How to win at evolution and survive a mass extinction Lauren Sallan
Congratulations.
By being here,
listening, alive,
a member of a growing species,
you are one of history’s
greatest winners –
the culmination of a success story
four billion years in the making.
You are life’s one percent.
The losers,
the 99 percent of species
who have ever lived,
are dead –
killed by fire, flood, asteroids,
predation, starvation, ice, heat
and the cold math of natural selection.
Your ancestors,
back to the earliest fishes,
overcame all these challenges.
You are here because
of golden opportunities
made possible by mass extinction.
(Laughter)
It’s true.
The same is true
of your co-winners and relatives.
The 34,000 kinds of fishes.
How did we all get so lucky?
Will we continue to win?
I am a fish paleobiologist
who uses big data –
the fossil record –
to study how some species win
and others lose.
The living can’t tell us;
they know nothing but winning.
So, we must speak with the dead.
How do we make dead fishes talk?
Museums contain multitudes
of beautiful fish fossils,
but their real beauty emerges
when combined with the larger
number of ugly, broken fossils,
and reduced to ones and zeros.
I can trawl a 500-million-year database
for evolutionary patterns.
For example,
fish forms can be captured by coordinates
and transformed to reveal
major pathways of change
and trends through time.
Here is the story
of the winners and losers
of just one pivotal event
I discovered using fossil data.
Let’s travel back 360 million years –
six times as long ago
as the last dinosaur –
to the Devonian period;
a strange world.
Armored predators
with razor-edge jaws dominated
alongside huge fishes
with arm bones in their fins.
Crab-like fishes scuttled
across the sea floor.
The few ray-fin relatives
of salmon and tuna
cowered at the bottom of the food chain.
The few early sharks
lived offshore in fear.
Your few four-legged ancestors,
the tetrapods,
struggled in tropical river plains.
Ecosystems were crowded.
There was no escape,
no opportunity in sight.
Then the world ended.
(Laughter)
No, it is a good thing.
96 percent of all fish species died
during the Hangenberg event,
359 million years ago:
an interval of fire and ice.
A crowded world was disrupted
and swept away.
Now, you might think
that’s the end of the story.
The mighty fell,
the meek inherited the earth,
and here we are.
But winning is not that simple.
The handful of survivors
came from many groups –
all greatly outnumbered by their own dead.
They ranged from top predator
to bottom-feeder,
big to small,
marine to freshwater.
The extinction was a filter.
It merely leveled the playing field.
What really counted was what survivors did
over the next several million years
in that devastated world.
The former overlords
should have had an advantage.
They became even larger,
storing energy,
investing in their young,
spreading across the globe,
feasting on fishes,
keeping what had always worked,
and biding their time.
Yet they merely persisted for a while,
declining without innovating,
becoming living fossils.
They were too stuck in their ways
and are now largely forgotten.
A few of the long-suffering ray-fins,
sharks and four-legged tetrapods
went the opposite direction.
They became smaller –
living fast,
dying young,
eating little
and reproducing rapidly.
They tried new foods,
different homes,
strange heads
and weird bodies.
(Laughter)
And they found opportunity, proliferated,
and won the future
for their 60,000 living species,
including you.
That’s why they look familiar.
You know their names.
Winning is not about random events
or an arms race.
Rather, survivors went down alternative,
evolutionary pathways.
Some found incredible success,
while others became dead fish walking.
(Laughter)
A real scientific term.
(Laughter)
I am now investigating
how these pathways to victory and defeat
repeat across time.
My lab has already compiled thousands
upon thousands of dead fishes,
but many more remain.
However, it is already clear
that your ancestors' survival
through mass extinction,
and their responses in the aftermath
made you who you are today.
What does this tell us for the future?
As long as a handful of species survive,
life will recover.
The versatile and the lucky
will not just replace what was lost,
but win in new forms.
It just might take several million years.
Thank you.
(Applause)