Ancient footprints suggest humans lived in America 21,000 years ago

New research has shown humans may have lived in the Americas for much longer than scientists first thought.

Fossilised human footprints found in New Mexico have been dated back to between 21,000 and 23,000 years ago, challenging the theory that humans came to North and South America about 15,000 years ago.

The footprints were discovered at the edge of an ancient lake bed in White Sands National Park in New Mexico, North America, in 2021.

Scientists had questioned whether the dating used when the footprints were first discovered was correct.

But further study showed the footprints were likely to be 21,000 to 23,000 years old, making them the oldest human footprints found in the Americas.

HOW WAS THE FIRST STUDY DONE?
In the first study, scientists used radiocarbon dating to find out the age of aquatic plant seeds stuck to the footprints.

The result showed the footprints were about 21,000 to 23,000 years old.

Some scientists were sceptical about this dating, saying the seeds may have absorbed ancient carbon from the lake the plants had grown in, making them seem older than they really were.

HOW WAS THE NEW STUDY DIFFERENT?
In the new study, researchers radiocarbon dated two different materials found at the site of the footprints, ancient conifer pollen and quartz grains.

About 75,000 grains of pure pollen were studied, with scientists saying land growing plants like conifer gave a more accurate idea of age than aquatic plants when radiocarbon dated.

Co-author of the study and research geologist at the United States Geological Survey Kathleen Springer said dating pollen was difficult and “nail-biting.”

The researchers also studied damage in the crystal lattices of ancient quartz grains to estimate their age.

The new study provided two different lines of evidence that supported the original date range of 21,000 to 23,000.

WHAT DOES THIS MEAN FOR OUR UNDERSTANDING OF EARLY HUMANS?
The findings of the study goes against the theory that humans first came to the Americas a few thousand years before rising sea levels covered the Bering land bridge between Russia and Alaska, about 15,000 years ago.

“This is a subject that’s always been controversial because it’s so significant — it’s about how we understand the last chapter of the peopling of the world,” said Cornell University archaeological scientist Thomas Urban, who was involved in the 2021 study but not the new one.

Ancient footprints can provide archaeologists with a snapshot of a moment in time, recording how people or animals walked or limped along and whether they crossed paths.

Animal footprints have also been found at White Sands.

While other archaeological sites in the Americas date back to a similar time, scientists haven’t been able to link them with humans.

“White Sands is unique because there’s no question these footprints were left by people,” said University of Kansas Associate Professor Jennifer Raff, an anthropological geneticist who was not involved in the study.

POLL

GLOSSARY

• fossilised: something from at least 10,000 years ago that has been preserved as a fossil
• sceptical: doubting something
• ancient: very old
• radiocarbon dating: a scientific method that measures the amount of carbon stored in an object to determine its age
• aquatic plant: a plant that grows in water
• quartz grains: tiny pieces of quartz, a crystal mineral made of silicon and oxygen
• crystal lattices: the repeating 3D pattern of atoms or groups of atoms in a crystal
• controversial: something that shocks or is challenging to accept
• significant: very important
• peopling: how humans came to live in the different parts of the world
• anthropological geneticist: someone who studies DNA to find out how humans evolved

EXTRA READING
New type of ancient human discovered
Oldest fossil of early human species is discovered
Early humans ‘ate no meat, swung in trees’

QUICK QUIZ
1. Why were scientists sceptical of the first study into the age of the human footprints?
2. What two materials were dated in the second study to measure the age of the footprints?
3. What is the name of the scientific method used to measure age in ancient objects?
4. When were humans originally thought to have come to America?
5. How did the discovery of the White Sands footprints change this?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. Who was it?
Who was the person who left the footprints? Use your imagination and perhaps your research skills, to write a story about or a description of the person who left the footprints and why they were in an ancient lake bed.

Time: allow at least 30 minutes to complete this activity
Curriculum Links: English, Science, History

2. Extension
What does this story show you about how scientists investigate fossilised remains? Use the information in the story to write paragraphs that answer this question.

Time: allow at least 20 minutes to complete this activity
Curriculum Links: English, Science, History

VCOP ACTIVITY
To sum it up
After reading the article, use your comprehension skills to summarise in a maximum of three sentences what the article is about.

Think about:

• What is the main topic or idea?
• What is an important or interesting fact?
• Who was involved (people or places)?

Use your VCOP skills to re-read your summary to make sure it is clear, specific and well punctuated.