Could an infectious disease (or diseases) wipe out the human race

Great Debates
1

I know that the Indians were wiped out (mostly) by a multitude of diseases hitting them at once which they had no immunity towards. Smallpox, plague, measles and probably various other diseases. I don’t recall what % died, but 90%+ sounds about accurate after the diseases hit.

The black death killed 30-50% of people. However today we understand how infectious diseases work. Even if we do not have a cure or even a treatment we can work to stop the spread via controlling/killing vectors, quarantines, etc. We would not be engaging in superstition to fight the illness we would be disinfecting doorknobs, not leaving the house, wearing respirators, quarantining the sick, etc.

So is it possible for a disease or a collection of diseases to wipe out the human race? Keep in mind even if 99% of us die that still leaves 70 million people, which is about the population in 2000 BC. And that was far bigger than the pre agriculture population of a few million. Even if 99.9% of us die that still leaves 7 million people, far more than were on earth after the Toba explosion when we were down to 10,000 or so.

I’m assuming nothing can really wipe us out except some astronomical phenomena like a giant meteor or gamma radiation or maybe a roaming black hole. Even so, within 100+ years even those things will not be fatal to all humans I’d assume either because we left the planet, or left the solar system, or can protect ourselves.

2

You’ve pretty much summed up the argument as best as I could put it: We have historical evidence of some truly horrific epidemics and yet none of them came anywhere near extinction level. Only a handful even show up as a net reduction in population during the times in which they struck.

However, two caveats:

  1. We’ve only faced “natural” diseases. Technology makes it possible to invent a disease that would not arise naturally,
  2. We’ve only faced “natural” dispersal mechanisms. Technology also give us ways to spread a disease much faster than anything we’ve seen before.

Still… I put disease very low on the list of things that might cause extinction.

3

While it is unlikely to create a complete extinction, there are two important things to remember. Even if there are 70/7 million people left, that doesn’t mean they’re close enough together to pool efforts for survival and rebuilding. And of those remaining people, a lot of them simply will not have the knowledge and skills to survive once the efforts of the remaining civilization are stripped away from them.

And yes, with technology it is possible to make an even better disease that has a much more realistic chance of wiping out all humans. Especially if the person intending to do so takes the time to research remote areas of human habitation and ensure the disease is released in those areas as well as populous regions.

4

Sure, but most species don’t die out just because of one single event. From what I recall, the ‘dinosaurs’ were generally on a long, slow decline before the big one hit which pushed many species over the edge. If something else had happened when the human race was down to a few thousand left it would have been curtains for us 70k or so years ago, after all. We got lucky and a second or third nasty event didn’t happen so we muddled through.

Basically, if we lost 99.9% of the human race we’d be pretty much at the edge. Civilization would probably start to collapse somewhere around 40-50% dead. Of those left in places like Europe or the US I’d guess most would die in the first couple of years from various things. Long term I doubt there would be very many survivors since it’s doubtful that the key people who still know how to do things without technology (like growing food or basic survival) would still be alive to teach the next generation. If, say, we also had other environmental collapses (due to, I don’t know, stay Global Warming or something like that) at the same time it could very well be the one two punch needed to finish us off as a species.

I seriously doubt that a natural or even a man made disease could have a 99.9% mortality rate, that’s just off the charts, but if it did I don’t think the fact that there would be a few million people world wide who survived the disease would necessarily mean much wrt the survival of the species.

5

7 million scattered randomly worldwide wouldn’t be enough to ensure survival, they’d just be too thin on the ground and most of them would never even meet.

But real diseases don’t work like that. The people who survive are either genetically resistant or they are living in regions that make the disease less efficient. Since genetic resistance runs in families, we’d generally expect that the people who survive will be fairly well concentrated in a few small areas. With that in mind, survival of the species becomes much more likely even at 99.9% mortality.

So long as a few groups of a few dozen manage to form up, the species will almost certainly continue. Sure, a lot of technology will be lost and civilisation will cease to exist, but humans will continue.

I don’t think the lack of knowledge would be the killer that most people make it out to be. The modern world has huge amounts of resources available, and any disease that can’t be fought or survived through deliberate quarantine will need to work very fast, within 12 months at the most.

The survivors are going to find themselves in a world with huge herds of domestic animals, massive seed reserves, entire cities full of metal, glass, cigarette lighters, solar panels and so forth. Even if all the canned food is gone, the amount of readily available food will be massive for decades after the event, as will the amount of other technology. Things like houses, solar panels and cigarette lighters will last for 40 or 50 years with no maintenance. Even allowing for an increase in predator number’s, decaying infrastucture etc, basic survival won’t be a problem for decades for anyone with the ability to cook or fire a gun.

And basic survival skills aren’t so thin in the ground even in the US that over the course of decades people won’t be able to work things out. Hunting remains a popular sport such that any group of 20 people will almost certainly contain at least one person who knows how to shoot a cow. Gardening will provide the same basic ability to grow crops. And of course in many other parts of the world the proportions of people who were raised on farm is much higher and the capacity for subsistence agriculture much, much higher.

So I really don’t think that survival is much of an issue. We have produced such a human-ideal world that it will take decades before basic survival will become much of a struggle at all, and the point where farming and hunting become essential, rather than simply a means of obtaining variety and luxuries will creep up gradually, such that the first generation born after the event won’t even notice the transition.

But I think that XT’s point can’t be understated. For the first 200 years humanity will be fairly fragile. With a few thousand groups of a couple of dozen people on every continent, many of the groups will die through random chance: fire, famine, cyclone, other plagues etc. just as they have throughout history. Any worldwide catastrophe that even prevents population growth will leave humanity on the knife-edge. It’s only after the population has increased and societies stabilised enough to permit dispersal into thousands of truly self-sustaining groups and contact between the groups that we’d be out of the woods.

But for my money, humanity would survive even 99.9% mortality.

6

One of the more likely causes of human extinction is a highly mutated, super resistant and rapidly transmissible 100% mortality virus. Either man-made or a stroke of natural bad luck, would take some time to start killing in the millions of numbers. Inability to deal with the enormous numbers of corpses would lead to many other disease processes and problems, shut downs of various human support endeavors (utilities, factories, medical, etc.).

Even a loss of 50 to 70% of worldwide population would likely render the remaining population at an unsustainable rate, with full extinction to come some years later, even after the virus may have burned out.

Rather an unpleasant end to a unique and versatile species.

7

Between 2.1 billion and 3.5 billion people remaining is not enough to sustain?

8

Typically though, viruses and bacteria are “trying” to find the sweet spot where they make their hosts sick enough to spread themselves via snot, sneezes, vomit, etc… but not so sick that they die before they can spread the disease.

Ebola doesn’t cut it, because it’s not that easy to get, although it is nearly that lethal without intense medical care. Measles is that transmissible, but not generally lethal. Same for influenza.

Anything to fit what Toastmaker is talking about would have to have a fairly unique profile- like a slow, highly contagious period without major symptoms, and then some kind of ramp-up to the lethal end. IANA doctor, but I’m not aware of any diseases that fit that profile.

9

No, I don’t think so, as odd as it sounds. Procreation rates would drop intentionally and for some very good reasons. Life in human clusters would revert back to a level of “civilization” not seen in many centuries and natural lifespans would start to drop.

Again, the full extinction would take many years given that the intact virus could be re-encountered at any time.

10

[QUOTE=bump]
Ebola doesn’t cut it, because it’s not that easy to get, although it is nearly that lethal without intense medical care. Measles is that transmissible, but not generally lethal. Same for influenza.
[/QUOTE]

The biggest pandemic on record was the Spanish Flu epidemic, so influenza is pretty lethal (even the run of the mill flu kills quite a few folks world wide every year). If anything was going to mutate to kill a large number of humans I’d put my money on influenza, though I’m not a biologist or epidemiologist nor do I play one on the SDMB so maybe I’m way off.

ETA: But it’s probably never going to be 99.9999% lethal.

11

No. luckily nothing even similar to that kind of virus has been encountered. In this hypothetical, it would most likely be either a serious mistake in the creation of a weaponized, man made virus. . . or alien in origin.

Again - this is interesting, but also truly hypothetical.

12

The nightmare scenario that I would consider would be something like an AIDS virus with the transmissiblity of small pox, such that there was a multi-year latency period between the time of infection and the onset of symptoms. So that basically by the time people started dying from it pretty much everyone was already infected.
Still even with 100% lethality this wouldn’t totally wipe out humanity. There are tribes in Asia and South America that are pretty much completely isolated from the rest of the modern world. If a plague wiped the rest of us out, chances are they would still be ok.

13

There’s a beneficial selection bias which hasn’t been brought up, which is that those who are most able to survive with minimal outside assistance are generally already living with minimal assistance, and those that couldn’t possibly survive on their own are living in contact with lots of other people. In other words, the pathogen is going to selectively kill those most unable to survive a catastrophe, while those most able to survive afterwards will most likely to survive the disease. This, it seems, will substantially increase humanity’s odds, because the survivors won’t be a random subset of the population, but will be the trappers, preppers, and Ted Kaczynski’s who can ride out the apocalypse with ease.

14

Ok, an intact virus that never goes away results in eventual extinction, presuming that the virus is 100% fatal and no immunity develops. But absent that billions of people won’t have that hard of a time. Initially there will be an abundance of existing technology and materials. Some remote populations may be stuck in a rather primitive lifestyle but remote educated people can get on boats and travel to major industrial centers and prepare for a future lacking a lot of technology if necessary. In the worst case the population may continue to decline from starvation, disease, and fighting, but it has a long way to go before it drops below a level that humans have already survived in the past.

15

What is odd is that, historically, humans have been pretty resistent to the social effects of mass pandemics - all things considered.

The Black Death killed something like 1/3 to 3/4 (depending on where you were) of the population of Europe in a relatively short time in the 14th century, and it was very traumatic - but society did not collapse, or even change very much, considering.

Reading accounts of the time, it certainly is mentioned that the end of the world was feared, but as soon as it had passed on, things continued more or less as they had, though there were long-term impacts - for example, the Hundred Years’ War just lumbered on.

According to medieval historian Philip Daileader in 2007:

I’m guessing that humanity and human society is pretty resilient in the face of mass mortality pandemics.

16

Probably so. I imagine a lot of it has to do with the difference of some kind of “The Stand” style pandemic where 99% of the human race dies off within a couple of weeks or some absurdly short time frame.

If we were to lose half the population over a 4 year period, it would be somewhat gradual- by way of example, if there were 100 people in your department at work, that’s like losing 1 person a month and one extra person each year. Which would be a blow, but slow enough for your department, and the company as a whole to adjust.

17

I guess so. Logically, there has to be some level of stress that would comprehensively ‘break’ society.

A possible example could the Smallpox pandemics that swept over the Americas - in North America, they may have ‘broken’ some of the Aboriginal nations, well ahead of the actual appearance of European colonialists. Esitmates are for morality up to 90% in some places, over a fairly short time. But evidence is scanty, and those societies were very different from ours - moreso even than Medieval.

18

The difference, I think, is how inter-dependent society is today, especially on logistics, and also how specialized we have all become. During the middle ages or before you just didn’t have the dependency on outside trade or just in time logistics like we do in most modern societies, and you didn’t have the hyper-specialization that we take for granted today. Back then if you wanted a pair of shoes or a shirt you probably made it yourself, or at most had one of your surfs make it, or you traded the guy or gal who could make the shoes directly for a pig or maybe some wheat or something. It’s not like that anymore in much of the world, so I think if a collapse happened it would be much, much worse…and I think a collapse would happen at lower levels of population decrease. And once it started to happen there would be a cascade effect through much of the industrialized world since even countries today are specialized into highly vertical services, products or resources they supply and wouldn’t be in a good position for a rapid shock to the entire system

The folks who would have the best chance of surviving are those who aren’t industrialized or dependent on modern systems at all…and like I said, all it would take to push some of them over the edge is another shock to the system. Global Warming will probably do in a lot of the folks left, since even if we stopped producing CO2 tomorrow in a world wide collapse it’s still building up and will take a long time to dissipate. Also, in our death throes we’ll probably do a lot of collective additional damage.

19

While modern society is very different from medieval, I think this is way overstating the case.

Medieval society certainly did have things like craft specialization by the 14th century (note the existence of wealthy and powerful “craft guilds” - of which my own, the Law Society of Upper Canada, is a sort of remnant. :smiley: ). In fact, I recently saw a program in which one of the subjects was a will made by a wealthy shoemaker in the face of the Black Death (apparently, one of many such to have survived - lots of people anticipated their own deaths).

On the contrary, I think the actual evidence demonstrates the opposite - that civilizations lacking more “modern” tech are more fragile, more prone to systemic collapse in the face of disaster. Witness the fact that such collapses appear to have been pretty common in precolumbian America, where the Mayans and the Mississippians both collapsed without any help from Europe.

Cahokia used to be more populous than any city in North America prior to the 1780s or so - and it vanished utterly. Even the Dark Ages in Europe did not lead to such complete vanishing of civilizations and cities; and since the Dark Ages, I don’t think there has ever been any question of civilizatons or cities being completely abandoned, despite wars and disasters.

The more primitive the technology of the group, the more fragile that group tends to be - the peoples who vanished completely under colonial rule tended to be the hunter-gatherers, like the aboriginal Tazmanians or Beothuks in Newfoundland. In contrast, the agricultural Iroquouis are still very much here, as are the Maya and Mexica. Even being bombed and nuked did not wipe out the Japanese in WW2 - it wasn’t long before they were back in the city-making business.

I contend that the higher the tech of the group, the greater the resiliance of society - not the reverse. At least, going by historical evidence.

This doesn’t mean that modern industrialized humanity cannot wipe itself out - only that it is likely to require more pressure to do so, and that any such pressure would likely do in the remnaining non-idustrialized societies first. Historically, they are more fragile.

20

A high infection rate virus that caused infertility would do it if we didn’t catch it early enough.