The connection between humans and fire goes back millions of years. What started with campfires and cooking grew into a burning addiction that catalyzed the Industrial Revolution and now shapes nearly every aspect of our society. Now, our ongoing reliance on fire in its many forms is changing the climate with explosive consequences for wildfires — and much more.
- Richard Wrangham is emeritus professor at Harvard University and the author of Catching Fire: How Cooking Made Us Human
- Jennifer Balch is a professor at the University of Colorado, Boulder, and the director of the Earth Lab at the University.
- Cathy Whitlock is a regents professor at Montana State University, and the director of the MSU Paleoecology Lab.
Transcript and Links:
Justin Angle Previously on Fireline:
[Jim See]: “The 1910 fire was one of the biggest fires in United States history.”
There’s something mesmerizing about a fire. I could stare at the flames for hours. And my kids and their friends are no different.
[Gifford Pinchot]: “The Bureau of Forestry was changed to the Forest Service.”
[Steve Pyne]: “We’re going to knock fire out of the landscape.”
[Smokey The Bear clip]: “You have so many reasons to protect your forests. Remember, only you can prevent forest fires.”
[News clip]: “It’s not getting any easier for firefighters at Yellowstone National Park. Forecast today is for winds of up to 60 miles an hour… ”
[Andrew Larson]: “And we have to get past the promise that forestry made the world years and years ago that we can control fire and put it out and regulate the forest in that way.”
Support for this program comes from Berkshire Hathaway’s Homeservices Montana Properties, First Security Bank, Blackfoot Communications, and A New Angle podcast.
Justin Angle There’s something mesmerizing about a fire. I could stare at the flames for hours. And my kids and their friends are no different.
[Victor Yvellez]: “Why do you think it looks cool?”
Justin Angle That’s our producer, Victor Yvellez, and he’s in my backyard with me, my kids and their neighborhood buddies.
[Kids]: “Because all the colors just sort of like mixing and smoking. But the smoke is not cool! What kind of colors are they? There’s like all warm colors, which I think is pretty much why they’re called warm colors, because they create fire. Fire! Fire!”
Justin Angle We’re all roasting marshmallows, and the kids are getting giddy. They get that they need fire to make their s’mores. But they also understand its raw power.
[Kids]: “It creates heat. And creates light when you’re camping. Well, heat keeps you warm so you don’t freeze to death. And then light is so you can see. Light is if you can’t see in the dark you pretty much need it.”
Justin Angle Here’s fire historian, Steve Pyne. You also heard him in our last episode.
Steve Pyne So for someone who’s interested in, the big question, what does it mean to be human? What does it mean to be human on earth? Fire seems to me a pretty good index. Terrestrial life on Earth has grown up with fire. Other animals knock over trees and dig holes in the ground. We do fire. It’s our ecological signature.
Justin Angle I’m Justin Angle, and this is Fireline: a series about what wildfire means for the west, our planet, and our way of life.
Kids don’t need somebody with a PhD to tell them how connected we are with fire. It’s almost like that relationship is in our DNA. After all, a big part of the history of Earth itself is a history of heat, burning, and fire1.
In this episode, we’re gonna look at the connection between humans and fire going back millions of years. How has our age-old effort to control fire made us who we are today? And where has that fiery relationship pushed us, as a species and as a society?
This is Episode 3 – Ring of Fire.
Justin Angle Richard Wrangham is an anthropologist, and a professor emeritus at Harvard2. He thinks a lot about fire.
Richard Wrangham The word focus derives from the Latin word for fire3. And it’s a reminder that people love to focus on fire. We love to sit around a fire and, and look at it. It’s very much associated with sociality, with gregariousness, with coming together around it.
Justin Angle Richard studies what we can learn from primates about what makes us, us. As in humans. And we’re going to dig into this one idea of his — a hypothesis about the role of fire in our evolution as a species. I caught up with him while we were both locked down from the coronavirus – me in my home in Montana and him:
Richard Wrangham Oh, I am talking from near Cambridge, England.
Justin Angle Would love to learn some about your development as a scholar.
Richard Wrangham I’ve always loved natural history, being in the wild. And when the time came for me to think of a career, what I really wanted to do was to think about the way that our environment had affected human evolution. I wrote to Jane Goodall —
Justin Angle That’s the famous primate researcher.
Richard Wrangham — and asked if she had any opportunities for people working with her, and I was very lucky because it was just a time when she wanted some research assistance. I spent a year as a research assistant with her in Gombe National Park in western Tanzania.
Justin Angle Richard went on to study a whole cornucopia of primates.
Richard Wrangham I worked with a monkey called Gelada Baboons in Ethiopia and vervet monkeys in Kenya. But it wasn’t long before I found my way back to starting a study of chimpanzees in Uganda.
Justin Angle You might be wondering – what’s with all the monkey business? Richard was interested in what we can learn about people from our not-so-distant ancestors – and in particular from what they ate.
Richard Wrangham There is something very fundamental about the difference in diet in humans and chimpanzees, and that is that humans absolutely rely on fire.
Justin Angle He means cooking our food. Instead of munching on raw meats and greens, we have microwaves and ovens and, of course, campfires. We’ve been using flames and heat for a long, long time.
Richard figured there has to be a reason why our culinary preferences are so ingrained in our species. But when he started looking into it, the benefits cooking brought us weren’t at all clear.
He thought maybe some experiments could help. He wrangled some mice in a lab to find out in a controlled setting:
Richard Wrangham what was the impact on the actual growth of the animals when eating their food raw or cooked.
Justin Angle I imagine a science lab straight outta the movies here. Richard in a white coat, mice chirping around in cages, and a mouth-watering mouse buffet of meat and veggies. Richard says the reality isn’t quite so picturesque
Richard Wrangham It’s irksome kind of work.
Justin Angle You have to make sure the mice are getting the same amount of exercise, eating the same amount of food, and all kinds of other stuff. But the end result:
Richard Wrangham is significant weight gain when eating these foods cooked compared to eating them raw.
Justin Angle So at least in mice, the little critters eating cooked food got a lot bigger, a lot quicker, than the ones on a raw food diet. But what about cooking made that possible?
Richard says there are two ways this happens. First off, cooking just makes food easier to digest. The body doesn’t have to use as much energy to process cooked food as it does raw food4.
Richard Wrangham The second way in which cooking increases the net energy gain for the consumer is that it reduces the amount of physiological work that has to be done by the consumer in digesting the food.
Justin Angle But how can we extrapolate this to our own species? Richard says:
Richard Wrangham The really critical thing in terms of what we eat and how we eat it is how much, very much less eating we do than our cousin apes.
Justin Angle As an example, imagine you’re a wildlife photographer, going out to the jungle to shoot some chimps in the wild.
Richard Wrangham You will be frustrated when you first arrive in the forest because they spend most of their time in a tree eating.
Justin Angle By cooking our food, we make it softer. We don’t have to spend as much time doing all that dang chewing. In our evolution as a species, once we figured this out:
Richard Wrangham that means that suddenly we got a tremendous amount of spare time.
Justin Angle Richard says, conservatively, like six more hours a day5
. That meant early humans could devote that time to other stuff. Stuff that required some serious mind power. And Richard hypothesizes that set off a chain reaction: starting somewhere about 2 million years ago, a period began in which our early human ancestors’ brain growth kicked into overdrive6.
Richard Wrangham This is the fastest recorded rate of brain size increase in any animal.
Justin Angle Richard says big brains need big energy. Before early humans figured out cooking — we just couldn’t have consumed enough calories to power that growth.
Richard Wrangham The amount of fuel that the brain needs is a lot.
Justin Angle Even though the brain’s only about two and a half percent of our body mass7, it uses about 20 percent of our total energy8.
Richard Wrangham Cooking by making food much easier to chew, enabled us to get enough energy in everyday to be able to fuel our big brains.
Justin Angle Richard says how we came to discover fire in the first place is —
Richard Wrangham Totally lost in mystery.
Justin Angle Some researchers suggest that hotsprings, or even lava flows inspired early humans to create their own fires and cook their food.
Richard Wrangham But these are very speculative points. The point I think that one can say is that once they discovered that some food was cooked, then they would have liked it straight away. And the reason one can say that is that all the animals that have been tested for the attitude to cooked food as opposed to raw food, love, cooked food.
Justin Angle That includes cats, dogs, mice, rats, — and also animals we’re a little more closely related to, like great apes.
Richard Wrangham So once our ancestors had been exposed to cooked food, then it’s very reasonable to think that they would have tried to get more of it.
Justin Angle Richard says controlling fire likely sparked a crucial series of events in the history of our species. With fire, we could cook food. And that cooked food gave us the energy necessary for our brains to grow. This ignited changes in other parts of our bodies, too. One place to look for evidence is inside our bellies. In our guts.
Richard Wrangham Humans, Homo sapiens, our species living today, we have a gut that is about two thirds of the size that it would be if we were great apes. So it looks as though the early Pleistocene humans, having those human, modern human like characteristics also had the small guts. And the reason that’s significant, of course, is that the small guts are only likely to be adaptive if they had discovered a way to cook their food.
Justin Angle Fossil records show these changes to our anatomy. Another shift in our skeleton suggests that we likely came down from the trees. Instead of a body built for climbing, we developed a body for walking on two legs.
This means we would have slept on the ground, and that would have made us a lot more vulnerable to predators. So Richard says our ancestors would have had to figure out how to stay safe in a harsh and violent world. There are lots of theories about how we did this:
Richard Wrangham I greatly prefer the notion that this was the time when fire was first used and fire was a way of seeing what was going on at night and protecting ourselves against the animals.
So those two features, the evidence of the smaller gut for more digestible food and the evidence of no longer climbing and therefore being committed to being on the ground, persuade me that it’s ninety nine point nine percent likely that the time at which our ancestors discovered fire around two million years ago, which is when the genus Homo evolved.
Justin Angle Richard’s research reminds me of this moment in the Disney movie, The Jungle Book. The main character, Mowgli, a human child alone in the wilderness, gets kidnapped by an orangutan named King Louie.
[King Louie from Disney’s The Jungle Book]: “Lay the secret on me of man’s red fire. But I don’t know how to make fire…”
Justin Angle Louie thinks Mowgli, as a human, knows one thing he doesn’t: the secret of making fire. So King Louie offers Mowgli a trade: safety in the jungle in exchange for humanity’s great knowledge.The ideas here are worth digging into. The movie illustrates this notion that’s been around for a long time:
Fire — learning to control and use it — helped make us human. Richard’s research helps show us how this might have come to be. And that control of fire has shaped the world we’re in today.
Jennifer Balch And I think it’s really important for us to remember that right now because it puts us in our rightful place with fire that we can and we have for millennia shaped fire.
Justin Angle Jennifer Balch is a geographer at the University of Colorado-Boulder9. She Zoomed with us while running a homeschool pod – you might hear some kids in the background.
Jennifer Balch I’ve been studying fire for nearly two decades all around the world, from the Amazon to the western U.S. to try and understand how fire regimes are changing. And what are the consequences for people and ecosystems?
Justin Angle Cooking food and lighting the savannas at night set in motion a relationship with fire that’s grown more and more complex.
Jennifer Balch We fuel our economy based on the combustion of fossil fuels. And we forget that that’s part of our continued story with fire.
Justin Angle Air conditioning, cars, mass manufacturing — the technologies and conveniences that power our modern world are built on the basis of burning.
In the late 1700s, the world began a rapid change10.
[Shell Oil video narrator]: “For most of us, living means working. So to get the most out of life, man looked for a way of making machines do some of their work.”
Justin Angle This is a Shell Oil video from the 1950s.
[Shell Oil video narrator]: “They turned to another form of energy. And discovering that heat could drive machines, they opened up a great new reservoir of reliable power. New industries were born and new towns built to serve them. (fade under) The arrival of the heat engine changed the whole way of life for people in many parts of the world.”
Justin Angle The video makes it sound like there’s been this steady progress since the dawn of the Industrial Revolution, all spawned by this great revelation that heat could generate power and drive society forward.
At a quick glance, there’s a compelling argument to be made for that idea. Case in point? Right now, you’re probably listening to this show on your cell phone. Or in a car. Or on your computer. But when we burn things, we also unleash carbon into the atmosphere. So as we industrialized, all that burning had an underside we didn’t expect.
[News clip 1]: “There is no question about the science. This year alone, we’re on track to have the hottest year ever on our planet.”
[News clip 2]: “According to this study, we could reach catastrophic climate change by the year 2030…”
[News clip 3]: “The images are stark, the impact staggering. Wildfires across the west, spreading. And scientists warn climate change is making it worse.”
Jennifer Balch It’s really about our relationship with combustion. And some of the ironies are when I see really dry fuels at the end of the fire season, that’s related to the warming that’s tied to our fossil fuel combustion and what we’ve pumped into the atmosphere over the last couple hundred years. And then I see a fire start because a power line goes down just like, wow, both of those elements are related to our energy addiction.
Justin Angle That power line thing? That’s not a hypothetical threat. Downed power lines in California have caused more than fifteen hundred fires over the last seven years11, including the Camp Fire, the deadliest in the state’s history12. In Oregon last year, power lines started at least 13 fires during a single windstorm13.
And climate change can actually make that risk higher. Scholars say extreme weather associated with climate change can create conditions ripe for power line failure – like those gale-force winds in Oregon14.
The IPCC – this huge organization comprised of experts from all over the world – says, compared to pre-industrial levels, we’re looking at one point five degrees of warming – that’s in Celsius – by the middle of the century at the latest15. How much the world warms, and how quickly, depends on global collective action to reduce emissions.
Especially in major countries like this one. 1.5 degrees already spells bad news — but if the world warms by 2 degrees, experts say we could see catastrophe: devastation to fisheries and coral reefs, massive biodiversity loss, fundamental shifts in ecosystems all over the globe.
A warming climate interacts with forests in all kinds of ways — from the kinds of trees and shrubs that thrive to where and how fires burn. So one way to understand what we’re facing in the future is to look back at the past.
[Justin Angle]: “Hey Cathy, Justin Angle.”
[Cathy Whitlock]: “Hello.”
Justin Angle And that’s Cathy Whitlock’s wheelhouse. She’s a Regents professor at Montana State University. That Regents thing? Cathy’s humble about it – but it’s actually a pretty big honor.
Cathy Whitlock Yeah, it’s cool. I don’t, you know, it doesn’t give me a parking space or anything that really amounts to anything. Probably secret handshake. No, no. I wish, I wish there was like a drinking club or something and there’s really not so
Justin Angle Along with our editor Nick, I visited her in her lab on the MSU campus. Cathy’s a paleoecologist16. That means she studies really old stuff to understand how our climate used to be. That’s important to make sense of what’s happening now.
One spot to look for that really old stuff?
Cathy Whitlock Lakes are the place because lakes are great repositories of environmental information. Everything that falls out of the air and lands on the surface of a lake has the potential to get buried in the sediments in the mud. And so we go to lakes in Montana and I go to lakes around the world, actually, and we get cores of the mud.
Justin Angle Cores. That means long, long tubes of mud drilled from boats or rafts anchored on a lake. The deeper you drill down, the older the mud. And when she says all around the world, she really means it – she’s cored from Argentina to Tasmania to Yellowstone National Park.
Over tens, and in some cases, hundreds of thousands of years, all kinds of stuff falls on the lake — little artifacts of what’s going on in the whole ecosystem. That stuff sinks and settles into the mud at the bottom.
That means each layer of the mud core is a time capsule: a glimpse of what the ecosystem was like long, long ago. The deeper you drill down, the older that time capsule.
When the core gets here, to the lab, the work begins. Cathy’s interested in what’s inside that mud. In particular, pollen. That shows what kinds of plants were around in a given time period17.
Cathy Whitlock You can see whether, for example, its pine was the dominant pollen type or sagebrush or grass or maybe tundra plants, things that grow at high elevations. And you do that for every level of the core. So you can think of it. You have fifteen thousand years ago and you can go younger and younger and younger. And what you see is that the composition of the pollen assemblage changes through time. And that’s telling you how the vegetation is changing, it’s changing in response to climate. So pollen is the best way of reconstructing past climate, going back over those timescales.
Justin Angle To piece together the puzzle of past climate data, her team uses chemicals to get rid of all the mud around the pollen, and then puts the remains under a microscope. Then, comes lots and lots of counting
Each click tallies pollen from a specific plant. We walk to another microscope-laden desk where, instead of counting pollen, her team searches for traces of charcoal.
Cathy Whitlock As you know, and fire happens, charcoal falls out of the air and lands on the lake and like pollen, it gets buried in the mud. And so we can, along with doing a reconstruction of the vegetation, we can reconstruct the history of fires.
[Nick Mott]: “So this could be all remnants of wildfires like a thousand years ago.”
[Cathy Whitlock]: “Yeah. Yeah. And often you’ll find a lot of charcoal all the way through a core, but you’ll find a peak of charcoal when there’s a fire, you know, a really level with a lot of charcoal.”
Justin Angle From all the data about the climate and wildfires tens of thousands of years ago, a distinct trend emerges:
Cathy Whitlock When we look at the past, we always see that there are more fires when the climate is warmer.
Justin Angle More heat equals more fire. Sounds simple, right? Well, there’s actually quite a bit going on.
Let’s break this down, starting with this one concept scientists call:
Cathy Whitlock Vapor pressure deficit.
Justin Angle That’s all about how easy it is for water to go from liquid to gas18.
Cathy Whitlock It’s a, it’s a measure of air temperature and humidity. And so it’s a measure of the ability of the atmosphere to sort of suck moisture out of the soil.
Justin Angle So the higher the temps, and the lower the humidity, the more moisture the atmosphere can sponge out of the earth, drying out all the sticks and leaves and shrubs and trees.
Then, there’s the weather itself. Let’s break it down by season. In wintertime, snow starts to pile up on mountaintops, covering up fuels and providing a reservoir of moisture for the hot summer ahead. But as the climate warms…
Cathy Whitlock When you have warmer winters you have less snowpack. Snow turns to rain, earlier in the year. The snowpack that you get melts off faster and so you’re left with less water in your high elevations as you go into summer. Warmer temperatures also means drier summers. And by the end of the summer, in the last few years, the trees are so dried out that they’re almost like standing matchsticks. They’re just ready to go.
Justin Angle The numbers bear this out. Here’s a statistic I mentioned back in episode 1: Fire season is nearly 80 days longer than it was back in 1970. 80 days. Scientists expect that to grow even more — by another three weeks in the next thirty years19..
Cathy Whitlock There’s a little bit of a debate maybe in the fire community where some people would say, well, climate is the primary driver and other people would say, well, no, it’s fire management and fire suppression that’s the problem. Probably those are both at play. But I would say ninety five percent of its climate driven. Fire suppression has really only had a measurable effect I think in the very dry forests, like Ponderosa pine forests. Most of our forests are not strongly affected by fire suppression.
Justin Angle This is a major point. How we view the causes of our increasingly devastating wildfires can impact how we react to the flames. Whether we blame suppression or climate change or both can inform the actions we take to mitigate fires, and to live alongside them.
However scientists and policymakers resolve this debate, Cathy says climate change isn’t just impacting the frequency and severity of burns. A big question now is what happens after a fire, when things start to grow again.
Cathy Whitlock The climate is changing. So the conditions where the previous forest established don’t exist anymore. And we’re already seeing that those species don’t necessarily return, but new things come in.
Justin Angle Especially at low elevations, plants like juniper and sage start to grow, rather than ponderosa pine. There’s grassland, where there once was forest. So a fire sweeps in, and since the temperatures are rising, that one burst of flame changes the whole ecosystem. One 2019 study suggests that in the Rocky Mountain West, by the middle of the century, more than 6 percent of all forests are at risk of never coming back if an extreme fire comes through, due to climate change. If you look a little farther down on the map, to the southwest, that number jumps to 30 percent.
Cathy Whitlock My perspective as a paleo ecologist is that we’ve seen really big climate changes, but it takes place over centuries to thousands of years. But what’s happening now is super fast. And the whole ecosystem really is, I think, in disequilibrium as a result.
Justin Angle Disequilibrium. The ecosystem has basically lost its balance. For Cathy, it all comes back to heat.
Cathy Whitlock Temperatures are driving everything. I think the way to look at it is that we’re due for more fires.
Justin Angle As climate scientist Jennifer Balch talked to our team, huge fires had just sprouted nearly outside her door in Boulder, Colorado.
[News clip 4]: “The timing could not be worse. As crews are already struggling to contain our State’s largest wildfire on record.”
Jennifer Balch So the east troublesome fire and the Calwood fire started on Saturday. And you know, what’s unusual about these, these two events is that, one, they started in October, and two, they grew really quickly.
Justin Angle Such big, volatile fires were nearly unheard of so late in the year. By the end of 2020, Colorado had seen its three biggest fires in recorded history.
Jennifer Balch And part of what’s going on here right now is that our fuels are really, really dry and they’ve been dry all summer long. We have not gotten any relief from rain or snow really in the last 30 to 60 days. So, Colorado is suffering under drought conditions right now. And this is all made worse by a warming climate. And in Colorado, in western Colorado and in northern Colorado, we actually see some climate change hot spots where those regions have seen warming. That’s twice the global average increase in warming.
We fire scientists have predicted an increase in wildfire activity and extreme wildfires out in the future, but not this soon. And so to see it happening this fast is really concerning. And you know I’ll talk about it in a calm way, because I’m a scientist and I’m trying to be as objective as I can. But this is me hitting the panic button right now.
Justin Angle That problem comes back to our addiction to burning, and therefore carbon and the emissions we release into the atmosphere. Forests are carbon sinks. They trap and store carbon. But when wildfires char a forest, that carbon pulses up into the air20. Which creates more warming. Which creates more fires. The relationship between wildfire and climate change is full of what Cathy Whitlock called positive feedback loops.
Cathy Whitlock Like a vicious cycle.
Justin Angle As I’ve made this podcast, I’ve started seeing the world around me in different ways. When I’m on a run, I don’t see trees and shrubs. I see wildfire risk, the legacy of where we built our homes and how we landscaped our forests. When I’m typing away on my computer or driving my car or cooking dinner, I see our age-old love affair with fire. Those things make my life immeasurably easier. But I also see another side of that love affair: the emissions from all that burning that contribute to a warming climate, and therefore yet more fire — and an existential threat to life as we know it.
I’m even hearing some songs in a different way.
[Johnny Cash song]: “I fell into a ring of fire…”
Justin Angle Like this one. I don’t think Johnny Cash had wildfire anywhere near his psyche when he sang “Ring of Fire.” But I can’t think of anything that better mirrors where we find ourselves today: in a ring of fire.
The story of our species starts and ends with fire.
[Voice 1]: “Not only a gift to us, but it’s more of a gift to the land. That’s what life is about. It’s not about me, it’s not about you. It’s about the next generation. That next generation depends on us. What we can do.”
Justin Angle That’s next time on Fireline.
Victor Yvellez Fireline is hosted by Justin Angle. Writing, editing, and production is by Nick Mott and me, Victor Yvellez. Our fact checking is by Aj Williams. Original theme music is by Travis Yost with additional music from Blue Dot Sessions. And our cover art is by Jessy Stevenson.
Additional support for this program comes from Montana Public Radio, United Way of Missoula County, and the Trailhead. Narration recorded at Studio 49 at the University of Montana’s College of Business.
Special thanks to Richard Wrangham, Jennifer Balch, and Cathy Whitlock.
Justin Angle If you like what you heard, please follow us — and leave us a review, wherever you get your podcasts.