Many people worry about the possibility of the end of all life on our planet. However, the Earth is by far the most habitable planet in our solar system and there's no reason to expect that to change for hundreds of millions of years.

The Earth may become uninhabitable between 500 million and a billion years from now. That may seem a short time, when you compare it with the billions of years the Earth has evolved for. But compared with the length of time there have been humans on the Earth it's a very long time.

To get an idea of who may need to deal with this issue, the idea is, to look at the last billion years. And then think about where we or our evolutionary cousins might be after another billion years after that. First some background though.

WHY THE EARTH IS LIKELY TO REMAIN THE MOST HABITABLE PLACE IN THE SOLAR SYSTEM FOR HUNDREDS OF MILLIONS OF YEARS

I've written about this in other articles, so just a short summary - you can read the other articles to find out more. It's hard to think of anything that could make it more uninhabitable than Mars, for instance. Even a giant meteorite strike, or a gamma ray burst, wouldn't do that. See Why We Can't "Backup Earth" On Mars, The Moon, Or Anywhere Else In Our Solar System.

Even after a major asteroid impact - there were huge impacts in the late heavy bombardment, 3.8 billion years ago and earlier - but there haven't been any impacts that large since then, anywhere in the inner solar system. It seems that Jupiter does a good job of protecting the inner solar system from the largest impacts (it tidally disrupts huge comets from the outer solar system into lots of small objects) and the asteroid belt is stable at least for tens or hundreds of millions of years.

So, for the size of asteroid we can expect today, the Earth would remain habitable for humans. 

HUMANS AND MANY OTHER CREATURES WOULD SURVIVE A DINOSAUR ERA ENDING TYPE IMPACT

The chance is of a Dinosaur era ending type impact in the next century is a tiny one in a million probability (these impacts happen roughly every 100 million years so chance of impact in any given century is about one in a million). Also, we are rapidly developing the ability to predict and also divert such impacts. 

Many creatures including birds, small mammals and fishes, even crocodiles survived the impact that ended the dinosaur era - and the dinosaurs couldn't build fireproof shelters, or get into boats, or travel to parts of the world safe from the impact. 

Humans, unlike dinosaurs, can build shelters, or travel, and can stockpile food and use technology to grow things even through a "nuclear winter". Many humans would survive such an impact. Even if it happened completely without warning (and we'd have some warning for such a large impactor)  there would be survivors in submarines, deep underground, in Antarctic research stations or whatever, somewhere on the Earth there would be many survivors.

See Is It True That An Asteroid Will Strike Earth On [Insert Date Here]? - Truth Behind Asteroid Scare Stories

TIMELINE OF HUMAN EVOLUTION

Here Ma = million years and Ka = thousand years and I'm just using the timeline from wikipedia Timeline of human evolution, which has many more steps, I picked out a few salient features from it.

Choanoflagellate - 900 Ma, may be similar to the early ancestors of all animals.

Sphaeroeca, a colony of choanoflagellates (approx. 230 individuals), in light microscopy. Sphaeroeca-colony

It took less than a billion years for some creature a bit like this to evolve to us. So, for all we know, some little creature like this around today may be the ancestor of whatever intelligent creatures roam the Earth a billion years from now (if the Earth survives that long).

Next in our evolutionary timeline:

Pikaia - early chordate (530 Ma)

File:Pikaia gracilens B.jpg
chordates are ancestors of all creatures with backbones, as well as others that don't. They have to have a notochord, a hollow dorsal nerve chord. They also have to have a tail and various other features at some point in their life cycle Chordate

(I know we don't have tails, but our fetuses do at one point in the early stages of gestation, like all chordates).

Ichthyostega (365 Ma, early tetrapod - may have spent brief periods out of water)

File:Ichthyostega model.jpg

Hylonomus (300 Ma, earliest known reptile)

Hylonomus

Cynognathus - an early reptile with mammal like characteristics (220 Ma).

File:Cynognathus BW.jpg

Juramaia sinensis - earliest known mammal fossil (160 Ma)



Juramaia

Plesiadapis - common ancestor of primates, treeshrew and flying lemurs, 85 - 65 Ma

Plesiadapis

Pierolapithecus 13 Ma (last common ancestors of us and Orang Utans)

the last common ancestor of the living great apes?

Then the great apes separate from us. Then after that the chimpanzees.

Chimpanzee–human last common ancestor - 7 Ma

Australopithecus afarensis - 3.9 Ma

File:Australopithecus afarensis.JPG

Homo habilis 2 Ma

Homo habilis

Homo erectus. 1.8 Ma

Homo erectus

Homo heidelbergensi 600 Ka

Homo heidelbergensis - also shows how they do these facial reconstructions

And then us

Researchers have found that Homo heidelbergensis was only slightly taller than the Neanderthal (SINC / José Antonio Peñas) see Scientists Determine Height of Homo Heidelbergensis

Here Homo heidelbergensis may be ancestor to Neanderthal and
Cro-Magnon
(modern homo sapiens sapiens), and we also have Neanderthal DNA so there was interbreeding between them as well, complicating the picture.

WHERE IS THIS HEADING?

So, where is this heading if you go forward another few million years? Then a hundred million years? Then a billion years?

Do you think there will be humans that look like us a billion years from now?

Could be. There are some species that stay exactly the same almost, for hundreds of millions of years.

For instance, the blue blooded horseshoe crab (with the copper based hemocyanin instead of the iron based hemoglobin in their blood) has hardly changed for hundreds of millions of years



It's hardly changed since this fossil 425 million years ago


Reconstruction of the fossil:


It is a bit different, modern crabs lack the blue member of each pair of legs - but compared with other species hardly changed at all.

That image is from a news story about how Horseshoe crabs aren't really "living fossils" -. They are not identical to their ancestors, e.g. lost some legs, but they are still on a slow track of evolution compared with most species.

ARE WE ON A SLOW EVOLUTION LIKE HORSESHOE CRABS OR FAST EVOLUTION?

So - might be that humans like Horseshoe crabs - that there is something very special about our current morphology that means we will stop evolving, or evolve hardly at all so that our ancestors even a billion years from now are recognizably human - as like us, say, as Homo Habilis.

But it sure doesn't look like that when you look over the last 10 million years or so, evolution from


Homo habilis
to us in just two million years.

And from

Cynognathus -.

File:Cynognathus BW.jpg
to us in 220 million years.

Rather looks as if we are going to keep evolving. Though where too, who can say.

Or maybe we will stop, maybe we have got to an optimal "final" stage of evolution for some reason like the horseshoe crabs?

SO WHAT HAPPENS NEXT?

Lots of ideas about it of course. One thing that complicates it is that we have technology, which is already making a difference.

Here are a few examples, but there are probably many more.

  • Technology to live in places we are not adapted physiologically to survive in, so the evolutionary pressure to change may be less - so maybe we don't change so much
  • We adapt to fit our technology, E,g, no longer need to be able to walk (machines take us everywhere) etc - so we no longer have legs. But maybe lots more fingers and fast responses so we can press buttons with great agility. Perhaps we evolve to a largely sedentary existence taken everywhere in machines, and the best survivors are those who can stay healthy with the minimum of exercise.
  • We become less intelligent because machines do everything for us
  • Or we become more able to deal with complex puzzles because our machines create increasingly challenging situations for us to deal with.
  • Medicine so we can correct many things and people can survive and have children and pass on genes that would never survive in the past. For a simple example - it is so easy to correct eyesight problems, that it is no longer going to make much difference if you are very short sighted. So then we might change more, because there is less to constrain changes in our DNA.
  • Ability to directly modify DNA - not doing much of this yet - but in future you may be able to design the DNA of your baby. Will humans do this? If so will this speed up evolution or stop it? That would depend amongst other things on our future decisions, how we use this technology if it is available to us

As well as that, as thinking beings we can make decisions about our own fate. To the extent that we can also have an overview of the entire pattern, we may be able to see where evolution is taking us long term, and then do something to change that pattern intentionally.

So anyway here are a few ideas just to get started thinking about it:

WE ARE AT A FINAL STABLE POINT LIKE HORSESHOE CRABS AND HARDLY EVOLVE ANY FURTHER AT ALL

I think that's unlikely, but we can't rule it out surely.

WE GO EXTINCT AND SOMETHING ELSE TAKES OUR PLACE, BUT WAY INTO OUR FUTURE

There it doesn't need to be anything violent. Could be, that's what we worry about now. But if we last through the transition period of the next few centuries to a long term stable high technology civilization, maybe it will be something slower than that.

It could just be that - after maybe anything from a few thousand to a few million years into the future, humans just don't have the dynamism of the young species we are now, and get fewer and rarer, and stop having children. Maybe could easily rescue the situation with technology but no longer see the point.

Might also feel that it is time for other younger and more vital species to take our place. Even to the extent of letting ourselves go extinct. Some future version of the Voluntary Human Extinction Movement - not much likelihood I think of that happening at present. But in future maybe our descendants might decide to do that, phasing out the human race by voluntarily ceasing to breed.

This could also be out of a deep understanding of evolution and life processes (which we don't have now).

Or we evolve to creatures that have lost their intelligence.

Then way into the future maybe some little creature that looks like this now


evolves to the future beings that have to deal with the Earth when the sun heats up or whatever happens then.

OUR PETS, OR DOLPHINS ETC EITHER CO-EXIST WITH US OR FOLLOW ON FROM US, "UPLIFTED" DELIBERATELY OR BY OUR INDIRECT INFLUENCE

Either dogs, or dolphins, or octopuses are either "uplifted" by us, or they evolve by themselves, maybe in response to the challenges of our environment. We are giving other creatures many intellectual puzzles to solve with our complex buildings and machines. So maybe that is a driver that will make other species more intelligent even if we don't direct that evolution ourselves? Even our tests, like scientists studying parrots and chimpanzees and teaching them language, or dolphins.

This is Alex the parrot, one of the cleverest of all the various creatures that have been tested for their intelligence. In some ways more clever than a Chimpanzee.



Alex participating in a numerical cognition

Maybe some time in the future parrots, or crows, or dolphins, elephants or octopuses become as intelligent as humans or more so.

And maybe we end up with several intelligent species sharing the planet. So then - not likely that they are around either after hundreds of millions of years - so maybe - their pets or uplifted species or descendants, might have a continuity of overlapping species like that eventually lasts through all those 500 million years.

For instance, just a fun idea, maybe the remaining technological beings way into the future on Earth will be pets of pets of pets of pets of ... of our parrots or dogs or other pets a hundred times removed say :).

WE SURVIVE BUT DIVERSIFIED AND HUGELY CHANGED

Our descendants are there a billion years from now - but evolved. If just following evolution, then there is no reason I think to suppose a single species 500 million years from now, would be astonishing. Many species that used to be humans. And some may be intelligent and capable more so than ourselves, some less so.

In that future some of our descendants perhaps will have lost intelligence and evolved to become whales, bats, or whatever. E.g. whales that a hundred million years previously were evolved from humans, and tiny bats, that again a hundred million years previously evolved from humans.

Especially if we do have a massive extinction, there would be many niches in the ecosystem, and some may be filled by human descendants. Of course nobody would do that deliberately, but over millions of years, it might happen almost imperceptibly, that we split into numerous species, and that some, or even all of those then lose their intelligence and forget language and become like animals again.

TECHNOLOGICAL STASIS OF OUR DNA

Maybe for some reason humans decide that C20 humans are "it" and don't want to evolve any more. If so, we could probably make sure that happens with near future technology

DESIGN YOUR OWN

We get so good at DNA that you can design just about any body you like for your children, and maybe even are able to reshape it while alive too. Stanislav Lem explores this

GO INTO VERY LONG TERM STASIS AS LIVING CREATURES UNTIL THEN

That could be traveling at close to speed of light. Or going into long term hibernation if we can learn to hibernate for a billion years. Or create some technology that will give birth to new humans a billion years from now.

Maybe wake up a few of us every thousand years, take a look at what is going on, help if we can, and then go back to sleep again. We could go into stasis on the Moon say, as a way to protect ourselves against non technological descendants, and because it is more stable. Or in a colony in the asteroid belt or even way out in the Oort cloud. And every few thousand years one of us wakes up, travels to Earth or just observes it from the distance to see what is going on, and if necessary wakes up more of us - or else - just decides nothing needs to be done and goes back to sleep again for another thousand or million years.

It is very like going extinct because in this future, as a species we no longer have the wish to continue. And feel it is time to leave the Earth to other species.

But perhaps though not so interested in accomplishing and surviving ourselves, we feel ethically that we can help other young species as they evolve. So we might use stasis or hibernation and keep a small population so we don't go extinct, in order to help those future species.

For instance maybe we have solved various issues ourselves and feel that we might be able to help them avoid them too by sharing our maybe hard won solutions.

Which - may or may not be that sensible and practical, I'm not saying this is necessarily a sensible decision from our present perspective. Anyway we might decide to do that.

WHICH IS WHY THERE IS NO HURRY

That's why I think that Stephen Hawking and Elon Musk etc's idea that we have to urgently become a multi-planet species to make sure we don't become extinct 500 million years from now is just kind of irrelevant to this.

Whatever we do in space, chances are that it is long forgotten by then. If we are able to manage Earth in a sustainable way, then Earth's by far the most habitable place in our solar system. If we try to terraform Mars, then - chances are it is just a failed experiment, that we don't manage to keep the momentum going and give up after a few centuries. But if we did keep going for say 10,000 years or 100,000 years or however long it takes - well - it will probably just unterraform over a similar timescale. Even a million years from now there may be almost no sign that the experiment ever happened.

Or - may be that we do change Mars - but in a way that makes it unusable for our future descendants. E.g. lose its volatiles, or introduce species that evolve there which become so problematical that no human can live there.

Through failure, or even if we succeed, is our vision of Mars what they want 500 million years from now? Are the lifeforms we introduce to Mars ones that they will be glad to find there, or ones that they will find a major nuisance? Will they like the climate we create?

Maybe some time we will have some insight into what our descendants, or our cousins (descendants of dolphins or parrots or whatever) will want 500 million or a billion years from now, or for some reason be sure we will be around by then ourselves. But at least in the near future, I can't see us making sensible wise decisions based on trying to make the solar system into what we hope these creatures will need so far into the future.

I think we need to look at what we need right now. And if we want to help our future descendants, I think best thing is to keep as many options open for them as possible, because we don't know what they will want, so to try to avoid doing things that are likely to restrict future choices and options.

THINGS WE CAN DO OVER THE NEXT BILLION YEARS

We can reshape the inner solar system if we want to, if we keep technology. Or rather, probably not us but these future creatures who come after us whoever they are.

We could start on a big project to save the Earth. For instance to move it slowly outwards as the sun gets hotter. If we start now - that means - some time in the next few hundred million years - i.e. yes with some urgency, but on these timescales, urgency doesn't mean in the next century or millennium.

Anyway if we started some mega project now, we could probably arrange to move the Earth, slowly, over the next billion years.

See David Brin's Let's Lift The Earth!

where he outlines an idea for a grand project to move the Earth outwards. Where - I think the details not so important, may be several ways to do it. But the idea that you start up a project where there are many immediate benefits as well as the indirect benefits of moving the Earth.

Also one that is automatic and that is beneficial in a more obvious way. In his example as a source of power that anyone can tap on the Earth with relatively simple technology even if they lose the ability to go into space.

So we might set up something like that, or many other ways we might be able to help our very distant descendants / second cousins in evolution many times removed. But it might not be in the most obvious way.

SO YES I THINK THE ODDS ARE PRETTY GOOD

So, my answer is, yes, understood this way, I think the odds are pretty good. That either we or one of the probably several thousand future technological species that arise on the Earth between now and then will find a solution.

With say a thousand future species, to tackle the problem, one of them may well eventually solve it. Even we might.

Which might involve moving the Earth. Or who knows, changing the dynamics of the sun, making sunshades making all the planets into a Dyson sphere, could be many future possibilities.

But, with only a few centuries of technology so far, I think that it is a little early to hope to have a clear idea of what the solution would be. Or even what the problem would be.

Or even, what species of creature would need to solve it, and whether e.g. it lives in water, or is a bird or on land, whether it is as big as a whale or smaller than a parrot. Whether it breaths oxygen even - the Earth's atmosphere has been oxygen rich for billions of years - but what if there is some future change in the Earth and an evolutionary update as revolutionary as the first oxygen breathers leading to future branches of the tree of life we can't imagine yet? Maybe by then they breath methane, or hydrogen sulfide, or they get energy directly from radioactive rock, or any of many other alternative metabolisms - some already in use on the Earth and some at present hypothetical.

Meanwhile, I think we can probably help by not messing things up, more than in any other way. And to preserve the diversity of life on the Earth and more generally in our solar system, because there is no knowing where the future solutions may come from. Or at this stage, even to know what branch of life the future intelligent species may evolve from that will need to solve this problem 500 to 1 billion years into the future

This originated in my quora answer to the question: What are the odds that a viable population of humankind will escape to another planet before the earth becomes uninhabitable?

Available on Kindle as End of All Life on Earth - a Billion Years from Now: Can it be avoided? And with time to evolve from microbes to us again several times over, who will be here?