Calico Early Man Site facts for kids

The Calico Early Man Site is a special place where scientists look for clues about ancient humans. It's an archaeological site located in the Mojave Desert in Southern California, near Barstow. This area was once home to a huge ancient lake during the Pleistocene Ice Age.

At the site, researchers have found:

• Stone objects that look like tools, found near where an ancient lake used to be. This lake, called Lake Manix, dried up about 18,000 years ago.
• Other stone objects found deep underground, in layers of earth that are very old. Some of these have been dated to be over 100,000 years old, and possibly even older, up to 200,000 years!
• A large, well-shaped stone tool called the Rock Wren Biface. It was found in a younger layer of earth and is thought to be about 14,400 years old.

Scientists believe that the stone objects found at Calico were likely made by early modern humans (Homo sapiens sapiens).

Exploring Ancient Life in the Calico Hills

The Calico Early Man Site is famous for its stone objects. These objects, which look like tools, along with pieces of rock that were chipped off during tool-making, are found in the Calico Hills. This area is in the middle of the Mojave Desert in southern California. Over time, this important archaeological project has been known by a few names, but today it's simply called "The Calico Early Man Site."

The Manix Basin: A Window to the Past

The Manix Basin is a large, bowl-shaped area in the central Mojave Desert. It's part of the Mojave River system, which is a river that sometimes flows and sometimes dries up. This river starts in the San Bernardino Mountains, about 200 kilometers away.

Long, long ago, between 400,000 and 500,000 years ago, a freshwater lake formed in this basin near the Calico site. This lake, called Lake Manix, stayed for a very long time, until the end of the Ice Age. At its biggest, Lake Manix covered about 236 square kilometers. It drained away suddenly about 18,100 years ago, possibly because of a lot of water flowing in or an earthquake.

Ancient Animals of the Manix Basin

The ancient lake and river beds at the Calico site hold many fossils of animals that lived there during the Ice Age. These fossils range from about 20,000 years old to more than 350,000 years old!

Some of the amazing animals found here include:

• Camels
• Horses
• Mammoths (like woolly mammoths)
• Saber-tooth cats
• Dire wolves
• Short-faced bears
• Coyotes
• Many types of birds, like flamingos, pelicans, eagles, swans, geese, and ducks.

Prehistoric Stone Objects: Tools or Nature's Work?

Thousands of rocks that look a lot like prehistoric tools have been found at the Calico site. Some are on the surface, and others are buried up to 8 meters deep. One stone from a main digging area was thought to be over 200,000 years old. However, this age might have been affected by other things in the soil. Scientists are now trying to date some of the confirmed stone objects using a method called thermoluminescence dating. While they wait for the final results, the styles of some objects suggest they could be 20,000 to 30,000 years old.

The big question at Calico is whether these "tools" were actually made by humans (called artifacts) or if they were shaped by natural processes, like rocks hitting each other in a river (called geofacts). Most scientists today believe that the objects found deep underground are geofacts.

The Big Debate: Artifacts or Geofacts?

Many scientists have questioned if the stone objects at Calico are truly human-made tools. Some researchers, like Vance Haynes, suggested that natural forces could have created these shapes. For example, rocks could have broken apart from earthquakes, weather, or by tumbling in rivers and mudslides. These natural breaks could look very similar to tools made by early humans.

Archaeologists who volunteer at the Calico site are still studying the objects found there. Many have been identified as geofacts, meaning they were shaped by nature. However, some are still thought to be possible artifacts and are being studied further and dated. As of 2025, new findings are being put together to share with local tribes, the community, and other scientists for review.

Looking at Flake Angles

One way scientists try to tell if a stone was shaped by a human or by nature is by looking at the angles of the "flake scars." These are the marks left when a piece of rock breaks off. One study compared the angles on the Calico objects to angles on rocks broken naturally and rocks known to be human-made tools. The study found that the Calico objects had angles very similar to naturally broken rocks, suggesting they were not made by humans.

Another study looked at different features of the Calico objects, like their length, width, and angles. They compared these to known ancient tools and concluded that the Calico objects were likely just naturally flaked rocks that happened to have shapes that looked like tools.

What Scientists Think Today

While there have been arguments supporting the idea that the Calico objects are tools, most scientists today agree that there is no clear evidence of human activity at the Calico Early Man site.

This agreement comes from several reasons:

• No other human evidence: Besides the stone objects, there haven't been other signs of human life, like human bones, animal bones with tool marks, or other types of artifacts.
• Very old dates: The site is incredibly old. The next oldest widely accepted human artifacts in the Americas are around 30,000 years old, and even those dates are sometimes debated. The Calico objects are much, much older.
• Too many "tools": Some reports suggest up to 60,000 possible tools. It's unusual to find so many tools without other signs of a settlement.
• Natural explanations: Studies have shown how natural processes could have created these stone objects.

History of the Digs

The story of the Calico Early Man Site began in 1959 when Ruth DeEtte Simpson, an archaeologist from California, visited Louis Leakey at the British Museum of Natural History in London. Simpson showed Leakey some stone objects from the Calico Hills that looked like ancient scrapers.

Leakey believed it was important to study the Calico Hills site. He thought that humans must have been in the Americas for much longer than 12,000 years for all the different native languages to develop. In 1963, Leakey received money from the National Geographic Society and started digging with Simpson. They found stone objects that they believed were 100,000 years old or even older. This would mean humans were in North America much earlier than most scientists thought.

Another archaeologist, Jeffrey Goodman, who worked with Leakey, also claimed the stone objects were human-made. Goodman even suggested they could be as old as 500,000 years, which would make them the oldest human artifacts in the world! However, most scientists have rejected these very old claims.

The geologist Vance Haynes visited the site in 1973 and argued that Leakey's "artifacts" were actually naturally formed geofacts. Haynes believed the stones were broken by natural forces in an ancient river.

Louis Leakey's wife, Mary Leakey, who was also a famous archaeologist, wrote in her book that she lost respect for Louis because of his involvement with the Calico Hills site. She felt it hurt his career. Louis Leakey continued to visit the site until he passed away in 1972. After that, the Bureau of Land Management took over the site, and it was opened to the public.

See also

In Spanish: Calico (sitio arqueológico) para niños