That or zombies or course.
Worse yet - both. Zombies spreading infertility-causing STDs :eek:
I have little doubt that we could engineer a disease that could destroy us. I think it’s pretty unlikely that one would naturally evolve, but there’s no reason to expect that an engineered disease couldn’t be 100% lethal and incredibly communicable.
We’re all talking about 99.99% or other small fractions, which is all well and good if there’s a fraction that survives, but a disease could certainly leave no survivors. Even those remote tribes that live with little contact with the outside world would be vulnerable to something with an animal reservoir, or spores that spread through the atmosphere.
Absent a 100% lethal disease, I think a sufficiently bad pandemic could lead to enough of a societal breakdown that a massive nuclear war breaks out, which could seal the deal.
I don’t think this is in any way as easy as you make it seem. There’s no animal that lives in every part of the world, and getting every person is a last mile problem, where you will spend more and more effort infecting a decreasing amount of people. Airborne pathogens generally can’t survive extremely cold environments as well, while humans can do so pretty easily. A bioweapon could no doubt be much worse than existing pathogens (and the nuclear war aspect is an interesting take), but I doubt it could get everyone.
I think saying things like “a disease could certainly leave no survivors” underestimates the wealth of human diversity. At any given moment, there are people in bunkers, on deepsea oil platforms, on antarctic expeditions, deep in caves, in submarines, in space, etc. We tend to extrapolate from our current environments, and most of us are sitting in front of computers in suburban or urban environments. But there are plenty of people pushing the boundaries of human experience.
It would have to be a disease that is extremely contagious (i.e., airborne), extremely persistent (lasts on surfaces a long time,) and has an extremely high degree of lethality. Also, it can’t lead to immunity, because then some survivors who caught it once but survived, wouldn’t die from it the 2nd time.
I don’t know if any disease meets all of those criteria. But then again, that might be where the genetic engineering comes in.
I’m not suggesting that it’s easy, just that there’s no fundamental obstacle. It’s probably beyond our reach right now, but I don’t think that will last for many more decades.
Anthrax spores can, so we know it’s possible. And I would argue that humans can’t really survive in cold environments very well at all. They can build small warm environments inside otherwise cold ones, and survive in those. We really are pretty fragile creatures.
Obviously, we’re both speculating here, but I don’t think we can reason about the limits on genetically engineered organisms from our (still pretty limited) knowledge of evolved organisms. It’s like arguing that there couldn’t possibly be such a thing as rifles because the fastest anyone can throw something is ~100 miles an hour. Or reasoning that we’ll never make it to the moon because there’s no bird that can fly there. In the macro world, engineering hasn’t simply exceeded the limits of evolved organisms—it’s completely destroyed them. I don’t see a reason to think that we won’t be able to do the same in the micro world.
[QUOTE=Malthus]
While modern society is very different from medieval, I think this is way overstating the case.
[/QUOTE]
I think I was understating it, to be honest. 
The point is they weren’t completely dependent on outside materials or manufacturing. Sure, there were specialized guilds for some things, but most of what they used was locally manufactured (often manufactured either by themselves or in their village or maybe in their province).
In today’s society, however, you’d be hard pressed to find many places where all of the essentials such as power, food, water, manufactured goods and parts are produced or even could be produced locally in the event of a break down. Our entire system relies on logistics, and if that breaks down, as it surly would in the even of 40 or 50% population loss it would cause a ripple effect that would most likely finish a large percentage of the survivors. At 40-50% we’d probably recover, eventually, but the breakdown would cause another 10% lose at least, maybe more. At 99.999% though? I would guess that most people in industrialized countries such as the US would be dead within a decade or so except maybe in some very isolated places where through luck or whatever you have folks who know how to do things like basic survival AND are lucky enough not to get sick or injured.
The reason for the collapse of many pre-Columbian Mesoamerican civilizations was the exhaustion of a key resource, often water. Modern tech based countries are very resilient to some disasters that would cause the collapse of pre-tech civilizations (for instance, if we had a civilization based solely in California or Arizona it would already have collapsed due to water depletion). True, ‘modern’ societies aren’t as susceptible to a single resource collapse, but I think they ARE more susceptible to a collapse due to a major disruption in logistics, which we are almost completely dependent on. And at the levels of death the OP is talking about it would hit tech based and logistics dependent societies even harder, and we are less prepared for it since we are all basically specialists these days. Even farmers are specialists (and we don’t have many of those, since the US has shifted much of our work force out of the agricultural sectors for decades).
I disagree with this as an across the board assertion, but since we don’t really have much historical evidence for a high tech society incurring these levels of rapid population decline it’s hard to really say. I think that you are right about high tech societies being more resistant to some types of resource collapse but I think you are over estimating how resilient they are to a logistics and transportation disruption on the order the OP is talking about.
…and still, Earth abides.
…a far sadder and poorer world without humans on it.
Madagascar will be safe once they close their port.
Not completely dependant, no. But far more like today’s society than otherwise. Many regions were quite dependent on supplies from outside - thinking again about the Hundred Years’ War, a key fact in that conflict was the relative interdependence, in the 14th century, of England (which produced wool) and Flanders (nominally a vassal of the French, which wove wool into cloth).
If 99.999% of the population suddenly died, the survivors would probably be able to live for at least a decade on the stuff just left lying around. How long would a single intact grain silo last someone? There would be generators, gas stations, canned food - all sorts of stuff, and no owners.
No-one knows for sure. Every decade, a different theory. Probably some combination of interrelated factors - increased warfare, drought, environmental degredation, etc.
Have any societies so far collapsed because of disruption of logistics?
Strikes me that, if our societies were so fragile this way, it ought to have happened - for example, in WW2, when all sides tried theor best, using bombs, sabotage, and whatever else they could think of, to disrupt each other’s logistics - and found that even massive bombing campaigns didn’t do the trick.
A die-off of 99.999% would without a doubt change society beyond recognition, but there would be a long, long “grace period” before the survivors would have to learn basic blacksmithery and farm creation. Namely, because a die-off of that magnitude would leave the survivors as inheritors of lots of useful stuff already in existence. The main skill will be in preserving, collecting and using what is already available - with only 1 in 100,000 left alive, there will be no competition for resources. The race would be to preserve those resorces from decay and destruction.
I’m just looking at historical examples. There are many examples of hunter-gatherers dissappearing totally due to stresses of various sorts, and few to none of higher-tech societies dissapearing totally (the Maya did not, of course, “dissapear”). Therefore, the logical conclusion is that hunter-gatherers are more vulnerable to dissapearing.
The most important part of that statement is your parenthetical phrase, (mostly). Relatively few survived, but survive they did, and in actual large numbers. It takes an awful lot to wipe out humanity.
The Master spoke about this, to some extent:
…many Americans are as vulnerable to smallpox as Native Americans were at the time of first European contact.
We may have already engineered an event that could bring about some of the scenrios being discussed here. Imagine smallpox being unleashed on the world today, where instead of just the America’s being vulnerable, all lands are. I think there is a non-zero chance of some existing scientific stock finding it’s way out, or someone discovering an artifact that could bring it back to an unprepared world.
I am not saying there is a big chance of this occuring, mind you. I dont think it would wipe out humanity, but could certainly trim our numbers a bit, at least until enough vaccine is manufactured, and delivered.