It isn’t “Solost’s” vote, either 
I agree it’s surprising that 'Heat death of the universe is as high as it is.
Oops! And here I thought you were some kind of lights out singer! LOL
Only in the sense Mrs. Solost wants to put my lights out whenever I sing around her 
I do like @Cervaise’s well done comment on how easily one leads to another, and glad @Si_Amigo brought up a true AI revolt, but still think it’s more likely we’ll end ourselves.
My niggle is somewhere between “Introduced genetic quirk” and “Natural plague”. And that I think, in addition to human screwup’s leading to scarcity (possibly even before making it worse!), we’ll have someone do something really, REALLY dumb with CRISPR or something similar becoming “cheap” and available. Some dink out there, some end-of-the-worldist, jihadist, or some third-rate GE company trying to make a commercial product on the cheap will end up releasing something that directly or indirectly (directly being a lethal plague, indirectly being like something that eats all cellulose or petrochem products rapidly) ends humanity or ties into Cervaise’s feedback loop of collapse.
Interesting thought-- if AI surpasses and replaces us, does that invalidate it as a reason for how humanity will end, since I stipulated “evolving into something else” as not a viable option? Because technically AI is sort of a synthetic evolution of humanity?
IMHO I’d adjudicate based on where these post-human creations originate.
Say we build completely artificial intelligent robots and they kill us all, as seen in the Terminator franchise. I would count that as robots killing humanity.
On the other hand, say we create brain-computer interface devices that allow you to augment your brain. For example, say you want to echolocate like a bat - you could be given some ear implants that let you pick up high frequency sounds and a different eplant that lets you create the sounds necessary. But unlike a bat, you don’t have the ability to process sounds into a 3d map in your brain - you can triangulate sounds, but not dozens of sources at once with enough fidelity to run through a forest with your eyes closed, for example. So you also get a brain implant that processes some of this information for you and then communicates it to the rest of your brain.
Maybe you get another brain implant that helps you with memory, artificially creating eidetic memory that can be curated.
Maybe you get a third implant that helps your brain process info by coordinating inputs from multiple other eplants and even your senses and sharpening or cleaning them up, somehow.
Obviously, none of this technology is currently possible, but we do see that the brain is remarkably elastic, learning to control a computer or prosthetic when the proper implants are used. So in theory it should eventually be possible to create devices that mimic or enhance brain functions and use them to give your brain additional capabilities.
Let’s say you’re doing all that for a while, but eventually the biological parts of the brain start to get older. Synapses die off. Something akin to dementia starts to set in. So you undergo a procedure where the worst impacted parts of the brain are replaced with artificial bits. Eventually, your brain is entirely non-organic, but you’ve had no more interruption of consciousness than any human undergoing sedation for surgery currently experiences.
And eventually, let’s say this becomes commonplace and widespread enough that all human beings have undergone that sort of procedure.
Are you human? It probably isn’t meaningful to say so anymore, no. But I think you’re clearly our descendant within the spirit of this question.
This seems a bit incongruous. You chose ‘heat death of the universe’ as the most likely option because you are optimistic about us eventually migrating out to space, even to other star systems eventually. But you rank ‘Alien invasion’ as the least likely option? What do you think future humans are going to do if they’ve been cooped up in spaceships for generations and finally find a livable planet with an intelligent species that has lesser technology, and is not cool with us moving in?
In about a billion years, the sun will get so hot that the oceans boil away and the earth will become uninhabitable. I don’t accept the fantasy of finding an inhabitable planet elsewhere.
That’s why i didn’t choose that. Even fiction doesn’t choose a totally fatal plague. Even Stephen King didn’t do it in The Stand. Someone is always naturally immune.
That’s a statistical question involving the Fermi paradox.
If it is possible to reach other stars - and our own example makes that seem likely, on a timescale of, let’s be generous, the next million years - then over, say, a billion years, there should be plenty of time for a species to expand to the entire galaxy.
It took around 2 billion years for Earth life to go from abiogenesis to us. If we reach space sometime in the next million years, then we can still use that 2 billion figure with the additional time we need being less than a rounding error.
So with very generous numbers, assuming we don’t wipe ourselves out, Earth life could go from single celled organism to galaxy conquering K3 civilization in 3 billion years.
Earth is 4.5 billion years old. When Earth formed, there were already other planets that were billions of years old themselves.
So if intelligent life had ever arisen in the history of the galaxy and reached the level of interstellar colonization, I’d expect them to have colonized every star in the galaxy before we were a twinkle in some pond scum’s eye. We, of course, would never have evolved in this scenario.
The odds that other intelligent life arose elsewhere in the galaxy close enough to us temporally to reach us in the blink of an eye between “smart monkey” and “spacefarer” - 200,000 years or so - rather than the 4.5 billion years prior or late enough that it’s impossible for them to ever have evolved because we got to them at the twinkle in pond scum eye stage - seems to strain belief.
If we are still around in a billion years and we still live on naturally occurring rocks in space, I’d be amazed.
I’m with Babale with humans lasting to the heat death of the universe, although I’m not putting this forward as a particularly optimistic scenario. A quadrillion, quadrillion years from now, there may still be some sort of civilisation of sentient beings, worrying about the eventual heat death. If these sentient entities have any record of humanity in that far-off era, that record could contain enough detail for the recreation of human bodies and minds on demand. I doubt that the demand for re-creating a human mind and body would be very great - but a quadrillion years is a long time, and maybe these far future entities would get bored occasionally.
I’d expect the far-future entities staring eternity in the face would retain as much data as physically possible - and it turns out that the human genome could be stored as DNA and would take up about three gigabytes. In the far future, all that remains of a trillion terrestrial and extraterrestrial species might be a few gigabytes of data each, and every now and then they might dig us up out of the database.
If these beings trace their descent to us, are they any less us than biological great great great…[insert 1 billion years here]…great grandchildren would be? They’d be further removed from us than we are from the earliest tetrapods to crawl onto land.
If anything, post-biological means of reproduction are likely to keep them (cognitively at least) closer to us.
The bible implies that an asteroid will hit obliquely, then every atom will separate. So I’m going with that.
That sounds like a much cooler bible than the one I read. Which bible makes this claim?
How many bibles are there? You should give me a bit find the references.
I put “Humans render the planet unlivable,” just because most extinctions happen when a species loses its habitat. The other means to extinction is being hunted to death, but that usually happens only to populations that are confined to a small area, and an invasive predator (or, occasionally, parasite) is introduced.
I very much doubt we are going to be wiped out by an invasive predator, because that goes into the alien invasion, and I just doubt that will ever happen. I believe there is life on other planets, but I’m skeptical that any of it will travel to find us.
That leaves loss of habitat.
Given that our niche is the ability to adapt an area and make it livable not matter how it starts out, it’s going to take a catastrophe to make it impossible for us to do this.
We might get hit my a meteorite, but I think our own stupidity is probably more likely to be our undoing.
I’m amazed that the lack of support for nuclear war. Apparently we’ve grown complacent after 78 years.
But 78 years is an eye-blink in the sweep of human history, and the long record of human savagery, ethnic and political hatred, and willingness to kill each other early and often and with as deadly a weapon as possible leaves me seeing nuclear war as by far the most likely extinction scenario.
I disagree. The nuclear bombs dropped on Japan killed an estimated +200,000, and COVID-19 has killed almost 7,000,000 (and still killing). While the Japan numbers are not technically a nuclear war, since only one side had the weapon, so far it’s been unlikely two countries with nuclear weapons attack one another (even India and Pakistan). Nukes appear to act as a big dick for a country more than an actual weapon - even countries at war that have them are not using them (Russia). It’s hard to imagine a scenario where multiple countries with nukes start firing them at one another, thanks to the idea of MAD. I agree with your description of the human condition and our inbred savagery toward one another, tho.
OTOH, diseases are killing people every day, and new strains are evolving all the time. The earth has an abundant, some say over- population of humans, with many living in conditions ripe for spreading disease. It seems more likely that a heretofore unknown lethal contagion will emerge before a global nuclear war wrecks us.
Humanity will end when Ketchup on a Hotdog becomes the Norm.