Technology
Solved: The Potato Origin Mystery
In this episode of Shortwave, we explore the surprising hybrid origins of the potato, tracing its lineage back to two distinct plant species: tomatoes and e-tuberosum. This revelation reshapes our und...
Solved: The Potato Origin Mystery
Technology •
0:00 / 0:00
Interactive Transcript
spk_0
For world-renowned cellists, Joshua Roman,
spk_0
Long COVID caused an identity crisis.
spk_0
That was probably the lowest point.
spk_0
No confidence in my ability to recover
spk_0
crisis of faith about what music meant.
spk_0
On the Ted Radio Hour, how he found his way back
spk_0
to music and a new sense of self.
spk_0
Listen on the NPR app or wherever you get your podcasts.
spk_0
You're listening to Shortwave.
spk_0
From NPR.
spk_0
Hey Shortwaveers, producer Berlim McCoy
spk_0
and the host chair today with a biology mystery
spk_0
that I learned about from Katherine Wu.
spk_0
She's a staff writer for the Atlantic Covering Science.
spk_0
And a couple years ago, she was talking to a scientist
spk_0
as part of her recent kick reporting on frogs.
spk_0
As one does.
spk_0
And she was talking to me about hybrids.
spk_0
The result of members of two different species mating.
spk_0
In this case, two different species of frogs.
spk_0
It just struck me as so bizarre that there would be a situation
spk_0
in which one frog was seeking out a mate of another species.
spk_0
It made zero sense.
spk_0
It had made zero sense to the researcher at the time.
spk_0
She discovered it.
spk_0
I basically had to know more.
spk_0
In her reporting, Katie learned that female planes
spk_0
spade foot toads that live in the North American desert
spk_0
actively choose to mate with males outside of their species
spk_0
when the pools they're in are at higher risk of drying up.
spk_0
They do this because it turns out that tadpoles from that unlikely union
spk_0
mature just a little bit faster, giving them a better opportunity
spk_0
to hop away as adults before the pools dry up.
spk_0
Which would be a mushy death if you're not quite ripe tadpole.
spk_0
But there's a catch.
spk_0
The offspring are less fertile, so the males are totally sterile
spk_0
and the females don't produce as many eggs.
spk_0
Because the fitness of hybrid animals across nature is often subpar
spk_0
like these froggy fertility issues or other health problems,
spk_0
biologists have long thought of interspecies mating as a disaster.
spk_0
Most of the time, think of the sterile hinnies and nules
spk_0
that come out of horse donkey unions.
spk_0
You think of kind of sad looking ligers that come out of lion,
spk_0
tiger unions and zoos.
spk_0
And this was really the predominant thinking for decades
spk_0
and decades and decades.
spk_0
That is until recently.
spk_0
There are these estimates that are probably under estimates
spk_0
at this point that something like 10% of animal species
spk_0
and 25% of plant species do regularly mate outside of their own species.
spk_0
And it's not a total disaster.
spk_0
It can't be otherwise that wouldn't persist over time.
spk_0
Scientists are finding that sometimes hybrids can form brand new traits.
spk_0
Neither of its parents could form anything that even looked like a potato
spk_0
and somehow their offspring did.
spk_0
Today on the show, the ingenuity of hybrids,
spk_0
we move from frogs to how scientists resolve the mysterious origins
spk_0
of a beloved staple crop, the potato.
spk_0
And how this and other hybrids stories are reshaping scientists' notions of them.
spk_0
You're listening to shortwave, the science podcast from NPR.
spk_0
Okay, Katie, let's start with where potatoes come from,
spk_0
which is from two very old distinct species of plants.
spk_0
Do you know what those two plants looked like?
spk_0
So it could not responsibly describe for you what to roughly
spk_0
9 million old plants looked like by the way.
spk_0
Sort of guess because both of their descendants are around today.
spk_0
So one of them was a tomato plant.
spk_0
We all can kind of picture a tomato plant like nice, beautiful,
spk_0
reddish kind of fruits on a leafy green plant.
spk_0
And the other one, if you've ever seen the top half of a potato plant above ground,
spk_0
it looked mostly like that, leafy green, some nice flowers on top.
spk_0
Okay, so these are the two parents of what resulted in the potato.
spk_0
And I didn't realize that this was like a lost love story that no one really knew the answer to.
spk_0
But apparently it's stumped scientists for a long time.
spk_0
Yeah, and a bunch of them put it to me this way.
spk_0
You know, just with all due respect to potatoes,
spk_0
their family tree is this total and complete mess.
spk_0
I can't relate actually.
spk_0
I think a lot of people can.
spk_0
Potatoes are messy, lots of family drama.
spk_0
But basically they know that there is more than 100 potato species around today.
spk_0
But when they try and trace those back in time and figure out where did all of them come from?
spk_0
What was sort of the inciting event that spawned this massive diversity of species?
spk_0
They end up getting stumped.
spk_0
Potato genomes are really complicated.
spk_0
And so they can't just piece it together really easily like they can for some other plant groups.
spk_0
But they had a couple ideas.
spk_0
So potatoes are within this big group called the Night Chades, which actually does include the tomato, one of its parents we now know.
spk_0
But this makes sense as a gardener.
spk_0
Yeah, but also eggplants and peppers.
spk_0
This is a very delicious, very productive family.
spk_0
But they couldn't figure out exactly where potatoes come from.
spk_0
The two main candidates were actually tomato and e-tube rosam, which is the other parent in the story.
spk_0
But scientists were basically always considering one or the other tomato or e-tube rosam.
spk_0
For the answer to now we both is a little bit mind-blowing because you don't expect it to be this love story that yields a hybrid that becomes the potato.
spk_0
You figure, what's most closely related to the tomato?
spk_0
No, it's mostly related to e-tube rosam.
spk_0
It was a team tomato or team e-tube rosam story.
spk_0
Team both was not on the table.
spk_0
Okay, and so is it that they thought that the potato part of the plant evolved either when it was in the lineage of the tomato plant or this e-tube rosam.
spk_0
And at some point the one with the potato crossed, and that's how their genes intertwined.
spk_0
But they never thought that it was this hybridization event, this coming together of two separate species that actually was the thing that created the what would become the potato.
spk_0
Right, so what was so confusing and frustrating about piecing together this origin story was if you looked at the potato genome,
spk_0
parts of it looked like the tomato genome, and parts of it looked like the e-tube rosam genome.
spk_0
And so it was like, well, okay, so which did it come from?
spk_0
Was it that it evolved from a tomato plant that somewhere down the line just invented the potato?
spk_0
And then maybe some ancient potato mixed with e-tube rosam, and that's how e-tube rosam stuff got in the potato genome.
spk_0
Or was it the total inverse?
spk_0
You know, descended from e-tube rosam then mixed with the tomato plant either on.
spk_0
Those are really the two main possibilities that people were considering.
spk_0
They didn't find that.
spk_0
All the species they looked at had roughly the same mix of tomato and e-tube rosam as each other.
spk_0
Like they all looked like the same mevli, which means that there was probably just one event that brought the tomato and e-tube rosam genomes together, which means hybridization.
spk_0
That's kind of the only option when you see the data that they saw.
spk_0
So there was one event, the two genomes mixed, and that spawned an early potato, and that early potato led to the hundred plus species we see today.
spk_0
It wasn't that tomato made a potato, and then weird stuff happened later on.
spk_0
It was that these two plants came together initially, and the potato was born and no one ever looked back.
spk_0
And so this big surprise, this hybridization event led to what we know and love is the potato.
spk_0
I suspect we also don't really know much about what that looked like, but I want to ask just for fun.
spk_0
What do you think it looked like? Like a tomato bit in the ground?
spk_0
So I have no idea what the first potato plant looked like, but it probably was not a tomato growing underground.
spk_0
Just given the way that plants produce different organs, tomatoes come out of the flowering parts of the plant.
spk_0
And so that is above ground.
spk_0
When we're talking about a potato, that is by definition an underground storage organ.
spk_0
It's a tuber. It has to come out of the underground system where a bunch of nutrients are being stored.
spk_0
A potato is basically a giant nutrient storage organ.
spk_0
And so you're never going to get a potato, you're never going to get a proper potato growing on the above ground portion of a plant.
spk_0
And you're never going to get a proper tomato growing on the below ground portion of a plant.
spk_0
Can uncovering this potato mystery help us with the spuds of today?
spk_0
Like it seems like really interesting science, but can it inform how we're growing food now?
spk_0
I think the answer for right now is maybe question mark, probably question mark.
spk_0
There's not a set in stone plan to fix everything that is wrong with potatoes today.
spk_0
But potatoes, the potatoes we eat, they do have issues.
spk_0
They are susceptible to disease and their genomes are kind of a pain to work with.
spk_0
So cultivated potatoes, the potatoes we eat, they have four copies of every chromosome.
spk_0
That's a real pain for breeders. Just trust me on this one.
spk_0
It is a huge pain for breeders.
spk_0
And so if they can figure out a way to just use this information to improve the potato genome, make it easier to work with, maybe that could be really interesting.
spk_0
One sort of out of the box idea that some of the scientists who worked on this project are playing with are using this information to help tomato plants make underground tubers.
spk_0
So making their own potatoes.
spk_0
They don't know if this is entirely possible and it will probably be extremely difficult if it is possible at all.
spk_0
But you know, it could be the case that someday you're eating fries and ketchup and they came from essentially the same plant.
spk_0
Oh my gosh, that would be so amazing.
spk_0
I will say scientists have kind of cheated their way to that solution before.
spk_0
The tomato and potato plants are still closely related enough that you can graft them on to each other.
spk_0
So you can, you know, it's like a Franken plant, right?
spk_0
You can name a ash them together and they stay alive and produce both things.
spk_0
Yeah.
spk_0
It's not quite the same as coaxing a tomato with genetic manipulation to make its own potatoes.
spk_0
But you know, it's a little bit more like organ donation.
spk_0
No place to do together.
spk_0
Or human centipede, whichever metaphor you prefer.
spk_0
Oh my gosh.
spk_0
What is a little grosser than the other?
spk_0
Yes, I need one of these plants now.
spk_0
So this example of a hybrid and like the frogs that we talked about earlier, what do they tell scientists about how useful hybrids are?
spk_0
I think these examples and a bunch of others that have emerged in recent decades are really helping to rewrite the evolutionary story on hybrids.
spk_0
It is still absolutely the case that most of the time when a species mates with another organism outside its own species, it's not going to work.
spk_0
They probably won't have successful offspring to begin with.
spk_0
But sometimes it does work.
spk_0
Sometimes those offspring do come to be.
spk_0
Sometimes those offspring can reproduce.
spk_0
And sometimes those offspring are so different in interesting and exciting ways from their parents that they're able to do things that neither of their parents could.
spk_0
And that can lead to really incredible events like making lots of new species, striking out into new environments, even potentially human evolution.
spk_0
It seems like there's hybridization in our own evolutionary history.
spk_0
So it can be a really powerful evolutionary force that can drive evolutionary innovation in a way that just meeting with a new species can't.
spk_0
Catherine Wu is a science journalist at the Atlantic.
spk_0
She has shown us for both of her articles on hybrids.
spk_0
Thank you so much Katie.
spk_0
Always good to be here.
spk_0
This episode was produced by me, Berlay McCoy, and edited by our showrunner Rebecca Ramirez.
spk_0
Tyler Jones checked the facts and Robert Rodriguez was the audio engineer.
spk_0
But Donovan is our senior director and Colin Campbell's our senior vice president of podcasting strategy.
spk_0
I'm Berlay McCoy.
spk_0
Thanks for listening to shortwave from NPR.