On the trail of wild beans in Peru

What he’s looking for is something more ancient than the Incas, and potentially more valuable than all their silver and gold. And if he finds it, he’s just going to look at it. For a few minutes. And then leave. We wind our way down to the valley floor, and past the little towns of Pisac and Lamay. Daniel scours the roadside, taking meticulous readings from the car’s odometer. Shunning UNESCO World Heritage Sites to comb wasteland, our driver clearly thinks we’re bonkers. At a non-descript verge, Daniels asks to pull over and dons his hiking boots. And he’s off, suitcase in hand. Long lurching strides that I scamper to keep up with; brief pauses to stoop and scan the roadside, before marching on. To passing traffic he must look like a hitchhiker searching for dropped keys. A hundred metres later and with no luck, I start to console myself: it’s been almost three decades. Anything could have happened. The story will have to be how we didn’t find treasure at all. Suddenly, Daniel stops. With a jab of his finger, he points into an impenetrable tangle of quite dead-looking bushes. As I catch up, he turns to me, eyes full of excitement, and says: “2312. It’s still here.” It’s a code that means bean. A wild, untamed bean. One that contains secrets. I peer uselessly into the undergrowth. After a few years at CIAT, I’ve seen my fair share of beans. But even with this really special one right in front of me, I can’t spot it. Daniel guides my eyes. And finally, there it is: Phaseolus augusti, a distant cousin of the better-known Lima bean. Far from dead, he explains that the pods have all opened, leaving their dried, twisted casings dangling from the vines. I get a flash of The Blair Witch Project and shake it away. Is that it, a bedraggled bean plant? That’s the treasure? I know; I owe you an explanation. So here goes. Once there was a plant. We’re talking about 8 million years ago, in what is modern day Mexico. This “proto-bean” – now long extinct - is the earliest ancestor of the beans that today feed 400 million people. Yes, the kinds the British have on toast and that Mexicans themselves re-fry. By 5 million years ago, proto-bean had spawned several genetically distinct progenies. Responding to natural variations in climate, some of these new plants started to move south. This happened at the excruciatingly slow rate of about five metres per year – a result of seed drop and regrowth, drop and regrowth. Little by little the plants adapted to the environments they moved through. This southerly saunter continued for 2.5 million years, taking the plants down through Central America and into South America. Some of them arrived here, in the Peruvian Andes – like the wild bean in front of us. Daniel can even point to the direction from which it first slinked into the Sacred Valley (north-west). Fast-forward to about 15,000 years ago, and the first hunter-gatherers arrived in the Andes. They would have stumbled upon the different wild beans while foraging. But the seeds were small, bitter-tasting and – here’s the deal-breaker – poisonous. It’s the reason you need to soak and cook beans even today. But what happened next changed the course of culinary history. They possibly saw birds feeding on the young, green pods of what is now known as common bean (P.vulgaris). Given that they didn’t promptly squawk in agony and drop out of the sky, the hunter-gatherers surmised – so the argument goes - that the immature beans were probably safe to eat. Some brave soul must have been the guinea pig. When he or she survived, they plucked some of the beans from their native habitat and started cultivating them - a process known as domestication. Daniel’s research suggests that for common bean, this happened around 6-7,000 years ago in Peru’s Apurímac region, not far from where we are in Cusco Province. Over time, natural mutations resulted in some of the domesticated plants producing bigger seeds than others. Easier to harvest and more fun to eat, the early farmers discarded smaller-seeded plants in favour of the larger ones. Over several centuries, domesticated beans tripled in size, soaking and cooking became the norm, and they became a staple food. The once-wild bean had been tamed. Now, fast-forward to the present day, and trails become roads, settlements become towns, and human activity has gobbled up many of the habitats for wild beans. But, whatever: they were small and poisonous anyway. Good riddance. Fortunately, that’s not where the story ends. Because there are still little pockets where wild beans endure. These ecological niches have managed to either repel, escape or adapt to the forces of modernity. They’re often unassuming wastelands, and the beans little more than weeds. Just sitting there, looking dead. That’s all well and good. But what about the treasure? Well, the fact the wild beans have survived so long means they probably have some kind of evolutionary advantage. And here, on the outskirts of Lamay, one particular strength is clear: at 2,940m above sea level, this is high. And high means cold. Nowadays, farmed beans can barely survive above 2,000m. So this particular wild bean – yes, this dead-looking thing amid a jumble of other dead-looking things - is actually right at the evolutionary frontier of cold tolerance. If you’re a crop breeder, that’s something akin to striking gold. And here’s why: if you cross cold-tolerant wild beans with high-yielding, large-seeded types, you could produce beans for farmers in cooler climates. Or ones that can be grown at different times of year. For a crop that’s already humanity’s most important source of vegetable protein, it’s a tantalising prospect. It also means a bean like this really ought to be conserved in a genebank somewhere. And fortunately, it is. Wild bean #2312 was collected back in 1987 on the same verge, by the same Daniel Debouck. Things were quite different then. He tells me that at one point he was bean hunting on the valley floor while overhead, government troops exchanged fire with rebels from the Shining Path. Undeterred, he and his Peruvian colleague took plant samples to the herbarium at the National University of San Marcos in Lima. They also shared out the seeds, taking half to the genebank at the National Agrarian University – La Molina, also in Lima, and the rest to CIAT’s genebank in Colombia, where Daniel continues to work. Retracing his steps today - in a much more peaceful Peru – is a quest to see how resilient or simply lucky an ecological niche can be. A lot can happen in three decades: a wildfire could wipe it out; invasive plants might choke it off; humans might build a burger bar on it. Think Joni Mitchell. It’s more than a hypothetical risk. Daniel has collected wild beans in parts of Mexico that are now urban areas; their evolutionary journey and all their genetic mysteries snuffed out by asphalt and bitumen. Fortunately, those seeds are safely conserved. Others weren’t so lucky. So why has this particular niche in Peru survived? Daniel notes that the rocky verge is unlikely to be developed for construction or farming. The absence of vegetation-clearing goats is a boon too. He’s happy to conclude that the niche is stable. I ask how he knows where to look for these little nooks of leguminous delight. “That’s my trick,” he replies with a grin. But as we begin the search for wild bean number two, it becomes clear that he has, in fact, several tricks. Daniel can read landscapes, picking up signals from nature. The presence of certain shrubs; soil type; proximity to water, all give little whispers that he’s tuned-in to. When the whispers converge into a chorus of clues, it’s just a matter of pulling over and having a look. He’s honed this quasi-mystical ability during a career spent on the trail of wild beans. Rummaging through undergrowth in 14 countries in the Americas, he’s discovered 15 new species, and deposited 3,270 new samples in the CIAT genebank. These and others in the nearly 38,000-strong CIAT bean collection have been shared freely with scientists around the world, and used to breed varieties that are tolerant to pests, diseases, drought and heat, and with higher levels of nutrients like iron and zinc. These are now grown by millions of people in Africa and Latin America. More breakthroughs are likely: one-fifth of the beans in the collection are yet to have their secrets unlocked. Near the ancient town of Ollantaytambo, our luck continues. The bean drumbeat draws Daniel to a supremely dusty roadside and there’s wild bean number two (#2313; P. augusti), caked in dirt but safe and well. Proximity to the town’s impressive Inca ruins seems to be its saviour: planning regulations prevent construction too close to the historic site. This niche, he concludes, is also stable. But further downhill, in the village of Puente Achaco, things weren’t looking so rosy for the final bean on our list. Work to dredge the Limatambo River had completely gutted the original collection site for a population of wild common bean. Daniel paced up and down a long stretch of road, rifling through hedgerows and staring into more tangles of weeds; almost sniffing the wind for beans. I found myself urging his magical powers to pick up the scent. Then, a couple of kilometres downstream, the sandflies started to bite: we were close. We crossed a bridge to an area which, in disconcertingly literal testimony to the aforementioned Joni, had actually been turned into a car park. And there it was: a solitary common bean plant hugging the perimeter. Daniel was delighted. He uncovered more plants nearby. Some of the pods showed signs of damage by feeding birds, harkening back to what those early hunter-gatherers might have seen. He popped one open to reveal the small, shiny, patterned seeds. Daniel can’t yet say what secrets they contain. But some kind of disease resistance is a possibility: surviving constant attacks for a few million years is a long time to be simply lucky. At the very least the seeds from this fragile niche are safely conserved. As we doused ourselves in repellant, I asked how he could be so sure that these beans are actually wild and not just escapees from nearby farms. Apart from visible clues like seed size, it’s ultimately about polymorphisms, he said. These are complex mutations in the beans’ DNA, like a genetic autobiography. After millions of years of evolution, wild beans have a huge number of polymorphisms. Domestication put the brakes on the number of genetic variations the bean could make; as a result, cultivated beans have far fewer. Impressed by the huge volume of history contained in seed in his palm, I asked a rhetorical question: “Can we take it with us?” “No. It stays here,” he replied, flicking the bean back into the undergrowth. To collect seeds you need an official permit for each trip. It’s a requirement with which Daniel has always dogmatically complied. But having spent a couple of days with him, I also knew that he was tipping the nod to something much more profound: the idea that this wild bean should be left to continue its evolutionary journey, whichever direction it may take.