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)