,” in the words of the researchers. Also, the skull fragments were encased in a small block of breccia (sedimentary rock), which also contributed to the delay, as it took years to carefully clean the specimens. What’s more, both fragments were badly warped and misshapen, making analysis difficult. It also didn’t help that the skull fragments were found without any supporting archaeological or palaeontological evidence, such as tools, animal bones, or other clues.
For the study, Harvati and her colleagues built 3D virtual reconstructions of the fragments using computed tomography (CT), in addition to performing physical analyses of the specimens. This allowed them to identify Apidima 1 and Apidima 2 as belonging to an early modern human and a Neanderthal, respectively.
Apidima 1 “presents a mixture of modern human and primitive features,” while Apidima 2 exhibited classical Neanderthal features, such as a thick, rounded brow ridge, according to the researchers. During the press conference, Harvati told reporters that the Neanderthal specimen was nothing out of the ordinary, and that it likely belonged to an early version of the species.
Previous work by other researchers calculated the age of the specimens to between 160,000 and 170,000 years old using a well-established technique called uranium series dating. For the new study, the team recruited Rainer Grün from Griffith University in Australia, who also used U-series dating, but he obtained a more extensive set of samples that included bits of bone from both Apidima 1 and Apidima 2 and their associated breccia. Despite the fact that the skull fragments were found next to each other in the cave, the samples were of different ages – the human fragment dated to 210,000 years old and the Neanderthal fragment to 170,000 years old. Though located close to each other, the fragments were deposited onto the cave floor at different times, but eventually came together through a series of complex geological processes, Grün said at the press conference.
Lack of associated evidence at the Apidima site makes it difficult to discern what conditions were like at the time, or why this location was attractive to early humans. The region may have been favorable for these pioneering hominins, who were seeking shelter from harsh environmental conditions or other stressors, said Harvati at the press conference. These humans may have hunted large game or exploited marine resources from the nearby sea. Sadly, we don’t know, but further work at the site could provide the answers, said Harvati.
Archaeologist Israel Hershkovitz from Tel Aviv University had several issues with the new study, including the lack of archaeological evidence, no clear chronological context, the incomplete nature of the specimens, and the severe distortions seen on the remnants, among other complaints in described in an email to Gizmodo.
Hershkovitz, who was involved in the discovery of the Misliya Cave fossils, objected to the use of the “replacement theory” for the analysis, namely the assertion that Neanderthals supplanted humans in this region.
“There is nothing in this paper to support this notion,” Hershkovitz told Gizmodo. “In fact, these two Homo groups could easily live side by side – I personally believe that this was indeed the situation, based on evidence from the Levant [the Middle East] – and occasionally interbreed. Many behavioral aspects, such as cave paintings... can be explained only if we accept the idea that H. sapiens arrived to Europe – and not just to southern Europe – very early in time and remained there since,” he said.
Hershkovitz also took issue with the dating, which he described as “unconvincing.” He said the skulls were found out of context, and not within a recognised archaeological layer which would have reliably confirmed the radiometric dates. Dating the breccia, he said, didn’t provide any information on the actual dating of the skulls, “especially when you do not know exactly where the skulls are coming from,” he said. He also didn’t like the large error bars assigned to the direct dating, which for Apidima 1 featured a plus-minus of 16,000 years (211±16 ka). So if we assume the lower bound of the direct dating, Apidima 1 could be as young as 195,000 years old – which places the specimen much closer in time to the Misliya fossils.
“The significance of the study lies in the fact that it adds to a growing body of evidence showing multiple, early dispersals of Homo sapiens out of Africa.”
Archaeologist Eleanor Scerri from Oxford University, also not involved with the new study, said the depositional context is “clearly complex,” and “U-series dating relies on understanding something about that complexity.” For Scerri, it seems likely that “the single dating method used on a single reconstructed skull will cause some controversy,” she told Gizmodo.
Disagreements about dating aside, Scerri said that the new results are, at face value, “believable,” given the fact that Apidima 1 is still some 100,000 years younger than the oldest known African fossils of our species and just a little bit older than the fossils found at Misliya Cave.
“The significance of the study lies in the fact that it adds to a growing body of evidence showing multiple, early dispersals of Homo sapiens out of Africa,” Scerri told Gizmodo. “Every time the Saharo-Arabian desert contracted – broadly on 100,000 year cycles – groups of early Homo sapiens seem to move out of Africa into Eurasia, until the desert gates close behind them.”
“I am not surprised, personally, that we are finding evidence of early dispersals out of Africa – after all, it is something that myself and my colleagues have made arguments for, for sometime,” said Scerri. “I did not necessarily expect findings to be as early as the Apidima cave claims, but it is certainly all within the realms of possibility, given what we know.”
As to why archaeologists aren’t finding more human remains outside of Africa from this early time period, it “seems likely that more will be found if people look out for this sort of evidence,” she said. At the same time, it also seems likely that discoveries will remain extremely limited. If these were small, discontinuous populations, she explained, then the possibility of multiple similar discoveries goes down.
It’s a discouraging thought, but we have to keep looking. Somewhere out there, the clues to our ancestral past are still waiting to be found.
Featured image: Katerina Harvati, Eberhard Karls University of Tübingen