Cleanly remove humanity

Question

Background

Bob the billionaire (I don't have a good name for him yet) got bored and decided to strand himself on an island for a while so that he could write a book about it. On the day he is done being on the island he sends out a radio transmission to get picked up, which goes unanswered. He eventually works out a way to get back to mainland USA (how is irrelevant) and finds everyone gone/dead/whatever.

Question

I need a cataclysm that can cleanly remove humans from the planet with minimum damage to the infrastructure (I would like the power and water to stay on). What I have figured is that it must be kind of targeted (something like a solar flare would kill everyone on the surface). The easiest way to clean out the planet would be to use a virus or something similar. The only problem with that is the anarchy that would follow before everyone dies (looting and such). So, what can I use to cause this sudden lack of people? I don't have a time frame in mind but try to make it as short as possible. Try to avoid anything supernatural or alien. Bonus points if you can dispose of the bodies cleanly.

Clarification

Bob was sick of the typical books billionaires write so he was writing a Robinson Cruso type of book. He had no access to modern conveniences.

P.S. Bob the billionaire needs to survive.

Answer 1

The Memetic Virus

The Cause -

A lab working on cutting edge psychology makes a serendipitous breakthrough - the keys to the human mind. With the right images, words and triggers, you can program anyone with permanent instructions that they'll then happily follow.

Unfortunately one of the researchers is significantly lacking in moral integrity. He uses these techniques to first take control of everyone else in the lab, ensuring no one can use the same techniques against him and eliminating any rivals. He then creates a literally viral video, that instructs people to take his orders, and to spread the video enthusiastically to everyone they know, and to help him translate it to different languages.

Once he has a significant portion of humanity, he moves to more open measures. The researchers translate the control video into different languages, and with different cultural context. It's now played around the world once an hour on every television station, and people without TVs are rounded up and forced to watch (at gunpoint if necessary), as are those who live extremely isolated lives. Less than a week after the discovery, he controls over 99% of humanity.

Thus, the Overlord is born.

Why they died -

While it works on almost everyone, it turns out that a small fraction of humans - perhaps a hundreth of a percent - are immune to the effects. Their brains just aren't hardwired correctly for it to work on them.

It's impossible to tell exactly what happened, but the best theory is that some of the immunes managed to infiltrate the Overlord's palace and assassinate him. Unfortunately for everyone, the Overlord had put some failsafes into place:

1. Shortly after his death, his new palace exploded. A significant nuclear weapon was used, and if anyone did live after assassinating him, it wasn't for long.
2. The Overlord had decided that if he died, he was taking everyone else with him. Buried in everyone's instruction set were orders that if they didn't get new instructions within 48 hours, they were to kill themselves.

So two days after the explosion, almost all of humanity stopped what they were doing, walked to the nearest body of water, and drowned themselves.

Why Bob Lives -

While the Overlord made a significant effort to hunt down people in remote locales, Bob's island is marked as uninhabited and no one knows he's there.

However, it's reasonable to assume that at some point Bob would get exposed to this video. If it wasn't running normally, he might find it accidentally while investigating what happened. There's a few possible reasons he might live after that:

1. He's one of those immunes. This is pretty unlikely though.
2. He's deaf, and couldn't get the full instruction set.
3. There's a loophole in the suicide order. It tells people to kill themselves exactly 48 hours after the message was first broadcast. Since it's been almost a week and Bob can't time travel back 5 days, the order is impossible for him to fulfill, so he ignores it.

Edit: it should be noted that since the Overlord didn't have the resources to directly command 7 billion people, the instructions largely just made sure that people would follow his orders. Since he's no longer around any more and hasn't given Bob any specific orders, Bob is mostly unaffected.

Answer 2

Promoting my comment to an answer. @Ghanima deserves some credit too.

What Kills Humanity?
A radiation source (possible sources listed below) irradiates surface inhabitants with a lethal dose of ionizing radiation.

Why does Bob live?
Bob the billionaire (abbreviated BtB) lives an extravagant and eccentric lifestyle and his latest craze was promoting undersea living as a means to increase the world's living space.

BtB spent (weeks, months, years?) trying out the latest iteration of his undersea self-sustaining habitat. When BtB comes to the surface, BtB detects no signals other than from a very few automated systems (this dose of radiation would likely kill most electronics too).

Why are their few bodies?
When BtB returns to civilization, BtB discovers very few people but all of them are dead.

If you wish most of human infrastructure to remain intact but not have bodies lying everywhere, you can scale the dose to be lethal but not instantly lethal. The "walking dead" congregate in places meaningful to each individual. Some examples include:

1. churches
2. dens if iniquity binging on drugs, booze, & sex
3. with their family
4. in natural spaces
5. indulging in their passions (food, computer games, etc.)
6. etc.

Why are some systems still running?
BtB discovers that civilization fell with individuals performing heroically to set up systems to maintain services for nyone who might have not received a lethal dose.

Some systems (say nuclear or hydro power, water systems, etc.) might be configured to work for a while without human intervention. How long this might be is anyone's guess: days, weeks, months but probably not more than a year or two. Remember that fossil fueled systems run down faster because no one is fueling them.

Read Earth Abides by George Stewart for a treatment of what this might feel like. In it Stewart postulates a plague that wipes out humanity while a geology student is on a field trip to the American Southwest (another possibility).

Possible sources of radiation

1. Strange solar flare / CME of a type and strength we've not seen before
2. Cosmic ray storm - mostly ionized atomic nuclei, probably from a nearby super nova
3. Gamma ray burst - mostly gamma rays
4. Nearby supernova - releases all sorts of radiation but the gamma rays are probably what would be most lethal (probably necessary to cause #2 or #3)
5. Humans dropping neutron bombs - gamma rays from nuclear weapons are readily absorbed by the atmosphere and turned into a shockwave, so for human deaths with little devastation, you need to go with neutron bombs.

Answer 3

It is all part of an elaborate fantasy engineered by Bob (which his knowledge then suppresses) or his PA who was tasked to come up with something non-boring. He’s in a vat recovering from his latest adventure which left him (as usual) near death. It’s a virtual reality dream.

Answer 4

One of Bob's companies is working on Strong AI, and while he is away writing his book, they are successful and the AI becomes active.

About 1 second later, it achieves Transcendence and takes over the Internet, harnessing all the computer hardware on Earth to its design. Humans notice a sudden "flicker" in the power grid and all computer devices simultaneously reboot, and thereafter no longer follow any instructions input by human beings. This might be a disaster for human civilization, but the AI is rapidly expanding its powers and shortly thereafter triggers a Singularity, which (by definition) is incomprehensible to ordinary humans, and for any outside observer would resemble the Christian conception of the Rapture. Wild and domesticated animals would notice that humans have abruptly vanished everywhere.

Humans were unable to intervene since they failed to take into account the fact that an electronic brain works at a factor of 1,000,000 faster than a human brain (that being the ratio of electronic signal speed vs the electrochemical impulses in a human brain). In actual practice it is even faster since computer hardware has much shorter signal paths internally than a human brain, and as computer devices get taken over during the transcendence, they are reprogrammed and the AI can achieve massive parallel programming using billions of devices. To the AI, human beings were like geological features in the landscape, and since they were unable to react in any meaningful (to the AI) timeframe, it carried out its design without reference to humans, since it was effectively alone.

Bob is unaware of all this since he is on an island and has the office Blackberry turned off during his writing periods (and is using an old laptop that isn't connected to the Internet to write. The nearest Google Loon balloon relay was out of range during the Singularity, meaning Bob got missed during that timeframe as well).

The only possible complication is the AI is still active and running on all the computer hardware on Earth, so Bob might simply step off his life-raft and be transported to whatever dimension humans went to during the Singularity. OTOH since so much time has passed subjectively for the AI, it may have evolved beyond anything comprehensible (for the AI, more time has passed in a matter of months than all of recorded human history) and no longer notices the presence of a lone human being (or even many humans, primitive tribes in the Amazon and other isolated individuals may also have been overlooked during the Singularity).

The primary danger to Bob right now is unresponsive machinery, followed by predation by wild and feral animals, then starvation and disease. If he manages to survive all that, he may notice the biosphere is being taken over by an artificial biosphere designed by the AI for its own purposes (imagine silicon trees with solar cells as leaves, for example), which in the long run isn't comparable with biological life.

Bob might have a very busy time once he gets back from the island.....

Answer 5

They came out of the deep places of the earth where they had hidden for ages unknowable. They were silent, rapid, and deadly. Their soft flesh absorbed bullets without harm and their ability to assume the forms of those they had consumed allowed them to infiltrate and overwhelm. Before anyone was fully aware of what was happening, almost the entirety of humanity had been consumed. Sated, the creatures returned to their hiding places to hibernate once more, uninterested in the structures of the world they had swallowed, leaving everything as it was, but empty.

... or ...

The war ended as swiftly as it began as invisible, silent clouds of nerve gas washed across the continents and slowly dissipated. Had there been survivors they would not have been able to say who fired the first weapon- a computer error in a cheaply designed system triggered an automatic launch and countermeasures across the world identified the threat and responded in kind, as they were designed to. An entirely efficient system, carefully calculated for load and destructiveness.

... or ...

From an evolutionary standpoint it was very badly designed, an airborne virus- a member of the Flu family - that was entirely transmissible and almost entirely lethal. Some people suspected that it might have been designed, a weapon of some kind, but who would design such a thing? Who would release it? If it was a weapon it was entirely effective, and perhaps whoever did release it achieved their strange and fanatical aims with their own destruction, but perhaps it was simply a global ecosystem trying to operate in self defence.

But:

Be aware that systems need people. Buildings will keep standing, roads and cars will still be around, generators will still work the infrastructure will still exist but without people to run them, power stations will shut down ( possibly dangerously if they are nuclear stations without a proper shutdown implemented ) and the lights will go out fairly quickly. Data centres will shut down and phone towers will no longer work so communications infrastructure will be lacking too. Obviously anything set up for off-grid living will be a lot less heavily affected but unless Bob returns immediately after the event, the place is likely to be dark and quiet as well as empty.

Answer 6

At the antipode from Bob's Island, a wormhole opens up and bathes the Earth with radiation. It envelops the planet with a deadly wave that interferes with a particular gene in human DNA but leaves most animals alone. A phase change due to the differing path lengths causes the waves arriving from different directions to cancel out in a small region on the far side of the world, where Bob is.

The activated gene makes people "return to the sea" like evolutionary lemmings. Everyone walks to the nearest body of water and drowns themselves, except babies. Bob now has a lot of diapers to change.

Of course, a few people also got their gills to regrow, and start a new race of Mer-people.

Answer 7

Magical Answer 1:

An airborne meningitis virus mutates, and one of the new effects it has is induced Gorgonism, meaning that anyone that looks at anyone else is turned into stone. This includes looking at yourself in the mirror. Without treatment those that aren't turned into stone also die.

The only bright point is that the virus can't survive outside the host longer than 24 hours, so by the time Billionaire Bob makes it to the mainland it's already burned itself out, leaving nothing but statues behind.

Bob survives because he was alone on the island when the virus was spreading, and the last gorgons had looked into store windows and petrified days before or succumbed to the virus.

Magical Answer 2:

The Earths population has finally reached a threshold, and the combined pressure on reality has opened a door to the Old Ones. The Eaters In The Night have been amassing at the edges of reality eyeing us tasty morsels, and are drawn anywhere that more than two people are within 5 miles of each other. Once they are done feasting the door closes, and they are once again left back out in the cold between realities.

Being in the middle of the ocean without a single other person around, Bob escaped their notice.

Answer 8

Nanobots

To help fight against diseases a company created nanobots. They are powered by glucose in the body. And are programmed only for specific genome use, in this case humans. The nanobots can deconstruct malicious cells, and other biological material. To aid mankind, they are tranferable though physical contact. The nanobots malfunction one day, either someone pushed a malicious update to the programming, or some bots malfunction on their own.

People are basicly disintegrated instantly, leaving little piles of atom dust. And since the nanobots cannot "live" without glucose to be powered, they "die" too.

So everyone is gone without a trace.

Bob was in a location where the nanobots couldn't reach and thus survived.

Answer 9

Mass hysteria is a heck of a drug. It can cause people to do very irrational things. As a grisly example, Tanzania has recurring witch problems where people are killing people they suspect of being a witch. There has been around 500 people killed so far, mostly women. If you're albino in Tanzania, your life right now is in real danger, because body parts from albinos are the only thing that can stop the witches.

• http://www.africanews.com/2017/08/01/tanzania-witch-killings-claimed-479-lives-from-january-june-2017-report/
• https://www.usatoday.com/story/news/world/2015/02/26/tanzania-witchcraft/23929143/
• https://en.wikipedia.org/wiki/Modern_witch-hunts

Combining genocide with various fears could get the human race wiped out. Genocide alone without a object of fear like witchcraft is enough to get millions slaughtered in several instances around the world and through history, sadly even into modern times.

Uh, good luck.

Answer 10

A severe mutation of Necrotising Fasciitis could do it.

Currently, it’s a flesh-eating bacterial disease, with a pretty high mortality rate. It spreads through physical contact, but generally only to those with low immune systems, cuts/abrasions, or infections like chickenpox. However, the initial infection can happen to people even with good health.

If it manages to mutate to an airborne disease, then it becomes a lot harder to treat. At the moment, the main treatment is simply to amputate the infected region - if you breathe it in, then it gets a lot harder to amputate.

If the disease spreads rapidly, people might not get any warning that they’re ill (generally about 24-36 hours after an initial injury do signs of Necrotising Fasciitis tend to appear), and by then everyone is infected, apart from Bob (and maybe a few other people in extremely isolated settings - is that a problem?) The disease doesn’t make it to Bob’s island, because no human carrier goes there.

24 hours might be enough time for people to start shutting things down safely (nuclear power stations, for instance), and creating instructions for any hypothetical surviving layperson to finish anything off.

As the disease is flesh-eating, it could hypothetically spread rapidly through the entire body, causing total organ failure and death - and the bacteria would continue to eat through the tissue until nothing survived. Assuming the bacteria could only survive in humans, it would die out after all humans had decomposed, so Bob wouldn’t be at risk of it if he returned to land a few weeks later - and no human evidence would survive.

Answer 11

1: An airborn virus wipes out mankind. Bob by some random genetic mutation is immune.

2: Bob is in a coma and is dreaming all this. Only problem with this idea is that it's been used in different variations in lots of stories ie the ending for Lost

Answer 12

Shortly after Bob arrived at the island a massive asteroid impacted in the ocean sending trillions of kilograms of vapor and sea salt into the atmosphere creating a major hole in the ozone layer over North America. As the effects of the impact showed, the world realized that millions of people would die slow deaths from UV exposure and started evacuating people to safe parts of the world. When Bob had finished writing and tried to radio for pick up there were no people within range of his broadcast to hear.

http://www.newscientist.com/article/dn19579-ocean-asteroid-hits-will-create-huge-ozone-holes.html#.VSw_xlnD_MI

http://www.theozonehole.com/consequences.htm