News took a turn for the ancient this week with the announcement in Science of the discovery of the “oldest known human fossil outside Africa.” The fossil, a prehistoric upper jawbone complete with eight teeth, was unearthed in a the Misliya cave in northern Israel and is roughly 200,000 years old. News sources are touting that this revolutionizes our understanding of human evolution, but why is the discovery so important?
Until relatively recently the conventional scientific narrative about human development maintained that modern humans (Homo sapiens) migrated from Africa into Eurasia about 90,000-120,000 years ago. Their movement there led to the displacement of other species like Neanderthals and Denisovans.
But the discovery of the Israeli jawbone disrupts this narrative, pushing back the exodus from Africa by some 50,000-60,000 years. Radioactive dating of items found in the cave shows that both the jawbone and tools found at the site date to between 177,000 and 194,000 years ago. Professor Israel Hershkovitz, a palaeontologist at Tel Aviv University, who discovered and studied the artifact, said, “What Misliya tells us is that modern humans left Africa not 100,000 years ago, but 200,000 years ago… This is a revolution in the way we understand the evolution of our own species.”
The earlier waves of migration, Hershkovitz said, would have coincided with periods of favorable weather. Deep sea cores show that the prehistoric Middle East went through arid and humid periods, so it is possible that the region would have been habitable during this period.
Other than meaning that Homo sapiens left Africa earlier than previously believed, why should we care? Well, not only did Homo sapiens migrate in waves, they mingled with and potentially even reproduced with other human species for tens of thousands of years. Various species of hominids were sexually experimenting in inter-species dating for much longer than was previously thought.
Of course, as with any initial study of an archaeological find, there are many reasons to exercise caution here. In the first place, can we be sure that a partial jawbone fragment really comes from Homo sapiens? The scientists involved in the study report that while the teeth in the fossil are slightly larger than would be expected, they lack several features that are found in earlier human species. Dr Gerhard W. Weber, who conducted the morphological analysis remarked, “It’s not a little bit modern, or on the border of being modern… It is really modern human.”
What we have here, therefore, would be the earliest modern human found outside of Africa. But the phrase “modern human” can be misleading. When researchers use the phrase they mean that the jawbone belongs to a person whose features are more similar to ours than those of Neanderthals. It does not mean that we have discovered the proverbial Adam or anyone’s greatx-grandfather Joe. This particular outpost of Homo sapiens may have left Africa and died out. The only way to further test this would be to conduct DNA analysis, which is notoriously difficult to perform on fossils found in the Levant.
As with much of the study of human evolution and prehistoric migration, these shifts in scientific thinking have political implications. Just as claims to house the “earliest” example of any human species are politically valuable to the nation in which it is discovered, so too claims about the behavior of early Homo sapiens can be used to make statements about human nature. One imagines that eugenicists would be appalled at the notion that Homo sapiens was getting busy with (and possibly passing genital herpes on to) our stockier Neanderthal cousins. And it kinda makes you rethink our exploitative relationship with those other close relatives, chimpanzees.
Political exploitation aside, the discovery of this jawbone contributes another piece of evidence to the already emerging picture of a prehistoric world in which hominid species lived alongside one another for much longer than was previously known. The Israeli jawbone is not the only find that changes the conventional understanding of prehistoric migration patterns and our evolutionary path. 300,000-year-old fossil finds at Jebel Irhoud in Morocco; 100,000-year-old discoveries from China’s Henan province; archaeological finds in Sumatra from roughly 70,000 years ago; and 65,000-year-old evidence from Northern Australia all also suggest that the dispersal of Homo sapiens began long before we thought.
So in some important respects this discovery is not itself earth-shattering, but it is another piece of data that calls our history into question. As Jonathan Marks, Professor of Anthropology at UNC-Charlotte, told The Daily Beast, the discovery is only revolutionary “in the sense that every fossil discovery revolutionizes our past. It’s not revolutionary in the sense that we now know we evolved from ducks. It just says ancient modern people (i.e., with teeth almost exactly like ours) entered Eurasia a little earlier that we thought they did last week.”