Fossil treasure from 74,000 years ago points to remarkably adaptable humans

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In 2002, a team of paleoanthropologists was working in northwest Ethiopia when they found carved stones and fossilized animal bones, telltale signs of a place where ancient people once lived.

After years of excavations, researchers discovered that hunter-gatherers lived there 74,000 years ago. As described in a study Published Wednesday in Nature, these ancient humans were remarkably adaptable. They made arrows to hunt big game. And when their world was turned upside down by a giant volcanic eruption, they adapted and survived.

That flexibility could help explain why humans of the same era successfully expanded out of Africa and settled in Eurasia, even as many previous raids had failed. “This indicates how sophisticated people were in this period,” said John Kappelman, a paleoanthropologist at the University of Texas who led the new study.

At the site, known as Shinfa-Metema 1, researchers discovered thousands of bones, some covered in cut marks, from gazelles, wild boars and even giraffes, suggesting that humans hunted these species.

The team also found 215 fragments of ostrich eggshells. Is possible that the people who occupied the place ate the eggs, or used the shells as canteens to store water. Scientists were able to precisely date the shell fragments, which contained traces of decaying uranium, to 74,000 years ago.

Around the same time, a volcano in Indonesia called Tuff It unleashed large amounts of ash and toxic gases that spread around the world, blocking out the sun for months.

Dr. Kappelman inspected Shinfa-Metema 1 for signs of eruption. By grinding rocks and dissolving them in acid, his team found small pieces of glass that could only have formed in a volcano. Scientists realized they had an extraordinary opportunity to study people who had survived this gigantic environmental impact.

After analyzing 16,000 fragmented rocks, the researchers concluded that they were arrowheads, not spearheads. If this holds true in future studies, the archery record will go back several thousand years. The invention of archery meant that hunters did not have to approach their prey at close range. Even children could hunt with arrows, and Dr. Kappelman suspects they used them to kill the frogs whose bones he and his colleagues also found at the site.

When Toba erupted, conditions at Shinfa-Metema 1 immediately became harsh. The brief rainy season became much shorter and the rivers receded.

Many researchers have assumed that such brutal changes forced people to seek refuges where the environment was more forgiving and where they could continue to survive using their old practices. But that’s not what happened at Shinfa-Metema 1. There, the fossil record shows, humans adapted by abandoning hunting mammals when their prey became extinct and fishing in shallow waters instead.

Dr. Kappelman and his colleagues gathered clues about how ancient people might have fished by observing the practices of modern Ethiopians living in the area. During dry seasons, fish can become trapped in isolated pools of water, for example. “It literally looks like fish in a barrel,” he said. “We think it would have been very easy to catch these fish.”

In Shinfa-Metema 1, it appears as if Toba’s environmental effects last only a few years. The rains returned, as did the mammals, and the local people began hunting them again. Fish bones became rare.

Dr. Kappelman believes this snapshot of a single site could help address the mystery of how humans expanded out of Africa. Scientists have long wondered how people could have crossed the Sahara and the deserts of the Arabian Peninsula to reach other continents. They have speculated that it might have occurred only during wet periods, when these regions were covered with plants. So, humans could have used their old survival tactics while traveling on the so-called “green highways” to reach other continents.

But Dr. Kappelman and his colleagues proposed that humans survived in arid climates by quickly devising new ways to find food, such as fishing.

During dry periods, they may have moved along seasonal rivers while fishing. Instead of traveling on green roads, the researchers argued, they traveled on blue roads.

Michael Petraglia, director of the Australian Research Center for Human Evolution, said the study’s combination of archaeological and environmental evidence from the time of the Toba eruption was extraordinary. “It’s incredibly rare anywhere in the world,” he said.

While Dr. Petraglia found the site’s interpretation compelling, he still favors the green highway hypothesis.

He argued that between 71,000 and 54,000 years ago, hyperarid deserts stretched across the Sahara and the Arabian Peninsula. “Blue highway corridors were virtually nonexistent,” Dr. Petraglia said.

Dr. Kappelman questioned whether deserts were so harsh and noted that the Nile brought some water through the Sahara to the Mediterranean. And while he acknowledged that a single site could not speak for all of humanity 74,000 years ago, he offered a point of comparison for other researchers who might find similar sites.

“It is a testable hypothesis that we are proposing,” he said.

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