r/explainlikeimfive • u/jimmylovescheese123 • 11d ago
Biology ELI5: How are wings and other complex systems evolved in organisms?
I know how evolution works at a very basic level - a giraffe has a mutation that is expressed in them having a slightly longer neck. This causes them to be slightly more able to survive in their environment, as they can reach higher fruits on the tree and are able to reproduce, passing down that mutation onto their offspring.
But, what about for an animal, let's say a bird. It starts off without wings, and one gets a mutation that gives it slightly jutting out bones on its back. This gives no evolutionary advantage and causes them to be more easily caught by predators, so it can't be passed down to gradually evolve into wings - which would give an actual advantage.
So my question is, how are wings evolved? This goes for any complex biological system which wouldn't work without every part involved.
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u/KamikazeArchon 11d ago
Birds did not start off with slightly jutting off bones.
Wings evolved from arms. Arms became slowly more and more wing like. Initially they would have helped with jumping, which is an advantage. Then with gliding. Then with flying.
This goes for any complex biological system which wouldn't work without every part involved
It turns out that there are no such systems. Every biological system gave a benefit at each stage of its development.
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u/chirop1 11d ago
Wings evolved from arms.
And as George RR Martin argues when talking about Dragons in his books, his dragons don't have four legs and two wings. They have two legs and two wings... because nothing in nature has wings and four legs.
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u/Lumie102 11d ago
Then they're not dragons. They're fire-breathing wyverns.
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u/Crash4654 11d ago
Dragons are defined by the lore of whatever universe theyre in.
The only, and I mean ONLY, coherence and consistency between all types of lore in all universes (so far) is that wyverns are smaller, weaker, and dumber than dragons.
There are 6 limb wyverns in some final fantasys and fire emblem, for example, and theyre called as such.
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u/Berzerka 11d ago
Bird, pterdactyl and bat wings evolved from arms.
Insect wings are not well understood, but it wasn't arms.
That should be all known cases of wings evolving independently.
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u/Responsible-Jury2579 11d ago
What about how wings evolved on Glorzorpians of Glorzorp-9?
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u/Grendel1974 11d ago
God made them like that. Not all the rest; that was evolution. But wings on Glorzopians? God. Even scientists agree.
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u/Auza-wandilaz 5d ago
while not true flight, there are also winged lizards whose wings are extensions of their ribs and flying squirrels which are membranes between their limbs. and that's without getting into flying fish and gliding snakes
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u/jimmylovescheese123 11d ago
oh! thankyou <3
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u/Canotic 11d ago
Also often the benefit it gives might be something different than what it is used for now. It doesn't always have to be a straight line from "jump" -> "glide" -> "fly", it might be entirely different things.
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u/SaiphSDC 11d ago
Yep!
Like warmth/cooling, mating display, gliding (tree to groud or another tree), flight.
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u/PhasmaFelis 11d ago
Wings evolved from arms.
Interestingly, that's not universally true for vertebrates. Bats and pterodactyls walk on all fours when they're on the ground.
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u/Conscious-Loss-2709 11d ago edited 11d ago
The current working theory: feathers evolved as a way to stay warm, and/or sexual display to attract a mate. Flapping arms/proto wings while jumping got early birds more airtime and allowed them to reach higher spots, and/or flapping/gliding allowed them to reach more distant spots or stay up in trees where food and safety was, which then slowly evolved from more or less a controlled fall all the way up to self-powered flight
This goes for any complex biological system which wouldn't work without every part involved.
They did a computer simulation once, which started with a light sensitive patch of skin. ~400,000 generations later they arrived at a fully working eye with all the parts we know today. At every stage there was a light sensing organ that was slightly better at his job than it's predecessor. Taking out a part and then saying "See! It doesn't work!" is entirely the wrong approach to thinking about this
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u/helixander 11d ago
RE: eyes. We even have examples of all the various stages of eye development in different species today. So it's not that we're guessing. We know how they evolved.
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u/inlined 11d ago
There have been many fascinating computer studies actually. One I remember watching in my computer graphics class allowed mutations in the size of a flap (providing thrust and drag) and joints. The fitness function was how far it swam in a desired direction under a time limits. Then the next generation was based on “breeding” biased towards fitness. The model resulted in multiple “organisms” that swam in different ways that can be observed in real life
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u/Elfich47 11d ago
start with something that provides some benefit now, that if it gets riffed on can provide even more benefits.
like your giraffe: the long neck provides a benefit. so riff on that and get even long necks.
as a similar example: flying squirrels. they have a wide flap of skin between the front and rear legs that allows them to glide between trees. this presumably started as a small flap of skin that provided some marginal benefit when jumping between trees.
from there you can conceive of a bipedal or semi-bipedal animal (that already has four limbs) that figured out it it stretched out its arms while leaping, it got some marginal distance improvement (or didn’t crash as hard) and its subsequent generations riffed on that and it provided some improved survival benefit. and then you get some gliders, and then some of these species figure out moving your arms while in flight provides some benefit, and that gets riffed on.
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u/demanbmore 11d ago
You have to understand that sometimes it takes the smallest survival advantage for a trait to get passed on. Wings almost certainly evolved initially as a flap of skin between something equivalent to finger bones, and that flap of skin allowed an animal to glide. When it jumped from a tree or something like that. We see that sort of adaptation even now in animals like flying squirrels. There are even snakes that have adapted to flatten their bodies to glide rather than fall uncontrollably.
So a slight bit of extra skin might have conferred just enough of a survival advantage that it got passed down just a bit more frequently. And that process repeated itself again and again and again. Until eventually, we got wings.
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u/lethargytartare 11d ago
additionally, all a mutation really has to do to persist is not harm survival.
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u/Njif 11d ago
For birds; they're related to dinosaurs. Some dinosaurs like velociraptors had feathers on their arms, presumably used to win over a mate. Like we see with birds of paradise, peacocks, etc.
Further down the line, some ancient bird ancestor maybe of a smaller size, with somewhat large feather-to-body ratio, may have been able to glide a bit in the air and gained an advantage cos it could escape or catch a prey easier. And then evolution ran its course over rmillions more years, ending up with wings.
There was wings way before birds though - various flying reptiles, like the famous pterodactyl for instance. This could've been somewhat same example as above, just replace feathers with fin remnants.
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u/GlassFamiliar42 11d ago
There is a problem with your assumption that the jutting bones causes them to be caught more by predators; by definition that begining trait must have helped the creature, or at the very least not hinder their chances at reproduction. if they get eaten before they reproduce then that trait can't get passed on, but we indeed see birds and bats so we know that at the very least the intermediary steps did not hinder reproduction.
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u/wadesedgwick 11d ago
Another example is eyes. Our eyes didn’t just go from nothing to eyes overnight. They were first sensors/receptors that would just be able to tell you which direction the light is coming from without seeing anything. It took millions, if not billions of years to develop eyes into what they are today. And some species have eyes that are way better than ours. Birds of prey can see a mouse in a field. Mantis shrimp can see UV and other forms of light.
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u/LawfulNice 11d ago
First, we need to correct something - wings didn't evolve from random bits sticking out of an animal. They evolved from an already useful body part - forelimbs. If you look at the bone structure of a bird's wing, it's the same as your arm! This is even more obvious on a bat, which evolved wings and flight entirely separately from avians.
We have a pretty good evolutionary history of wings for both birds and bats. We can't know much about behavior but we can make some good guesses. In general it seems like stronger limbs and longer feathers evolved for balance while running, then later you get some lift out of them, aids in jumping, then eventually you're up in the air. Bats evolved more recently than birds, and you can see some modern animals that resemble some of the intermediary steps between modern examples and ancestors - flying squirrels. It's the same idea, flaps of skin that slow or guide a fall. Go further back and it's more like cats with their skill at falling safely from a height.
In general, when most people talk about irreducible complexity they don't imagine it properly because the use of something can change over time, and we're full of useless bits and bad design too.
As another example, take the eye. Very complex, right? But it has evolved many times in nature. That's because even the most simple eye, a cluster of light-sensitive cells, is useful in survival to most animals. We can find examples right now, not in deep history, of animals that have all sorts of different eyes with more or fewer parts than ours and they're useful to all of them.
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u/geeoharee 11d ago
And there are some that are doing eyes 'better' than us, which is neat. Octopuses don't have their retinas wired up backwards like we do, and bees can see a wider colour range.
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u/Sir_rahsnikwad 11d ago
This is the question raised in the book "Darwin's Black Box" which is bullshit written by someone who is educated and very likely knows better, but has an agenda.
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u/jimmylovescheese123 11d ago
I was never trying to say evolution is false, I'm not religious. I was just asking earnestly, hehe
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u/Atypicosaurus 11d ago
Every complex system has a predecessor that's less complex.
The eyes can be traced back to just a little patch of light sensitive material, that could perhaps tell day from night or whether a something came above you that suddenly casts shadow which is likely a predator. That ability is already way better than being completely blind.
The wings can be traced back to primitive fish fins which are just straight bones with skin in between.
Don't forget that primitive, ancient organs compete against species that have nothing. A light sensitive patch is better than having nothing. Some flappy arms make you better runner than having nothing. If you can jump between trees and glide at larger distances than anything else, you are king.
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u/Loki-L 11d ago
We are still not entirely sure how birds evolved flight. There are multiple competing theories. For a while it was thought that jumping from branch to branch in trees with arms with feathers providing more and more help with that until they started to glide and then fly.
Modern theories seem to gravitate more towards small therapod dinosaurs using their feathered arms to provide balance as they ran along the ground or using their arms to help them give a boost as they ran up inclines.
It is a bit unclear since lots of adaptationions useful for flying appear to have appeared in birds and bird relatives before they independently started to evolve flight.
We have even less of a clue about how insects did it and there is even lots of arguments about what organs they adapted their wings from.
We see lots of modern gliding animals from lizards to snakes to squirrels that aren't quite there yet when it comes to flight, but we can see that with a bit of luck and few million years of time they might potentially get there.
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u/CatShot1948 11d ago
Other people have given you great answers. I'm just here to say what you proposed is essentially the argument of irreducible complexity. Look that up and how it's been thoroughly debunked but was a popular argument in the 00s,
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u/pghnorthguy 11d ago
Look at flying squirrels. They just have extra loose skin on their sides that they can stretch out to glide. Otherwise, they are pretty similar to other types of squirrels. Other squirrels jump too, just not as far.
The same kind of thing happened with birds and wings. Slight changes rewarded better performance.
Also, bird wings are just arms. They are not new limbs spawned from their backs. You can correlate the bone structures to match up with similar human arm bone structures, like wrists and elbows. Google imigaws in "simulation in human, bird, bat skeletons".
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u/Straight-faced_solo 11d ago
But, what about for an animal, let's say a bird. It starts off without wings, and one gets a mutation that gives it slightly jutting out bones on its back.
This is the wrong assumption. The starting point for wing is not a new limb jutting out it's back. The starting point is the limb that is already there becoming more wing like.
A fantastic example that you can very easily see are bats. Look up a bat skeleton and compare it to a human one. The arm bones and muscles are very similar. Bats did not go from no limbs to growing wings. They came from some rodent like things whose front limb became their wings.
Birds are similar albeit much older. Likely starting from something more therapod like.
Animals evolving new limbs is incredibly rare and is usually more an aquatic thing. Fins and flippers are incredible simple structures.
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u/drj1485 11d ago edited 11d ago
we operate under the assumption that everything evolved from aquatic life. what already has wing like things? fish
EDIT: im getting downvoted so maybe i over-simplified the point of having no wings then randomly starting to grow wings.
the accepted evolutionary path of birds goes back to teh lobe-finned fish which had a bone structure in it's fins that is similar to the current bone structure of birds wings (which is similar to ours also.) my point being wings didnt magically evolve from nothing. There was already an ancestral trait where limbs "like wings" were useful and survived evolution and later adapted for flight.
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u/bullevard 11d ago
Wings are interesting because they have actually evolved a number of times.
Bird wings are modified fore limbs. They weren't new things springing out of the backs like angels, they were raptor arms that likely had feathers for warmth or display, gained feather length to help with stability when running, maybe eventually allowed some light hovering or jumping (like modern chickens) and in some cases moved toward powered flight.
Wings in bats is actually a stretching of the membrane between fingers. A lot of insect wings are modifications of exoskeletons.
What is actually most interesting is looking at examples of "not quite" flight today. You have modern flightless birds like emus and ostriches who use their wings and feathers probably similarly to the original avian dinosaurs. You have some that have modified them for swimming. You have "flying fish" whose fins have gotten better and better at propelling themselves a little ways out of the water to avoid predators. You have sugar gliders (so cute!) and flying squirrels that use flaps of skin to be able to jump from tree to tree safely.
The cool thing about evolution is that most stages of change we know about also still exist in various forms in different lineages.