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Enlarge / A view of the Apidima 1 skull from behind (left), above (center), and below (right). The scale bar represents 5 cm.Harvati et al. 2019

A few fossilized bones from the back of a skull may prove that our species spread into Eurasia much earlier than previously suspected. A new study of the partial skull, which was excavated from Apidima Cave in southern Greece 40 years ago, suggests that the fossil is Homo sapiens and that its roughly 210,000 years old. That makes it the oldest member of our species ever found outside of Africa.

The fossil, known as Apidima 1, is likely the remains of a member of an early wave of humans who spread into Eurasia. Based on genetic studies and the fossil record, anthropologists think these early pioneers failed to gain a successful foothold and ended up being replaced by Neanderthals (for a while, at least).

A new look at an old skull

Archaeologists excavating Apidima Cave in the 1970s found the partial skull lodged in a chunk of breccia, just a few centimeters away from a broken and distorted Neanderthal skull called Apidima 2, which dated to 170,000 years old. For decades, archaeologists assumed Apidima 1 was a Neanderthal, too. But Eberhard Karls University of Tübingen paleoanthropologist Katerina Harvati and her colleagues recently took a second look at Apidima 1. The partial skull included just the right pieces of bone to reveal something important: the skull was rounded at the back—a feature thats unique to Homo sapiens.

And according to uranium-series dating, the skull could be as much as 210,000 years old. Thats a few thousand years older than Misliya-1, the previous holder of the Oldest Human Outside Africa title (at 194,000 to 177,000 years old). It fits pretty well with the growing pile of evidence that the earliest humans (like many of our hominin relatives) spread farther and faster than anthropologists have previously given them credit for.

“We never imagined anything like this for this area, but in hindsight, it's not actually a very surprising result,” said Harvati. Evidence of Homo sapiens in Israel dates to at least 177,000 years ago, and southeastern Europe was probably an important route from the Levant into Europe and parts of Asia. “Its not actually so unimaginable that some of these populations would have expanded their range to reach southeast Europe,” said Harvati.

Let the scientific debate begin

Harvati and her colleagues CT scanned the bone so they could digitally reconstruct the broken, distorted pieces of skull, then performed statistical analysis of how its dimensions and shape compared to other fossil skulls from humans, Neanderthals, and even older hominins. Consistently, the analysis suggested that Apidima 1 was human.

But thats not to say there wont be some debate, especially about the fossils age. Most calcium carbonate rocks, minerals that precipitate out of flowing water, also contain some uranium. By looking at the ratios of uranium isotopes in a rock or fossil, geochemists can date when it formed. In this case, Harvati and her colleagues came up with several potential dates, some of which are much earlier than 210,000 years ago. Geochemist Rainer Grün of Griffith University says that those earlier dates are probably the product of uranium from the breccia deposit—where the partial skull ended up after being washed through the cave sometime after death—leaching into the fossil bone over time.

Its pretty common for paleoanthropologists to re-analyze, re-date, and argue about fossils, especially when theyre the centerpiece of a superlative claim like this one. Although Apidima 1 isnt that much older than Misliya-1, its the oldest Homo sapiens fossil in Europe by a margin of about 150,000 years, and thats a significant claim. Its probably reasonable to expect to hear more about Apidima 1 in the future, one way or another.

A long, complicated relationship

“It's a fantastic coincidence that you have two skulls together, 30cm (11.8 inches) apart,” said Grün. “In all of Greece, you have one more skull—thats it—in that timeframe. It's a wonder of nature that you find the two together.” The human and the Neanderthal probably died around 40,000 years apart, in different places in the labyrinthine Apidima cave system. At some point, water flowing through the cave washed both skulls down into the same chamber. The uranium isotope ratios in Apidima 1 were different from the surrounding rock, suggesting that they started out in different places and formed at different times. The Neanderthals signature, meanwhile, was more similar to the surrounding breccia.

  • The two skulls appear to have washed into cave A with sediments that later solidified into breccia. Harvati et al. 2019
  • A view of the Apidima 1 skull from behind (left), above (center), and below (right). The scale bar represents 5 cm. Harvati et al. 2019
  • The Apidima 1 partial cranium (right) and its reconstruction from posterior view (middle) and side view (left). Katerina Harvati, Eberhard Karls University of Tübingen.

The result may offer an uncanny fossil snapshot of our complicated history with the Neanderthals. Genetic studies of Neanderthal DNA have suggested that those living in Europe sometime after 270,000 years ago met early waves of human migrants. Those encounters left traces of human alleles in Neanderthal genomes, in the same way that Neanderthals, in turn, left traces in our modern genomes. Harvati says that Apidima 1 may be part of that long-lost group of humans who mingled with Neanderthals and then, apparently, disappeared.

Genetic evidence suggests that non-African populations today all descend from the wave of humans who dispersed into the rest of the world between 70,000 and 50,000 years ago. Older waves of dispersal, humans who left tools and bones at sites like Misliya, Qafzeh, and Skhul Caves in Israel, seem to have faded away without leaving descendants behind. And at several of those sites in Israel, the fossil record contains Homo sapiens remains in earlier layers, followed by Neanderthals in later ones.Read More – Source

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Ars Technica

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