Why are these 32 symbols found in ancient caves all over Europe?

There's something about caves --

a shadowy opening in a limestone
cliff that draws you in.

As you pass through the portal
between light and dark,

you enter a subterranean world.

A place of perpetual gloom,
of earthy smells, of hushed silence.

Long ago in Europe,

ancient people also entered
these underground worlds.

As witness to their passage,

they left behind mysterious
engravings and paintings.

Like this panel of humans, triangles
and zigzags from Ojo Guareña in Spain.

You now walk the same path
as these early artists.

And in this surreal, otherworldly place,

it's almost possible to imagine

that you hear the muffled footfall
of skin boots on soft earth,

or that you see the flickering of a torch
around the next bend.

When I'm in a cave,

I often find myself wondering
what drove these people to go so deep

to brave dangerous and narrow
passageways to leave their mark?

In this video clip,

that was shot half a kilometer,
or about a third of a mile, underground,

in a cave in Spain,

we found a series
of red paintings on a ceiling

in a previously unexplored
section of the cave.

As we crawled forward, military-style,
with the ceiling getting ever lower,

we finally got to a point
where the ceiling was so low,

that my husband
and project photographer, Dylan,

could no longer achieve focus
on the ceiling with his DSLR camera.

So while he filmed me,

I kept following the trail of red paint
with a single light,

and a point-and-shoot camera
that we kept for that type of occasion.

Half a kilometer underground.

Seriously.

What was somebody doing down there
with a torch or a stone lamp?

(Laughter)

I mean -- me, it makes sense, right?

But you know,

this is the kind of question that
I'm trying to answer with my research.

I study some of the oldest
art in the world.

It was created by these
early artists in Europe,

between 10,000 and 40,000 years ago.

And the thing is

that I'm not just studying it
because it's beautiful,

though some of it certainly is.

But what I'm interested in
is the development of the modern mind,

of the evolution of creativity,
of imagination, of abstract thought,

about what it means to be human.

While all species communicate
in one way or another,

only we humans have really
taken it to another level.

Our desire and ability
to share and collaborate

has been a huge part of our success story.

Our modern world is based on a global
network of information exchange

made possible, in large part,
by our ability to communicate --

in particular, using graphic
or written forms of communication.

The thing is, though,

that we've been building
on the mental achievements

of those that came before us for so long

that it's easy to forget that certain
abilities haven't already existed.

It's one of the things
I find most fascinating

about studying our deep history.

Those people didn't have the shoulders
of any giants to stand on,

they were the original shoulders.

And while a surprising number
of important inventions

come out of that distant time,

what I want to talk to you about today
is the invention of graphic communication.

There are three
main types of communication,

spoken, gestural --
so things like sign language --

and graphic communication.

Spoken and gestural are
by their very nature ephemeral.

It requires close contact
for a message to be sent and received.

And after the moment
of transmission, it's gone forever.

Graphic communication, on the other hand,
decouples that relationship.

And with its invention,
it became possible for the first time

for a message to be
transmitted and preserved

beyond a single moment in place and time.

Europe is one of the first places

that we start to see graphic marks
regularly appearing

in caves, rock shelters
and even a few surviving open-air sites.

But this is not the Europe we know today.

This was a world dominated
by towering ice sheets,

three to four kilometers high,

with sweeping grass plains
and frozen tundra.

This was the Ice Age.

Over the last century,

more than 350 Ice Age rock art sites
have been found across the continent,

decorated with animals, abstract shapes,
and even the occasional human

like these engraved figures
from Grotta dell'Addaura in Sicily.

They provide us with a rare glimpse

into the creative world and imagination
of these early artists.

Since their discovery,

it's been the animals that have received
the majority of the study

like this black horse
from a cave in Spain

or this unusual purple bison
from La Pasiega.

But for me, it was the abstract shapes,
what we call geometric signs,

that drew me to study the art.

The funny this is that at most sites

the geometric signs far outnumber
the animal and human images.

But when I started on this back in 2007,

there wasn't even a definitive list
of how many shapes there were,

nor was there a strong sense

of whether the same ones
appeared across space or time.

Before I could even
get started on my questions,

my first step was to compile a database

of all known geometric signs
from all of the rock art sites.

The problem was that while they were
well documented at some sites,

usually the ones
with the very nice animals,

there was also a large number of them
where it was very vague --

there wasn't a lot
of description or detail.

Some of them hadn't been visited
in half a century or more.

These were the ones
that I targeted for my field work.

Over the course of two years,

my faithful husband Dylan and I
each spent over 300 hours underground,

hiking, crawling and wriggling
around 52 sites

in France, Spain, Portugal and Sicily.

And it was totally worth it.

We found new, undocumented geometric signs
at 75 percent of the sites we visited.

This is the level of accuracy
I knew I was going to need

if I wanted to start answering
those larger questions.

So let's get to those answers.

Barring a handful of outliers,
there are only 32 geometric signs.

Only 32 signs

across a 30,000-year time span
and the entire continent of Europe.

That is a very small number.

Now, if these were random
doodles or decorations,

we would expect to see
a lot more variation,

but instead what we find
are the same signs

repeating across both space and time.

Some signs start out strong,
before losing popularity and vanishing,

while other signs are later inventions.

But 65 percent of those signs stayed
in use during that entire time period.

Things like lines, rectangles
triangles, ovals and circles.

Like we see here,
from the end of the Ice Age,

at a 10,000-year-old site
high in the Pyrenees Mountains.

And while certain signs
span thousands of kilometers,

other signs had much more
restricted distribution patterns,

with some being limited
to a single territory,

like we see here
with these divided rectangles

that are only found in northern Spain,

and which some researchers have speculated

could be some sort
of family or clan signs.

On a side note,

there is surprising degree
of similarity in the earliest rock art

found all the way from France and Spain
to Indonesia and Australia.

With many of the same signs
appearing in such far-flung places,

especially in that 30,000
to 40,000-year range,

it's starting to seem increasingly likely

that this invention actually traces back
to a common point of origin in Africa.

But that I'm afraid,
is a subject for a future talk.

So back to the matter at hand.

There could be no doubt that these signs
were meaningful to their creators,

like these 25,000-year-old
bas-relief sculptures

from La Roque de Venasque in France.

We might not know what they meant,
but the people of the time certainly did.

The repetition of the same signs,
for so long, and at so many sites

tells us that the artists
were making intentional choices.

If we're talking about geometric shapes,

with specific, culturally recognized,
agreed-upon meanings,

than we could very well be looking

at one of the oldest systems
of graphic communication in the world.

I'm not talking about writing yet.

There's just not enough
characters at this point

to have represented all of the words
in the spoken language,

something which is a requirement
for a full writing system.

Nor do we see the signs
repeating regularly enough

to suggest that they were
some sort of alphabet.

But what we do have
are some intriguing one-offs,

like this panel from La Pasiega in Spain,
known as "The Inscription,"

with its symmetrical markings on the left,

possible stylized representations
of hands in the middle,

and what looks a bit
like a bracket on the right.

The oldest systems of graphic
communication in the world --

Sumerian cuneiform, Egyptian hieroglyphs,
the earliest Chinese script,

all emerged between 4,000
and 5,000 years ago,

with each coming into existence
from an earlier protosystem

made up of counting marks
and pictographic representations,

where the meaning
and the image were the same.

So a picture of a bird would really
have represented that animal.

It's only later that we start to see
these pictographs become more stylized,

until they almost become unrecognizable

and that we also start to see
more symbols being invented

to represent all those other
missing words in language --

things like pronouns, adverbs, adjectives.

So knowing all this,

it seems highly unlikely that
the geometric signs from Ice Age Europe

were truly abstract written characters.

Instead, what's much more likely

is that these early artists
were also making counting marks,

maybe like this row of lines
from Reparo de Za Minica in Sicily,

as well as creating
stylized representations

of things from the world around them.

Could some of the signs
be weaponry or housing?

Or what about celestial objects
like star constellations?

Or maybe even rivers, mountains,
trees -- landscape features,

possibly like this black penniform
surrounded by strange bell-shaped signs

from the site of El Castillo, in Spain.

The term penniform
means "feather-shaped" in Latin,

but could this actually be
a depiction of a plant or a tree?

Some researchers have begun
to ask these questions

about certain signs at specific sites,

but I believe the time has come
to revisit this category as a whole.

The irony in all of this, of course,

is that having just carefully classified
all of the signs into a single category,

I have a feeling that my next step
will involve breaking it back apart

as different types of imagery
are identified and separated off.

Now don't get me wrong,

the later creation
of fully-developed writing

was an impressive feat in its own right.

But it's important to remember

that those early writing systems
didn't come out of a vacuum.

And that even 5,000 years ago,

people were already building
on something much older,

with its origins stretching back
tens of thousands of years --

to the geometric signs
of Ice Age Europe and far beyond,

to that point, deep
in our collective history,

when someone first came up with the idea
of making a graphic mark,

and forever changed the nature
of how we communicate.

Thank you.

(Applause)