Kind: captions
Language: en
so that is a human footprint so there's
a human footprint right there yeah and
so if you look that is amazing here's
the hill okay right here
scattered across the landscape are human
Footprints from thousands of years ago
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each track is a trace of an ancient
person
the shape of their bare feet locked in
the sediment
but how long ago were these people here
in order to date the prince
team has dug a trench
it reveals layers of sediment deposited
over many years
along the shore of this ancient Lake
stamped on these buried surfaces are
human prints
and the farther down they are the older
they are
but just how old are they
I can put them both on okay I'm sure
to help find the answer David has been
joined by geologist Kathleen Springer
and Jeff Bugatti who was also an expert
in radiocarbon dating
you've cut across section what are you
trying to see with the cross so the
footprints of prints themselves are just
an impression on a Surface there's
nothing to date it's an inorganic thing
you have to find something organic that
you can date above and below the
footprints and get good dates on them so
that you can actually say that footprint
is between these two ages
in this trench Kathleen and Jeff have
made a crucial find
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sandwiched in the layers above and below
the footprints
are scatterings of ancient seeds
precious organic material which the team
can date
that way they can establish a window of
time for when the prints were made
there were actually plants growing on
this on this surface when you know these
Critters were the same layers that have
the tracks we'll have absolutely or
above and below them yes so above and
below them that that way we can
constrain in Time same your seeds are
effectively little time pieces right
they're like little clocks
little capsules
um yeah and basically the the these
things are really resistant to to Decay
and so they look like they were put down
on the on the landscape just yesterday
but in fact they might be tens and you
know tens of thousands of years old
there yeah at the U.S Geological Survey
lab Jeff has been analyzing the seeds
they found in the sediment layers at
White Sands
radiocarbon dating to calculate the age
of the seeds and from that the age of
the footprints
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it's the moment of truth
after more than a year and a half
Kathleen and Jeff managed to find out
the age of the footprints
so tell me
what were the dates of those Footprints
we were able to document that humans
were in White Sands National park
between 23 000 years ago and about 21
000 years ago 23 000 years ago that's
way older than there's been good
evidence for humans in North America
it's about 10 000 years older than sort
of the established sort of thought of
when humans arrived in the Americas and
you get tracks at more than one layer
which means it wasn't just one group of
people at one moment in time but it was
many groups of people over a lot of time
two thousand years I mean 2000 years
itself is a long it is duration but the
fact that they were here 23 000 years
ago yeah crazy blows my mind I mean if
you are mine yeah
dates are correct that would make the
White Sands Footprints the earliest
direct evidence of humans ever found in
North America