The destruction of the Amazon rainforest continues at a rapid rate. Plants, animals, and many tribal cultures face extinction: in the 20th century, 90 tribes disappeared in Brazil alone. Today, we focus on the contribution to climate change from carbon released by forest destruction. Sometimes obscured by this peril is the perhaps incalculable sacrifice in terms of potential new agricultural or medicinal products – in just one example, ACE inhibitors and beta-blockers are based on compounds derived from neotropical species.

In my fieldwork as an ethnobotanist – a scientist who studies how tribal peoples use local plants – I have repeatedly observed that the Amazon’s indigenous people know, use, and protect rainforests far better than Western scientists or park guards imported from urban centres. But these tribal cultures – and, in particular, their knowledge – are disappearing far more rapidly than the rainforest itself. Even in the all too rare instances where neither an Amazonian tribe nor its ancestral forests are physically threatened by outside forces – typically, the extractive industries – the culture itself more often than not degrades or disappears when it comes in contact with the outside world.

Perhaps the most fragile of these Amerindian cultures are the isolated groups, those few ‘lost tribes’ who have chosen to avoid contact with the outside world. The recent historical record amply demonstrates that contact can devastate these hunter-gatherer bands: within a few years of making contact, 50 per cent of the Nukak tribe of the northwest Amazon and 80 per cent of the Akuriyo tribe of the northeast Amazon were dead. And these fatalities were not equally distributed among all age groups: the most vulnerable were both the very young and very old. Because they typically are the repositories of tribal knowledge, when the elderly members of a small tribe die, much if not most of the oral wisdom dies with them.

These isolated cultures represent an unexpected and vivid link to the deep past, when humanity was born and survived in seeming simplicity and relative harmony with nature. In our ever-urbanising and stressed-out world, isolated peoples hold a mystic and almost iconic identity in the continuum of how humans live and have lived from ancient times to the present. We often yearn for a sense of simplicity and clear orientation, and we have linked this gap in our modern lives to romantic perceptions of how life once was, or how it could be again. Our current fundamental detachment from nature creates a yearning in many of us for a reconnection to the earthly ways that we ascribe – fairly or unfairly, correctly or incorrectly – to isolated tribes. Romanticism aside, the study of cultures with an extremely intimate relationship to the natural world may suggest a means to revitalise the spiritually barren aspects of our daily lives and to live in far greater harmony with our environment.

The subject of what constitutes truly ‘uncontacted’ peoples inspires debate. Many argue that every tribal community in the world – no matter how remote – has had some historical contact with outsiders. The website of Survival International, a leading cultural preservation organisation, states: ‘Everyone has neighbours, even when they’re some distance away, and they’ll know who they are.’ They further define ‘uncontacted tribes’ as ‘peoples who have no peaceful [my italics] contact with anyone in the mainstream or dominant society.’

The biologist John Terborgh describes these groups as ‘societies that have no regular [interaction] with the modern world, though they might have second or third-degree contact through trading partners or ‘co-linguists’. They live with no or few manufactured implements other than perhaps the odd machete or axe acquired through trade, often isolated by linguistic barriers as well as the physical barriers of remoteness.’

Further, any attempt to strictly define ‘uncontacted’ leads down a rabbit hole. If the last Karijona maloca (longhouse) in the Chiribiquete region of the northwest Amazon was seen in 1904, and longhouses are once again being spotted there from overflights in small planes, can we say with any degree of confidence that these people are Karijonas, and that they therefore do not represent an uncontacted group? If a Colombian missionary met a tribe of isolated Indians near the Yari River over 20 years ago, presented them with machetes and pots, and they then fled and he was unable to find them again, can we say that they have been contacted? If a single Trio Indian had a single encounter with two previously undocumented tribes, are those tribes considered ‘contacted’?

Sooner or later, for still isolated groups, contact with the larger society is all but inevitable. And recent history very likely predicts their future: they will be ‘civilised’ through settlement in large sedentary villages of other tribes. Once there, their changes in diet, lack of agricultural knowledge, and exposure to disease will prove disorienting and disheartening. Through the deaths of the elders and intermarriage into the dominant tribe, their culture will begin to disintegrate.

So how do we know what they know, and what is lost when these tribes disappear? To demonstrate what information may be lost when tribal peoples and their forests disappear, this essay will briefly touch upon the case histories of three tribes: the Akuriyos of Suriname, the Uru-Eu-Wau-Wau of Brazil, and the Matses of Peru.

When first contacted by missionaries in 1968, the Akuriyo tribe consisted of small bands of hunter-gatherers living along the Suriname-Brazil border in the northeast Amazon. They had no agriculture or sedentary villages, only ephemeral housing structures, and carried fire with them from campsite to campsite. Not knowing how to swim or build canoes, they avoided most major rivers but did frequent the banks of these rivers in the dry season to collect iguana eggs, a favourite food.

A striking aspect to all who met or observed them after the initial contact was how vigorous, strong and healthy they seemed. The two neighbouring tribes – the Trios to the west and the Wayanas to the east, both noted for their detailed knowledge of rainforest flora and fauna – were in awe of both the Akuriyos’ rainforest knowledge and their abilities as hunters. Employing one of the few means of measuring their ecosystem knowledge, the late anthropologist Peter Kloos documented 35 Akuriyo names for honey. Almost all of the very young and the elderly died within two years of contact – before I began my research with the few who were left. Today there exist fewer than 40 Akuriyos, and less than a handful who remember life prior to contact.

There are approximately 2,000 Matses Indians living along the Brazil-Peru border. Up until 1969, they earned a fierce reputation for killing all trespassers on their land. In October of that year, the indefatigable National Geographic photojournalist Loren McIntyre set off in search of the Matses, then more widely known as the Mayorunas. He had a floatplane drop him off alone near the headwaters of the Javari River, where he made a small camp, which was soon surrounded by Matses men. At their encouragement, he followed them into the rainforest. After a few days, they began a tribal dance, once again inviting the American to join them. At the conclusion of the ceremony, the Matses opened palm leaf baskets, removed green monkey frogs from the containers, made cuts in their forearms, and rubbed the amphibian skin secretions into the wounds.

The frog skin slime was highly hallucinogenic. After the ceremony, the Indians explained to the explorer that they employed the frog exudate for hunting magic – it made the hunter smarter and stronger, and allowed him to see where the animals would be found the next day.

Later lab analysis of the frog skin yielded a host of new peptides, many of which are active in the human body. Several are currently being studied as a means of increasing the permeability of the blood-brain barrier, among the holy grails of modern medicine. Another substance from the skin of the green monkey frog is a novel compound named ‘dermorphin’, a non-addictive painkiller 30 times more potent than morphine.

Thanks to this revelation by McIntyre and those who followed in his footsteps, there is a widespread acceptance that Amerindian knowledge of rainforest compounds is not limited to plants. As a result, scientists have searched for and found new medicinal applications for elements in Amazonian insects and other frogs as well.

In 1987, I received a call from the National Geographic Society, asking for my help. The German-Brazilian photographer Jesco von Puttkamer had some interesting photos of a recently contacted tribe and they wanted the opinion of an ethnobotanist.

Von Puttkamer and Loren McIntyre had just returned from Rondônia in southwestern Brazil where they were visiting the Uru-Eu-Wau-Wau tribe. Both men already had extensive experience with Amazonian Indians but were struck by a novel observation. They showed me a photo of a tapir that the Indians had brought down with their arrows, and the animal was covered in blood.

Most Amazonian arrow poisons come from two plant families – the moonseed and the Strychnos families – and kill through asphyxiation. Based on this photo, it seemed that the animal had bled to death, indicating the use of an arrow poison with strong anticoagulant properties.

Research by other botanists determined that the Indians were extracting this poison from a tree in the Brazil nut family, a group of plants previously not known to contain bioactive principles, and that the active compound was indeed a powerful anticoagulant. Given that the populations of the world’s rich nations are ageing, and that the market for anticoagulants is commensurately sizeable, plants and plant compounds that reduce clotting have significant market and therapeutic potential.

To take full advantage of rainforest products, proper means of rewarding local tribes and national governments must be put in place. Further, provisions must be made to protect the forest’s peoples, cultures, plants, and animals. Virtually all of this is endangered, with the foremost threats including gold mining, logging, cattle ranching, fires, and roadbuilding. This essay represents a brief attempt to provide a glimpse of what is at stake – and what might be lost.

This essay originally appeared as How Do We Know What We Do Not Know in Knowledge and Information: Perspectives from the Engelsberg Seminar, Axess, in collaboration with Axel and Margaret Ax:son Johnson Foundation, 2018.