12 may 2012
Not far from West Palm Beach in southern Florida, people once lived
alongside giant ground sloths, mammoths, tapirs, mastodons and other
enormous creatures.
The discovery adds the far southeast corner of the United States to
the list of places in North America where humans coexisted with massive
creatures more than 10,000 years ago. The finding also adds to a growing
body of evidence that modern humans spread rapidly after arriving in
the Americas, though it’s still not clear when and where they first set
foot on the continent.
“We found that humans came into Florida before the extinction of
megafauna -- they were in Florida by 10,000 years ago,” said Bruce
MacFadden, a paleontologist at the University of Florida, Gainesville.
This is “clearly documenting that humans were widespread in North
America.”
In 1913, construction of a drainage canal turned up fossils in Vero
Beach, Fla., about 90 miles north of West Palm Beach. When geologists
followed up, they unearthed the bones of all sorts of ancient animals
that lived during the last Ice Age, including jaguars, capybaras, bison,
peccaries, mastodons and other creatures, large and small. Alongside
the animal bones in the same layer of soil lay human skeletons.
At first, the scientists assumed that the co-mingled bones came from
animals and people that lived at the same time. Soon after, though, a
famous archaeologist from the Smithsonian Institution who came to see
the fossils raised doubts by proposing that people arrived long after
the giants were gone and that the human bones came from more recent
burials.
Despite subsequent archaeological finds in other parts of the United
States showing that people coexisted with extinct megafauna during the
last Ice Age, which ended about 10,000 years ago, controversy about the
Vero Beach fossils has lingered. Complicating matters, the bones are too
weathered to allow for radiocarbon dating, which would offer clear
dates and ages.
To settle the debate, MacFadden and colleagues looked instead at
levels of rare earth elements in 24 human bones and 48 animal bones from
the site, now held in museum collections. Over time, fossils left
underground absorb these elements at a predictable rate.
Both types of bones contained similar levels of rare earth elements,
the researchers reported in the Journal of Vertebrate Paleontology. The
technique couldn’t accurately date the bones, but it showed that they
had all been in the ground for the same amount of time. That meant that
they had lived at the same time, too. Many of the animals involved are
known to have gone extinct when the last Ice Age ended.
The new findings echo what other studies have shown in Montana, New
Mexico, Arizona, Ohio and elsewhere – that people lived alongside
mastodons, mammoths and other massive mammals more than 10 millennia
ago, said Kenneth Tankersley, an archaeological geologist at the
University of Cincinnati.
Scientists still don’t know whether people thought of the giant
animals that shared their territory as friends, enemies or food. In some
places, evidence suggests that ancient people hunted giant beavers,
bear-sized peccaries and mastodons, though the Florida bones offer no
clues. Also unanswered is why all of those enormous animals went
extinct.
As scientists puzzle over those questions, they are also still trying
to figure out when modern Homo sapiens arrived in North America in the
first place. The oldest clear evidence comes from the Monte Verde site
in Chile, where human skeletons date back to more than 14,000 years ago,
Tankersley said. But genetic evidence suggests that people may have
arrived in the Americas more than 20,000 years ago.
Together, ongoing research confirms oral histories of indigenous populations that have been passed down for generations.
“All along, Native Americans have been saying, ‘We’ve always been
here,’” Tankersley said. “That’s what this study is showing, that that’s
the case.”
