New Fossil From Israel Pushes Back Time Modern Humans Left Africa
The recently discovered portion of a human jaw has been dated to 177,000 years old. This strongly suggests that our species is older than we previously believed.
One of the persistent puzzles in modern human origins research has been when and where the earliest modern humans originated and when they first spread throughout the world. A new fossil find from Israel is helping to answer some of these questions.
It has been thought for some time that the earliest modern humans first evolved in Africa. The oldest fossils found that can be assigned to Homo sapiens have been discovered in Morocco at the site of Jebel Irhoud. At this site, a 315 thousand-year-old fossil skull was recently discovered that, while having a primitive long and low skull with sloping forehead and very strong muscle markings, nonetheless possessed a face that would have been indistinguishable from that of someone walking around today.
If the dating of this fossil is correct, it is about one hundred thousand years older than the earliest fossil of true modern humans. The first of these finds was in North Africa, at the sites of Omo and Herto. The fossils found at these sites were dated to 195,000 years ago (Aubert et al., 2012) and 164,000 years ago (Haile-Selassie, Asfaw, & White, 2004), respectively. But while we have fossil evidence of early modern humans that lived in Africa, the question of when those humans first left the African continent has eluded us.
Up until very recently, the earliest modern human remains found outside of Africa came from China and the Holy Land. These include fossils from the site of Daoxian, in China (Liu et al., 2015) and Mugharet-es-Skhul and Jebel Qafzeh in Israel (Grün et al., 2005; Stringer, 2001). These fossils date from between 80 and 110 thousand years ago. In Europe, the earliest modern humans do not appear in the fossil record until 34-37 thousand years ago (Jöris, Street, Terberger, & Weninger, 2011). This paucity of information has left a puzzling fifty to sixty-thousand-year gap for which we have known next to nothing about early modern human migration.
New Fossil Evidence from Misliya
All of this changed when workers at the Israeli site of Misliya, near Mount Carmel, unearthed a modern human fossil consisting of a portion of the left part of the face and roof of the mouth, and having a complete quarter set of teeth (Hershkovitz et al., 2018). Three independent radiometric methods have dated this person to between 177 and 194 thousand years ago.
How do we know that this fossil represents a modern human? First, the section of the face that is preserved is not puffy or pulled-out from the middle of the head, as it is in Neandertals and other archaic human samples. Second, while the teeth are large by modern standards, they are smaller than those of Neanderthals and have a modern human shape. These features place this fossil firmly in the camp of modern humanity.
This find doesn’t only help us understand the migration of early modern humans. It also places modern humans in the Middle East at the same point in time as the first modern human samples from Africa. This strongly suggests that our species is older than those African remains. Given the modern aspects of the those fossils, it is now quite possible that modern humans originated even earlier, between 250 and 300 thousand years ago.
Additional Behavioral Evidence
Also discovered with the remains at Misliya was a layer of fully-formed Levallois stone tools, an industry which is known to be an outgrowth of the Middle Stone Age in Africa and may date as early as 400 thousand years ago (Basell, 2008). This is a flake industry in which a large rock is taken and its edges are punched out. Then a large flake is knocked off that can be used as a tool. This is a technique that was widely used in Africa and, later, in Europe. Although it has been associated with archaic Homo sapiens, (the Neanderthals used a variant of it almost exclusively for close to 100 thousand years), this discovery represents the earliest known direct association with modern humans.
How Does This Fit with What We Already Know?
What does this mean for our understanding of the origins and behavior of modern humans? This new find has firmly established the Middle East as a migration corridor for early modern humans. It also strongly suggests that, while the earliest known modern human fossils date from 190 thousand years ago, the origin of our species is likely fifty to sixty thousand years earlier. This is consistent with recent genetic studies of African populations, which show evidence that modern humans diverged from their archaic forebears between 260 and 350 thousand years ago (Schlebusch et al., 2017). From this corridor, these modern humans were able to move east to China and Australasia and north and west, eventually to Europe. In these areas, they likely met and mixed with the descendants of archaic groups that had previously migrated out of Africa.
As we begin to understand the roots of modern humanity and how our modern human ancestors populated the earth, fossil remains like those of Misliya give us invaluable clues to how this process took place and point to future discoveries that will, hopefully, provide a clearer picture of our past.
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