Children's science magazine article originally written for The Helix.
Sometimes scientists go to extreme places to do their research. Scientists who study the earliest humans often find themselves underground.
Old Bones for New Information
Studying the bones of ancient humans helps scientists understand how we have evolved over time. Sometimes scientists dig into the Earth to find the bones they need. But some scientists crawl under the Earth, deep into caves to do their research. Caves can help shelter bones from destruction over time just like layers of soil help preserve bones in other places.
Skulls out of the Pit of Bones
Sima de los Huesos, the Pit of Bones, is a cave in Atapuerca, Spain. Thousands of years ago when human ancestors made Atapuerca home, there were many caves with streams nearby. Atapuerca is 1,000 metres above sea level, so ancient humans could have seen far into the distance. The area would have been a great place to live.
The first time a hominin skull was found in the Pit of Bones was 1976 when a mining engineer noticed pieces of skull while he searched for bear bones. Since then, scientists have identified bones from 32 different individuals who lived about 400,000 years ago. The oldest and most complete human skulls ever found have come out of the Pit of Bones. Studying the bones has revealed information about the height and eating habits of the ancient humans.
Dr. Lee Arnold from the University of Adelaide is a member of a team that uses ancient human skulls to study how humans evolved. His study revealed that the jaw bones of Neandertals were the first feature to begin changing shape when they arrived in Europe after migrating out of Africa.
During their digs in the Pit of Bones, scientists found no bones from animals the ancient humans would have hunted. The only tool found in the cave is a ceremonial stone axe, nicknamed “Excalibur” by researchers. This may mean that the Pit of Bones was a burial site rather than a home.
Now over 150 scientists come to Atapuerca every summer digging season to do more research. To get into the Pit of Bones, scientists must crawl 500 metres through underground tunnels called Cueva Mayor.
“We have to walk very slowly through the cave passages because they are very slippery and muddy. Some parts of the cave are also very narrow and require us to crawl through and slide along on our stomachs,” says Arnold.
Then, researchers abseil down a 13 metre long, dark shaft. Fewer than 10 people can fit in the Pit of Bones at one time because it is so narrow. Researchers must also carry oxygen tanks because the air inside the Pit sometimes has very little air for breathing. It can take an hour to travel from the surface into the Pit!
Diving for Science
Some caves are not only dark, but wet. Hoyo Negro, Black Hole, on the eastern portion of the Yucatan Peninsula, Mexico is an underground cave full of ocean water. In 2007, scuba divers mapping the tunnel system discovered Hoyo Negro and found animal bones and the full skeleton of a 16-year-old girl who lived 13,000 years ago.
Image by Roberto Chavez Arce.
Dr. James Chatters from Applied Paleoscience in Washington, USA is part of a research team that works with specially trained scuba divers to do research in the caves by taking pictures and videos of the bones. To reach the cave entrance, they drive nearly 10km on a bumpy road through a jungle.
“Occasionally we see wild turkeys, coatis, iguanas, and peccaries run across in front of us or we see toucans and other birds in the trees overhead,” says Chatters.
Once they arrive at the cave, the researchers and divers must climb down a 9 metre ladder to the surface of the water. To get to the cave, the divers then swim through over 1,200 meters of flooded tunnels. Divers can only safely spend about three hours underwater because they need to go 43 metres deep to reach Hoyo Negro!
When the animals and girl were alive, the ocean was much shallower than it is now so the caves and tunnels would not have been completely flooded. The caves may have had some fresh water for drinking or made a good place to shelter from bad weather. The girl could have been walking through the dark tunnels searching for a drink and suddenly fallen into the deep hole of Hoyo Negro.
The discovery of the full skeleton of the girl from Hoyo Negro was very exciting for scientists. They continued returning to the cave many times between 2007 and 2013. They studied the shape of her skull and collected DNA from the ancient bones! This information revealed that ancient humans living in North and South America, the Paleoamericans, were originally from areas around the Bering Strait between modern Alaska and eastern Russia.
Modern researchers who are interested in ancient humans have to be creative and adventurous to find the data they need. Can you imagine being both a scientist and an explorer?
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