# Human extinction scenarios



## matt-browne-sfw (Oct 15, 2007)

Wikipedia has a comprehensive list of what could happen to our species. What is your opinion about it? What are reasonable threats and what are extremely remote scenarios?

In my opinion global warming with a runaway greenhouse effect is quite serious and I also think that major volcanic eruptions are underestimated. Otherwise bioweapons based on genetically altered viruses could prove to be very dangerous.


Here's the Wikipedia article:

Various scenarios for the extinction of the human species have originated from science, popular culture, science fiction, and religion (see apocalypse and eschatology). The expression existential risk has been coined to refer to risks of total and irreversible destruction of human life, or of some lesser, but universal and permanent detriment to it.

The following are among the extinction scenarios that have been envisaged by various authors:

* Severe forms of known or recorded disasters
      o Warfare, whether nuclear or biological; see World War III.
      o Universal pandemic involving a genetic disease, virus, prion, or antibiotic-resistant bacterium.
      o Famine resulting from overpopulation (see Malthusian catastrophe)

* Environmental collapses
      o Catastrophic climate change as a result of global warming or the effects of extensive deforestation or pollution. (E.g. the warnings of James Lovelock#Mass human extinction)
      o Loss of a breathable atmosphere, for example due to an anoxic event, or destruction of the ozone layer.
      o Occurrence of a supervolcano.
      o Extreme ice age leading to Snowball Earth

* Long term habitat threats
      o In 1.4 million years Gliese 710 will be only 1.1 Light years from Earth, and might catastrophically perturb the Oort cloud
      o In about 3 billion years, our Milky Way galaxy is expected to pass through the Andromeda galaxy, which may or may not result in a collision
      o In 5 billion years hence the Sun's stellar evolution will reach the red giant stage, in which it will expand to engulf the Earth. Before this date, its radiated spectrum may alter in ways Earth-bound humans could not survive.
      o In the far future the main risks to human survival could be heat death and cooling with the expansion of the universe.

* Evolution of humanity into a posthuman life-form or existence by means of technology, leaving no trace of original humans
      o Commentators such as Hans Moravec argue that humanity will eventually be supplanted and replaced by artificial intelligence or other forms of artificial life; while others have argued that humanity will inevitably experience a technological singularity, and furthermore that this outcome is desirable (see singularitarianism).
      o transhumanist genetic engineering could lead to a species unable to inter-procreate, accidentally resulting in actual (rather than pseudo) extinction.
      o Humans will continue to evolve via traditional natural selection over a period of millions of years, and homo sapiens will gradually transition into one or more new species.

* Extinction in a whimper
      o Preference for fewer children; if developed world demographics are extrapolated they mathematically lead to 'soft' extinction before 3000 AD. (John Leslie estimates that if the reproduction rate drops to the German level the extinction date will be 2400[6]).
      o Political intervention in reproduction has failed to raise the birth rate above the replacement level in the rich world, but has dramatically succeeded in lowering it below the replacement level in China (see One child policy). A World government with a eugenic or small population policy could send humanity into 'voluntary' extinction.
      o Infertility: Caused by hormonal disruption from the chemical/pharmaceutical industries, or biological changes, such as the (controversial) findings of falling sperm cell count in human males.
      o A disruption, chemical, biological, or otherwise, in humans' ability to reproduce properly or at all
      o Disease: The 'weak-gened' and birth-defected are kept alive by medicines. This is the opposite of nature, where the weak are less likely to survive and successfully reproduce, leaving the species genetically 'strong'. Eventually everyone has weak/flawed genes, and these defects become increasingly severe, until the human body is unable to fight diseases, even with the help of advanced medicine. In the end, disease ends the human species. Arguably however if this point was reached natural selection would again become a factor, potentially reversing this 'decline'.
      o Voluntary extinction

* Scientific accidents
      o In his book Our Final Hour, Sir Martin Rees claims that without the appropriate regulation, scientific advancement increases the risk of human extinction as a result of the effects or use of new technology. Some examples are provided below.
            + Uncontrolled nanotechnology (grey goo) incidents resulting in the destruction of the Earth's ecosystem (ecophagy).
            + Creation of a naked singularity (such as a "micro black hole") on Earth during the course of a scientific experiment, or other foreseeable scientific accidents in high-energy physics research, such as vacuum phase transition or stranglet incidents.
      o Biotech disaster (E.g. the warnings of Jeremy Rifkin)

* Scenarios of extra-terrestrial origin
      o Major impact events.
      o Gamma-ray burst in our part of the Milky Way (Bursts observable in other galaxies are calculated to act as a "sterilizer", and have been used by some astronomers to explain the Fermi paradox). The lack of fossil record interruptions, and relative distance of the nearest Hypernova candidate make this a long term (rather than imminent) threat.
      o A black hole may suck the Earth in.
      o Invasion by militarily superior aliens (see alien invasion) — often considered to be a scenario purely from the realms of science fiction, professional SETI researchers have given serious consideration to this possibility, but conclude that it is unlikely. [7]
      o Gerard O'Neill has cautioned that first contact with alien intelligence may follow the precedent set by historical examples of contact between human civilizations, where the less technologically-advanced civilization has inevitably succumbed to the other civilization, regardless of its intentions.
      o Solar flares may suddenly heat the earth, or the light from the sun may be blocked by dust, slowly freezing it (eg. the dust and vapour may come from a Kuiper belt disturbance).

* Scenarios of extra-universal origin
      o E.g., since it is entirely possible that the space of our universe, the Big Bang, and all its consequences are events taking place within a computing or other device on another cosmological plane, if this process were to end then everything within the universe would summarily vanish.


Any thoughts?


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## Overread (Oct 17, 2007)

Well the most likley ones to my thinking would be either warfare, e.g. biological or the evolution of a super virus (that one is very possible, ever wonder why government groups keep making such a fuss about things such as bird flu?)


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## Dave (Oct 17, 2007)

Overread said:


> ....wonder why government groups keep making such a fuss about things such as bird flu?)


More people died world-wide of Spanish Flu in 1919 than were killed on the battlefields of WW1, but it won't wipe us out, neither will AIDS, and neither did the plague or Black Death. Some small population would survive as it has many times in the past after climate changes.

I just keep thinking of bacteria on an agar plate and the classic Bell curve when the population expands rapidly using up all the resources available then poisons itself on it's own waste products. There was a computer program for very early PCs called LIFE that did the same thing in real-time.

That's what is going to kill us.

Either that, or nuclear warfare, or an asteroid as supposed caused the mass extinction that ended the Dinosaurs. There have been many mass extinctions in the geological record, so nothing new in that scenario. I would hope that our technology might help us survive, but it would probably make little difference.

The End is Nigh!


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## Nik (Oct 17, 2007)

*Eggs in one basket...*

Um, we're *horribly* vulnerable while confined to Earth.

Big list of natural stuff that could 'do the dirty' on us: Super-volcanoes are good candidates for that dubious honour, especially if they team with 'basalt floods'. A 'dinosaur killer' impactor could still sneak up...

Once we have Moon, Mars & asteroids tamed, we'd need a nearby supernova or unlucky alignment of GRB jet...


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## matt-browne-sfw (Oct 17, 2007)

Dave said:


> More people died world-wide of Spanish Flu in 1919 than were killed on the battlefields of WW1, but it won't wipe us out, neither will AIDS, and neither did the plague or Black Death. Some small population would survive as it has many times in the past after climate changes.




In evolution viruses are also forced to survive. Stupid viruses that wipe out their hosts complete will disappear. This is why the Spanish flu did not kill everyone on this planet. But a genetic engineer could create a stupid virus for a one time kill...


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## Rawled Demha (Oct 17, 2007)

i dont think we could die out from biological attack. our own bodies would develop immunity from it, even if it went right down to the wire, we would eventually develop natural resistance to any killer disease.

chemical weapons, however, are a different matter. chemicals are on a level with nukes, in that if the whole world went completely crazy and decided it had enemies hiding out in every corner of the planet (not entirely ridiculous), they you could say bye-bye to all life, let alone humanity.


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## Curt Chiarelli (Oct 18, 2007)

Several scenarios acting in conjunction with one another is the most likely culprit, although I'm really laying my bets upon human stupidity to tip the scales. Our race is like bacterium in a closed system similar to a Petrie dish, choking to death on its own excrement.


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## Spartan27 (Oct 18, 2007)

Most interesting subject.

I don't believe or think that a virus can kill us all off. Our bodies are way to complex for that.

A super volcano can wreck havoc on this earth, but doing us totally...nope.

A killer astroid/comet (depending upon size)....maybe 90%...but not all. The reason why I say this is because a larger mass will be detected even if all we have is a 1 hour window, we would be able to alter telemetry and launch our missles. Perhaps the effect at a minimum would be enough to alter it's coarse. If not, it's back to the stone age for about 6 million or so people.

Nuclear holocost (war, WWIII)....probably not, same net effect as killer astroid.

Alien Invasion....now that's an interesting thought. Let's say, a rouge or nomadic militaristic alien civilization would come to earth. Without a super weapon that would completely destroy the earth, In the beginning we would have a very tough time. But through the years, we would turn the tide. Assuming that the aliens have "scanned enough" and identified their weaknesses from earth bound bacteria/germs/viruses. If not, then the HG wells ending would occur. If they did their homework and have "protected" themselves, this would have to be an on-going "immunization" process and one that we would eventually identify and explote. The biggest problem with this type of scenario is the fight is here and not someplace else. This also assumes that our military has been neutralized from there tech. This then means we fight a guerrilla warfare tactic/strategy. 

Just remember, if they live...they can be killed and die. The issue is will we have enough People to do it and whatever resources at our disposal.

If the civilization is a terra-forming type, we would not stand a chance.


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## ray gower (Oct 21, 2007)

Think it really depends on what you mean by extinction. 

By our very nature we are not the same humans we were even a hundred years ago- Homo-Sapien-19th Century is extinct (bar a few exceptions), we are taller, generally live longer etc. So our version of our race is simply living on borrowed time.

As a civilisation, we will destroy ourselves with the same ignominy as every other civilisation, not in some great blaze of glory on some cause or sacrifice, but in a dirty back-biting whimper because we have given up such visions in favour of selfish self-destruction. It is terribly tempting to say we can see the makings of that end all around us. It is not global war, plague or warming that will destroy us as a civilised race, that simply thins the numbers. It is the fight for the last gallon of petrol or something equally useless.
To hope otherwise, I fear, is wishful thinking that flies in the face of all history.
It is not the end of world for the human race. In a few hundred years a new 'human civilisation' will appear.

To destroy the human race we need something much larger than worldwide destruction, we are simply too adaptable. Nor can we rely on the favourite wayward asteroid theory, the Earth has been hit by them before, five times in the last 700 million years or so, and while they might render all life virtually extinct in a local area e.g. America, Russia, China etc. There will always be pockets of survivors.

So I think to truly eradicate mankind we have to look much further up the scale, to the point where the Earth itself is destroyed. That will happen naturally I understand, when the Sun burns itself out. But remembering that the Sun is a burning nuclear bomb, I wonder how much encouragement it would take to become unstable early?


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## matt-browne-sfw (Oct 27, 2007)

Extinction in a sense that an entire species disappears. From the dawn of time till today more than 99.99 % of all species have died out.

A comment about alien invasion: I think that's quite unlikely. But it could happen right here on Earth in the form of a "technological singularity" i.e. AI developed by humans evolves further and it could turn into "unfriendly AI" and claim the Earth for itself. That's more likely compared to aliens coming from outer space...


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## ray gower (Oct 27, 2007)

With one or two exceptions, extinct species have died out because the conditions they required to thrive were too localised and they lacked the wit or ability to migrate to an area where they could continue to live, or died out through competition. 

Humans are a different matter: We are not in competition with anything other than ourselves, are highly mobile, adaptable and can reason and plan a future, not simply wait to see what happens when the sun comes up, plus we already live in every climate that the Earth can provide. So even if the global catastrophy were to affect the whole planet there will be a few isolated pockets that manage to struggle through. Even if the global population were reduced to a few thousands, it is not automatically the end of our race, we've been there and done it. It would however mean the end of our civilisation. Whether we (in the West) could learn to live without our mobile phones or cellophane wrapped food is another matter, but we would not die out because of a catastrophy.


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## matt-browne-sfw (Nov 11, 2007)

ray gower said:


> With one or two exceptions, extinct species have died out because the conditions they required to thrive were too localised and they lacked the wit or ability to migrate to an area where they could continue to live, or died out through competition.
> 
> Humans are a different matter: We are not in competition with anything other than ourselves, are highly mobile, adaptable and can reason and plan a future, not simply wait to see what happens when the sun comes up, plus we already live in every climate that the Earth can provide. So even if the global catastrophy were to affect the whole planet there will be a few isolated pockets that manage to struggle through. Even if the global population were reduced to a few thousands, it is not automatically the end of our race, we've been there and done it. It would however mean the end of our civilisation. Whether we (in the West) could learn to live without our mobile phones or cellophane wrapped food is another matter, but we would not die out because of a catastrophy.



Good points!


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## woodsman (Nov 12, 2007)

Yeah what Ray said, I've always thought, that in theory, although our population would be greatly diminished, very few events could wipe us out now. An most events will hardly be unforseen, which is more than can be said of those that wiped out life at other points in our history. 

One interesting thing is: How quickly would we, as a race, respond and start to bounce back from a major catastrophe - Super volcano etc...? Any thoughts/ideas anyone?


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## ray gower (Nov 12, 2007)

It is claimed that when the Supervolcano Lake Toba in Samatra exploded some 75,000 years ago, more than 60% of all life on Earth was wiped out and the world's human population was reduced to a few tens of thousands. 
Lake Toba - Wikipedia, the free encyclopedia
Toba catastrophe theory - Wikipedia, the free encyclopedia

Now whether we would take another 75K years to get back to this point is moot.
Obviously we are more capable of reasoning than Neanderthal Man, so one might think it ought to be a lot shorter. But is it?

The cost of our 'Thinking Civilisation' is that relatively few of us are actually capable of translating that knowledge to practical skills. Consider our position in the circumstances? 

For the first few years we would be scavengers, living on what we could find, tinned, dried or recently dead. Fine, survival is a case of what you can find and keep hold of, nothing much is needed, though brute force may be helpful.

One might be a computer wizard, but without electricity what use is a computer?
Vehicles are of little use, you must refine oil to make them work and those currently pumping it out the ground are in the same survival state as everybody else, even if they weren't, they have no fuel to operate the pumps!
One might be able to work metal, but would one know how to actually dig it up and refine it in to some usable state, also remembering that most readily available resources have already been exhausted.
Could one develop a working loom to make cloth, make candles from tallow, shelter from whatever is available, grow, grind and bake wheat, create a fire to bake the bread without firelighters and matches etc. The list is almost endless and reality is very different to what we are taught, even with technology to help us.

In short we will be living in the same conditions as our Neanderthal relations. A few years, 2 or 3 generations at most, of being a hunter gatherer, living hand to mouth will surely destroy our 'thinking' advantage. 
Until we can learn to farm efficiently enough to have the necessary surplus to support a growing population, there is too little time and value in teaching the next generation to read, let alone be nuclear scientists.
We might not be thrown back 75,000 years, but 7,000 to the Stone Age must be a real danger?


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## Pravuil (Nov 18, 2007)

Well...as you can see from Matt's long list of possible outcomes (there are a myriad more as well) the world will nigh inevitably end somehow. Even if we do prevent one apocolyptic event another threat will spring up to present us with destruction as a people, whether it be through genocide or a world sundering asteroid. The best we can do as humans is strive to prevent that which can be prevented, and maybe even postpone or more miraculously stop that which is thought of as inevitable, through means of human ingenuity. Regardless..there has to be an end that will consume us. Even if we do overcome the chiefest of threats our planet could be destroyed by a problem thought of as unthreatening and too trivial to be taken into proper regard. Summarily I believe the best we can do is let everyone sit back and relax, let the more intelligent people do there work to extend our span on this good Earth, and enjoy life until that ever imminent event occurs.


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## matt-browne-sfw (Nov 20, 2007)

To prevent global warming with a runaway greenhouse effect we all need to contribute. Both with good ideas and by changing our behaviour.


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## Pravuil (Nov 21, 2007)

This is more than vaguely reminiscent of one of those Hybrid commercials....no offense directed at you Matt.


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