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Evolution is possibly the field of science

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that tells the most stories.

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It tells a lot of stories,

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but unlike the myths and tales
we tell children

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we try to reconstruct them
using evidence, facts and signs.

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A bit like Sherlock Holmes.

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But stories, we know, are slippery:
they have pros and cons.

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They can fascinate us,
but they can also deceive us.

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They may present us
with false reconstructions.

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Many years ago, a colleague of mine,
far more illustrious than me --

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his name was J.B.S. Haldane,

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and he was one of the fathers
of population genetics --

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was in a very formal salon in Oxford

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in the presence of theologians,
ladies and princesses.

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And one of the ladies asked him,

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"Excuse me, Professor Haldane,

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but if you were to imagine the Creator,

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how would you see him?
How do you picture him?"

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It was a somewhat loaded question

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because Haldane was known to be
an atheist, a disbeliever, a communist.

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He was a bit of an oddball,
especially in England in those days.

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And Haldane replied,

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"Look, ma'am, I don't know.

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But if I were to imagine the Creator,

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I think he has

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an inordinate passion for beetles."

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What did Haldane mean?

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He meant that if we look
at the earth and biodiversity

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from an evolutionist's point of view,

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the first thing we notice

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is that we are at the edge
of the empire,

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we are not at the centre of this story.

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We are one of the many wonderful species
created by natural history.

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The story I'm about to tell you
is the result of very recent research.

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So let me tell you what we discovered
but a few months ago

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and decisively disrupted our way
of telling the story of human evolution.

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Basically, it is the story
of a disappointment,

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but a constructive disappointment,
a disappointment that is good for us,

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that makes us think,

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that once more sets in motion

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the great questions
that science is able to raise.

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Where do we come from?
Why? What are we doing here?

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What is the place of man in nature?

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The beginning of the story
is in this image that you see behind me.

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It is a fascinating, mysterious page
written by Charles Darwin himself,

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dating back to July 1837.

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If you remember the dates,
it means he was very young.

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He was born in 1809,
he was not yet thirty.

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He had just returned

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from a wonderful five-year voyage
around the world, which we've all studied.

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He came back in 1836
and, as soon as he got back,

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he began writing
in these private notebooks.

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Very private.

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So secret that they were
to practically become

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the only Darwinian writing
that he decided never to publish.

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He is known to have said,

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"I entreat you never to circulate

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what I wrote as a boy
just back from my voyage."

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On one of these pages,

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there is this beautiful diagram
that he called The Tree of Life.

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And he wrote, see, "I think…",

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because, for the first time,
he was writing to himself,

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he was talking to himself about
what he'd understood about evolution.

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That is, evolution is a tree

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and like a tree it has a trunk,
so common ancestors,

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and then it has ramifications,

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species that diversify over time

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and then become extinct,
that multiply and so on.

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An interesting story, a plural story,
made up of many different species.

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Why am I telling you a story
that is actually a disappointment?

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It is because when we applied
this Darwinian idea --

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already back in 1837,
then he became famous,

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and 20 years later he published
"On the Origin of Species" --

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when we dealed with human evolution,

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scientists themselves
actually made an exception.

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And I say scientists themselves,
not lay people or opponents of evolution.

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And if you look at how Thomas Henry Huxley
reconstructed human evolution,

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you'll see that it's very different
from the tree I showed you before.

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The first was a story
of diversity, of multiplicity,

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of coexistence of different species.

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This is a very different story,

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where there's only one species at a time,
we proceed in a linear fashion.

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This is a great story of progress.

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It's what a colleague of mine,

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who was very important in my training,

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his name was Stephen Jay Gould,

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called "our great illusion".

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The illusion that Homo Sapiens,

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who is always placed at the end,
at the far right,

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should represent
the culmination of evolution.

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The illusion that the Story
should necessarily lead to us.

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Surely this image
is very familiar to all of us.

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We always come across it,
in newspapers, on television,

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we have seen it many a time.

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What we have recently discovered
is that this exception is not valid.

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It's been proved wrong,
we've called it into question.

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Human evolution
did not take place that way.

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I'll show you other
alternatives to this image

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that is used in advertising,
it is used everywhere.

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My favourite one is that one
at the top right corner.

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It appeared in a feminist magazine

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and it compares the slow and gradual
but progressive evolution of the male

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with that of the female,
very stable actually.

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I've found all sorts
of variants of this image.

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It's a sort of major icon.

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An iconography.

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Even today, when we publish articles
on human evolution in newspapers

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they always illustrate it with this image.

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It also happened to me recently.

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The first line of my article was,
"There are no missing links in evolution."

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And they accompanied it with this image
showing the missing links of evolution.

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So it's something very powerful,
deeply rooted in our minds.

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The version that I definitely choose
as the absolute best in the world

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is this one that was proposed
in The Simpsons

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where evolution culminates inexorably
and wonderfully in Homersapiens,

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whom you see at the far right.

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Why is this exception very strange?

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Because while we kept on upholding
this great iconography of hope,

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scientists forged ahead

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and rewrote the evolutionary stories,
the natural stories of the species

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in a very different way.

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This image is less easy to understand
than the previous ones

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but it is wonderful.

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Let me tell you one thing:

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I think that if an alien
were to fall to Earth

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and we were to tell him

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about one of the great achievements
of science and knowledge --

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yes, true, we have
the theory of relativity

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and a lot of discoveries
in the field of physics

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but I'd show him this picture,

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and say "Thanks to science,

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the species Homo sapiens
has managed to do one thing:

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it's managed to assemble
and reconstruct the Tree of Life,

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that is, to decode kinship
across all living beings,

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but really all of them, from bacteria
up to the most complex animal,

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up to the jaguar, the giraffe,
to the humans

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who have inhabited
and do inhabit now this planet.

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This Tree of Life brings together
all the living beings we know."

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And you see that it is a tree,

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it has many branches,
there are many species.

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If you want to find yourself,
it is extremely complicated

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because we're here,
the animals in here,

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and we happen to be closer related
to mushrooms than to plants,

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another thing we don't really like.

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And among animals

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you have to go from twig
to twig to twig for nine times

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before you find Homo sapiens.

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In other words, we're at the edge
of the biodiversity empire

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as Haldane said with that funny quip
when he wanted to shock the lady.

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The same thing holds true
if we approach our personal history,

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that of our family: we find
the same pattern, can you see?

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I don't want to go into this
because it is a bit too technical,

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but if you look at this image
we are here, we are this species,

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we are in this genus, the genus Homo.

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If you look back, you find a story
of major ramifications like these.

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What you find is a bush, not a ladder.

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You don't find linearity,
you find multiplicity.

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And interestingly,
if you look at such schemes

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and you draw any time line --

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imagine you have a time machine,

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choose any epoch,
10 million years ago, for example,

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and draw the line --

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you will discover that at any time
of evolutionary history

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there were many different species
existing at the same time,

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more or less related to one another.

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Here you see that if you start from today,

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Homo Sapiens shares
a common ancestor with chimpanzees

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who lived some 6/7 million years ago,

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and going further back
he shares one with gorillas,

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with orangutans, gibbons
and with all the other living beings,

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so this is a very synthetic,
very powerful image.

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Why was this powerful image
of evolution called into question?

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As is often the case in science,
there's a bit of inertia,

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new ideas sometimes have
a hard time to be accepted,

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then one is submerged by anomalies.

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That model didn't work and in the end,
though reluctantly, we abandoned it.

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This is a beautiful discovery
made in 2009,

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and it is so important that Science
devoted no less than two covers to it.

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So, the most important discovery of 2009
is our possible ancestor called Ardi,

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from Ardipithecus.

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If you look closely at it,

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you can see that it has a mix
of modern and archaic features.

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It is a bit ape-like as you can see
from its very long upper limbs

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and its divergent big toe,

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yet it is perfectly bipedal,
with a flat face

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and therefore presents
a mix of characters.

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Now, interestingly, we discovered

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that our ancestor wasn't to be placed

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at the beginning
of the evolutionary process

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but lived at the same time as others.

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Look, this is pretty incredible.

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This is a valley in Ethiopia,
a single valley in Ethiopia.

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We Sapiens also originated
in that area, in one of those valleys.

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In just one of these valleys

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there were no less
than three different human genera,

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here shown in different colours,

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and none of them happened to disappear
or be replaced by another one.

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They simply lived together in a bushy way.

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Some died out, some new species appeared

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and that complicated
and interesting image of evolution,

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which concerns us directly, was created.

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So this is how my colleagues and I
rebuilt human evolution.

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See, time flows from bottom to top.

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It's a real bush.

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You see that from the days
of our common ancestor with chimpanzees

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there have been about 20, maybe even 22,
some even say 25 different species.

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That's anything but a linear evolution.

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It's a lot more complicated,

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there's loads of different species.

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Even here, wherever you draw a line,
you find a lot of species coexisting.

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What we have recently found out,
in the last year and a half,

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and what actually shocked us
as we hadn't been expecting it,

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is that this is true
even in very recent times.

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If you look here,

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Homo sapiens is at the top right
and we are the last twig, this one.

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This is the present.

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If you just go a little back in time,
even only 40/50,000 years,

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you discover that there were
other human species on Earth.

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And we have recently found out

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that up to 30, 35, 40,000
years ago at most, mind you,

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five human species coexisted on Earth, 
at the same time.

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That's something we hardly figure out:
five different human species!

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If an alien had fallen to Earth
40,000 years ago,

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he would have seen us Sapiens

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roam around with four other human forms.

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This, of course, opens up
many important and intriguing questions.

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This is one of the latest discoveries,

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made in Indonesia
on a small island called Flores.

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We found storks 1.80 m tall,

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mice 1.50 m long, tail included,

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and small Hominini,
which hardly ever exceeded 1 m in height.

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This is a relative of ours,
a cousin of ours,

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discovered a few years ago on this island

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where it had been stuck
for hundreds of thousands of years,

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and had become very short.

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This is an evolutionary mechanism called
insular dwarfism and it often occurs.

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It also occurred in Italy.

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As you may know,
dwarf elephants lived in Sicily,

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they were as big as a large dog.

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Dwarf mammoths lived in Sardinia.

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This is because when large
warm-blooded species get stuck on islands,

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it is better for them to become smaller,
in terms of natural selection.

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But incredibly, this is the first time

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that we see this occurring
in a human species.

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But even more shockingly,

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so much so that it took us a few years
before we actually accepted the fact,

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this specimen here,

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immediately called
Hobbit Man, by scientists,

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that Hobbit Man on that island, Flores,

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carried on and survived
until 12,000 years ago,

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the day before yesterday.

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At school, almost all of us studied
the Egyptians, the Sumerians,

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the civilizations who invented
writing, the pyramids.

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Take the pyramids, go back
a few thousand years

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and on Earth there was
another human species, related to us,

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with whom we coexisted

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and whom we also met
as we actually visited that island.

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We know that because Homo Sapiens

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went in Australia
long before their extinction.

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00:13:03,280 --> 00:13:06,600
And we also know that we met,
we saw each other.

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But there have been even more shocking
close encounters of the prehistoric type.

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This is the latest discovery;
the paper is from April 2010.

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In short, in a cave in the Altai mountains
in southern Siberia, on Asia,

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we identified another human species
whose existence we had had no inkling of.

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We knew that this cave, the Denisova cave,
had already been inhabited by two species:

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we the Sapiens,
already 40/50,000 years ago,

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and the famous Neanderthals,
we've all studied about at school.

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You know that Neanderthal
was not an ancestor of ours,

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he was a cousin of ours.

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We coexisted with him:

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even here in Italy,
in these valleys, in these areas

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there were villages inhabited by Sapiens
and others by Neanderthals.

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We probably communicated,
maybe we even swapped technologies.

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There are sites where
sometimes an innovation,

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which had already appeared
in a Sapiens settlement,

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was then found in
a Neanderthal one and vice versa.

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This shows that there was an interaction.

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Our evolutionary history
is checkered with alter egos.

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We have never been alone.

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We've been alone on this planet
for a very short time indeed.

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And in that cave,
scientists expected to find remains

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of either Sapiens or Neanderthals
or possibly both of them.

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00:14:17,720 --> 00:14:22,440
They took a little finger,
a phalanx, from a skeleton,

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brought it back to Germany
and extracted its DNA.

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That can be done today: we don't live
in Jurassic Park, but it can be done!

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You extract the DNA
and see which species it belongs to.

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It turned out it belonged
to neither Sapiens nor Neanderthal

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but to yet another species.

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00:14:36,840 --> 00:14:39,760
So a very complex history of coexistence.

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00:14:39,760 --> 00:14:43,040
You must be wondering about
something that we are all curious about,

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00:14:43,040 --> 00:14:48,000
because evolution, Gould said it himself,
is a story of death and sex

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00:14:48,000 --> 00:14:50,640
and we're always very interested in both.

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00:14:50,640 --> 00:14:57,120
Well, we don't know what caused
these species to disappear, to die out.

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They all became extinct very recently,

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and I know that you suspect we might
have had something to do with this.

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00:15:03,960 --> 00:15:06,280
We probably did play a role
in their extinction,

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00:15:06,280 --> 00:15:09,920
but we don't know exactly how,
as nothing dramatic happened.

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00:15:09,920 --> 00:15:12,320
We can state for sure,
it was not a genocide.

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00:15:12,320 --> 00:15:14,030
We did not kill them off directly.

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00:15:14,040 --> 00:15:18,560
Something else must have happened
that led to their progressive regression.

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00:15:18,560 --> 00:15:19,960
The fact is that, recently,

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00:15:19,960 --> 00:15:22,650
we became the only human species
left on the planet.

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00:15:22,650 --> 00:15:26,600
Then there is the sex side
and this is also surprising.

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00:15:26,600 --> 00:15:28,040
Up to a few months ago

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00:15:28,040 --> 00:15:31,680
I would have told you that
different species could not interbreed.

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00:15:31,680 --> 00:15:33,960
We thought there was a genetic barrier.

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00:15:33,960 --> 00:15:37,120
But the last discovery we made
proved that this was not the case.

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00:15:37,120 --> 00:15:40,640
Actually, all non-African Sapiens,

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00:15:40,640 --> 00:15:43,760
that is those who came out of Africa
and remained out of Africa,

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probably have a 4 to 6% proportion
of Neanderthal traces in their blood.

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00:15:49,440 --> 00:15:53,800
So we carry some traces
of Neanderthal DNA in our blood.

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00:15:53,800 --> 00:15:55,840
How is that possible?

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00:15:55,840 --> 00:16:00,200
The only explanation, or at any rate,
the most plausible explanation

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00:16:00,200 --> 00:16:04,070
is that at least at some time in the past,
possibly in the Middle East for some,

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00:16:04,070 --> 00:16:06,640
for 10/15 thousand years
we may have mated.

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00:16:06,640 --> 00:16:11,960
We had fertile matings,
so the two species interbred for a while,

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00:16:11,960 --> 00:16:17,800
then they separated, one of them died out
and we Sapiens had the upper hand.

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00:16:17,800 --> 00:16:23,000
But this is a dogma that is refuted
because our genome is not only ours,

319
00:16:23,000 --> 00:16:24,840
so we must not be too jealous.

320
00:16:24,840 --> 00:16:26,449
It is a cloak of Harlequin

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00:16:26,449 --> 00:16:29,280
in which there are traces
of other species.

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00:16:29,280 --> 00:16:32,480
We are not alone, not even in our genome.

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00:16:32,480 --> 00:16:35,340
I'm now showing you this image
because we came out of here.

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00:16:35,340 --> 00:16:38,240
This is another very recent fact:
the strait of Djibouti.

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00:16:38,240 --> 00:16:41,680
Populations of the Sapiens
crossed this small passage,

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00:16:41,680 --> 00:16:45,840
and then met the other species
that had left earlier:

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00:16:45,840 --> 00:16:49,280
the Neanderthals, the Denisovans
I have just shown you,

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00:16:49,280 --> 00:16:52,120
and then the Indonesian species.

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00:16:52,120 --> 00:16:55,040
This is a summary
of everything I have told you:

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00:16:55,040 --> 00:16:56,350
we ventured out of Africa,

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00:16:56,350 --> 00:16:59,960
we did so repeatedly
from 100/120,000 years ago

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00:16:59,960 --> 00:17:03,920
and when we came out,
we met other existing living forms,

333
00:17:03,920 --> 00:17:05,560
human species related to us.

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00:17:05,560 --> 00:17:10,920
We coexisted, we sometimes mated
and then we colonized the whole world.

335
00:17:10,920 --> 00:17:12,510
We're the only one, for example,

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00:17:12,510 --> 00:17:15,340
who arrived in Australia
and then colonized the Americas,

337
00:17:15,340 --> 00:17:18,040
because in the ice ages
the world was different

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00:17:18,040 --> 00:17:19,850
from what it appears to be like here.

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00:17:19,850 --> 00:17:22,990
There were entire continents
that are now submerged, like Beringia,

340
00:17:22,990 --> 00:17:26,240
or this whole area which was passable.

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00:17:26,240 --> 00:17:30,320
So you could get there
without crossing the sea

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00:17:30,320 --> 00:17:33,680
from South Africa to South America.

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00:17:33,680 --> 00:17:37,160
One of the consequences, of course,
of this whole story

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00:17:37,160 --> 00:17:38,310
is, first, that perhaps

345
00:17:38,310 --> 00:17:41,280
we need to look at evolution
with a little more humility,

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00:17:41,280 --> 00:17:44,520
without thinking of ourselves
as the ultimate end,

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00:17:44,520 --> 00:17:46,979
especially since we interbred.

348
00:17:46,979 --> 00:17:48,190
And interestingly,

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00:17:48,190 --> 00:17:51,910
but I'm saying it only now, in closing,
because I didn't want to shock anyone,

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00:17:51,910 --> 00:17:54,780
we also know that the interbreeding
was asymmetrical.

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00:17:54,780 --> 00:17:57,960
It was always a Neanderthal male
with a Sapiens female.

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00:17:57,960 --> 00:18:00,640
That for us Sapiens boys
is really disheartening

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00:18:00,640 --> 00:18:01,800
(Laughter)

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00:18:01,800 --> 00:18:04,980
because we had our females
stolen from us 40,000 years ago already,

355
00:18:04,980 --> 00:18:07,760
so evolution punched us in the stomach.

356
00:18:07,760 --> 00:18:09,979
But the second consequence
is more serious:

357
00:18:09,979 --> 00:18:12,360
if this is our history,

358
00:18:12,360 --> 00:18:15,760
then what we have always called
"human races" do not actually exist.

359
00:18:15,760 --> 00:18:17,480
We are a young species,

360
00:18:17,480 --> 00:18:19,410
we all come from a very small group

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00:18:19,410 --> 00:18:22,200
and there was no time
to separate human races.

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00:18:22,200 --> 00:18:26,800
So let's delete the concept of human race
from the language of science.

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00:18:26,800 --> 00:18:27,960
Thank you!

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00:18:27,960 --> 00:18:28,960
(Applause)