Area denial organism for pre-industrial human beings on Earth

Question

It has occurred to me that the human species has had it lucky. Homo Sapiens evolved in Africa, and spread to most of the world with relatively primitive technology. The last land settled by humans was New Zealand, settled by polynesians around 750 years ago.

There are places that humans can't go, of course. Antarctica is too cold and too far from anywhere, and humans can't survive long-term in the sea. However, I can't help thinking that we've had a lot of luck that there haven't been animals, plants or micro-organisms that could have denied us access to an entire continent that was otherwise hospitable.

So, my question is, What sort of biological threat (if any) could have prevented humans from successfully colonising an entire continent before the start of the industrial era?

The threat would have to be endemic to the target continent (and not forming an obstacle to reaching the place), and not able to migrate to wherever humans may already be established. In effect, I'm asking answerers to design an organism that would keep humans from successfully colonising a continent. The closer this organism is to a real organism that is or was present upon a real continent, the better, and obviously the more well-described and plausible the organism, the better. I'd also prefer it if this organism was not a non-human tool-using species. As a bonus, the longer the threat could deny humans access to the chosen continent after the start of the industrial revolution, the better.

For the sake of the question, let's suppose that the 'denied' continent is either the Americas or Australia, given that those continents are fairly isolated from Eurasia/Africa from where humans originated. Let's say that the Industrial Era began circa 1750 AD.

Answer 1

Gorse is already pretty close to this. The plant itself is like a combination of wild blackberries, thistle, and hawthorn. If the climate is right (cool and damp) it will spread like those weeds, growing on even the thinnest coating of soil over rock, and will choke out other plants. Destroying gorse is a major undertaking and it will grow back from any fragment of missed root, but it is possible with primitive tools (axes, mattocks, and fire).

To make it truly deterrent, you need to add one thing: urushiol. This is the oil in poison ivy that makes 97% of humans allergic to contact with the plant. If gorse produced urushiol, even if it only grew in the littoral zone of a continent, it would make the place proof against human colonization until at least 19th century technology is developed.

Attempts to hack out "poison gorse" would be disabling to nearly everyone involved, and burning it would be worse, as the smoke carries the urushiol and inhaling it can be fatal (especially without 20th century or later medical technology).

Of course, there are other plants more toxic than poison ivy -- including some that will induce pain so intense that people have killed themselves to escape it after unknowingly using the leaves for intimate contact applications. Provide any hardy weed-like plant species (ideally ones with thorns like blackberry, gorse, etc.) with poisons like that and it will become an interdiction agent even for animals that naturally eat both gorse and poison ivy -- only animals specifically adapted to them can live in them or feed from them.

Answer 2

Other Hominid

Earth has a species that is extremely good at eliminating apex predators and other potential competition.

Humanity.

We've removed a number of very capable species from entire continents - from all of the Ice Age Megafauna to lions, and brown bears, and wolves. To the extent that these creatures exist in Europe and North America, it's because the locals have made an active effort to rescue them from the extinction that we initiated.

Humans are really good at removing "unwanted" competition.

So build a human analog.

Think carnivorous, pack hunting chimps or extremely aggressive flavor of gorilla.

Or perhaps look closer to home. The last common ancestor between chimps and humans is ~10 million years ago, and anatomically modern humans arose ~2 million years ago. So pick a hominid that existed between those times, and have them find the forbidden continent first.

Probably better to keep these hominid more animal-like than human-like for your purposes - it's not a forbidden continent if you can talk to the locals and work something out; they've got to kill and eat you before you have a chance to barter for your life.

Answer 3

This is a Frame Challenge

From the moment the invaders arrived, breathed our air, ate and drank, they were doomed. They were undone, destroyed, after all of man's weapons and devices had failed, by the tiniest creatures that God in his wisdom put upon this earth. By the toll of a billion deaths, man had earned his immunity, his right to survive among this planet's infinite organisms. And that right is ours against all challenges. For neither do men live nor die in vain. (War of the Worlds (2005))

The truth is that humanity is incredibly adept at overcoming problems. That's the entire point of evolution and becoming the pinnacle of that evolution: the remarkable engine of our existence has become one that both consciously and unconsciously fights off attackers and can dynamically adapt (at a cost...) to pretty much anything that's thrown at us.

Therefore, asking "what biological threat" is the wrong question. It doesn't matter if you pick a plant, or an animal, or a disease, or a roving band of aliens, or anything else. That's just the MacGuffin that lets you get on with your story. There's literally only one variable that can rationalize late colonization of a continent.

Time...

The earlier humanity steps foot on the continent the longer it has to learn to overcome whatever you've put in its path, which it will eventually do. Armor plated rhinoceros? Run it off a cliff. Particularly nasty disease? Isolation, change of diet, and time. A dangerous plant that could keep humanity from settling in? How'd life evolve there in the first place? We can analyze like this with everything. Humanity has already done this with everything. There isn't a biological-what that will stop colonization.

Your only choice is to find a reason to delay stepping foot on the continent in the first place. A method that requires industrialization to overcome.

How do we do that?

1. Using Zealandia as a basic reference, let's assume your world is entering a cooling period, so the ocean is receding fast — exposing a continent very late in your world's development. Technology required: dikes on a continental scale, engine-driven pumps, earth moving.

2. Using Australia as an example, let's make the continent a little smaller and push it a little further toward the pole. This would make the continent a lot harder to get to. However, the Age of Sail was able to overcome just about every ocean-borne obstacle in a very short period of time. Nevertheless, technology required: storm stabilization, off-shore ports/platforms, heating.

You know, part of the problem is that humanity has this insatiable curiosity — an absolute ache to know everything. People were traversing the oceans long before the Age of Sail, just not efficiently. Thus, your desire to deny access until after industrialization strains credulity. And offends the Vikings. I'm just sayin'...

3. The continent, for reasons I can't explain, is 100% surrounded by sheer cliffs, which would make landing anywhere disastrous. Make it basalt or some really hard rock that rationalizes glorious waterfalls from amazing heights that haven't worn down into traditional deltas. Technology required: elevating machinery, off-shore ports/platforms, steel cables.

Whatever the solution, it can't be biological as humanity has already proven its ability to overcome every biological problem: the blessing of being a problem-solving species with a great immune system (well done Mother Nature!). Your solution must be one that delays access to the continent in the first place. Of course, that does suggest one somewhat implausible biological-what...

4. A very large, particularly aggressive and fairly ubiquitous sea monster that keeps shipping to the shores until the invention of ironclads. Or perhaps something small, somewhat barnaclish that can chew through timber in a week, making open sea sailing... problematic.

And the reason that works is that there's no practical way to keep a region clear once cleared of the infesting whatever-it-is. The problem is so large that it can't be solved without a minimum of technology (steel hulls). Example of the problem: outer space.

Like I say, a MacGuffin to delay colonization.

Answer 4

A disease would do the trick. Humans show up, and they die. They'd soon avoid showing up. Especially somewhere remote like Australia with no known resources worth having.

Perhaps something like lethal dengue fever which kills people even today sometimes. A mosquito bites them and they're history while learning a whole new World of pain on the way out. The disease might be prevalent in marsupials and non lethal to them, but deadly to humans.

Answer 5

Lack of Iodine

Iodine deficiency is a chronic problem for many inland areas, but some areas have a more severe deficiency than others. There are regions in North America that tribes would pass through but not settle in. Not until there were ways to import seafood was it feasible.

This region is much more deficient.

The shores might feature settlements, in that case. Perhaps they are too vulnerable to flukes without the hinterland to back them up.

Answer 6

Incompatible essential amino acids

As far as we can tell, there was only one (successful) origin of life on Earth, and every living thing is related. That means that most of our biochemistry is compatible - you can eat pretty much anything and break it down into the kind of chemical building blocks your body needs.

But suppose you had a planet with two independent origins of life that then developed two incompatible biochemistries - for example, L and D chirality on amino acids. Any given species from L-origin would be nutrient-deficient if its only source of protein was D-origin plants and animals.

These two origins would have to have been separated for long enough for a robust and diverse flora and fauna to have evolved. On Earth, life likely began in the ocean, so we need a world with two oceanic basins completely separated by land from one another. In each basin, first unicellular and then multicellular life arose, each with its own biochemistry.

By the time multicellular life was moving onto land, the life emerging from each ocean was fundamentally incompatible with one another. If the strip of land separating the two oceans was narrow enough, it would likely develop a mixed flora and fauna of both L and D types, but the land on the "far side" of the oceans would be filled with species of almost entirely one type.

If humans originated from apes in the L region of the world, they could, with pre-industrial technology, cross the land separating the oceans and explore the far shores of the D region. But the farther they pushed into the D region, the less nutritious the endemic food would be. With pre-industrial knowledge of chemistry (amino acids were first described chemically in the 1930's), humans would likely not understand that everything that seemed perfectly edible - grains, nuts, fruits, game animals, all providing usable calories - was ultimately lacking in essential amino acids for them and that they were becoming malnourished. They could survive as explorers, bringing their own food with them, and they could even attempt colonies, planting the crops and bringing the domesticated animals from home. But their animals would become malnourished as well, any human children and domestic animal young would quickly exhibit metabolic diseases, and unless they were able to tend enough crops to produce all of their own dietary needs, without supplementing it from local food, while at the same time realizing the necessity to do so, ultimately their colonies would be doomed to fail.

Both exploration itself and supplying colonies would be made more difficult by the land barrier between the oceans. Even in the age of sail, it was preferable to sail around the tip of South America than to land in central America, cross the jungle on foot, and construct new ships on the shore of the other ocean. Similarly with Africa and the narrow distance by land between the Red Sea and the Mediterranean. The impetus for building the Suez Canal and Panama Canal was to make these journeys possible for ocean-going ships. In a world of completely separate oceans, where "sailing around" is not a possibility, you would need to establish a port with a ship-building capability on the nearest shore of the other ocean before extensive exploration and colonization was possible, and any such port would be largely dependent on local foods. If the land you had to cross was wider than the isthmus of Panama, that would pose considerable logistical difficulties.

Answer 7

Pathogenic Microbes

Because anything human can seek and locate, human can exterminate.

So it must be invisible.

A airborn bacteria with a life cycle relying on geographically-specific combinations of animals and\or plants, innocuous to them but very fast in infecting and killing humans.
The plants\animals involved should otherwise be relatively common outside the Zone, but not all together, making it close to impossible to realize is the presence of that specific combination that kills the people.
Bonus point for one involved species looking extremely similar to another completely unrelated species to increase confusion.

Once you are in the Zone, it's basically granted you get infected and die before you can reach the "other" side.

Infected humans are infective agents as well, but they show symptoms very fast and the infecting range is very limited so people just stay X days away from the Zone which is enough to keep people from infecting populated centers... which also keeps them from developing antibodies by mass-infection.

The pathogen should have a short life-span unable to survive and reproduce outsie the Zone, as well as making easy to contain the occasional infection before it becomes an epidemic. Which in turn makes extremely unlikely for natural resistance to occurr.

Answer 8

1. A poisonous variant of Kudzu Kudzu is an extremely fast growing vine that probably originated from either Japan or China. It can grow about a foot a day and will grow over literally anything. Also, its practically impossible to get rid of. It has extremely deep root systems which can't be pulled out and if you damage the root system I believe the roots just split into separate plants. In the parts of the world it has spread to, people regularly have to just cut it down with mowers or goats - at regular intervals. Even if a fictional variant was only half as poisonous as poison ivy, early man wouldn't be able to settle in such an area as keeping village and farm areas clear of the poisonous Kudzu would be a full time occupation and any paths they cut through it to get around would disappear in days. Its a fun example as it would be area denial by a plant that is closer to irritating then deadly. You could literally have a situation where the humans have gone to "war" with poisonous kudzu on a fairly narrow land bridge as humans were pushed off one continent by the spread of the irritating weed and the humans understand that if it gets passed the land bridge it will swamp the new continent as well.

2. Rampant bulldog ants There are several species of ants which are hazardous to live near, as once you annoy them, they will keep attacking you - and will often follow you great distances to continue the assault. You can kill a wolf that is stalking you but killing ants doesn't really stop an ant attack. You are literally forced to flee until the ants stop chasing. Ants usually keep each other in check as hives will start attacking each other when they collide or will split into smaller, fighting hives if one hive gets too big. Change this behaviour slightly and you have a continent awash with ant hives all over the place. Humans can travel there but its not safe to sleep in those lands - and its hard to colonize a place when you can't lie down at night.

3. T-Rex with no fire aversion. There is a reason that mammals didn't bother to evolve while there were large predators around. Include an intelligent predator which is larger then an elephant and most humans will takes their odds at just swimming into the ocean over playing with giants.

Answer 9

Parasites

The difficulty with (many) diseases is that they are very specific in their mode of attack, and co-evolve with the target population. That is, it's a little implausible that a spectacularly lethal to humans, wildly contagious virus would exist in a place where humans have never existed. (Never mind that such diseases tend to grow less lethal over time, because killing the host too quickly dries up the evolutionary swimming pool.)

However, more sophisticated organisms can be a bit more adaptable. Sure, maybe there's a flesh-eating bacteria that the local fauna has adapted to, and humans would not have a resistance in to, something like that, but don't sell our immune systems short. Next step up is a slightly more sophisticated organism like malaria (single-celled, but not a bacteria).

It's significant to note that, except for native Africans, who were somewhat more adapted, the inner continent of Africa was in fact largely unexplored until (and well into) "industrial times," because non-native settlers / explorers (and their non-native livestock) would eventually succumb to "tropical" diseases (malaria beingvthe big one). (This resistance to exploration was why Africa was called "The Dark Continent".) Parts of Central America were likewise resistant to settling, because of similar conditions.

However, this was all climate-based. While the jungles were considered impenetrable, the coasts of Africa were explored (and settled) by foreigners. It's quite plausible that regions of a continent could be uninhabitable by humans (other than those who had been there for a long time), but the whole thing? That's a tougher sell.

Anyway, aggressive parasites, which also affect other organisms to a lesser extent, seems like your best bet. Malaria, African Trypanosomiasis (sleeping sickness), filariasis (wait, that one's not lethal, it's just nightmare fuel), brain-eating amoeba...

Don't drink the water, don't go swimming, don't let the bugs bite you.

Answer 10

In the US in the 19th century, Locusts were a major problem for settlers. They could swarm in their billions, eating everything in their path. They were largely defeated by accident: the locusts bred on marsh and mud on riverbanks, and were probably largely defeated by the river trade which drained the marshes and cut down trees close to rivers for fuel.

Answer 11

Lack of vitamin C

A treatment for Scurvy was historically demonstrated in 1747, matching your year of 1750 almost exactly. The area could lack berries or citrus fruits, perhaps just not in significant amounts due to birds or rodents eating them. Once the solution is understood, implementing it and therefore spreading across the new continent becomes easy. Historically it did take a few decades to become universally accepted.

Answer 12

Most answers focus on things that would harm human settlers directly, but I think there's an easier way to get this effect. This continent is densely populated with a pest species roughly based on the Rasberry crazy ant. They build large underground colonies with multiple queens and are extremely resilient (we really don't have any good way to deal with them in modern day, if you try to kill them they just reproduce faster). They love to crawl into and swarm inside enclosed spaces, like appliances, wall cavities, or boxes.

The problem isn't that they attack the humans (their bite is relatively tame). The ants cause a problem because they go after the humans' stored food reserves. If you pick fresh crops and can cook and eat them fast enough then you'll be fine. But if you try to store that food, you'll wake up tomorrow to find that the ants have already eaten most of it. They're so small that they can get into the impossibly tight gap in a jar lid or the seam between planks in a crate. They leave live plants alone, but anything that is harvested or that falls to the ground will start seeing ant damage within hours.

You have no practical way to store food for more than a day or two. There's no way you can harvest and store enough food to survive through winter. Any seeds you collect this year will be long gone before you can plant them next year. If you try to put too much food in one place (like a cellar or silo), the ants will swarm it and start turning it into a new nest. They've spent millenia building underground tunnels that cover pretty much the entire continent, so they can surprise you anywhere, at any time, and in overwhelming numbers. The end result is a continent where you cannot stay long enough to explore in any meaningful way. You'd have to subsist solely on foraging. That might be possible in the fertile interior during certain months, but the coastal areas don't have much that's edible for humans so you won't survive long enough to make it that far.

An industrialized society would have some advantages because we have pest-proof food packing processes like vacuum sealing. The ants would present new problems, though, because they can swarm inside machines to the point where they break something, sometimes even shorting out an electrical circuit and causing a fire.

The first time you're able to really explore this continent is after you have boats propelled by mechanized motors. They will give you the power to navigate up the swift-flowing rivers and into the interior of the continent. You can survive ant-free as long as you stay on the water.

Answer 13

Tse-tse flies and sleeping sickness

There's a precedent for this:

In sub-Saharan Africa, the tsetse fly (genus Glossina) is a vector for Trypanosoma parasites, which cause African trypanosomiasis (sleeping sickness) in humans and nagana in livestock. This parasitic disease severely affects cattle, making it impossible to establish large-scale herding or farming in infested regions. The fly thrives in humid and savannah environments, creating vast zones where agricultural and pastoral activities are limited. If such a vector had evolved on a different continent, its role as a biological barrier could plausibly have denied humans access to the ecological benefits of domesticated livestock, stalling settlement and development in those regions before industrial advances enabled control of the disease.

Note that humans did somewhat overcome this, they do live there, so it would not be a working barrier to the peopling of other lands. However, the population density in the affected areas is low and human development is pretty bad, forget about science.

Answer 14

Shipworms - eg. Teredo Navalis

Why attack the humans when you can just eat their boats?

The Worms

According to Wikipedia on these little guys:

Teredo navalis is a very destructive pest of submerged timber. In the Baltic Sea, pine trees can become riddled with tunnels within 16 weeks of being in the water and oaks within 32 weeks, with whole trees 30 cm (12 in) in diameter being completely destroyed within a year. Ships' timbers are attacked, wrecks destroyed and sea defences damaged.

To suit the needs of your world, I suggest just making them breed a bit faster and have this continent be far away from the homeland. This combination gives the shipworms enough time to weaken the boat to the point that it sinks well before the intrepid explorers can make it back home.

The Expeditions

This leaves basically two options for each expedition.

Fast - they arrive, do some exploring, resupply, and leave. They don't notice the damage until it's too late. When they do notice the problem, they're almost entirely helpless to stop it. You can try to de-worm the ship, but most of them will be on the outside hull under the water line. The ship starts taking on water and eventually just sinks, if the weakened hull doesn't break apart in a storm first. Everyone dies quickly.

Slow - the arrive and take their time exploring more of the coast and maybe going up a few rivers. They do notice the damage either shortly before they leave or soon enough after that they can turn around. Many of the individual people survive the first week or two. Some people die off early, learning the hard way which berries are poisonous, which snakes and spiders are venomous, and which areas have large predators. On a timeline of years, any attempts to make another ship to sail home end up infested with worms and fail. On a timeline of decades they don't have the women to replace their population. If there are a few women in the group, they are also more likely to die in childbirth. Everyone dies eventually.

The History

In the ancient days, you get the classic /here be dragons/ on maps, because anyone who says they're going there never comes back. Even the more amazing navigational and logistical feats of Polynesian explorers would fall to these tiny worms.

In a more industrialized era, you start to get metal ships and people taking less stock in old folk tales. It was believed by Eratosthenes around 240 B.C. that the Earth is a sphere and he had a good estimate of its size. Eventually someone with a metal ship would try the long way around, and stumble on a pristine continent.

Answer 15

An ecosystem dependend on a mineral

There are two qustions to answer here. First why the organism(s) makes an area uninhabitable. Second why only this area is no-go.

So introduce a plant. Rapid growing like a weed. Destroying any human farm produce. Make it poisonous or at least non-edible. You may add animal species that feeds on the plant if you want, as long as those animals are a threat to humans (directly or as hosts for micro organisms) and/or not useful as a source of food or skin/fur/etc.

The reason this plant is contained to one continent is that it requires a specific mineral in the soil. This mineral could realistically be contained to an isolated geographical location. This way, even if explorers brought the plant-of-doom, it would not spread in the old world.

Answer 16

Fungi

There are exist a lot of fungi with many different properties.
Some fungi are poisonous and some have spores which can be bad for your health when you get them into your lungs.
Some fungi can even work as a huge network among an entire forest and can become several kilometers/miles large.

If you do some fancy combinations, you could get a usually harmless fungus which covers huge portions of a continent, but with a season where it distributes its spores (e.g. in autumn).
The wildlife could have adopted to the spores, but the spores could be harmful for humans, especially in big amounts.

One bonus effect: The continent could be habitable most time of the year, but not for a permanent stay.

Answer 17

https://en.wikipedia.org/wiki/Ragweed

It grows everywhere, and it protects local animals from human hunters- rewarding these for spreading it. Now- add a narcotics property, so that those tasked with "removing" it become addicted to the stuff- and some anti-touch contaminate similar to poison ivy. https://en.wikipedia.org/wiki/Poison_ivy

Touch it and you are addicted and rotting alive at the same time. Of course- when you have nature adapt to a smart organism (as it had time too in africa) you see all kinds of nasty things pop up - being propped up by the thinning out ecosystem.

The plant could spread a human version of cordyceps on destruction https://en.wikipedia.org/wiki/Cordyceps or life in a symbiosis with lethal organsim- like the https://en.wikipedia.org/wiki/Tarbagan_marmot who is a repository for the black death. Kill the plant, it alerts its friend, who then bites you infecting you with rabbies.

Answer 18

A mirrored continent

No, I'm not resorting to fantasy (completely), I mean molecules in organisms that could, depending on whether or not it is in the right side of the mirror, either heal you or kill you.

Some background:

In some organic molecules, they have the property of chirality, aka "handedness". This means they can be "right-handed" or "left-handed", just like your left hand and right hand. They behave in the same manner in most physical properties but interact with other chiral molecules differently. Think of it as trying to put on a left-handed baseball glove with your right hand, it just doesn't fit.

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Why does that matter?

Many, many organic molecules are chiral. In fact, a lot of your enzymes in your body is chiral, and can only process certain molecules in the correct handedness. If you're lucky, human body can ignore, have a different effect from, or correct the wrong handedness. In other cases, enzymes will process the molecule in a way that can kill you or even your unborn child.

However, let's imagine a scenario where there's a separate continent from the main Eurasia since early Earth, Ailartsua. It is itself a completely different origin of life, and all organism living in or nearby has adopted the opposite chirality from Eurasia, to the point where common sucrose in Ailartsua was (2S,3S,4R,5R,6S)-2-{[(2R,3R,4R,5S)-3,4-Dihydroxy-2,5-bis(hydroxymethyl)oxolan-2-yl]oxy}-6-(hydroxymethyl)oxane-3,4,5-triol instead of (2R,3R,4S,5S,6R)-2-{[(2S,3S,4S,5R)-3,4-Dihydroxy-2,5-bis(hydroxymethyl)oxolan-2-yl]oxy}-6-(hydroxymethyl)oxane-3,4,5-triol. (That's the chemistry way of saying it's a complete mirror image of the "real" sucrose)

For the sake of this question, let's assume there evolved a complete ecosystem in Ailartsua based on all of these mirror plane molecules, and Ailartsua was really, really far away from Eurasia. Early explorers finding Ailartsua will (painfully) discover that although there's many exotic fruits, animals, and fish throughout Ailartsua, they may survive for a short period, but will somehow deteriorate in health over time (kidney, liver, and possibly pancreas fail, among other possible damages to human body). Worse, any attempts on bringing offsprings may result in severe birth defects which will almost always lead to deaths or severely disabled children. It was therefore named "Ailartsua" by European colonists after how the continent has caused ail and the nearby islanders' name to the continent, "Artsua". The colonists in the 1600s found that in order to prevent the mysterious "Ailartsua syndrome", all food must rely on growing crops that originated in other continents (which consistently yields low in Ailartsua) and imports from overseas. Such burden was overwhelming and the settlements were greatly limited in size and population. Later, the British empire('s love for land down under) found another use of Ailartsua: as a sentence for prisoners who committed heavy crime, and shipped loads of them to the land down under. It more or less stayed like that until mid-1800s.

In our timeline, the existance of chirality was not discovered until 1802, and was only possible after physicists had an idea what plane polarized light and chemists became familiar at analyzing molecular structures through crystallization. This means Ailartsua is off-limits for large scale human settlements at least until early-1800s, when scientists can finally analyze what went wrong in Ailartsua and make practical solutions and/or large scale food freight became viable.

Side note: Food tracking became a concept much earlier in this world as what better poison could it be than a poison that looks the same, tastes the same and smells the same as genuine fruit?