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About 74,000 years ago, Mount Toba in Sumatra experienced a massive eruption, one of the largest in Earth's history, likely causing a massive disruption to the world's climate.
Some scholars They suspect a volcanic winter caused by a volcanic eruption It was a shift large enough to wipe out most early humans due to genetic evidence suggesting a sharp decline in the human population. But now, a recent study of an archaeological site in northwestern Ethiopia that was once occupied by modern humans has added to a growing body of evidence that suggests the event may not have been so horrific.
Instead, the new research finds that humans at this site, known as Shinfa-Metema 1, adapted to the arid conditions caused by the volcanic eruption in a way that may have facilitated humanity's pivotal migration from Africa to the rest of the world.
Microscopic fragments of volcanic glass were found alongside stone tools and animal remains in the same layer of sediment at the Shinfa-Metema 1 site, near the Shinfa River in Ethiopia, and show that humans were occupying the site before and after the eruption more than 4,000 miles away.
“These fragments are less than the diameter of a human hair. Even if they are as small as (that) they are Still “It's large enough to analyze chemistry and trace elements,” said John Kappelman, a professor of anthropology and geological sciences at the University of Texas at Austin and lead author of the study. Published Wednesday in the journal Nature.
By piecing together clues from fossils and artifacts found at the site, along with geological and molecular analysis, the team began to understand how the humans living there advanced despite the potential climate shift brought about by the volcanic disaster.
To understand the climate at the time of the volcanic eruption, Kappelman and his colleagues analyzed oxygen and carbon isotopes, variations of the same element, from ostrich eggshells and fossilized mammal teeth. This work shed light on water consumption and revealed that animals ate plants that were more likely to grow in drier conditions.
“Isotopes are incorporated into hard tissues. So for mammals, we look at their teeth, their tooth enamel, but we also find it in ostrich eggshells.”
Analysis of the flora and fauna of the site also found an abundance of fish remains following the eruption. The study indicated that this discovery may not be surprising given how close the site is to the river, but fish are rare in other Stone Age sites from the same period.
“People start increasing the proportion of fish in their diet when Toba comes. They catch and process almost four times the amount of fish (than before the eruption),” he said.
“We think this is because if the Toba region is in fact causing more drought, that means it will be a shorter rainy season, which means a longer dry season.”
The team hypothesized that, counterintuitively, a drier climate explained the increased reliance on fish: as the river shrank, fish were trapped in water holes or in shallow streams that fishermen could more easily target.
The fish-rich openings of water likely created what the team described as the “Blue Corridor,” along which early humans moved north out of Africa once the fish were depleted. This theory contradicts most other models that suggest that the main human migration out of Africa occurred through “green corridors” during wet periods.
“This study…demonstrates the great resilience of Homo sapiens populations and their ability to easily adapt to any type of environment, whether very humid or very dry, including during catastrophic events such as the intense eruption of the Toba volcano,” he said. Ludovic Slimac, a researcher at the French National Center for Scientific Research and the University of Toulouse, said in an email. Slimak was not involved in the research.
The study's authors were also able to explore the geology of the ancient riverbed, suggesting that it flowed more slowly and less at that point than it does today.
“We can do that just by looking at the gravel,” Kappelman said. “A very active river can move larger rocks and pebbles than a river that is not (active). What (gravel) we find for the ancestral river is smaller than the river today.”
The researchers also discovered the remains of several small triangular points, which interestingly rank among the earliest examples of the use of archery and provide evidence that the site's inhabitants may have used bows and arrows to hunt fish and other larger prey.
Slimak, who studied similar points discovered in France dating back 50,000 years, agreed with the new study's assessment of the artifacts.
“The authors also highlight very clear indications that archery was present here 74,000 years ago,” Slimak said. “So, there is every reason to… regard these ancient Homo sapiens as carrying already highly advanced technologies, largely free from natural and climatic constraints, crucial factors for understanding their later migrations, across all continents and under all latitudes.”
It is likely that ancient species of humans left Africa several times, but archaeologists and geneticists largely agree that the most significant spread of Homo sapiens, our species – which eventually led to modern humans living in every corner of the world – occurred about 70,000 to 50,000 years ago. since.
Chris Stringer, a professor and research leader in human evolution at the Natural History Museum in London, said the new research offers another possible scenario for how this dispersal occurred while not ruling out previous theories, which he described as an “interesting paper.”
“I'm sure each of these proposals will generate controversy among the professionals involved, but I believe the authors have presented a plausible (though not definitive) case for each scenario they propose,” Stringer said via email.
“Of course this new work does not mean that wet corridors were not yet important channels for dispersal out of Africa, but this work adds additional reliable possibilities during drier phases.”
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