When Insects First Flew

When Insects First Flew


Vertebrates get a lot of credit for being
able to fly. Birds, bats, and pterosaurs all took to the
skies, with the help of modified forelimbs that served as wings. But spare a thought for the insects, who evolved
flight only once, and never looked back. They were the first animals to ever develop
the ability to fly, and, arguably, they did it the best. That’s because evolution usually works with
what it has; new body structures don’t crop up very often. But in the case of insects, they didn’t
use modified limbs to fly. Their wings were a brand new innovation in
their physiology. And in fact, this development was so unusual
that scientists are still working on, and arguing about, how and when insect wings first
came about. So, I’ll tell you up front: There’s a
lot we don’t know. But one thing that experts do agree on is
that the ability to fly was something totally, completely new when insects acquired it. And it allowed them to take over the world. I’d like to show you the very first known
insect, as well as the first flying insect, but I’m afraid I’d start a brawl among
the paleontologists who study these things. Because, the fact is, almost every early insect
fossil has been disputed, or has been accused of being a different type of arthropod, or
even an artifact of modern contamination. One contender for the first insect ever is
known as Rhyniognatha hirsti, discovered almost a hundred years ago in Scotland. This little guy is more than 400 million years
old, and it looks like just an ink blot to somebody who doesn’t know what they’re
looking at. In 2004, some American researchers interpreted
Rhyniognatha as a flying insect — even though the fossil didn’t have any wings. Instead, they looked at its mouthparts and
decided they resembled those of a mayfly. But this conclusion was challenged in 2017,
by another team that used high-tech photography and decided that Rhyniognatha was more likely
a kind of centipede, not an insect at all. Much less a flying one. If Rhyniognatha isn’t an insect, then the
contender that everyone seems to accept as the earliest known insect are some very fragmentary
pieces of exoskeleton found in Gilboa, New York. These little fragments are about 380 million
years old, and are thought to have belonged to insects from the order Archaeognatha, a
group that includes some of the most primitive insects still alive today. Now, the earliest fossil evidence of a flying
insect seems to be the mayfly-like critter called Delitzschala bitterfeldensis from 325
million years ago. And, you’ll notice there’s quite a big
gap between the probably-earliest-insect and the appearance of winged insects in the fossil
record. Paleontologists have noticed this, too, where
fossils of insects are few and far between. They call it the Hexapoda Gap. For roughly 65 million years, basically the
second half of the Devonian Period and the first half of the Carboniferous, insects existed
and continued to evolve, but for some reason, they weren’t preserved very often in the
fossil record. This gap complicates the issue of when flying
insects first appeared. Right now, there are two main, competing theories. One theory holds that, if Rhyniognatha was
a flying insect, that would mean that the pterygotes — the taxonomic group that includes
flying insects — first came about in the early Devonian, say, more than 400 million
years ago. But, they didn’t become very numerous or
diverse, which would explain why they’re not represented well for those 65 million
years, until they suddenly exploded in diversity in the late Carboniferous. The other theory assumes that Rhyniognatha
was not a flying insect, so Delitzschala is the earliest one we know about, which appeared
tens of millions of years later. In this case, flying insects would have evolved
before Delitzschala, but not as early as Rhyniognatha — and we just don’t know when, thanks to
the gap. And sure enough, there’s some evidence to
support both of these theories. On one hand, molecular data for the origin
of flying insects line up with the age of Rhyniognatha, suggesting it or something that
lived during the same time might’ve been the first. A big, ambitious study published in 2014 used
genetic data to estimate the age of the entire insect class. They sequenced DNA from 103 species of insects,
representing every order known to science. And then they used this massive amount of
data to construct an insect tree of life, estimating when each group of insects diverged
from their common ancestors. Studies like this are based on the idea of
the molecular clock, which hypothesizes that mutations build up at a certain rate. When that rate of change is compared to what
we see in the fossil record, it can be used to estimate when a certain group first evolved. And the results suggested that flying insects
could have originated 406 million years ago, in the early Devonian — and that the common
ancestor of all insects lived a whopping 440 million years ago, in the Silurian period. So, the study didn’t weigh in on whether
Rhyniognatha, specifically, was a flying insect, but it said the timing makes it at least plausible. Now, the competing theory relies more on hard
fossil evidence to determine when insects first took flight. Of course, insects are small and fragile,
so they don’t make for great fossils. But insect wings fossilize pretty well, and
some scientists argue that when we start seeing wings 325 million years ago, like in Delitzschala,
it’s safe to conclude that the wings evolved not long before. But one thing that most paleontologists agree
on — and yes they do agree on something! — is that, when wings finally appeared, they
changed everything. The ability to fly allowed insects to escape
predators and forage for food in ways, and in places, that no other creature could before. Winged insects represent the vast majority
of insects today, and that diversity may be the result of the success that the power of
flight gave them. But because wings appear to show up so suddenly
in the fossil record, we don’t really know how this evolutionary breakthrough came about. There aren’t a lot of transitional fossils
to work with. So, how did wings evolve in the first place? For a long time, it’s been an open question
as to whether insect wings evolved as brand new structures, or were adapted from some
pre-existing body part — the way bird wings evolved from forelimbs. Some genetic and fossil evidence supports
the idea that wings started out as gill structures. Many species of aquatic insects have flat
extensions on the thorax and abdomen, when they’re in their nymph phase. They sometimes have patterns that look like
the veins of wings, AND they can even flap! But, while the gill origin theory has received
a good deal of support, more scientists now seem to lean towards the wings being a brand
new kind of structure. In recent years, scientists have hotly debated
whether the body tissue came from the top of the insect, known as the notum, or the
side of the body, known as the pleura. And again, there are good arguments on both
sides. The notum would have provided the stiff, rigid
structure that wings need to create lift and support the insect in the air. But having them develop on the sides of the
body would have offered maneuverability. And in fact, research has found that the genes
that create moveable joints in insects activate on the sides of the body. Since an insect’s legs develop from its
sides, and they obviously move, then possibly those same genes or similar ones would be
needed to give the wings their ability to flap. A study of ancient insects conducted in 2017
said: Why not both? It provided support for the hypothesis that
wings could have come from both the top and the sides. This research looked at insects from the late
Carboniferous, like Idoptilus. In its nymphal form, it had two pairs of wing-like
structures, plus a third pair of stiff lobes extending from the sides that might have been
used for thermoregulation. The authors believe these lobes represent
what the earliest form of insect wings were like. Most of the structure came from the top, providing
rigidity, while the flexible wing joint came from the side of the body. And even though these young insects probably
couldn’t fly, those lobes could have been used to glide. So it could be that the ancestor of all pterygotes
had three pairs of lobes, too, which could have been used to glide from the tops of,
say, scale trees. And then, those lobes were adapted for use
as wings, as insects developed the musculature needed for powered flight. In the end, we don’t know for sure when
insects first flew. Or where their wings even came from! For now, the origins of insect flight remain
one of paleontology’s great mysteries. But we do know that the evolution of flight
played a key role in helping insects thrive as they do today, living on every continent
and in nearly every ecosystem, as one of natural history’s greatest success stories. Thanks for joining me today, and thanks to
all of our patrons who help make these videos possible. And we want to thank our first two eontologists,
Duncan Miller and David Rasmussen. Thank you so much for your support! If you’d like to join them, head over to
patreon.com/eons and pledge for some cool rewards. Now, what do you want to know about the history
of life on Earth? We love your suggestions and you know we read
them because this episode is proof of that! And if you haven’t already, be sure to go
to youtube.com/eons and subscribe!

91 thoughts on “When Insects First Flew”

  1. Do an episode on, What if we had bigger brains? I'm thinking in terms of communication, understanding, learning quicker, more compassion, less gullible, less greed, better memory.

  2. I'm writing a paper over Paleoentomology, and this information is great! i've already used some of the information form your Trouble with Trilobites and Carbiniferous videos, and it is all great! It does not help, however, that the scientific community cannot come to one conclusion over the origin of insect flight. Still, great video!

  3. They may have developed just some body parts to lure mates, like hardened scales that could be lifted or moved. Eventually, just the way some birds develop very long feathers only for display, they may have developed these parts so large and wide that they finally gave support, and became more useful for surviving than for mating. at that point they evolved for flying instead of for showing off.

  4. I think I found a math error at 2:44. 380 – 325 is 55, not 65. Dear PBS, let me know if you'd like me to proof your scripts 😉

  5. I like this new tendency to present uncertain things as uncertain things instead of presenting them as scientific facts. This way we can have less Jerry Smiths creating a fuzz because Pluto is not a planet.

  6. To the people that doesn't study or is interested much in paleontology, it's true, a lot of paleontologist disagree with each other in almost everything.
    I, who studied paleontology just because I got interested since I was a kid, am against the idea that dinosaurs died from a meteorite, for example. I still feel like the impact of a meteorite doesn't kill big animals, but leave small animals alive.

  7. Maybe insects that came from the water that had paddle like limbs on the sides to swim moved to land? To get the basic structure of wings?

  8. Before us humans came along, insects had already pioneered:
    -biorobotics
    -flight
    -shapeshifting
    -chemical weaponry
    -engineering and urban construction
    -thermal sensory equipment
    and many other things
    Kind of makes me feel a bit inadequate, I've gotta say…..

  9. Wouldn't epigenetics undermine the concept of a predictable mutation rate, since genetic expression has more than one way to be modified? Also, since evolution doesn't have to be random mutation driven, it does open up the possibility that wings developed specifically to be used for flight.

  10. 2:25 Delitzsch and Bitterfeld are small cities in Germany. I live about 45 kilometers away from them. It's cool to see something like this is was found (and maybe lived) so nearby.

  11. Lmao now I just noticed the old inaccurate illustration of prehistoric aquatic reptiles in the background

  12. Like many things, insect wings may have started just as protective shells that they used to flap to scare predators, lure mates, or threaten rivals, and at some moment they became so large or shaped in such a way that the flapping suddenly lifted them for the first time. From that point on evolution did the rest is promoting those who got an advantage from that.

  13. I would like to know about the impact that the power to fly in insects had in the rest of the nature. Thanks! (Excuse my poor English, thanks for this too).

  14. Yay! Beautiful clear voice, thank you pbs please have this lady narrate all your episodes! The guy that narrates the science/space videos is hard to understand
    Thank you for this episode
    PapaBless🙏

  15. I'll tell you exactly when flight first appeared.

    It was on a Thursday.

    I've always had the hang of Thursdays.

  16. Maybe those gill structures evolved into solar panels to warm the insect up, and the muscles that aim them at the sun evolved to flap and cool the bug like fans when it got overheated, and the flapping evolved into flight.

  17. Got me imagining that first moment a bug flew. And we thought humans doing it almost 400 million years later was a big deal. It was literally never done in the 4 billion years Earth existed prior.

  18. she's a master of teaching! I bet she could tell any story,like a tale from Grimms Bruder, will still be soooo nice to listen; toda

  19. 7:30 Idoptilus with bigger thermo-regulating wing nubs about to get eaten in the morning while its wing nubs are up…

    Breeze comes up in the early morning and blows Idoptilus away …due to its bigger wing nubs.

    Idoptilus thinks, "Hey, neat trick. I can just try to thermo-regulate whenever a predator approaches!"

    Survival of the "fittest" and voila: ever bigger wing nubs.

  20. When did insects stop flying and disappeared almost overnight? The day we turned on 5G! NOT A PREDICTION A FACT.

  21. Thanks for the great content!!! Please make a video about the origin of phloem and zylem. Or maybe one about the origin of plastids.

  22. – For a Limited Time Only Glamour Shots By Deb are 75% Off –
    She's trying to raise money for college

  23. Imagine how much it must have freaked out early humans to see little angry bugs flying around them

  24. Arthropods had also conquered the land long before our ancestors crawled out on land.

  25. Insects were also the first to reach sentience a race of praying mantis beings were the earths dominant sentient life form up until the first tree eating microbes formed and destroyed the worlds o2 supply.

  26. Another perfectly narrated video 👏🏻 As a non-native English speaker, thank you for your clear and beautiful pronunciations 💖

  27. maybe look into the eras on which plants started flowering? flowers are definitely used to attract potential pollenizers. I get hammered and watch these videos. Absolutely love these videos.

  28. Maybe the wing it didn't evolve from anyting previous. I would imagine the further back in time to go the smaller the creatures get. Now creature living in water would have to propel himself through water and offend would involve first and the fin which convert to a wing as it moved on land.

  29. For someone with hyperacusis or sensory processing illness that background noise is unbearable. Another video I can't watch. Would love some feedback, honestly curious if its even that popular for people without hearing/processing issues? This channel has super interesting content, does it need background 'ambient' music anyway?
    Thanks for reading

  30. Well no one saying anything to this beautyfull girl carrying us eons in the past?
    Well hands down to her, perfectly explayning us this stuff, with such a beautifull voice and smile. Well done.

  31. Wings started as little solar panels to help insects warm up quickly and maintain high metabolism to be able to move quickly and avoid predators.

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