The Age of Giant Insects

The Age of Giant Insects

This episode is supported by The Great Courses Plus Even though we often refer to this time in
history as the Age of Mammals, we should probably be calling it the Age of Insects. Because, just looking at the numbers, there
are way more of them than there are of us. Humans alone number more than 7 billion at
this point, which is … a lot. But insects? Try 10 quintillion! We may like to think we’re in charge because
we make the rules and, well, we’re bigger than they are. But insects, and other arthropods, weren’t
always so small. About 315 million years ago, they were not
only abundant. They were … enormous. To meet the biggest invertebrates to ever
crawl across the Earth, we have to go back to the Carboniferous Period, from 298 million
to 358 million years ago. That’s when you’d find the likes of Meganeura. It was a griffinfly, a giant relative of today’s
dragonflies, that had a wingspan of about 70 centimeters. That’s about the size of a pigeon — more
than three times larger than the biggest living dragonfly. Meager by comparison was Stephanotypus, another
griffinfly that was still some 40 centimeters across, about as big as a robin. And this greatness in size wasn’t limited
to insects! You see out-sized arthropods all over the
world during this period… like Arthropleura. You know those cute little millipedes you
find curled up under rotting logs in the woods? Now imagine one of those about two meters
long and a half meter wide, shuffling like a living carpet over the undergrowth. It was probably the largest arthropod that
ever walked on land. So. What allowed these invertebrates to get so
big? The answer … is oxygen. Take a deep breath. Right now, the amount of oxygen in atmosphere
is about 21 percent. But back in the Carboniferous, it was nearly
35 percent! That’s because the Carboniferous was a time
of incredible, runaway plant growth. Huge forests full of ferns, mosses, and some
of the earliest vascular plants had taken over much of the planet. They sucked in carbon dioxide and pumped out
oxygen in enormous amounts. Now, you might be thinking: Earth has lots
of trees now. So what’s the difference? Well, today, that big log you find in the
woods with all of those bugs under it? That log is being decomposed by bacteria,
among other things, that take in oxygen, and release CO2. But in the Carboniferous, those wood-eating
bacteria didn’t exist yet. So Earth’s giant, primordial forests were
taking in lots of carbon dioxide and pumping out lots of oxygen. That’s what plants do. But since the trees weren’t decomposing,
the CO2 wasn’t being released back into the atmosphere. The result was an all-time high in the world’s
levels of atmospheric oxygen. And that’s what made giant arthropods possible. Because, arthropods don’t breathe the way
we do. They have a system of external openings called
spiracles, that lead to a branching network of tubes called tracheae, that diffuse oxygen
through their bodies. And this puts a limit on their body size. Arthropods can only get so big before they
can no longer draw enough oxygen from the air. But in the Carboniferous, the abundance of
oxygen in the atmosphere made it easier for arthropods to get the O2 that they needed,
which allowed them to reach record-breaking sizes. In fact, paleontologists have managed to make
this happen today in the lab, by experimenting with modern insects. By raising dragonflies, beetles, and other
insects in controlled, oxygen-rich enclosures, scientists at Arizona State found that successive
generations of arthropods can grow faster and larger. But, of course, it’s possible to get too
much of a good thing. So, some scientists have proposed another
theory — that arthropods got huge not because they could, but because they had to. Lots of oxygen might have been a beneficial
for grown-up arthropods, but it also could’ve posed a threat to their larvae. Young invertebrates can’t control their
intake of air like adults can, and too much oxygen can be deadly. So researchers at Michigan State have suggested
that ancient arthropods began producing bigger larvae, so they’d take in less oxygen relative
to their body size. And those bigger larvae resulted in bigger
adults. But, you know enough about natural history
at this point to know that even the biggest creatures don’t stay on top forever. About 275 million years ago, during the Permian
Period, the world changed, yet again. The levels of atmospheric oxygen started to
plummet — why, we’re not sure. Ancient climate shifts might’ve had something
to do with it. But as oxygen levels fell, the interiors of
the world’s continents got warmer. This shrunk the big swamps that were acting
as natural carbon sinks. So, swamps weren’t pumping out as much oxygen
as they used to, and, on top of that, decomposers finally appeared that were able to start breaking
down all of the dead wood. As these microbes took in oxygen and released
carbon dioxide, global levels of O2 dropped even more. And with less oxygen available, it became
increasingly hard for the giant arthropods to survive. By about 305 million years ago, the two-meter-long
Arthropleura could no longer be found on the forest floor. By 299 million years ago, the last of the
Meganeura had flapped its wings. The arthropods that followed never got quite
as spine-tinglingly large as their ancestors were. But, of course, everything turned out fine
for them! Today, we’re totally outnumbered, both in
biomass and in diversity, by insects, arachnids, and other land-based arthropods. But if there ever was a time that was a true
Age of Insects, it was probably the Carboniferous Period, when arthropods of all kinds were
living large. Thanks to the The Great Courses Plus for sponsoring this episode. The Great Courses Plus is a digital learning service that allows you to learn about a range of topics from educators including Ivy league professors and other educators from around the world. Go to and get access to a library of different video lectures about science, math, history, literature, or even how to cook, play chess, or become a photographer. New subjects, lectures, and professors are added every month, like the Introduction to Paleontology series taught by Professor Stuart Sutherland. You can learn about everything from Earth’s shifting crust to Taxonomy and more! With The Great Courses Plus, you can watch as many different lectures as you want – anytime, anywhere without any tests or exams. Help support the series and start your free one month trial by clicking the link below or going to What do you want to know about the story of
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and subscribe! If you think dragonflies are fearsome, wait till you see their babies. Our friends at Deep Look filmed them shooting out their super-fast mouthpart to catch a meal. Check it out here.

100 thoughts on “The Age of Giant Insects

  1. imagine an army of ants coming close to a settlemeny or human successfully donesticated them xD

  2. Oh man I know everyone's thinking this wish we could go back in time and just breathe the sweet sweet oxygen giant bugs that you could ride like a horse lol and they probably even try to eat us that would be awesome 😂

  3. Yey Michigan! We's got them good fresh lakes!
    Unfortunately they are being polluted by us humans. It's a huge effort to try and keep the lakes clean sometimes we have a small group and we go out on small boats and get trash out giant logs and test the water. It takes all day and we will never be done! 🥺😓

  4. That means that for every living human there are almost as many insects as there are humans in total.

  5. We need another Carboniferous Period's level of vegetation in order to remove excess CO2 out of the atmosphere. Nearly 35% more oxygen then. We'll have to limit the population of the decompers.

  6. Not entirely convinced — if high oxygen levels disfavored small arthropods, it should have kept the Carboniferous from having small arthropods. But at least some small arthropods did exist during this time — for instance, a very quick search turned up Trigonotarbida, of which the smaller members were only a few millimeters long, indicating that it was possible to evolve resistance to the slowly (over millions of years) rising levels of oxygen:

    Likewise, it probably would have been possible to evolve adaptations to oxygen levels falling slowly (again over millions of years), if something else hadn't gotten in the way. Of course, the most obvious thing to get in the way would be the land vertebrates that already existed but were evolving better adaptations to living on land at this time.

  7. The carboniferous period. The one time when a can of raid and a fly swatter just really wouldnt cut it.

  8. My view: There were giant insects because there were no higher life forms on land yet. Later in the Carboniferous (whatever the O2 levels) the CO2 levels dropped enough to allow adult amphibians to come ashore. Salamanders (Dimetrodon, Eryops…) and frog and toad ancestors (Scutosaur, Dinocephalia(?), etc) would find giant insects easy prey. Then the first reptiles (Gorgonopsids, etc) found the large sluggish amphibians easy prey, and much later the birds and placental mammals outcompeted the reptiles. (If there was a giant meteor that somehow wasn't tidally disrupted (vis: comet Shoemaker-Levy 9) at the Roche limit, it had little or no bearing on the end of the dinosaurs.) In each case, only much smaller niche environments were suitable for smaller species of the more primitive forms and the more advanced ones took over the apex roles.

  9. I dont know 🤔. Most people dont know what they doing for breakfast lunch dinner ect ect .. how yall know what happened way back when

  10. question: 1:42, so answer is oxygen, but we have patients in hospital using gas tanks to breathe in oxygen which is about 100% over 35%, how come they don't grow BIG like Dinosaurs?? I mean, they need to grow like dinosaurs right if the answer is 35% oxygen. ?? – Byon

  11. ………this is two years old post. Today the insects are dissappearing. .. Monarch butterfly of North America, the high plains Bogong moth of South East Australia……
    …….I noticed she didn't use the word bug, it's an american word but used by all english speakers these days. I'm still wondering if it can be substituted for arthropods…..
    ……..fires would start off very easily with oxygen at 35% ; so what prevented these fires? Was it perhaps a very high humidity ?

  12. There is a problem when the microbes learn to breakdown wood, the wood from the past was koal. so the theory don't hold.

  13. Um… The age of dinosaurs would have been the age of bugs too. I mean they call it the age of the dinosaur because they were the most prolific and influential creatures of that time. The age of man is no different.

  14. Im learning about this in my college biology class. When my professor talked about there being a lot of oxygen in the air millions of years ago i knew where it was heading and I was like “HES GOING TO TALK ABOUT THE INSECTS FKJSNANSM” in my mind.

  15. Anyone else recognize the song in the background 0:42? Because I recognize it from that "dollhouses of death" video too. What is it called??

  16. 1:20 that moment when you’re in a cave in Ark and an Arthropleura comes by and you already know that you’ll come out naked

  17. I’ll get giant scorpions. From pumping oxygen in a giant tank.
    Give I some time

    Or a dose or two of radiation and it’ll speed up

  18. Sorry but with life comes decay the only reason life exists in earth is because of carbon hence carbon based life forms

  19. Just imagine. Our ancestors had to live in the age of nope. The screaming and terror must have been something out of a Lovecraft novel. Spiders the size of your head. Able to hunt small mammals like cats and dogs.

  20. Even more viruses, that’s not quite a fair comparison, trying doing it in biomass, and per species, insect is not a species

  21. Imagine those things in your garden or worse yet, getting in your house and having them fly around… damn! I hope those things don't sting!

  22. How about the bitty guys running most of our systems? Are we just fancy high maintenance mobile homes for them?

  23. This channel is nice but I wish they did both measurements so everyone could understand it without constantly googling or giving up and closing it.

  24. I'm going to start breathing pure oxygen because I want to be bigger. It really would boost my self esteem to be a bit bigger.

  25. With the concentration of atmospheric oxygen that high, fires in the forests must have also been colossal.

  26. I am curious about this oxygen difference. Any or all other 'factors' notwithstanding, how would life currently look if this forty % reduction in oxygen levels had not occured ?
    Further, when considering that which has changed exclusively as a result of said change, what can be expected in the future if this trend continues ?
    What will be affected and how ?

  27. Soooo, we could raise insects with more oxygen and make them actually worth eating? 🤔
    This could be an interesting solution to the too large number of animals we currently raise for meat today.

  28. Suggestion. Use more science. You said that the Griffenfly, a relative of today's Dragonfly, was three times bigger because of a wingspan three times that of today's largest dragonfly. Wrong! You have to realise that is volumetrically CUBED in mass. So it was about 10x larger! Use science and get more credibility, please.

  29. In the 70s when I was younger I walked into a small yard near my house where in it I actually saw giant ladybugs…All colors and sizes…if i had someone as a witness when this happened I would've been famous for having found these unique insects…I never saw them again in that garden.

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