Study: Footprints in New Mexico May Be Oldest Sign of Humans
2023-10-12
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1New research confirms that a fossil of human footprints found in the U.S. state of New Mexico likely represents the oldest direct evidence of humans living in the Americas.
2The footprints were discovered at the edge of the remains of an ancient lake in White Sands National Park in southern New Mexico.
3The research, published recently in Science, suggests the fossil dates back to between 21,000 and 23,000 years ago.
4The estimated age of the footprints was first reported in Science in 2021.
5But some researchers questioned the dates.
6Researchers wondered whether seeds from lake plants used in the early dating may have taken in ancient carbon from the lake.
7If so, this could have changed the radiocarbon test result by thousands of years.
8The new study presents two additional lines of evidence for the older date range.
9It uses two different materials found at the site, ancient tree pollen and quartz grains.
10The reported age of the footprints questions the belief that humans did not reach the Americas until about 15,000 years ago.
11That was a few thousand years before rising sea levels covered the Bering land bridge between Asia and North America.
12Thomas Urban is a scientist who studies ancient humans at Cornell University in New York.
13He was involved in the 2021 study but not the new one.
14He said it is an area "... that's always been controversial..."
15Urban said such studies are important because they deal with the last part "of the peopling of the world."
16Thomas Stafford is an independent scientist who studies ancient humans and the Earth in Albuquerque, New Mexico.
17He was not involved in the study.
18He said that while he "was a bit skeptical before," he now believes it.
19Stafford said it is an important finding if three completely different methods show findings from a similar time period.
20The new study separated about 75,000 individual pieces of pollen from the same area in rocks where the footprints where found.
21Kathleen Springer is an Earth scientist researcher at the United States Geological Survey and helped write the new paper.
22She said the process of dating pollen is very difficult.
23She added that scientists believe radiocarbon dating land plants gives more correct results than dating plants living in water.
24But she added there needs to be a large enough number of plants to study.
25The researchers also studied damage to the structure in ancient small pieces of quartz to produce an age estimate.
26Ancient footprints of any kind - left by humans or large animals - can give scientists some idea when they are from.
27They may record how and where people or animals walked and if their paths crossed.
28Animal footprints have also been found at White Sands.
29Other ancient sites in the Americas point to a similar time period.
30These include ancient art made from animal remains in Brazil.
31But scientists still question whether such materials really suggest that humans were living in the Americas then.
32Jennifer Raff is a scientist who studies ancient human genes at the University of Kansas.
33She was not involved in the study.
34Raff said, "White Sands is unique because there's no question these footprints were left by people, it's not ambiguous."
35I'm Andrew Smith.
1New research confirms that a fossil of human footprints found in the U.S. state of New Mexico likely represents the oldest direct evidence of humans living in the Americas. 2The footprints were discovered at the edge of the remains of an ancient lake in White Sands National Park in southern New Mexico. The research, published recently in Science, suggests the fossil dates back to between 21,000 and 23,000 years ago. 3The estimated age of the footprints was first reported in Science in 2021. But some researchers questioned the dates. Researchers wondered whether seeds from lake plants used in the early dating may have taken in ancient carbon from the lake. If so, this could have changed the radiocarbon test result by thousands of years. 4The new study presents two additional lines of evidence for the older date range. It uses two different materials found at the site, ancient tree pollen and quartz grains. 5The reported age of the footprints questions the belief that humans did not reach the Americas until about 15,000 years ago. That was a few thousand years before rising sea levels covered the Bering land bridge between Asia and North America. 6Thomas Urban is a scientist who studies ancient humans at Cornell University in New York. He was involved in the 2021 study but not the new one. He said it is an area "... that's always been controversial..." Urban said such studies are important because they deal with the last part "of the peopling of the world." 7Thomas Stafford is an independent scientist who studies ancient humans and the Earth in Albuquerque, New Mexico. He was not involved in the study. He said that while he "was a bit skeptical before," he now believes it. 8Stafford said it is an important finding if three completely different methods show findings from a similar time period. 9The new study separated about 75,000 individual pieces of pollen from the same area in rocks where the footprints where found. 10Kathleen Springer is an Earth scientist researcher at the United States Geological Survey and helped write the new paper. She said the process of dating pollen is very difficult. She added that scientists believe radiocarbon dating land plants gives more correct results than dating plants living in water. But she added there needs to be a large enough number of plants to study. 11The researchers also studied damage to the structure in ancient small pieces of quartz to produce an age estimate. 12Ancient footprints of any kind - left by humans or large animals - can give scientists some idea when they are from. They may record how and where people or animals walked and if their paths crossed. Animal footprints have also been found at White Sands. 13Other ancient sites in the Americas point to a similar time period. These include ancient art made from animal remains in Brazil. But scientists still question whether such materials really suggest that humans were living in the Americas then. 14Jennifer Raff is a scientist who studies ancient human genes at the University of Kansas. She was not involved in the study. Raff said, "White Sands is unique because there's no question these footprints were left by people, it's not ambiguous." 15I'm Andrew Smith. 16Christina Larson reported this story for The Associated Press. Gregory Stachel adapted the story for VOA Learning English. 17________________________________________________ 18Words in This Story 19fossil - n. something (such as a leaf, skeleton, or footprint) that is from a plant or animal which lived in ancient times and that you can see in some rocks 20controversial - adj. relating to or causing much discussion, disagreement, or argument 21skeptical - adj. having or expressing doubt about something (such as a claim or statement) 22unique - adj. used to say that something or someone is unlike anything or anyone else 23ambiguous - adj. able to be understood in more than one way