# Humanity after 100 million years?

I'm writing a science fiction novel set 100 million years in the future, but humanity is still the same basic form we have today, biologically speaking. Would 100 million years of evolution drastically change our biology or would scaling back the time frame to 50,000 years in the future be a better plan?

• Pfft, it's quite possible that in 5000 years people may look like almost anything they want, so I wouldn't care about evolution, but why people would want to look like they do now. – Mithoron Jul 25 '16 at 22:35
• Globalizazion and the low sexual selection has stopped evolution for humans, if the situation doesn't change humanity will remain the same forever. – άλεξ μιζέρια Jul 26 '16 at 9:49
• "Evolution has stopped for humans". Never heard of such an incredible claim before. Evolution does not happen only in isolation. – ypercubeᵀᴹ Jul 26 '16 at 10:36
• @άλεξμιζέρια: "evolution" isn't the same thing as "speciation". Even supposing that speciation requires reproductive isolation, it doesn't follow that evolution does. Agreed there needs to be some kind of selection, though: if everyone is precisely equally likely to have children then evolution by selection can't happen. We'd still randomise the genetics through mutation even then. – Steve Jessop Jul 26 '16 at 11:50
• @MatthewRock That doesn't make any sense. Humanity has (almost?) not changed at all biologically during the last couple thousands of years. – JimmyB Jul 26 '16 at 13:03

There is no way of telling what humans would have become after 100,000,000 years. None at all. Evolution doesn't have a plan or a set course. Natural selection leads all species towards being better-adapted to their environment, but in that vast period, there's no telling how the real world environment will change. As an author, you can decide that for your story, but the ways in which humanity would change in response to any specific environmental change are not obvious.

The additional twist is that in the past few thousand years we've begun to modify our environment significantly, and now live in large numbers in many places that can't naturally support them (e.g., the water supply in California, or artificial heating in high northern latitudes). We don't really know how we'll change now that we can set aside many normal environmental factors, or if we'll be able to carry on doing so for thousands of years, let alone millions.

The classic SF novel Last and First Men addresses these issues: over its span of two billion years, many human species rise and fall. It's well worth reading if you want to write on this scale.

The 50,000 span is easier and safer, if less ambitious. Humanity will probably still be recognisably the same species over that span.

• Its True that evolution is at work at all times, But its important to note that Genetic modification and cybernetics will become very big in the future. Genetic modification trumps evolution and cybernetics means humans will have all but surpassed natural selection. We can use these to choose how we change (or not change) in the future, so its not just evolution to look out for. – Ryan Jul 26 '16 at 15:59
• These things may well become important, but we don't how much effect they will have, or for how long they will be used. Evolution by itself will do a great deal in ten million years, and makes the minimum-change answer "We have no idea" all by itself. – John Dallman Jul 26 '16 at 19:07
• Yes, we indeed do not know, but the sheer fact that we will be able to control it is far more than enough for a story. If Humans can control it, and the Story teller controls the Humans, then the Story teller has control over it. They can say whatever they want and do whatever they want, so 100 million years or just 10 thousand, They decide what every human from "now" until then decided, including if they wanted to remain "Human" or not, and just whatever Things from evolution they kept (if any), or even if the completely suppressed it since 2025. – Ryan Jul 26 '16 at 19:59
• @Ryan Genetic modification doesn't really trump evolution, in that humans who genetically modify themselves may be more likely to reproduce, and so future generations will be better at genetically modifying themselves. – immibis Jul 26 '16 at 23:15
• Nitpick: natural selection is not the only force at work and evolution does not optimize (at the species level, although its more debatable at the ecosystem level). Trite example (noted by Darwin himself) is the peacock's tailfeathers. – Jared Smith Jul 27 '16 at 13:50

Let me put it this way; primates have been around for only 50 million years (give or take). Of this 50 million years, humans have been around for only 2 and recorded history has only been around for about 14000 years. It is extremely unlikely that human would look even remotely similar 100000000 years from now. Even 50000 is unlikely for human to be the same.

Though there is a spark of hope; for the first time in human history humans are selecting mates based on love and not biological features, so it is possible for either of these goals to exists, however unlikely.

• Even based on love instead of biological features, DNA mutations are still going to happen. Therefore changes are still going to propagate through the species as a whole. You can't keep the species biologically stagnate for so long, something is going to get through. Though I'd imagine with tools for editing/correcting DNA, and a lot of motivation and work, it would be possible to artificially stagnate the species. – Thebluefish Jul 25 '16 at 22:37
• How is "love" different from biological features? As far as i can tell "love" is selecting on biological features. I would have expected (and I believe we have seen) more interesting situations in cases where mates were selected based on political expediency since that seems to actually have little to do with biological features (hence all the deevolution/inbreeding) – DRF Jul 26 '16 at 6:14
• Sorry but your last paragraph makes me laugh. Love is nothing else than choosing the partner by biological features. We may be smarter and whatever but from my POV "falling in love" for a human being is exactly the same as for any other kind of animal. We may try to justify it in some ways and it may be more affected by social behaviour than other species of animals but it's still just a biological fact. In fact if we decided our partners by rational decisions (!= "love") then that might make a difference (well, basically we would be doing artificial selection on our own species). – Bakuriu Jul 26 '16 at 9:48
• Due to globalization every new gene get's spread in the population and fades away, therefore evolution is incredibly hard to happen even with mutations. – άλεξ μιζέρια Jul 26 '16 at 9:51
• Those two things - 'spread in the population' and 'fades away' - are mutually exclusive. Either the new mutation (say green hair) spreads in the population, so there are lots of people with green hair, and lots of people with normal hair colour who carry the green hair gene. OR the green hair gene doesn't spread and 'fades away' (i.e. is not passed on). – DrBob Jul 26 '16 at 11:06

Organisms can exist largely unchanged for tens of millions of years if there is no real reason they should evolve. Evolution is a two-way street. So while humans have evolved very quickly up until now, there are plausible reasons why humanity could not further involve. I would suggest looking at Sharks and Crocodiles as examples. Both of these species have existed largely unchanged for tens of millions of years with primary differences being in size and other aesthetics. Humans will definitely change aesthetically, most likely larger eyes and less hair, but in the large part you could force them to be pretty much the same if they are so perfectly suited to their environment like a Crocodile is. You could even introduce this artificially through technology.

• Crocodiles and sharks still live in the same habitat. They don't change because there is evolutionary pressure for them to stay the same. Humans evolved to run long distances in the African savannah. That evolutionary pressure is completely gone now. – BlindKungFuMaster Jul 26 '16 at 8:39
• Crocs and sharks have NOT survived unchanged. There is a constant turnover of species, each different from its predecessor. Crocodylus genus, for instance has only been around since the late Miocene, so any of the modern crocs which are in that genus (e.g. Crocodylus niloticus, the Nile crocodile or Crocodylus acutus, the American crocodile) have only existed for a few million years. The croc bodyplan is very successful and survives, but the individual species perish and are replaced. – DrBob Jul 26 '16 at 11:12
• I agree. The interesting factor here is that within a very short time frame going forward, humans will largely exist within synthetic environments created to specifically favor them. In other words, like the crocodile but even more so, our environment will NOT change going forward because we now create our own environment. Take us into space and this is even more clearly the case. Pressure to "adapt" is largely absent, just a random mutation factor which we will have the technology to "correct" if we want to. – JBiggs Jul 26 '16 at 17:16
• Humans will definitely change aesthetically, most likely larger eyes and less hair We are becoming animé characters. – Renan Jul 26 '16 at 18:57

I would be shocked if homo sapiens exists 100My from now.

Either we will have done ourselves in by then or we will have advanced far beyond what we are now. There are a bunch of very stupid things in our genes, I would be very surprised if we haven't cleaned up our genome by then even if we have done nothing else. Fixing the flaws will make an organism that can't breed with Mark 1 humanity and thus it will be a new species, not Homo Sapiens.

In practice I think we would be many species by then as some groups decided to make changes that others didn't want to do. That's assuming we are even biological entities by then.

• Can't see, why there was a downvote here, this is the only truly correct answer. In 100 Ma, our descendents will be unrecognizable to us. That's enough time to rebuild the civilization hundreds of times and biological drift alone would alter us. But we surely would've taken evolution into our own hands a few times by then (a madman every 10 million years is far more than enough). – Chieron Jul 26 '16 at 7:56
• Well, it's ludicrous to say it's a correct answer because it's simply a wild (albeit educated) guess regarding anything that far in the future. Technically it's a guess even at 50,000 years or 500 years because we have no way of knowing what may occur. Still, Loren Pechtel's answer is a pretty good one. – Jesse Williams Jul 26 '16 at 18:04
• @JesseWilliams Very few answers on Worldbuilding are truly correct in a technical sense. That doesn't mean they can't be plausible, well-reasoned and well-articulated, which because we deal almost exclusively with hypotheticals here is about as good as you can get in response to most questions. (Exceptions do exist.) – a CVn Jul 26 '16 at 18:38
• I agree - that's my point. @Chieron said "Can't see, why there was a downvote here, this is the only truly correct answer." That made no sense to me because of the nature of this forum. – Jesse Williams Jul 26 '16 at 18:58

If there are no technological interventions, then humans will have long evolved away from their current form in just an eyeblink of time. Our remote hominid ancestors fist emerged about 5 million years ago, and distinctly hominid species can be traced back to @ 2 million years ago. Depending on how the environment changes, humans could evolve into almost anything (imagine a seal like creature evolved to hunt for food in the water).

There were two books by Dougal Dixon which looked at this idea way back in the 1980's, the first was called "After Man", which supposed that the human race became extinct along with a lot of other species; creatures like rats evolved to fill multiple niches (deer like creatures to sabre toothed predators) as one example.

"Man after Man" did the opposite, technology and civilization failed and human beings evolved to fill various niches, including some who became herbivores and others which evolved to prey on them (due to the damaged environment and genetic engineering, evolutionary pressure selected against general intelligence in favour of instinctive behaviours to ensure survival; an author's handwave).

If any human creatures existed 100 MY from now, they would almost certainly be recreations done as a hobby or art project by very advanced post humans, AI, or aliens (see A.A. Attanasio, "The Last Legends of Earth", set a billion years in the future).

Is your novel set on Earth or on other planets too? If there are people on other planets, natural selection will be altering them to adapt to, say the low gravity of Tau Ceti IV or the high uv of Sirius B III.

If they are stuck on Earth all that time, then there will be a few 'dinosaur killer' asteroids hitting, and mega volcanic stuff as continents drift around, along the size of the Yellowstone supervolcano blowing its top. Might be able to pack in a few ice ages too. All of those will potentially (unless your people have super high tech to prevent the disasters) cause periodic and massive population crashes.

Whenever there is a population crash, there is potential for genetic diversity to be lost by accident. And for previously rare genes to become common by accident.

Imagine, for instance, an asteroid hits tomorrow, and people only survive in large numbers in Australia. Future humanity would only have the genes and physical characteristics of the ethnic groups currently in Australia. Plus whatever new mutations arise and whatever they genetically engineer into themselves.

You might want to reign in your timescale. We're already tinkering with genetic engineering and mechanical enhancements 10,000 years after we first scratched runes into rock. "Humanity" could become a machine race in just a few hundred years if the transhumanists have their way.

Imagine explaining the concept of a machine-borne infomorph - or even the internet - to a caveman. Now imagine how incomprehensible things will be to us when given 10,000 times the advancement. In 100My our descendants would be as far past us as we are past a protein chain.

There's a rather haunting story (Baxter?) which I read, following humanity pretty much unchanged from the survivors of the disaster which ends our civilisation, to the approaching death of the planet as the sun starts to expand. Actually, more a set of word-pictures scattered across a billion years, rather than a story with a plot.

The underlying thesis, is that humans cannot regain a high-tech society because we have dug up and dissipated the key resources accessible to low tech. Future attempts, after millions of years of geological "recharging", will fail to reach our level due to scarcities, but only after again dissipating the key resources.

On the other hand, evolution will do little to re-shape us, because humanity even in a primitive state, changes the environment to meet our needs, rather than being changed by the environment. We kill the predators. We protect weaker members of our tribes. We uproot the weeds. We plant our crops. We tend our flocks and herds.

There are holes in the arguments. For example, evolution can be driven in unexpected ways by sexual preference. That's how the Peacock's tail and the Bower bird's bower happened: random accidents of the female bird's preferences spread over millions of years. Likewise, I think that a high-technology civilisation would eventually be re-attained by humanity, if we don't go extinct after the fall of this one. But equally, there has never before been a species that modifies its environment in the way that (even primitive) people do. So just maybe, recognisable humans will be around until Earth dies.

Food for thought:

## Evolution via natural selection has ended

Survival of the fittest no longer applies. In fact, humanity has become extra conscious not to discriminate against any physical or mental disadvantage, but to make an effort to include and support them. This means any of those traits which may be genetic have a much better chance of remaining than in past scenarios.

## Evolution continues externally through technology

In the past, if it got cold, the warmer/hairer beings survived and flourished. Now? Just put on a jacket. Not as fast as your fellow humans? Get a bike, or a car. Instead of forcing biological change, any difficulty in our environment now brings out technological improvements.

So, now our "evolution" is voluntary and conscious, the question becomes: How do we want to change? And, when do we want to change?

• natural selection has not ended, and natural selection is not survival of the fittest. Natural selection is about allele proportions in the gene pool. It is mostly about how many offspring your offspring have compared to everyone else. – John Nov 22 '16 at 2:18
• ^ but that's the point, what we would call the best/most desirable human beings aren't having 13 kids each, while the less perfect humans are having less kids. Instead we've made tech that lets healthy people not have kids (contraception) and enables less healthy people to stay alive and have kids. – Mirror318 Nov 22 '16 at 3:02

Natural selection is the primary motivating force behind evolution. It is the mechanism by which a group of organisms is more likely to pass on traits beneficial to their survival as the individual members who pass them on are more likely to survive. For example, giraffes with longer necks are more likely to find food then their short-necked friends, and are thus more likely to survive and pass their genes on to the next generation, resulting in longer-necked giraffes.

As all humans, without regard to their genetic traits, survive to pass on their genes to the next generation, and there are no traits which make you more likely to survive (and eventually procreate), humans do not evolve by natural selection.

That said, recent research does show minor changes in humans over time such as smaller teeth, smaller brains and so on. Personally, I think these changes do not reflect much considering that technology changed our lives so much faster than evolution ever did. That means that research conducted, even with humans from hundreds of years in the past, cannot come to any real conclusions considering the technological changes made in this interval (such as nutritional changes, medical improvements, changed lifestyles, awareness to pollution problems and so on).

I also think that as our technology improves we become more and more adept at adapting our environments to us (as opposed to natural evolution, which adapts the organism to the environment), and so lose the need to evolve, and thus, the mechanisms which drive it.

Bottom line, I think that humans in 100 million years will be vastly superior to us mentally, but will probably look very similar to us.

• not all humans survive to reproductive age, not all humans attract mates or reproduce, not all humans reproduce at the same rate, there are many traits that affect these things. Human are evolving, and will continue to evolve as long as any of these are true. – John Nov 22 '16 at 2:28

If the time span is basically arbitrary and not relevant to the plot, then 50,000 years is much more believable, and still seems an incredibly long amount of time. Because I think the chances of humanity being biologically the same and still living on Earth after 100,000,000 years are very very slim. So slim that you would need a convincing explanation as to why humans have not changed.

So really, I think the future is so open that you can predict whatever you want. Whether the reader finds it plausible is down to how good your plot and writing and backstory are.

The best way to understand how different the world might be in 100 million years' time is to consider how different it was the same length of time in the past.

100 million years ago, some of the first flowering plants were evolving, alongside the first bees. Some early mammal-like creatures did exist at this point, but without most of the features we would consider to make them true mammals. There were no snakes or ants. This is the age of the dinosaurs, but at this point even many of the most well-known dinos (T-Rex, Tricerotops, et al) have not yet appeared.

Evolution is a slow process, but at this scale the world is a completely different place. Entire classes of species have risen and fallen multiple times in that space of time. You should read the evolutionary timeline article on Wikipedia, as it can give some good insights into the topic.

Others have commented that "evolution has stopped for humans". They are basing this assertion on changes in our behaviour that have occurred in the last dozen or so generations or less. This is completely the wrong scale to think of evolution. Evolution hasn't stopped; it just isn't noticeable at that scale.

In the absence of world-changing cataclysms, you'd need to be looking at tens or hundreds of thousands of years to see noticeable evolutionary changes.

In a 100,000,000 years I think the safest answer is : We'll be evolved beyond a level we can comprehend. If such an "entity" would be sent back to 2016, it would be seen as a divinity.

Think about humans, 10,000,000 years ago we were tiny stupid monkeys living in trees, 100,000,000 years ago, we were some sort of hamster. Now from a hamster's point of view, we are gods, even beyond that. We can fly to space which is something a hamster's little brain can't comprehend.

In a few centuries at most we will probably have completely mastered genetic engineering. We will be able to "control" our evolution.

Then what we do from there will depend on our goals. Making ourselves healthier would be the first thing we ll do. By that I mean make our bodies naturally more resistant, increase our lifespan, have limbs that can regenerate etc...

We ll also try to make ourselves "better". In such an advanced world, physical strength would be even less relevant than in our current world (where it's mostly for esthetics). I think we ll try to make ourselves smarter.

Then there wil be some evolutions "just because we can". For example water breathing abilities, flyting abilities, all sort of skills from the animal world that can be applied to us.

Then maybe milleniums after that when we reach a level of intelligence orders of magnitude above our current levels our goals would probably be different.

Looking at the hamster vs us, look at 100,000,000 years of slow random evolution achived. Imagine what can happen in the same timespan if it s controlled by some super intelligent being... That s why I think that even the most imaginative sci-fi writers can't imagine how we ll decide to evolve and how we ll be in 100,000,000 years.

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