Discovery Of Oldest Stone Tools Outside Of Africa Hints At Unidentified Human Ancestors
It was long thought that Africa was where the human species first developed, but now, a new discovery published in the journal Nature challenges that idea, or at the very least pushes back the timeline for humanity’s emergence out of Africa.
A team of archeologists, anthropologists and geologists recently published a study in the journal Nature, detailing a substantially large find of ancient stone tools located in the Loess Plateau region of northern China. The finds included unmodified hammerstones and other crafted stone tools, and together they suggest that a species of hominin (the bipedal humanoids that include the genus Homo) had settled in the region approximately 400,000 years earlier than previous archaeological evidence indicated – sometime around 2.12 to 1.26 million years ago.
New Finds In Northern China
This makes the China site the oldest known hominin site outside of Africa, predating a site in Dmanisi, Georgia by somewhere around 300,000 to 500,000 years. Various finds at other sites across eastern Asia and Europe have given credence to the idea that diverse human populations established themselves throughout Eurasia after the Dmanisi settlement was created.
John Kappelman, geologist and biological anthropologist at the University of Texas explains why the new China finds are so significant. Kappelman explains that although there was already evidence for early hominins existing outside of Africa and across Asia in the past two million years, the new find moves this date back and also demonstrates that dispersal occurred all across Asia.
The team of archeologists dug at the Shangchen site for 13 years, from 2004 to 2013, and during those years they discovered not only the many stones that were documented in the study but also bone fragments from pigs, deer, and antelope. These bone fragments have not yet been examined for signs of hunting.
The researchers were careful to document how deep in and where in the many layers of silt and soil each item was found. The research team also examined the magnetic polarity of each layer of sediment, which can provide clues to the age of the artifacts in that layer, although because the exact timeframes for the occasional magnetic reversals the Earth undergoes have yet to be determined, the sediment age had to be estimated. The estimations were made by comparing the polarity of the unearthed minerals in the sediment to a reference dubbed the Geomagnetic Polarity Timescale.
According to the estimates made with the GPTS dating method, the artifacts unearthed in China were left there over approximately 800,000 years ago, during a period of time that saw major fluctuations in the region’s temperature. The climate of northern China went from wet and warm to dry and cold multiple times during this period, and the frequent fluctuations in climate likely limited the hominins in their attempts to expand. The warm weather soil layers yielded approximately five times more tools than the cold weather layers did, which supports a theory that the Loess hominins thrived during warmer phases and faced hardships during colder periods. Kappleman explains:
It appears that these early populations were limited by climatic extremes, and only were able to expand north during warmer intervals. What they were doing with the tools remains to be demonstrated, but the circumstantial evidence suggests that they might have used them to process food items.
Homo erectus Or Another Species?
Unfortunately, due to a lack of fossils, it’s impossible to say which species of hominin were responsible for the creation of these tools. Even if the excavation team had managed to find fossils at the dig site, our maps of the human evolutionary tree are so lacking it would be difficult to say with any certainty which hominin species was responsible.
There’s some possibility that Homo erectus, the toolmakers who inhabited the Dmanisi settlement were responsible for the creation of the tools, as it has already been documented that the species of hominin were capable of making stone tools and also had the sort of anatomy required to cross continents. However, the fact that the oldest known fossils of Homo erectus are about 1.8 million years old – substantially younger than the newfound tools – puts this theory in question.
At the moment, the oldest known fossil of a hominin species is a jawbone found in Ethiopia and dated to around 2.8 million years ago. Kappelman explains that since no fossils of earlier hominins have been found outside of Africa, some archaeologists believe that a yet to be identified species of Homo was the first to migrate off the African continent.
Michael Petraglia, a paleoanthropologist from the Max Planck Institute, explains that while it’s a possibility that Homo erectus occupied China in the period that the tools were uncovered, given the age of the site and the possibility that artifacts from even earlier in history may be found, another species of the genus Homo may have been responsible for occupying Asia first.
The director of the National Center of the Study of Human Evolution (CENIEH), María Martinón-Torres, says it would be worthwhile to re-examine Chinese fossils categorized as H. erectus, and that the species has been used as a blanket term when “not all hominins found in Asia fit in the Asian H. erectus taxon”.
As more fossils are discovered and more becomes known about the history of hominins around the world, some researches are suggesting we abandon the model which suggests that there was a single population of individuals that gave rise to homo sapiens. Researchers like Eleanor Scerri, an archaeologist from Oxford University, argue that the features which distinguish humans from other hominins emerged in a patchwork style in many different populations all across Africa, and only after hundreds of thousands of years of interbreeding to the species known as Homo sapiens emerge.
In the meantime, more archeological work will unveil more details about the identity of the mysterious hominins, whether Homo erectus or a new species altogether. The researchers want to examine collections of sediment older than 2.1 million years which couldn’t be done at the northern China site because those regions are now covered in farms. Other areas of Asia are quite likely to yield important finds, and the research team can’t wait to start digging again.