# What evolutionary pressures would lead to fairies?

Consider this a remake of my "Why might a group of insects evolve to resemble humans?" post. Fairies are a common trope in fantasy works, residing in woodlands and swamps some characteristics of fairies and their associates are:

• being 11 in tall
• have raven level intelligence (optional)
• are erect bipeds
• have butterfly/moth like wings
• are capable of flight
• are nocturnal
• live in large groups
• have an average life span of 3 year
• are capable of imitating human laughter
• look surprisingly humanoid. (optional)
• have proportionally larger heads and eyes

Now given these characteristics, so what species would fairies have evolved from, what evolutionary pressures would lead to them?

NOTE: magic does not exist in my story

• Human level intelligence is probably right out considering brain mass and energy requirements for a biological brain with human sapience levels. – Dragongeek Feb 9 at 23:49

There is no evolutionary pressure I know of that will do this

You have two impossible conditions (technically three including the optional one, but it's optional). These are 'bipedal, with wings' and 'looks surprisingly humanoid'. A creature the size of 11 inches would have no reason to look humanoid - in fact, it would have several reasons not to. This is because of the square-cube law - that is, muscles become far more efficient at smaller sizes. Human anatomy is custom built for out glorious range of height from around 4-7ft. If you were building it on a smaller size, you'd use muscle grouping that aren't the same as ours, not to mention that the face would be designed slightly differently. After all, we're omnivores designed for a massive diet. A creature 11 inches can't have our diet, and thus the it's mouth would be a lot of misspent energy if it replicated ours. Similarly, eyes don't work the same on a smaller scale, so just having two scaled-down eyes would more or less render your poor fairies blind.

Bipedal with wings is also an issue. Having six limbs isn't a problem - you can base it off of insects. But a bipedal body is just wasteful on that small of a scale - there's no point. An exoskeleton would serve better than skin at that size, not to mention that the interior anatomy of a bipedal animal is drastically inferior to an insects at that size. There are methods of creating 'fairy-like insects', certainly, but if you want it to look like a human, it's not going be an evolved life form.

• An exoskeleton would serve better than skin at that size... there are plenty of mammals that are 11 inches or smaller. Plenty of birds, reptiles, and amphibians too, for that matter. – cowlinator Feb 11 at 4:05

Protection or selective breeding

People may be less likely to kill off creatures that look very human compared to some that don't. There is a reqal-world precedence for this in "Samurai crabs", a species of crabs with a shell that bears a pattern resembling a human face, which many believed to be the face of an angry samurai. It has been hypothesised that crabs with shells resembling samurai were thrown back to the sea by fishermen out of respect for the Heike warriors, while those not resembling samurai were eaten. Thus, the more closely the crabs resembled a samurai face, the more likely they would be spared and thrown back, causing selection for this sort of look. Similarly, 'faeries' that somewhat resemble humans may have been selected or even bred to more closely resemble humans.

Cuteness may also be a factor. People tend to find squirrels cute and hence refrain from killing them - we even feed them. If squirrels looked like rats, we would not be so kind. Similar forces could have caused selection for cute humanoid faeries.

A fairly big caveat is evolutionary timeframes. Humans haven't existed long enough for evolutionary pressure to produce 'surprisingly humanoid' beings from very different species. Selective breeding is far more likely - just look at how dogs have been bred from wolves to all sorts of sizes and looks.

As for what species may be the root, on Earth insects would be the most likely candidate. It is far more difficult to add limbs or wings through breeding than to remove them. Insects have six legs and four wings, so all we need to do is regress one fair of legs into nothing (or accept fairies with four arms). The thorax (which is where all insect limbs and wings are attached) would have to be expanded and elongated, while the rear body would have to be much reduced, perhaps ending up looking like a sort of short, stubby tail. The bodies would be exoskeletal rather than having soft surfaces. They would have mandibles rather than mouths like ours. Their overall shapes might be made to resemble humans, but all sorts of details would stand out.

Another candidate might be a mammal similar to a bat or flying squirrel, or perhaps some kind of flying monkey built along similar lines - but then, the wings would have to double as arms, and they would be leathery rather than insectile. On the other hand, it will be far easier to breed them to have bodies and faces that are very close to humans.

You might be able to create "fairies" with evolutionary pressures and a bit of chance but they would never hold up to close scrutiny in the "human-like appearance" category. For example, a realistic fairy could be:

• Large, six-limbed insect with wings for flight
• When they're flying, the two pairs of rear legs hang down together and the two forelegs hang to the sides, imitating a somewhat human silhouette
• They have some sort of bioluminescence similar to fireflies and when humans see them in the dark, only a small, somewhat-human shaped figure is visible, floating in the air
• Fairies live in swamps or dense jungle and due to their light and their somewhat human shape, have evolved to lure people into swamps, wait for them to die, and then eat them
• An insect living for three years isn't unheard of
• These creatures may hunt humans and other lure-able prey in packs or swarms, giving the illusion of a society
• Maybe, they have some sort of sound organ similar to cicadas or grasshoppers which lets them imitate a human laugh or something equally creepy

I would like to add, in addition to the answers given, that a squishy, fleshy body/limbs is not impossible with the fairies being insects. Look at caterpillars. Fairies needn't be hard/scaly i think.

Secondly, not all insects have scary inhuman mandibles. Butterflies don't have them for instance.

And thirdly, while the face may not ever have really the same parts as a human face has, it's possible that like the aforementioned samourai crab, the fairy has some shapes/colors that give the impression of human lips, a nose, eyebrows. Much like this caterpillar resembling a snake: https://www.earthtouchnews.com/wtf/wtf/this-is-not-a-snake-its-one-of-the-best-mimics-in-nature/

One last comment regarding intelligence: if brain size is an issue (being too small to be sufficiently intelligent), there is a kind of wasp (trichogramma) which is so extremely tiny that it evolved smaller neurons so that its head didnt need to be so big (amongst other adaptations). So it may be possible that the fairies miniaturized neurons to increase intelligence.

A strange way to get to fairies could be if their were human-like marsupials that evolved to grow extremely slowly and do no parental care. They may make small wings for their larvae to fly around with. Although this isn't much like what you describe in the question, it could definitely be called a fairy.

Fairies as described in the question could evolve from a Microraptor or similar creature, which became more able to fly, and lost its hindwings. Its hand would become more able to grasp, and it would become more intelligent and social. It may find humans, and see them as some sort of gods, and so they would create masks to appear as humans, and pluck their body feathers, in order to become more like humans.

Would the size of the fairies matter if the world around them was bigger?

They could have evolved to about 4ft to retain a humanoid appearance. Wings could be a newer evolutionary trait to escape to higher sections of trees if hunted by animals that are huge in comparison. Trees could be massive, as well as any other plant and animal.

It could be a matter of perception of the size that makes all the difference. They know they're small, their world is huge and tThey wouldn't know any better unless faced with a human. Measurement and size is only really drawn to the human perception of size who have made those tools to measure such things

Humans(or human like creatures) have been around for a lot longer.

In our word human society changes very quickly on an evolutionary time scale, meaning there hasn’t been enough time for animals to evolve complex features in response to us.

A lot of the previous answers rely on fairies to evolve in response to human activity, looking more and more human to avoid getting killed. This makes sense, but I can’t imagine a bug like would evolve into a humanoid in the time scales we see on Earth.

I could however imagine a species that looks and acts very similar to us, with some sort of difference that prevents them from developing the kind of tech that would lead to changes in human life. They could have more trouble than us imagining 3D objects coupled with Amish like religious beliefs. Maybe they could be living in a world without fossil fuels that prevents them from industrializing. Maybe they evolved away from having the brain structure to develop new technology after Developing farming tech. In effect, these people could be more like ants evolving agriculture than humans coming up with new ideas

Whatever the case this leads civilization to be stuck at a medieval tech level for millions of years, giving enough time for life to adapt to human’s presence. A large type of insect began evolving to have a more human like appearance, with marking that mimic human faces and the like. They don’t have to actually have human like features just the appearance of human like features.

This could even fit in with classic Tolkien characterization of fantasy races. Dwarves for example as a sort of clockwork like creature in their behavior, with a lot more instinctual motivations for their behavior rather than cultural ones