Ahh, autumn in New York City.
The crisp air, the rustling leaves, and OH GOD what is that smell?!
It smells like somebody threw up all over Brooklyn!
Don't blame him, blame this tree: the ginkgo biloba.
[music playing]
The ginkgo biloba is a weird tree.
It was here before every flowering plant on Earth, and watched dinosaurs play under its
leaves, and then go extinct.
Or turn into pigeons.
Out of the five categories of plants that make seeds, the ginkgo - just one species
- is all on its own.
It's kind of an evolutionary oddity.
And their seeds smell awful.
Beneath your feet that squishy carpet oozes out the same chemical found in rancid butter.
That seems like a strange strategy if your goal is to make baby trees.
Unfortunately for plants, the apple doesn't fall far from the tree.
Now, unlike their airborne cousins, seeds need to be carried off so they don't compete
with their parents for nutrients and light.
Fruits are plants' way of tricking animals into eating their seeds.
So while we'll throw this away, for animals everything goes in, and then later, everything
comes out.
Complete with fertilizer!
Besides my dog, who would eat a seed that smells like a dead animal?
Well, the ginkgo is calling out to be eaten by a creature that's been dead for millions
of years.
We'll get back to that, but first, consider the avocado.
Now, the avocados we eat today aren't that different from ones that grew in Mexico and
Central America hundreds of thousands of years ago.
They've got a thick skin, nice nutrient-rich oily flesh, and right there in the middle,
this ridiculously big seed.
Something had to carry that seed away.
The problem is that nothing alive in Mexico or Central America today could eat an avocado,
seed and all, without choking to death, or experiencing some serious discomfort.
No one told the avocado, but it keeps making a fruit for an animal that doesn't exist anymore.
Hey look!
An avocado tree!
And a giant ground sloth.
He's hungry, and he's about the size of a moving truck, so reaching those avocados is
no problem.
Since avocado seeds contain toxins, he just chews them enough to break open the flesh,
and down they go, skin, seeds and all.
And as he walks off, his guts go to work.
Since avocados contain natural laxatives, it's not long before, well, you get the idea.
Every so often, one of those could grow into a new tree.
In fact, this is how it worked for a bunch of weird tropical fruits.
The one thing they have in common is that the animals they used to depend on are all
extinct.
These living plant/extinct animal relationships are what's called an evolutionary anachronism.
Biologists Daniel Janzen and Paul Martin made this idea famous back in 1982.
In fact, all of us carry evolutionary anachronisms: goosebumps, our appendix, facial hair.
These are traits that we evolved but are no longer being selected for.
Prehistoric megafauna, the animals that used to disperse all these seeds, went extinct
by about 10,000 years ago.
Since then, all these plants have just been limping along without them.
Normally, these evolutionary anachronisms might be the first step to these plants going
extinct, but since we agricultural apes have been planting orchards full of them for thousands
of years, it's not really an issue.
We've sort of side-stepped natural selection.
The avocado should have gone the way of the dodo, except that we think it tastes good.
Just like there's no reason the ginkgo biloba should exist, except that it gives really
nice shade.
It's kind of nice that we can do more than just drive things to extinction, that we can
save plants whose friends are all dead.
Thanks to some ghosts of evolution, a ginkgo tree grows in Brooklyn, dropping stinky seeds
and waiting for a creature that will never come.
If you want to read more about weird fruits, evolutionary anachronisms and extinct megafauna,
check out Ghosts of Evolution by Connie Barlow, there's a link down in the description.
Special thanks to Brian Switek, the internet's best paleontology writer for special help
with this episode, and to Mike Rugnetta from Idea Channel, because he emailed me asking
about stinky fruits and started this whole thing.
Thanks a lot, and stay curious.
[outro voiceover]