44 | New Scientist | 9 April 2022
for sure. Still, footprints do pitch us closer than
ever to the emotions of ancient people.
The evidence does strongly suggest that fear
hung in the air that day, and maybe in more
than one species. The giant ground sloth acted
oddly when it crossed the woman’s northerly
tracks. Its own footprints show that it reared up
on its hind legs and shuffled around in a circle.
The obvious conclusion, says Bennett, is that it
had picked up the woman’s scent and, anxious
about the possible presence of hunters, was
scanning the landscape. This might have been
typical sloth behaviour, says Bennett. There are
plenty of other ground sloth tracks elsewhere at
White Sands. They show that the beasts usually
trundled in a roughly straight line, he says. But
some trails are different. “Suddenly, the prints
do an about-face and head off at a different
angle,” he says. “And when we look at that point
of inflection, we’ll find a human footprint.”Landscape of fear
One collection of prints at White Sands,
described by Bennett, Bustos and their
colleagues in a 2018 study, even captures a
sloth hunt, with humans literally walking in
the animal’s footprints before attacking. But
if sloths did fear humans, the same doesn’t
go for some other animals. Mammoths and
even camel trails don’t deviate when crossing
human trackways, telling us they had a more
relaxed attitude to early Americans. “It’s really
breathing life into these animals,” says Bennett.
The footprints at White Sands aren’t all
about the gruelling struggle to survive though.In unpublished work, Bennett and his team
have discovered some that seem to record a
moment of pure joy. The researchers found a
chaotic mess of footprints belonging to a gang
of children, the oldest no more than 6 years
old. The tiny prints are focused around the
large impressions left by yet another ground
sloth. The logical conclusion, says Bennett, is
that the children were splashing in the muddy
puddles left in the deep sloth footprints. “Kids
have always liked to jump in puddles,” says
Bennett. “These are stories that can connect
people with the past.”
Beautiful tales aside, footprints still have
the capacity to throw up surprises about the
grand sweep of human history. It turns out
White Sands might end up at the centre of one
much-debated question: when did humans
first begin to populate north America?
For decades, it was assumed the first settlers
were connected to a style of stone tool first
found at another site in New Mexico called
Clovis. Today, the consensus is that the Clovis
culture – which is about 13,000 years old – isn’t
the earliest evidence of human activity in theAmericas. Instead, the accepted archaeological
and genetic evidence suggests people began
living there about 15,000 years ago. But there
is a nagging suspicion this isn’t the final
answer. A number of archaeologists have found
evidence that they claim shows humans were
in north America thousands of years earlier,
at the peak of the last glacial period. However,
the evidence is contested.
White Sands is throwing up new clues.
The whole area is composed of layers of rock
of different ages that are exposed in different
places. One day, Bennett and his colleagues
found a set of human tracks padding across
the dirt and vanishing beneath a small hill.
This suggested the tracks were older than the
hill – particularly ancient, then. Crucially, the
researchers could test their hunch, because
the dirt around the prints contained grass
seed that could be radiocarbon-dated. In
September 2021, they reported the results:
the 61 footprints were between 21,000 and
23,000 years old. It is the most incontrovertible
evidence yet that the peopling of America
took place much earlier than we thought.
“White Sands is a fantastic discovery,”
says Ciprian Ardelean at the Autonomous
University of Zacatecas in Mexico, who has
also found archaeological evidence suggesting
that humans were in the Americas much
earlier than 20,000 years ago. He doesn’t
think ancient footprints should overshadow
traditional artefact-based archaeology. But he
has previously suggested that White Sands
might come to be seen as pivotal in the story
of the earliest Americans.
This kind of legacy doesn’t interest Bennett.
But he does hope the work at White Sands will
encourage other archaeologists to go looking
for footprints elsewhere in the region. Because
the most remarkable part of this story is that
White Sands might prove to be unremarkable
in the grand scheme of things. “There are
many other playas in the American south-
west,” says Bennett. This means there could be
millions of other fossilised human trackways
out there, waiting to tell their ancient stories
of what life was like in the deep past. ❚Colin Barras is a science writer
based near Ann Arbor, MichiganJAVIERTRUEBA
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SF
/SCIENCE^PH
OTO^ LIBRAR
YA 3.7-million-year-old
print preserved in ash
in Laetoli, Tanzania“ Children were
splashing in the
muddy puddles
left in the sloth
footprints”