In the early 1980s, author Dougal Dixon published the cult book After Man: Zoology of the Future, which imagined what life might look like a million years into the future.
Dixon envisioned shrews that use their tails as parachutes, flying monkeys, and extremely long coiled snakes that slither and catch birds in flight.
He also envisioned nocturnal birds impaling their prey on long spines that protrude from their chests and birds with flower-like faces that appear to lure pollen-seeking insects right into their hungry mouths.
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Decades later, Dixon says his book was not an attempt to predict the future, but an exploration of all the possibilities of the natural world.
"Popular books on evolution, even when they don't do it on purpose, suggest that evolution is something that happened in history," he says.
"That is not true. Evolution is taking place even today, and it will continue to take place in the future, long after we are gone."
And while Dixon's book was fiction, most biologists agree that, millions of years from now, the Earth will be completely different.
"I think it will look like an alien planet," says Athena Aktipis, an evolutionary biologist at the University of Arizona.
Whatever happens, it will seem strange and unbelievable to us - just as today's world, dominated by mammals, would seem impossible from the perspective of the era in which the dinosaurs lived.
So what could life look like in the future?
What creatures might evolve in, say, 100 million years, given everything we know today about life on Earth and evolutionary principles?
Let's start by going back many millions of years to the era when there was already life on our planet.
At the time of the Cambrian explosion, some 540 million years ago, according to Jonathan Losos, an evolutionary biologist from Washington University in St. Louis, the Earth was inhabited by a large number of rather "twisted" creatures, which seemed to have come out of a cartoon.
"The Burgess Shale in Canada was a truly bizarre menagerie," he writes in the book Amazing Stories: Fate, Probability, and the Future of Evolution.
One of the animals, a hallucigenia, with a thin, tubular body covered in rows of large spines and stiff clawed appendages, looked more like "something out of an episode of Futurama."
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Consequently, it is not impossible that similar, strange and unusual creatures will arise in the future.
"Almost anything you can think of has already appeared somewhere, at some time, in some species," says Salmon.
"It only takes time, and something unexpected will appear."
According to Losos, the world of biological possibilities is vast, and apparently we haven't seen it all yet.
"To begin with, I am not convinced that life on Earth has revealed to us every possible way or even most of the possibilities of survival on such a planet," he wrote.
However, it is still difficult to predict which possibility will be used in the future.
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Salmon's book analyzes the arguments both for and against the predictability of evolution - the only question is whether history would repeat itself if the same conditions were to occur.
The evidence is fragmented and we simply do not know to what degree evolution is predictable and whether it can be repeated over long periods of time.
If we add to all this the element of probability - a huge volcanic eruption or an asteroid hitting the Earth - firm predictions become almost impossible.
However, we can predict some things.
First of all, we have to highlight the influence of a great evolutionary force that is already changing the world around us - Homo sapiens.
If humans progress for millions of years, they will have an evident influence on the future of evolution, and natural selection will give birth to new varieties of life that will survive in the changed, polluted world we are creating.
"We can already see the evolution of a bird's beak specialized for extracting food from cans, or rats that developed greasy fur to wade through toxic sewage," writes paleontologist Peter Ward in his 2001 book The Future of Evolution.
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Ward envisions various possibilities for new types of species that have "weed" characteristics.
They are hardy, adaptable creatures that don't mind coexistence with humans and are capable of using their world - domestic cats, rats, raccoons, coyotes, crows, pigeons, sparrows, starlings, flies, fleas, ticks and intestinal parasites.
On a hotter, drier Earth warmed by humans, the lack of water could also trigger new adaptations.
"I can imagine animals that have developed unusual traits if they didn't take advantage of the moisture in the air," says Patricia Brennan, an evolutionary biologist at Mount Holyoke College in Massachusetts.
"Larger animals could get extended sails or flaps of skin that could elongate and collect moisture in the early morning.
The decorative collars of some reptiles could become very large and oversized, so they wouldn't collect water that way."
In a hotter world, Brennan also predicts an increase in naked mammals and birds:
"Mammals could lose fur on some parts of their bodies to be able to collect water in skin pockets.
On a warm planet, warm-blooded animals could have difficulties, so birds in warmer regions could lose the feathers that give them shape and line to avoid overheating, while mammals could lose a large part of their fur."
In the future, people may decide to directly manipulate life - in fact, this is already happening.
Researcher Lorin Holt told the BBC's Future and Deep Civilization series earlier this year that one possible trajectory for life could be "post-natural".
In such a scenario, genetic engineering, biotechnology, and the influence of culture could redirect evolution down radically different paths, from mosquitoes carrying the genetic code to mechanical pollinator drones.
The evolution of life could be entangled with the wants and needs of humanity itself.
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However, there are also alternative paths of evolution in the future: our most enlightened descendants could, for example, decide to leave nature to find its evolutionary course again, because otherwise humans could become extinct.
Extinction in particular can lead to the erasure of evolutionary innovations.
In essence, mass extinction resets the evolutionary clock, Ward says.
After previous mass extinctions, he says, plants and animals on Earth have changed radically.
During the Permian extinction, some 252 million years ago, about 95 percent of marine and 70 percent of terrestrial species were eliminated, including the reptiles that had fins on their backs, as well as the massive mammal-like reptiles that then ruled the Earth. .
This gave dinosaurs room to evolve and take over the dominance of land animals.
This outcome was unexpected and improbable, just like the one when mammals replaced dinosaurs after the Cretaceous-Tertiary mass extinction.
"It was not only a turning point, but something we might call a turning point," Ward writes.
"Mass extinctions changed much more than the number of species on Earth. It also changed the appearance of the Earth."
Some scientists think that, after the extinction, it is possible for completely new life forms to appear with new abilities.
In the first billion years on Earth, for example, the life of oxygen-breathing animals was unimaginable, because oxygen was not present to a large extent, and cells were not evolved enough to be able to use it as energy.
That changed forever with the Great Oxidation, some 2,4 billion years ago, when the arrival of photosynthetic bacteria led to Earth's first mass extinction.
"Thanks to microbes, the whole planet had oxygen and that caused big changes," said Leonora Bittelston, an evolutionary biologist at the Massachusetts Institute of Technology.
"There were many evolutionary innovations that were difficult to predict before they happened - but the moment they started to appear, they changed our planet."
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So it begs the question - if humans die out, what kind of crazy and sophisticated things will happen in the next 100 million years?
Will trees start walking or feasting on animals after killing them with toxic fumes or poison darts?
Could marine life be changed by spiders going into the water and using nets to collect sardines, or by fish learning to fly instead of feeding on insects or birds?
Could deep-sea animals start projecting their own holograms to fool predators, attract prey, or impress mating partners?
Perhaps killer whales or catfish could regain their ancestral land-running abilities to be effective hunters on land?
Could we also see organisms inhabiting previously poorly explored habitats: perhaps light but poisonous fungi could float through the air like air jellyfish and engulf and consume everything they come across?
Could insects and spiders build silken nests in the clouds to feed on photosynthetic organisms in the sky?
And if plants or microbes evolved with the ability to absorb and concentrate sunlight like solar panels, would green oases of life swell on ice glaciers as well?
None of these fantastical creatures sound impossible, says Aktipis.
Many of them are based on what already exists in nature: sea spiders, as well as those that sail through the air, exist.
There is also a world of microbes in the clouds, as well as a scorpion fish from the depths that has bioluminescent balls to attract its prey.
Some species of killer whales and catfish can come ashore to hunt, and small, independent oases of life thrive on the ice where there are remnants of cryoconite, a black dust made of soot, rocks and microbes.
Joe Wolfe, an evolutionary biologist from Harvard, notes that there are trees that "walk" very slowly, thus approaching water sources.
She thinks it's possible for trees to evolve and hunt by using poisonous gases or even thorny branches.
Finally, we already have carnivorous plants such as Venus flytrap.
She also points to the existence of spiders that feed on fish and says that clouds inhabited by microbes could possibly originate from the multitude of tiny organisms (picocyanobacteria) that live in the upper layers of the ocean.
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All that is needed for these unusual adaptations in nature is an extreme environment.
There are already plenty of such places on Earth and that will not change.
Just imagine, for example, how male scorpionfish would respond to the critical absence of potential mating partners in the ocean depths.
When a male finds a female, he actually mates with her body.
"Since he's unlikely to find a female again, he surrenders and becomes just an incidental reservoir of sperm for her," says Christine Hook, a behavioral ecologist at the University of College Park in Maryland.
"We could see more animals doing this kind of thing, and I can imagine eventually animals that are able to self-fertilize when the search for a mate turns out to be futile."
Based on what we know about nature, we should not assume that creatures in the future will remain confined to their present habitats.
Lin Caporale, a biochemist and author, points out that some flying fish can already hunt insects (and even birds), while some fish are able to walk along the shore and climb trees.
Even squid sometimes fly above the surface of the ocean, using water droplets as propulsion and fins as wings.
This potential for habitat modification also leads to some truly fantastic possibilities.
Think of a frog and its throat that can swell on the outside like a gas bag used for mating calls.
In the book, Ward predicts that it will evolve into a "zeppelinoid," a new type of floating animal that will rule the lower atmosphere.
Evolution could give the frog the ability to make hydrogen from water and store it in its throat, thus helping it to jump and possibly fly through the air.
Her legs - now no longer needed for walking - could become dangling tentacles used for feeding.
Frogs could also gain in size through evolution, if they would not avoid ending up as food themselves, even to the size of a blue whale.
Giant zeppelinoids would float through the air like jellyfish, use their tentacles to hunt game such as deer or graze treetops.
They would completely fill the sky, and their shadows would dominate the landscape - it would be the age of flying frogs.
Zeppelinoids, says Ward, are "a fairy tale - but even in this story there are hints of reality".
There was once the first flying organism, as well as the first swimming organism, and we know that many more species evolved from them, as evolutionary innovations allowed them to take over a habitat they had never inhabited.
Given that our understanding of evolution and genetics is incomplete and that much will depend on chance, no one knows for sure what the future will look like.
Predicting evolutionary winners in the future is like predicting winners in the stock market or forecasting the weather, Ward says.
We have some data that allows us to predict something, but there is also a large degree of uncertainty.
"We can only guess about the colors, habits and forms of the new, evolved fauna".
Salmon agrees with that. "At the end of the day," he says, "the possibilities are so vast and uncertain that it has become pointless to even speculate about what life might look like, because there are too many open questions."
Life could change in different ways."
But if the strange phenomena we have today are a kind of guide, then we would have to count on the possibility that evolution could take some surprising paths in the future.
By the way, much of the current natural diversity and individuality still remains unexplored.
Indeed, Dixon notes that several of his original and "purely speculative" creations that he describes in his book After the man from 1981, subsequently discovered: walking bats, for example, as well as snakes that are able to grab a bat in flight.
Here is what he wrote in the foreword to the 2018 edition of the book:
"So many times I've come across new ecological or evolutionary processes that I thought would make everyone laugh if they were in my book."
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