OPPOSITE Just how suitable are tropical forests for human activity? It was long assumed that leaving these challenging environments helped spur human development, but now research is overturning this view. Here we see Panga ya Saidi cave, which lies 15km from the coast of Kenya. Roughly 78,000 years

Rethinking the jungle: the forgotten story of humanity and tropical forests

Humans and jungles are often seen as a poor combination. It is easy to write off the environment as challenging at best and a ‘green hell’ at worst. But could it be that tropical forests have repeatedly helped rather than hindered humanity’s progress? Patrick Roberts told Matthew Symonds why it is time to rethink the archaeology of the jungle.

Start

We all know the story about humanity turning its back on the jungle. While our distant ancestors originally evolved for a life of climbing and foraging in tropical forests, it proved a thankless world to master. Instead, the first step on our human journey is often seen as the moment when our ancient relatives quit the trials of the jungle in favour of a great open space: the African savannah. It was there that the bounty of abundant big game and the development of sophisticated stone tools created the conditions that ultimately allowed humanity to spread around the globe. As for the jungle, it can be easy to assume that most of us never looked back. Even the modern English word comes from the Hindi jangal, which originally meant a place away from human settlement. To this day, tropical forest is often thought of as a pristine environment, unsullied by human activity. But could it be that this seductive narrative of our success owing much to an early decision to shun a hostile and unrewarding environment is just a myth? In a new book, Patrick Roberts has taken a fresh look at humanity’s relationship with the jungle. The startling results lay bare a debt to tropical forests that stretches from long before our early human ancestors down to today.

OPPOSITE Just how suitable are tropical forests for human activity? It was long assumed that leaving these challenging environments helped spur human development, but now research is overturning this view. Here we see Panga ya Saidi cave, which lies 15km from the coast of Kenya. Roughly 78,000 years
Just how suitable are tropical forests for human activity? It was long assumed that leaving these challenging environments helped spur human development, but now research is overturning this view. Here we see Panga ya Saidi cave, which lies 15km from the coast of Kenya. Roughly 78,000 years ago, this was home to humans who were skilled at making the most of jungle resources. PHOTO: Mohammad Javad Shoaee. Dr Patrick Roberts

The air that I breathe

‘I think that in archaeology there has long been this stereotype that jungles act as barriers,’ says Patrick. ‘Because of modern Western views about what cities and agriculture should look like, we can see tropical forests as inhospitable, when that is not necessarily the case. One example that stayed with me was when I was travelling up the Amazon with my student Victor Caetano Andrade. You step on to the boat, and first of all you’re amazed by the mass of water – it’s like being on the ocean, but you’re on a river – it’s really remarkable. Once you’re out of the cities, you can see the edges of the river and they’re flanked by green. So it really seems to fit with this idea of an untouched wilderness. But as we moved slowly upstream, I remember Victor saying, “Oh look, we’re coming up to a village now.” At first, it seemed to me that nothing had changed. But when I looked closer, I saw a concentration of plants like palm trees and Brazil nuts. It wasn’t open-field agriculture like we’re used to in the West, but those stands of trees in the Amazon are still a legacy of people manipulating the range of species present for millennia.’

RIGHT & INSET A modern village on the bank of the Amazon. As you travel down the river by boat, it is possible to tell when one is approaching, because stands of trees useful to humans, such as palms and Brazil nuts, begin to appear. While open areas to grow crops can occur in the villages, these are comparatively small spaces between the trees, rather than large fields.
A modern village on the bank of the Amazon. As you travel down the river by boat, it is possible to tell when one is approaching, because stands of trees useful to humans, such as palms and Brazil nuts, begin to appear. While open areas to grow crops can occur in the villages, these are comparatively small spaces between the trees, rather than large fields. PHOTOS: Dr Patrick Roberts.

‘Even when we reached the village, there was an open area to grow maize, but it was still mixed in with stands of palms. So the local population is growing food without clearing all of the trees away. What is also fascinating about these villages is that they are standing on soils – what we call Amazonian Dark Earths – that have been created through human presence, activity, and modification over thousands of years. Various studies have shown, too, that the dominant trees across the Amazon Basin are often those that have economic benefits for humans, suggesting that such societies have been influencing biodiversity over parts of the rainforest that seem superficially “natural”. One recent analysis shows that plants useful to humans have populations six times larger than others. So, while there might not be obvious cities or villages all across the landscape, the legacy of human activity is still there. Once we start seeing the jungle as an environment that can be used in a variety of different ways, rather than somewhere that prohibits forms of agriculture and settlement we are used to in the West, it becomes easier to understand how important tropical forests have been to human history.’

BELOW The African savannah. Our early human ancestors apparently started taking an increasing interest in such environments between about 4 million and 2 million years ago.
The African savannah. Our early human ancestors apparently started taking an increasing interest in such environments between about 4 million and 2 million years ago. PHOTO: Dr Patrick Roberts.

To appreciate the full impact of forests on human life, it is necessary to turn the clock back to well before the era studied by archaeologists. Instead, if we contemplate the Earth in the early Cambrian period – that is, a little over 500 million years ago – we find a world where oxygen levels were three times lower than today, meaning we would need breathing tanks to survive. ‘At that time, there was basically only rock above sea level,’ says Patrick, ‘there was no soil to speak of. That is what the world looked like before plants and forests took hold. They transformed the atmosphere into the one we depend upon today, through the absorption and trapping of carbon dioxide and the creation of soil through root systems that interacted with fungi. One thing we sometimes lose sight of is that not only are tropical forests the most complex ecosystems around today, but, when they eventually emerged during the Carboniferous period ~350-300 million years ago (so named because of the coal eventually produced by the swampy masses of trees around at this time), they were also the first complex ecosystems on land. These are what sustained some of the first reptile ancestors and the first mammal ancestors. So, however you look at it, these forests really had a founding role.’

ABOVE The Amazon River is vast, but while the forest on its banks can resemble a pristine wilderness, this jungle has been modified by human activity for thousands of years with lasting, visible legacies remaining in its soils, species, and structure.
The Amazon River is vast, but while the forest on its banks can resemble a pristine wilderness, this jungle has been modified by human activity for thousands of years with lasting, visible legacies remaining in its soils, species, and structure. PHOTO: Mikhail Makeev/Dreamstime.

‘Jump forward many million years and, of course, the jungle was where our great ape ancestors lived. Ever since Darwin, we’ve had a prejudiced view that not only our closest relatives – such as gorillas and chimpanzees – but also their modern environments, tropical forests, are somehow stuck in time. These forests can be seen as a primeval place we used before we could stand upright or make stone tools or control fire. With that in mind, it’s fascinating to look at our great ape ancestors today. Which one is actually bipedal the most? Given how we view our own development, we might assume that it would be the ground-frequenting chimpanzees. But it’s not. It’s the orangutans that are still living in jungle, using bipedalism high up in the branches to extract sugary fruits. That is a really amazing thing to think about – that bipedalism might have forest origins, or at the very least does not only have to have happened in open grassland.’

ABOVE Excavations under way at Panga ya Saidi cave in Kenya. Although the cave only lies 15km from the coast, the Late Pleistocene occupants seem to have specialised in exploiting forest and some grassland resources.
Excavations under way at Panga ya Saidi cave in Kenya. Although the cave only lies 15km from the coast, the Late Pleistocene occupants seem to have specialised in exploiting forest and some grassland resources. PHOTO: Mohammad Javad Shoaee.

There is no question that a point was reached, between about 4 million and 2 million years ago, when our early human ancestors started to take an increasingly keen interest in more open grassland environments. Even so, there is ample evidence that certain hominins still retained an attachment to woodland and forest. A fine illustration of this comes from considering some sites that are associated with sophisticated stone tool types, such as the Acheulean. While we are supposed to associate such kit with open environments, in some cases the true context was forest or woodland around a lake. From that, it is not a great stretch to imagine our hominin ancestors recognising that such places are good for protection and well stocked with a range of different plant resources. On top of that, it is important to note that our understanding of the period is hugely biased by finds from eastern and southern Africa. Very little is known about what was happening in western and central Africa, which is where most of the rainforests are today. There is a good chance that plenty of sites await discovery in those regions. Either way, though, the evidence seems to suggest that there was not just a one- way journey from jungle to savannah; instead, we should imagine a huge amount of variability.

By the time we get to the origins of Homo sapiens, we have a scenario where, rather than our species being forced to exist in a single habitat, it became the master of a range of different environments. ‘I worked at Panga ya Saidi cave in Kenya’, says Patrick, ‘where they subsequently found the oldest known human burial in Africa, which dates back about 78,000 years ago. That’s a great example of one of those early cultural behaviours that we often think of as “human”. The increasingly frequent appearance of behaviours such as burial, symbolism, art, and complex technologies in the archaeological record of our species is often associated with coasts, where there are abundant protein resources that allowed our species time to experiment, or in grassland areas where we had to adapt to periods of aridity. While this cave in Kenya is indeed on the coast, it’s also in a tropical forest, and when we look at the animal remains, there is no sign of intensive use of marine resources, at least during the earlier Late Pleistocene levels. Instead, all the evidence points towards exploitation of forest resources, with some use of grassland. We did isotope analysis on two sets of human remains, one of which was an isolated tooth as old as the burial. The results fit the general picture by showing a reliance on woodland food, but with some sustenance coming from other habitats. Personally, I think we’ve been doing this since we emerged as a species about 200,000 years ago. Once we start to get sites in western and central Africa, we’ll really be able to see this. That’s just what our species does: it makes use of forest.’

BELOW Objects found in Panga ya Saidi cave include ostrich eggshell beads (top left), a cowrie shell (bottom left), bone points or needles (top right), and a bone needle, with the detail of its tip showing smoothing from repeated use (bottom right).
Objects found in Panga ya Saidi cave include ostrich eggshell beads (top left), a cowrie shell (bottom left), bone points or needles (top right), and a bone needle, with the detail of its tip showing smoothing from repeated use (bottom right). IMAGE: Dr Jennifer Miller.

Seeing the woods

If jungle and woodland could play a role in human origins in Africa, what happened as our species began to move out across the rest of the world? ‘We once thought that humans moved into places like South and South-east Asia when the climate made the forest go away,’ says Patrick. ‘There’s this big Indian Ocean rim narrative, which basically sees humans sticking to coastal resources and island-hopping as they spread from region to region. But we can now see that it’s not true. When humans get to places like Sri Lanka, Indonesia, and New Guinea, they move straight into their tropical forest environments and use them in different ways. I was really lucky, because I did my PhD research on a site in Sri Lanka, which is a beautiful place to work and was what set me on this path of rethinking the jungle. It was a topic that Sri Lankan archaeologists had already been working on, and they had frequently said “Hang on! We’re finding microliths, human remains, and bone tools – all in rainforest habitats.” Sri Lanka is slap-bang in the middle of the Indian Ocean rim, so why would all of the earliest sites – dating back about 45,000 years – be deep in the rainforest if human expansion depended on coastal resources?’

ABOVE Wet lowland tropical rainforest in Sri Lanka. It was once thought that humans moved into South and South-east Asia by relying on coastal resources along the Indian Ocean rim. Now, though, there is evidence for human groups living deep in the rainforest from about 45,000 years ago.
Wet lowland tropical rainforest in Sri Lanka. It was once thought that humans moved into South and South-east Asia by relying on coastal resources along the Indian Ocean rim. Now, though, there is evidence for human groups living deep in the rainforest from about 45,000 years ago. PHOTO: Dr Patrick Roberts.

‘This is where isotope analysis is perfect, because you really are what you eat, so we can track the long-term reliance on certain types of food. The earliest isotope sample we have from Sri Lanka dates back to about 36,000-38,000 years ago, and that is from an individual who was in the rainforest, and relying on rainforest resources. We can see from later samples that this continues through time, right down into the Holocene and also after farming is introduced. While you eventually get some people starting to grow millet as a crop, others continue to focus on the forest. This result was amazing to me, because it was really the first evidence that humans not only could live their lives in rainforests, but were choosing to do so since their first arrival in Sri Lanka. What is even more amazing is that you get sharks’ teeth and marine shells emerging from these rainforest sites. This was once taken as evidence that these people came from the coast and were temporarily using the forest. Now we know from the isotopes that wasn’t the case, so we should be looking at populations on the coast and in the forest, who were communicating with each other. Which means that once again it’s about mastering different environments.’

Animal remains recovered during excavations at Fa-Hien Lena cave in Sri Lanka show the range being exploited by its human occupants. The number of specimens found is shown to the left (a), while the minimum number of individuals is given to the right (b). The remains indicate that human groups living in the cave were adept at hunting the small mammals living in the surrounding rainforest. IMAGE: from O Wedage, N Amano, M C Langley, K Douka, J Blinkhorn, A Crowther, S Deraniyagala, N Kourampas, I Simpson, N Perera, A Picin, N Boivin, M Petraglia, and P Roberts, ‘Specialised rainforest hunting by Homo sapiens ~45,000 years ago’, Nature Communications 10 (2019); http://creativecommons.org/licenses/by/4.0/..

Even if some communities were choosing to live in the rainforest, one area where they could reasonably be expected to lag behind groups occupying more open environments is perhaps crop cultivation. After all, rainforest soils rapidly lose fertility once vegetation is cleared, making them poorly suited to relentless, field-based, monoculture agriculture. The emergence of farming in the Fertile Crescent around 11,000 years ago is often taken as one of the great defining moments in human development. Of course, it took off in different parts of the world at different times, with farming only really beginning in Britain about 6,000 years ago. It might be assumed that the first appearance of crop-growing in rainforests would come some significant time after that, but the possibilities presented by cultivation seem to have captured the imagination of at least some groups living in jungle at a remarkably early date.

ABOVE The view from the mouth of Batadomba-lena cave in Sri Lanka. Early human fossils dating back to about 38,000-36,000 years ago have been found here. Material from the cave suggests that these humans were enjoying meals that included primates, mouse deer, giant squirrel, mongoose, nuts, and starchy plants.
The view from the mouth of Batadomba-lena cave in Sri Lanka. Early human fossils dating back to about 38,000-36,000 years ago have been found here. Material from the cave suggests that these humans were enjoying meals that included primates, mouse deer, giant squirrel, mongoose, nuts, and starchy plants. PHOTO: Dr Patrick Roberts.

‘There’s an amazing site in New Guinea called Kuk Swamp,’ says Patrick. ‘It’s in swampy terrain up in the highlands, and archaeologists started excavating it in the 1970s. There has been some controversy about exactly how old it is, but from at least 10,000 years ago humans were intensively manipulating the landscape and creating a mixture of forest and more open areas, apparently complete with artificial drainage. Although it can be very hard to identify domesticated plants from things like starch, the general consensus is that by 7,000 years ago there is a domestication of banana, taro, and even an ancestor of sugar cane. So we can see this long-term trajectory of forest management turning into domestication. In essence, the landscape is being prepped so that you can grow plants like bananas, which like forests, alongside plants like taro, which need open, drier ground conditions. For a long time, Kuk Swamp was an isolated early example, but now we’re starting to see something similar in the Amazon. Very early cultivation techniques were appearing repeatedly across the Tropics.’

‘We see another dimension to the situation in New Guinea at a site called Kiowa. That’s at the same altitude as Kuk Swamp, and is about 100km away. At Kiowa, the chronology also spans the period when a gradual trajectory towards farming was playing out at Kuk Swamp, but at Kiowa the groups continue to stick with a hunting and gathering lifestyle. They rely on the same animals in their diet from about 12,000 years ago through to historical times. Today, there is a tendency to think of agriculture as this desirable place that we want to get to, but in New Guinea we have these two communities that were reasonably close to each other, and one moved towards farming while the other didn’t. Of course, the Kiowa hunter-gatherers may well have been modifying the forest, but they didn’t see an advantage to pursuing cultivation. I think that’s a useful perspective to bear in mind. Multiple different adaptations can give good solutions within the same ecological context.’

BELOW A mass spectrometer. This machine was used to generate isotope data from human tooth enamel samples found in Sri Lanka that demonstrated these individuals specialised in consuming rainforest resources.
A mass spectrometer. This machine was used to generate isotope data from human tooth enamel samples found in Sri Lanka that demonstrated these individuals specialised in consuming rainforest resources. PHOTO: Mary Lucas.

Urban jungle

If we tend not to see Western-style agriculture in jungle environments, this absence is even more true of full-blown cities. ‘Compact, European-style cities can be incredibly resilient in Europe,’ says Patrick. ‘Just look at Rome or London. There can be a remarkable longevity to them. But once again, this is not the only way to go. A famous example here is probably the Classic Maya, with their urban centres in the rainforest of North and Central America. It was often assumed that these were compact cities, and that the ceremonial centres full of impressive architecture were the be-all and end-all of the urban area. From that, it was only a small step to conclude that the Maya city-states drove themselves to “collapse”, because they were trying to sustain something that was simply not possible in a delicate tropical environment. Now, thanks to LiDAR – that is airborne survey using lasers – we can look beneath the modern rainforest canopy to see the remains of vast cities. Alongside the ceremonial centres, there are causeways, farmers, hydrological networks, and so on’ (see CWA 96).

‘Having farming within the urban network gives us a different sense of how cities can be arranged. And once again, this farming doesn’t involve endless fields of maize, it’s patchworks interspersed with forest. That shouldn’t be surprising, because these cities were founded by communities who had long ago learned to live alongside the forest. That’s not to say there weren’t problems. In some seasonal forests access to water became unreliable and droughts worsened. But even then, when a “collapse” came, it was focused on the elite and the ceremonial centres, with farmers still working the landscape afterwards. They might move to new locations with more reliable access to water, but it’s not a complete collapse. After all, there are still Indigenous Maya groups there today, and they are still practising mixed forms of food production. So that general technique is resilient – it’s the ceremonial centres that are more vulnerable to external changes.’

ABOVE The magnificent ceremonial core of the Classic Maya city of Tikal. It was once thought that such monumental centres made up the entirety of Classic Maya cities, but it is now appreciated that these settlements sprawled over vast areas, allowing food production suited to a forest environment.
The magnificent ceremonial core of the Classic Maya city of Tikal. It was once thought that such monumental centres made up the entirety of Classic Maya cities, but it is now appreciated that these settlements sprawled over vast areas, allowing food production suited to a forest environment. PHOTO: Quoc Anh Lai/Dreamstime.

‘It’s not just the Classic Maya who were building cities in the jungle. You see something similar at Angkor in Cambodia, while there were also garden cities in the Amazon, which may have been supporting millions of people across the Basin. Seeing just how much is possible in the jungle raises the question of why, then, do we have this view of it as being removed from human activity? I think that has a lot to do with European arrival in the Tropics. When that happened, especially in the Americas, it came with a spread of diseases, which the locals did not have immunity to. There was political and economic change, too. One example of that was the desire to bring indigenous groups together, so that control and the extraction of labour would be easier. That, alongside other abuses, had the unfortunate side effect of increasing the spread of disease, which developed into the worst epidemiological disaster on record. The latest estimates from across the Neotropics are that we are potentially talking about 90% of the indigenous population dying. If so, you’re looking at a population that was approaching the size of that in Europe, before being reduced to the scattered bands of hunter-gatherers and isolated farmers that we imagine today. In Asia, Africa, and South Asia, disease may have played a lesser role, but early colonial authorities there tended to destroy, marginalise, or gloss over the great indigenous civilisations that once flourished in those regions. Equally, opening Western-style fields or creating vast pastoral landscapes could obscure the traces of earlier attempts to live with the forest in different ways.’

If you go down to the woods today

While many of us think of tropical rainforests as a distant thing, they continue to have a significant impact on people all around the world. ‘They are responsible for something like a third of terrestrial rainfall,’ Patrick points out. ‘They are part of climate cycles that extend across the Atlantic and Pacific. Even beyond that, a lot of the food that we take for granted has its origins in tropical forest. Maize, for example, and the humble chicken – now one of the most numerous animals on the planet. My view is that we could think more about what jungle still does for us. We’re a weird species in some ways – we’re really good at empathising in certain situations, but not in others, especially if it’s something we can’t see personally.’

BELOW The ruins of Angkor Wat, Cambodia, were ultimately reclaimed by the jungle. Just as with the Maya cities of South America, airborne LiDAR survey is revealing that the urban settlement at Angkor Wat, and across the Greater Angkor region, extended far beyond the monumental core.
The ruins of Angkor Wat, Cambodia, were ultimately reclaimed by the jungle. Just as with the Maya cities of South America, airborne LiDAR survey is revealing that the urban settlement at Angkor Wat, and across the Greater Angkor region, extended far beyond the monumental core. PHOTO: Sergeychernov/Dreamstime.

‘But the jungle also encourages us to see a way in which our species is special. There’s now this emerging picture about how our species is characterised by the diversity of environments that it can inhabit. Rather than focusing on that familiar story of humanity emerging into the African savannah and embracing a new destiny, we should look at how versatile we were, and perhaps still are. Even today, there are populations in high-altitude mountain areas where limited oxygen is available, or living in tropical rainforest, or on coasts, or in deserts, and so on. I think it’s an ability to adapt to this variability that really captures what it means to be human. And it’s certainly something we’re going to rely on if we are to face the challenges of the 21st century.’

FURTHER READING
For an engaging and preconception-shattering account of the jungle – ranging from its earliest days, through humanity’s interaction with it, down to the present – the latest book by Patrick Roberts is highly recommended: Jungle: how tropical forests shaped the world – and us (Viking/Penguin, 2021; ISBN 978-0241472743, £25).

Patrick Roberts also discussed his article in more depth on a recent episode of The PastCast. You can listen to the conversation here.