This is from the Sandbox.

Star Wars fans, picture a setting like the forest moon of Endor, albeit planet-sized and without Ewoks running about. For everyone else: Imagine a dense deciduous forest, with trees packed close together, stretching across the entire planet. The planet itself is Earth-like, and has Earth-like vegetation, trees, and forest creatures.

The main creatures are, for all intents and purposes, humans. They'll actually be humanoid, and not exactly human, but they won't have any major differences that will impact this question. They dwell in large treehouses, built in the mid- to upper- layers of the trees. The houses are accessible via rope ladders from the ground, although many are able to climb the trees outright. Tree-to-tree travel is made possible through rope bridges, though the more nimble can walk form branch to branch, making short jumps along the way.

How would transportation develop in such a world? I do have one idea: small, one-person gliders that fold up and can be carried. They can help when getting from one tree to another where there aren't any branches or bridges. They're used more often when traveling from the canopy layer to somewhere closer to ground level.

Restrictions:

  • The rope bridges can't hold any substantial weight.
  • The materials at hand are all that can be found in a forest: Wood and some rock, as well as leaves, branches, etc. (The gliders are made out of sticks and animal skins, by the way, so any animal-based vehicles are also on the table.)
  • There is no electricity use, but there are metals available, primarily iron. They are able to primitively produce iron.
  • The plants (and some animals) here are those found in a deciduous forest.

The trees are close enough that it's impossible for any vehicles larger than a small car (e.g. a Mini Cooper) to feasibly go through.


Finale

Thanks to everyone for the comments and answers. I've thought a lot about the various suggestions over the past few days, and I've realized that no one method is going to be enough. I've decided on a combination of methods:

  • The canals created by Abulafia and the boats discussed by Bill Blondeau
  • The mini-airships suggested by ninesided (for small loads of freight, I think)
  • The rope/ziplines invented by ckersch (and the resultant industry of rope-making)

and, as a plot device to lead up to a conflict . . .

  • The burning of a small part of the trees, as suggested by Pavel Janicek

This is what I love about Worldbuilding - collaborative ideas always morph into something I could never have dreamed of.

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    What sort of forest is your planet covered by? Earth forest vary significantly based on where they are, and I'd imagine that the transportation systems developed in an Amazonian rain forest would vary significantly from those found in the Redwoods or the eucalyptus forests in Australia. – ckersch Jan 24 '15 at 21:57
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    Just a tangent, but when you mention primitive iron production, do you mean working meteoric iron, or actually smelting it from ore? Because those are very different things. Back in the bronze age (and the stone age before it), iron was a rare and mysterious "star metal" that very occasionally fell in chunks from the heavens, accompanied by noise and bright light. It could be worked, but because of its rarity and presumed heavenly nature, it was mainly used for jewelry and ceremonial objects. The invention of iron smelting was a huge technological revolution that changed all that. – Ilmari Karonen Jan 25 '15 at 2:48
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    Are there any rivers on that world? I suppose there should be, because dense vegetation requires a water cycle with rainfall which means there will be surface water. – Philipp Jan 25 '15 at 19:27
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    An idea: reduce the gravity. I imagine that this would make for a more vertically-oriented forest -- taller trees, easier ascent and less hazardous descent. A rope bridge could hold a lot more mass. It would also take a lot less upper body strength to brachiate. Finally, it would make gliding a lot more practical. A primitive civilization with no real understanding of aerodynamics could plausibly produce gliding apparatus in imitation of the many gliding animals that might exist. – Thom Smith Jan 26 '15 at 20:45
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    Why do they need to travel and for how long? For example, if you're talking about a low-food value forest, then you're going to develop systems that allow you to go long distances, haul gear/supplies at low energy cost so you can forage and return with stuffs. Alternatively, if food (energy) is plentiful in a scavenge sense (berries, berries EVERYHWERE!) then hey, maybe you'd just run. Humans have stupid good endurance, just not top speed. – tanantish Jan 26 '15 at 23:22

12 Answers 12

up vote 12 down vote accepted

Cool question, and potentially a pretty cool world. :-) A few responses to your proposed planet and civilization, working towards questions of transportation:

Planetology of a forest world

There's a bit of a problem in your initial description of the planet:

Imagine a dense deciduous forest, with trees packed close together, stretching across the entire planet. The planet itself is Earth-like, and has Earth-like vegetation, trees, and forest creatures.

There's an inherent conflict here: An Earth-like planet, with "Earth-like vegetation, trees, and forest creatures", is not at all compatible with the concept of a more or less uniform, world-spanning forest of deciduous type. There's simply too much variation in climate, terrain elevation, weather patterns, and distribution of moisture to permit this kind of thing, ecologically speaking.

You could address this by postulating an incredibly dominant tree species (or stable group of collaborating species) for your forest - capable of establishing terminal forest conditions in everything from arid cold weather to hot humid areas, and managing elevation without difficulty. Alternatively, you could modify your world to reduce the tendency to climatic variation. I'm guessing that the former would be less difficult. You may want to do both.

(Of course, you could reduce the area of coverage of your forest, leaving parts of the world empty of the human habitation that depends on the forest for housing, food, and materials...)

Surface travel

So here's a world-spanning forest. Forested terrain isn't easy to traverse on foot unless there are known pathways through the trees. Pathways provide not only easy passage through undergrowth, but also are navigational aids: if you are traveling under a forest canopy, it's terribly easy to get lost unless you are following a trail. I think your serious consideration of tree-level bridges is a good acknowledgement of this... as a corollary, your stone-age/early iron age civilization isn't likely to have the resources to keep very many surface roads clear of forest regrowth. One perhaps significant question: are their areas of forest, similar to terminal pine forest in our world, that suppress undergrowth and leave a pleasant and easily traveled forest floor? I realize that you've specified deciduous trees, but I don't think the ecological dominance of pines is limited to conifers... These areas would make a large difference in traversability on foot.

Water transportation

One of the most important remaining topographical questions is, What are the bodies of water like?

For a lot of purposes, water transportation is the cheapest way to move people and goods over distances. Navigable creeks and streams can handle canoes or similar; larger rivers permit rafts and flat-bottomed boats; lakes (even narrow ones) will support open boats, rowboats, sailboats; larger lakes and seas give you larger vessels and kayaks.

Most of these vessels are attainable by stone-based technologies, and easier still if you have iron tools. Consider the birchbark canoe, the dugout, the curragh and kayak made of waterproofed skins stretched over frames of bent branches.

Large planks, for larger vessels, are not typically something we'd associate with stone technology: however, the easiest to build are riven (or "reeved") planks, which are excellent for clinker-built (aka "lapstrake" hulls; reeved planks are are apparently within reach of a determined stone-age woodworker.

Air transportation

When it comes to your interest in gliders, I tend to agree with ckersch's concerns about the difficulties of the initial leap in concept. I do not think the means of building gliders would be outside the reach of a patient and craftsmanlike stone + iron civilization

There are a couple of planetological tweaks that could make air travel more plausible:

  • Denser atmosphere makes for easier winged flight. Poul Anderson, in The Man Who Counts, made the atmosphere of the planet Diomedes quite thick in order to support the weight of the intelligent winged race his human characters were dealing with. (And because he was Poul Anderson, he also took care to describe the unfamiliar behavior of things like sound and wind in that dense atmosphere.)

  • Large flying animals would make ready mental models for flight on a human scale - the kind of thing that gliders would emulate. Could your world (especially with a heavier atmosphere) host a lot of large soaring birds/bats/pterosaurs/whatever? (Of course, if it supports enough of them, the temptation for people to ride them would be significant... ;-)

  • Nice answer. I like the flying creatures idea - and yes, the world could absolutely support them. – HDE 226868 Jan 25 '15 at 16:30
  • I'm accepting this because you gave me quite a few ideas for details of the setting, and because you made the world as a whole a lot more realistic (i.e. the issue with the one climate over the entire world). – HDE 226868 Jan 27 '15 at 0:16
  • Dude, now that's how it's done. – Starrdaark Jul 15 '17 at 20:46

Canals

When you imagine a giant forest, it's not possible to do so without imagining substantial rainfall. The forest creates its own rainfall pattern, ala the rainforest but a dry-climate forest tends to burn down or the trees die.

If you have a lot of rain, you will also have rivers. Whether it's a winding river like the amazon depends on the terrain, but there's going to be plenty of rivers and side-rivers. Boats will be the No. 1 mode of transport. If the humanoids have the time and resources for it, they can build canals and sluices to ferry themselves, livestock and other goods from their homes onto the main waterways.

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    Another benefit of canals is that you can move logs with them. On a tree-covered planet, there's probably going to be lots of forestry. – ckersch Jan 24 '15 at 23:14
  • What could they make the canals out of? Wood? Their iron technology isn't too advanced to make enough, nor would it be high-quality. – HDE 226868 Jan 25 '15 at 16:30
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    @HDE226868 they would dig them into the ground, not build them above. But when you want any canals above ground: large tree-trunks hollowed out, the connections filled with clay or tree resin. – Philipp Jan 25 '15 at 19:35
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    @HDE226868: Canals were first dug in prehistoric mesopotamia, not sure what level they were on, but I think you're thinking of aqueducts. You can also imagone that they dam and reroute the river in places, a feat beavers accomplish. – Abulafia Jan 25 '15 at 20:07

Gliders don't seem like a terribly feasible solution given how close together you describe the trees as being. Developing an effective glider also requires fairly advanced knowledge of aerodynamics. In our world, Da Vinci was the first to conceptualize them, and researchers are divided as to whether or not he understood that an airfoil was required.

Primitive gliders are also large and heavy. Dragging one up a tree, even if it could fold, would be difficult. Developing strong rigid folding mechanisms might also be beyond the abilities of a paleolithic society.

The first thing that would probably be developed is better rope. If effective rope is what's holding people back from building effective rope bridges, it will be the easiest advance for people to develop. Following rope, if the trees are close enough and tall enough to make ground transportation impractical, ziplines might be an effective way to branch out in terms of transportation. They could connect tall trees across moderate distances, with multiple lines connected by ladders allowing people to make long journeys.

Another major source of transportation could be animals. Earth forests have creatures like buffalo and deer, which are more than capable of navigating around trees. Domesticating such animals would provide a way of moving heavy things about, and also give your forest people a source of food.

  • Any idea what the rope could be made of? Would vines be feasible, or would hemp fiber be a better choice? – HDE 226868 Jan 25 '15 at 16:28
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    Lots of plants are feasible for making rope, so it would mostly be dependent on what's available. The main criteria is that they posses long fibers that don't break when bent. Red cedar bark, hemp, jute, raffia palm, bamboo and rice straw are all examples of possible materials. – ckersch Jan 25 '15 at 17:13
  • Another problem with gliders -- takeoff. Unless there's some kind of slingshot to give it significant forward speed, the trees had better be awfully high to allow a glider dropped from a tree to gain enough speed to pull up and keep from crashing in the ground - ideally the slingshot would give it enough forward speed to let it climb above the treetops. Even if that problem is solved, tree to tree transportation seems like it would be very difficult (ignoring the question of how to land it) since the glider would lose altitude unless it could find a suitable updraft. – Johnny Jan 26 '15 at 8:07
  • The ancient Inca and modern Peruvians make simple suspension bridges out of grass. Yes, whatever grass was around. NOVA did a special on it. – Schwern Jan 26 '15 at 19:55

Okay, you are going to hate me for this, but I am going to say it:

Burn the forest. Burn it down

It is one of the things we, humans did in Quaternary to Earth forests.

Fun fact: Great Britain used to be one big forest in some day in history.

It will allow you:

  • Start the agriculture revolution and provide food for more people
  • Build roads
  • Dominate the planet

EDIT: Burning down my house? Did I go mad?

No, not at all.

First, the Stone Age in the title caused me thinking that the population of the humanoids is really low.

So, basically, there have to be big unhabited areas - perfect spot to burn them down. Obviously this strategy has some downfalls, but, I am in anti-hippie mode. So stop hugging the trees and burn them :)

EDIT 2: But you would not burn down your house, would you?

No, I would not burn down my own home. And I do not expect the tree people do the same. I am just expecting them to provide some space for themselves.

See this quickly drawn picture: enter image description here

Some facts:

  • If you live off the trees and jungle, you are very low in population (see native people from Brazilian rain-forest as example)
  • So there are going to be HUGE places completely uninhabited.
  • If you want bigger civilization, you need to feed it.
  • To feed it, you need to have fields (= agriculture revolution)
  • To have the fields, you have to have free land
  • And best way of getting free land is to burn the trees down
  • I won't hate you because it's a really brilliant idea. I hadn't thought of it. The only reason I don't think it's a good fit for this civilization is that it would involve burning down their homes and all traces of their former lives. It would have to take something drastic to force them to do that. I also think that Arthur Dent might be against the idea. :-) – HDE 226868 Jan 24 '15 at 21:39
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    @HDE226868: Are you saying it takes something drastic to force humans to mess up the place they live in and eradicate what sustains them? I'd say it comes quite naturally to us – Abulafia Jan 24 '15 at 22:34
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    @Abulafia Grim laugh. Perhaps, but burning down the trees has a bigger short-term impact than global warming. Burning your house down is a lot more immediate and in-your-face than waiting for temperatures to rise. – HDE 226868 Jan 24 '15 at 22:38
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    see my edit. Basically, the title made me think that population number and density israther low – Pavel Janicek Jan 25 '15 at 7:15
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    Anyway, you are talking about a society/culture that is used to living off the forests (and organized around that fact). Then that society would decide to burn the forests without knowing anything about agriculture or the alternative lifestyles they could develop... Not the wisest of ideas. Makes all sense as if all of the London population suddenly decided to burn the city and emigrate to Antartica, just to find out if they are better off with the exchange. – SJuan76 Jan 25 '15 at 18:59

Domesticated Giant Spiders! Big as a horse but with more legs to make them much more stable on uneven ground. Their webbing could provide the "better rope" that ckersch is looking for and their ability to climb walls makes them good for vertical as well as horizontal travel.

Any form of transportation needs to deal with the naturally uneven terrain found in a forest. Travel within settlements and between nearby ones is going to be on foot, with a mix of man-hauling and pack animals for moving cargo. Strong beasts of burden such as oxen or horses tend to be plains-dwellers; in a world-spanning forest, your pack animals are likely to be analogs to the dog or llama, or perhaps something deer-like. The lack of level, open terrain means that animal-drawn vehicles are unlikely to develop, with the possible exception of sledges used for hauling heavy loads (such as a stone monument to a local ruler) over short distances.

For long-distance travel, the main form of transportation is going to be boats. A world-spanning forest means plenty of rainfall and a well-developed river network. People may build canals between different drainage basins, but without draft animals and large-scale metalworking, even a short canal is a major undertaking. With stone-age technology, the majority of vessels are likely to be canoes and rafts.

Road networks are likely to be local rather than long-distance, leading between nearby settlements or to the nearest major river. Counterintuitively, roads are unlikely to follow the course of rivers: the abundant water and the break in the forest canopy provided by the river means that the undergrowth will be much thicker along river banks than anywhere else.

Trying to operate a glider in a forest would be a disaster. With the materials available, you're looking at something similar to Otto Lilienthal's early gliders, only heavier because you're using skins rather than fabric. Figure a wingspan of 6 to 10 meters, a weight of 30 kg, and a glide ratio of around 5. You'll have trouble finding gaps in the forest large enough to fly through, you'll be essentially unable to maneuver around unexpected hazards (such as a deer in your landing zone), and with the forest blocking the updrafts that a glider relies on for distance, you'll be unable to travel more than a hundred meters or so at a time.

Airships! If you had a readily available natural source of lighter-than-air gas (vent in the earth or a swamp that gave off gas), you could skin yourself some beasts, sew up a big balloon, fill it with gas and build yourself a sky-barge! You'd have no easy way of powering it but you could pull it along with ropes as was done with early canal boats. Would take some ingenuity, but definitely feasible.

  • Creative. This could help me bring back the "aerial" theme. – HDE 226868 Jan 26 '15 at 15:15
  • I like this idea a lot. If the balloons are sufficiently big, you could imagine that they could be pulled by teams of tenders who could take turns swinging on the guide ropes. You could move a lot of people and material pretty long distances this way at a fairly low energy cost as long as you don't mind it being slow. Balloons would also make gliders much more feasible. They can be used as elevator launch platforms by floating up to high elevations and then being winched back down for re-use. – Jenn Jan 26 '15 at 19:18

If the trees are as large and close together as you say then walking from one tree to another might be a pretty easy thing. The branches should overlap a bit. There will also likely be vines for swinging between.

If the humanoids evolved on the planet quite likely they would have evolved long claws to help climb the trees. (Chewbacca's home world is full of very large trees, some forest so tall that most don't ever see the floor, nor want to, that's where really dangerous stuff lives...)

I also think it's likely they could have flaps of skin like flying squirrels to glide between boles, if there it enough room to bother with. Or maybe the clothes they wear will double as a glide?

The thing is, if what they have is trees, what can be made from trees, and found on the forest floor, what do they have to trade that can't be carried? What are they trading that needs to move? Trade is the main reason for the need of larger modes of transport. Quite likely on a world like that there would be some large animals, maybe some birds large enough to fly a passenger or two and maybe some goods.

There might also be large arboreal species that could double as a 'pack mule' carrying things from tree to tree.

You will of course always have rivers, otherwise you are stuck with dirigible's since the clearing of enough space to make a runway would be very prohibitive .

Forgot this was stone age...

For square mile type of distances I honestly don't think you'd find any real technology/transport evolution unless there's a really good reason to travel fast - a square mile, corner to corner, will take you less than an hour to traverse at human speeds we do 3mph as a walk as it is. Drop to half of that speed for broken terrain perhaps? That's still not a long time.

Speculating from this then - and since there's no value in going down to ground level for personal transport (cargo haulage is a new issue) so the tech innovation will be at treetop/village level where people will begin to map out the best/least congested treetop routes. Those will be bound with rope supports/handhelds to improve speed of movement, and also would end up being curated (branches sliced and diced to keep them clean and clear). If you have sufficient duration of time horizon, you could also get into people curating superhighways via basic topiary-type setups so you'd train the upper branches to entwine and create your roads.

For cargo haulage - personal packs/attachments would be something of note - I'd wager even at stone age level (and definitely moving forwards) you'd get better load-carrying techniques. things would be strapped to the body and weight would be split evenly to keep mobility up, so it'd feed into a general look/feel.

If you get past stone age, and for those abovementioned highways, your mass/speedy transit could be in the form of ziplines since you'll already have the clearways aboveground and well.. ziplines! :D

This will be a short answer, but I can't shake of my mind this idea:

Velociraptor Riders.

Image a world that some Dinos never went extinct. Imagine your tree-people taming a rather large raptor-like dino and using it like a chocobo. Heck, those beasts can even be used as "warhorses".

They can be bred for mounts and for food (Raptor Eggs, yummy!), are agile enough to dash around the woods, even on hard terrain, and can be really nasty guard dogs.

Also, your trees are really close to each other. Using trunks as bridges instead of ropes bridges would be rather easy.

Roads

Unless I'm missing something in this question, why wouldn't regular ol' boring surface roads develop? There are plenty of roads through thick forests here on Earth. The Mayans and Aztecs even built them through dense rain forests. If the forest is similar to Earth's Redwood forests, the tall trees will block out a lot of the sun making the surface easier, not harder, to build road through compared to 'normal' Earth forests.

What is the purpose of this transport? If it is just for moving about, why would they need vehicles at all? What cargo would they be transporting significant distance which wouldn't just be carried in a backpack?

The large size of the trees (big enough for villages to be up in the canopy instead of on the ground) indicates significant distance between the trees, with plenty of open space for ground transport.

Transporting lumber (logs for construction perhaps) would probably be done simply by hauling along the ground for short distances or floating down rivers for longer distance. Dragging the logs might using ropes and crude pulleys in the above branches to lighten big loads or get over rough terrain, as I would imagine their knowledge of rigging would be fairly advanced living up in the trees. Split logs could even form basic wooden tracks/causeways along the ground if needed to facilitate moving heavy loads like stone.

It is not hard to get to constructed rafts and more advanced designs once people start floating things down the river. With large trees, one could even conceive of rafts of dugout canoes carrying considerable cargo.

But aside from moving heavy cargo, why would anyone go down to the ground if they live up in the trees? Climbing up and down huge trees takes a lot of energy - it is probably far more efficient to just go from tree to tree.

My first thought would be something akin to a flying squirrel suit - very thin split leather stretched between the limbs to aid in jumping branch to branch - but that wouldn't be very plausible (though a fun idea, humans are too heavy for that to be much more than a panic desperation in case of falling, and still probably isn't worth the weight and clumsiness of always wearing it). A more likely tool would be a grapple hook on a long rope - toss it over to the next tree and swing over. Some metalworking should allow a release mechanism on the grapple so a small control line could be used to disengage the mechanism and not need to worry about climbing all the way up to it for retrieval.

More common pathways might have a set of swinging ropes - fixed at common places for people to swing back and forth at will. Upgrade that a bit to rope bridges and you have most travel well covered. The most heavily traveled pathways would likely use something akin to the root bridges of Cherrapunji. Over the course of many years, they use hollowed out logs to direct secondary roots (which grow higher up the trunk of the tree) to grow across the river until they eventually take root in the other side, thus growing a bridge. After a couple decades, it is strong enough to take considerable foot traffic.

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