How Poisons Have Shaped Life On Earth

FLORA LICHTMAN: This is Science Friday. I’m Flora Lichtman. When I say poisons, you might think of cyanide, arsenic. But have you thought of acorns? What about the cup of coffee you had this morning or the mums growing in your window box? My next guest will tell you, toxicity is in the bloodstream of the beholder. A new book tells the story of nature’s giant cauldron of toxins and how they shaped life on Earth through a chemical war that began around 4 billion years ago.

Dr. Noah Whiteman is an evolutionary biologist at UC Berkeley and the author of Most Delicious Poison, the Story of Nature’s Toxins from Spices to Vices. He joins me from Berkeley, California. Welcome to Science Friday.

NOAH WHITEMAN: Well, thank you, Flora. It is wonderful to be here.

FLORA LICHTMAN: Let’s start with getting our terms straight. Will you define poison for me?

NOAH WHITEMAN: Well, that’s going to be hard, Flora, because–

FLORA LICHTMAN: I like to start with a hard ball on this show.

NOAH WHITEMAN: I would say that my definition of poison, as I talk about in the book, it sort of, I would say, is a chemical that is produced, in our case, we’re talking about other organisms producing them. So these are like biological poisons, toxins. And for me, the definition is really a chemical that damages cells and the ability of cells to operate.

And toxins can be adaptive. In other words, they can be produced because they give the bearer an advantage, usually with respect to other organisms, so an offense or defense. Or something could be toxic like carbon dioxide that is just a byproduct of metabolism. So the way I think about it when I think about these poisons as adaptations is whether they give their bearers an advantage through the toxic mechanism.

FLORA LICHTMAN: So toxin and poison, the same thing or different things?

NOAH WHITEMAN: Well, I would say they’re probably different in the sense that a poison, it sounds like there’s intent there, right? And so I think that’s important. Because of course, when we think about evolution, we don’t think of intent. But we think of what has been selected for through evolution by natural selection in this case, to give the cell or the individual that is producing that chemical an advantage somehow.

FLORA LICHTMAN: So a toxin, like oxygen can be a toxin at a certain dose. But a poison is something that an organism makes to fend off other organisms?

NOAH WHITEMAN: Exactly.

FLORA LICHTMAN: OK, tell me what led you to write this book.

NOAH WHITEMAN: So I had been studying poisons that are produced by plants that they use to defend themselves against enemies like caterpillars. And one of the ones that I focused on was the monarch butterfly, which obtains poisons from the milkweeds that they eat. And the monarchs get them when they’re caterpillars, when they’re eating the plant. And they imbibe these toxins. They keep them in their body. And that’s what protects the monarchs from bird attack, which is also why they’re brightly colored. That’s sort of co-evolved with the toxicity part, the warning coloration part.

FLORA LICHTMAN: Oh, they co-opt the toxin from the plant?

NOAH WHITEMAN: Yes, so–

FLORA LICHTMAN: That’s cool.

NOAH WHITEMAN: It is. And so then, OK, I was studying that. And then at the same time, sadly, my father was suffering from alcohol use disorder, which is the more modern term for alcoholism. And he’d been spiraling for decades and eventually died in 2017 from complications from that. And it was in the aftermath of that that my worlds kind of collided that I’ve tried to keep apart, the sort of professional scientific life and this world of pain when it comes to thinking about my dad and his situation.

And I realized that he was using alcohol to numb his pain and keep his own demons at bay. And in a way, it wasn’t that different from what the monarchs were doing at a superficial level. And so I think to make sense of it all, I began to look at these two threads and then started weaving them together. And the book was born, I think, as a way to cope with all of it.

FLORA LICHTMAN: I’m sorry about your father. I read in your book that your dad was a naturalist too. It seems like that that’s another thread to this.

NOAH WHITEMAN: Yes, he was. And so we lived in Northeastern Minnesota, first in Duluth and then about an hour north of there in the middle of a bog. And I say bog like a Minnesotan. I’m sure you noticed that. B-O-G is what I’m trying–

FLORA LICHTMAN: As a Midwesterner, I embrace it and celebrate it.

NOAH WHITEMAN: Thank you. Well, yeah, so he was an outdoorsman and knew a lot about nature and taught me a lot about what I knew about the natural world up there. And that kind of stuck with me. That has served me well throughout my life. And it’s something I’ve taken for granted, I think, being exposed to all of these creatures from a very young age and with a lot of information about them, which came partly through my dad, who sort of gave me the skills to learn more, if that makes sense, to be curious and to just appreciate all of life, whether it was a caterpillar, or a bear, or a tree, or a blade of grass.

FLORA LICHTMAN: Your milkweed work makes me wonder. How many poisons do I encounter every day? Say, I’m on a walk in my neighborhood. This is going to be a hard assignment. But give me two common poisons that you think will surprise me.

NOAH WHITEMAN: Well, if we were walking together, at some point, you’d be like, Noah, slow down. There’s a lot going on.

FLORA LICHTMAN: You’d be pointing out more than two is that what I’m gathering?

NOAH WHITEMAN: Yes, you can’t follow directions, Dr. Whiteman. But if we walked by a foxglove plant, have you ever seen a foxglove plant? They have kind of pretty pink purple or white flowers.

FLORA LICHTMAN: Tall.

NOAH WHITEMAN: Tall, and apparently are called foxgloves because someone thought foxes could fit their paws in the floral tubes.

FLORA LICHTMAN: That is so cute. I love knowing that. Thank you.

NOAH WHITEMAN: I know. But the truth is behind that cuteness is something pretty toxic. So the same kinds of toxins that milkweeds produce are also produced independently in the foxglove. And they evolved to do that independently, which is really interesting. And so there are heart poisons in those plants.

And what’s interesting about those is that they probably evolved at high concentration to prevent organisms from eating them. But at the same time, humans have co-opted those. And William Withering conducted the first clinical trial in modern medicine in Britain hundreds of years ago using digitalis, foxglove, to treat congestive heart failure. And we still use that drug, the drugs that are in those plants.

So that’s one. And then the other, let’s go back to your acorn because there is a set of toxins that is very ubiquitous across plants. And they’re called tannins. And oaks are famous for making tannins, including what you mentioned in the acorn, which are filled with them. And so to eat them, they need to be treated to get rid of the tannins. And so the tannins bind to our salivary proteins. And that helps keep them away from our digestive tract. But if there’s too many, they sort of get through. And they can cause problems.

FLORA LICHTMAN: What kind of problems? Could they be deadly if you have enough of them?

NOAH WHITEMAN: Yeah, so there’s a set of tannin-like compounds in green tea. And that compound has been used as a weight loss supplement. And it was so dangerous at high levels that has caused people to have to have liver transplants, for example.

FLORA LICHTMAN: Wow.

NOAH WHITEMAN: Yeah, and as you said before, there’s some nuance here. And it is– as Paracelsus said, it’s the dose that makes the poison at some level. Biting a foxglove plant isn’t going to cause huge problems. But it quickly escalates, if that makes sense.

FLORA LICHTMAN: There– obviously, there are millions of species on this planet. What percentage of species have to deal with toxins, or make toxins, or have been shaped by toxins?

NOAH WHITEMAN: That is a great question. Most are dealing with them at some level. If you think about just plants and the insects that eat them, the two of those groups are most species of life on Earth that have names, which is amazing. And it is hypothesized that chemicals produced by the plants in defense against those herbivores are partly responsible for driving the diversification of each group. And that is called the theory of coevolution.

And even things like bacteria are, of course, their worlds are mostly chemical. And you can think of the battle between bacteria and fungi, like penicillin is a chemical that is produced by fungi that kills bacteria. And we’ve co-opted that.

FLORA LICHTMAN: So toxins are actually shaping life on this planet?

NOAH WHITEMAN: Yes, that’s the idea. That–

FLORA LICHTMAN: I’m with you.

NOAH WHITEMAN: And one of the ways I like to think about it is that organisms that can’t move very fast or don’t move much at all, things like plants, mushrooms, many, many microbes, and even small animals, they’re the ones that use toxins as– often as defenses.

FLORA LICHTMAN: They can’t run away.

NOAH WHITEMAN: They can’t run away. They’re stuck in the ground or close to that.

FLORA LICHTMAN: Let’s talk about my favorite toxin, coffee.

NOAH WHITEMAN: Yes, coffee. Mine too. And I only had one cup this morning. I’m working on my second cup. And I know the dose that I need in order to make it through the day, like you do probably?

FLORA LICHTMAN: Yes, I love to think about my coffee routine. And I gather from your book that, you also like to think about this.

NOAH WHITEMAN: I do. So I have a chapter on caffeine and nicotine. And in that chapter, I do talk a lot about coffee, tea, and chocolate, which all produce caffeine. Or in the case of chocolate, theobromine, which is a derivative of caffeine. And what’s interesting is that caffeine was one of the– I don’t want to say first, but very early alkaloids, which is another type of chemical family that plants make that was sort of nailed as an insecticide, a natural insecticide that evolved five different times at least in plants. And the study that focused on this, the title was something like caffeine is a natural insecticide. And I think this surprised a lot of people and may surprise you.

FLORA LICHTMAN: Well, I mean, I have lots of questions about this. At low levels of poisoning, do insects display the same traits as I do when I’m overcaffeinated? Or do they get jittery, and have darting eyes, talk too much and too fast?

NOAH WHITEMAN: They do have seizures, actually, it’s more of a problem for them than it is for us, I would say.

FLORA LICHTMAN: Well, I was going to ask, if I’m overcaffeinated, does that mean I’m being low level poisoned?

NOAH WHITEMAN: Well, there is a limit on what is safe to consume. If it’s toxic to an insect, it doesn’t always mean it’s going to be toxic to us. But we ought to carefully look at that and think very carefully about the dose. And so yes, there are safe levels of caffeine to consume. For humans, it’s about 400 milligrams a day, I think. And if you go above that, yes, there can be toxic effects. And people have hurt themselves, and unfortunately, have ended up ending their lives because of overdoing it.

FLORA LICHTMAN: This is Science Friday from WNYC Studios. I’m talking all things poison with Dr. Noah Whiteman, author of Most Delicious Poison. Are there other toxins in coffee beans? And can you prepare coffee so that there’s less of them?

NOAH WHITEMAN: Yes, so one of the illustrations in the book, which was done by Julie Johnson, is of a French press, which I used to use, and pour over little ceramic thing with a paper filter in it. And then there are three chemicals illustrated. One is caffeine, of course. And then the other two are terpenoids.

So terpenoids are the most diverse natural products that are produced by other organisms. And one is called cafestol, conveniently, C-A-F-E-S-T-O-L, get it, cafestol? And then the other is called kahweol. And that is probably derived from this Arabic word for coffee. And those two diterpenoids are also found in coffee beans. And they are the most potent inducers of LDL cholesterol in the human diet.

In other words, they raise the bad cholesterol levels. And so that may pose a problem if it’s long-term heavy use. I mean, this is the reason why so many people are on statins in the United States, high LDL levels. So that’s a potentially long-term health issue there. So the paper filter removes almost all of those two diterpenoids, cafestol and kahweol.

But the French press plunger does not. And the same is true for boiled coffee. Whereas the paper filtered ones, and actually, the gold mesh filter ones in an auto drip, this is very nuanced, they also remove them.

FLORA LICHTMAN: Paper filter.

NOAH WHITEMAN: Paper filter.

FLORA LICHTMAN: Add it to your cart.

NOAH WHITEMAN: Or gold mesh for an auto drip if you’re fancy.

FLORA LICHTMAN: So I learned from your book that my pantry is filled with toxins, red pepper flakes, nutmeg. I want to talk a little bit about how our taste for toxins shaped history. Tell me about that, how these spices went global.

NOAH WHITEMAN: Well, there was this strange obsession with Asian spices in Europe for a long time in Middle Ages. And part of the mystique was that these were things that were unusual and couldn’t be grown or purchased locally in Europe. But many of them actually do trigger these particular receptors in our mouths called TRP receptors, like the red pepper receptor, the wasabi receptor, the mint receptor.

And those seem to titillate our tongues in some way that we like. But there were other things going on culturally in Europe that are really interesting about why this sort of obsession with spices, and why food was so spiced, and all of that. So this was sort of at its zenith in the middle late part of the 15th century and kept going.

But that pushed European nations to begin to go around Africa to try to get to Asia in search of things like black pepper, ginger, nutmeg, mace, cloves. And eventually, Columbus, of course, is motivated by the same thing and ends up in the Bahamas, even though he thinks it’s Southeast Asia in search of spices.

So these chemicals that the plants are making presumably as defenses against pathogens and things like insects, they’re not making them for us. But we’re searching them out. And the consequences of that are enormous, of course, because the 500 years that have gone by since have all been sort of triggered by these initial events.

FLORA LICHTMAN: Our taste for spice and toxins, what do you think it tells us about ourselves?

NOAH WHITEMAN: Well, that’s a really interesting question. For me, when I look at how other organisms deal with these things and things like monarchs that are seeking them out, that are sequestering them, that are using them as tools. And they’re not alone. Many other animals do this as well.

And that’s innate, I would say, in them. And in us, we have this culturally transmitted, very similar cultural evolutionary history, where we’re doing the same thing. Every human society taps into these chemicals and plants, fungi, and other organisms. And so in a way, we’re participants in this war of nature too, just like them.

We’re not divorced from the natural world. We depend on it, just like they do. When I think about my interaction with nature, of course, it’s wonderful to have a vista in front of you or to see a beautiful bird. But to actually experience it through smell or taste or through what it does to my behavior or my thought process, there’s not much else like that. And so in my mind, this chemical channel that you and I were talking about that’s part of this web of life, it allows us to have a more intimate interaction with it, I think.

FLORA LICHTMAN: Noah, thanks for joining me today.

NOAH WHITEMAN: Oh, it was my pleasure. Thank you so much.

FLORA LICHTMAN: Dr. Noah Whiteman is an evolutionary biologist at UC Berkeley and the author of Most Delicious Poison. To read an excerpt, visit sciencefriday.com/poison.

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