Why Don’t Birds Lay Square Eggs?


Hey smart people, Joe here. What shape is an egg? Chances are you’re picturing this: It’s
generally round, a little fatter at one end, and it probably came out of the non-clucking
end of a chicken. The chicken egg is the egg that most of us
know, which makes sense considering there’s 2.5 chickens for every person on Earth, they’re
what most of us eat, and we’ve been indoctrinated with them from a young age. “This is a plastic chicken egg” (Hatching noises) But is this shape really “egg-shaped”? In 2017, scientists analyzed the shape of
nearly 50,000 eggs from 1,400 different bird species, and plotted them based on how elliptical–or
squished–they are, and how pointy–or asymmetrical–one end is. And chicken eggs are outliers. Most bird eggs aren’t shaped like this. Bird eggs come in many shapes. Nearly spherical eggs like owls, pointy cone
eggs of shorebirds like the common murre, even the tiny tic-tac eggs of hummingbirds…
and everything in between. Scientists have been wondering for a long
time how and why all of these different egg shapes came to be. But before we inv-egg-stigate those questions,
let’s take a minute to appreciate just how eggcellent eggs really are. Dad yolks, gotta love em. [MUSIC] More than 350 million years ago, the ancestors
of every land-dwelling, backbone-having animal alive today began to crawl out of the water,
and they pretty quickly colonized every terrestrial habitat on Earth. And one evolutionary innovation made that
possible more than any other: Eggs with shells. Although many other animals lay eggs, the
evolution of the shell allowed reproduction away from BLEEP environments. Wait. I can’t say BLEEP (moist)? Are you serious? Well… I guess I don’t wanna get demonetized, so… Eggs with shells allow reproduction away from
wet environments. These self-contained life-support systems
keep everything inside from drying out, and it meant that reptiles and the early ancestors
of mammals could travel, see the world, set up shop in every corner of Pangaea. The ancestors of mammals eventually moved
all the egg and baby-growing business inside our bodies–except for these weirdos. So many questions. While reptiles from crocodiles to turtles
to snakes to dinosaurs stayed in the egg business. Reptile egg shells range from leathery to
hard, but one special branch of the dinosaur family tree eventually took natural shell-ection
to the next level: Birds. What makes a bird egg so eggstra cool is this
hard shell. It’s strong enough that this many eggs can
support my full body weight without breaking. (Drumroll)
I’m standing on two dozen eggs. They said it couldn’t be done! I’m so afraid to move. And that strength comes from the shell’s
shape. If you watched my video about the science
of igloos, you remember that this shape, called a catenary arch, distributes tension and compression
more evenly than a half circle shape. Along with the microscopic protein and mineral
nanostructures in the shell, this shape makes egg stronger than it would be if it was another
shape. This brings me back to our original question:
What is an egg’s shape? An oval is a 2-dimensional curve whose name
literally means “egg-shaped”. Unlike an ellipse, there’s no exact geometric
definition for an “oval”, but they can be constructed by joining other arcs of different
radii. They generally only have one axis of symmetry,
and by rotating an oval along this axis, the surface of revolution we create is called
an “ovoid”. That’s “egg-shaped”… at least according
to math. But while the shell gives this shape strength,
the shell doesn’t make the egg egg-shaped. If you dissolve away an egg shell, which is
rich in calcium carbonate, with an acid, like vinegar, it maintains its shape. The “egg shape” isn’t caused by the
shell. It’s caused by this squishy inner membrane. It starts with an unfertilized egg cell, added
to a blob of yolk, and squeezed down a stretchy tube called an oviduct. As it travels it’s fertilized by sperm,
wrapped in those membranes and inflated with fluid like a balloon. The shape of the egg is determined when those
membranes form. Over the years scientists have had a lot of
hypotheses about why different birds create eggs of different shapes. One hypothesis is the more spherical the egg,
the less shell material it takes to cover. Another is, depending on how many eggs a mother
lays, different egg shapes could snuggle better during incubation. Or maybe birds that are born ready to walk
and feed themselves might grow better in one shape versus another. And for birds that nest on cliffsides, pointier
eggs tend to roll in circles instead of rolling off the edge. These are just a few of the possible answers
people came up with. But when those scientists from earlier analyzed
thousands of egg shapes from across different families of birds, the best correlation they
found was between shape and flying ability. Birds that are better fliers have more streamlined
bodies, and their organs are more tightly packed, which puts a limit on how wide an
egg you can squeeze through that egg-making tube. Inside a computer, those scientists were even
able to virtually form every egg shape we know of by changing just two things: the stretchiness
of the membrane and how it’s squeezed. The most common egg shape among all birds
is something closer to this. A little pointier than our so-called “typical”
chicken egg. Trust me, they’re different. They measured. Thinking about it in the eyes of eggvolution,
it’s not that pointy eggs give acrobatic birds an advantage, it’s just a natural
consequence of having a narrow body. And we do know the first dinosaurs that laid
pointy eggs were the group that gave rise to birds. But here’s one important thing to remember
about how evolution works: Body shape might be the best answer when we look at all birds,
but that doesn’t mean it’s the only answer. Different families of birds might get different
evolutionary eggvantages from different shapes. Even if a bird’s body isn’t that skinny,
maybe a pointy egg really does keep it from rolling off the edge of a cliff, or make it
easier for the parents keep it warm. Natural selection can happen on many levels,
and there can be evolution inside of evolution. So, are all eggs egg-shaped? Well, you could say “egg-shaped” just
means whatever shape an egg is. But that’s not a very satisfying answer. What it means to me is… there is no egg-shape,
because nature’s made so many different shapes, for different reasons. In the end, the question of why different
birds lay different shaped eggs isn’t settled. And that’s ok. Because that’s how science works. If it was wrapped up with a neat little bow,
we wouldn’t have any questions left to incubate, and no new ideas left to hatch. Stay curious.

100 thoughts on “Why Don’t Birds Lay Square Eggs?

  1. A good and helpful video smart people
    I have a suggestion for you
    Can you make these video little short
    About 5 minutes???that would be more comfortable for us

  2. I guess we CRACKED the EGGSCITING mystery of eggs, and your dad yokes are absolutely amazing! But this is pretty boring so OMLETting this one go.

    (p.s) I get CHICKS

    no I dont

  3. 1:15 STOP RIGHT THERE, CRIMINAL SCUM! Nobody breaks the law on my watch! I’m confiscating your right to make jokes. Now pay your fine or never make jokes again.

  4. If Joe is just a mediocre intellect or slightly below that, which is my assessment, would that explain why Joe does this full time lame ( no ever new breaking insight ) blather blog rather than vigorously pursue his own Ph.D thesis work ? Seems odd someone who claims high intelligence, would "NOT " further their relentless personal extensive spent work of 30 years ? Is that Curious ? I GUESS it is o.k. to not be intelligent. A Ph.D discarded is absurdity cubed. The defense rests.

  5. Before the video
    Me: …because it would huuurrrt?
    After the video
    Me: …so we don't know but maybe it depends on the size of the bird.
    …'ight…

  6. Okay so 45 seconds in and if it's not in the later videos. Ima gonna blow your mind… Eggs are WOMB shaped. The shape of an egg is determined by the shape and size of a fowl's womb – kinda averaged out. If HUMAN's laid eggs it would be a similar shape but a lot bigger and the thin end would come out first.. the difference here is that bird wombs develop a shell inside them where mamalls just develop a loose sack. This is because mammals like humans are expected to get WAAAY bigger than the average human cross-section to it has to pop in the womb. Where eggs are laid earlier and are actually the size of the womb… There's Biology!

  7. There's some tomatoes / chemically engineered / to fit in boxes.

    There's some people / chemically engineered / to fit in boxes.

  8. a sphere is much more aerodynamic than a cube, it is much easier for a sphere -like egg to pass through a female genitalia than a cube, so evolution would strongly favor eggs having a sphere like shape. No great mystery here

  9. I was afraid to say oval because I felt like it was too similar to – uh – you know
    And now you tell me that's because they're based off of the same word

  10. I saw this a said really loud; because that ain't gonna fit in a chicken coochie

    Moral of the story: I have detention for 3 days :/

  11. most people: all shapes and sizes of your bodies are beautiful! be yourself!
    joe: eggs dont have a real shape. all eggs are beautiful because nature has made all them all perfectly unique ✨

  12. Well, there is a place, Lost in the Andes where square chickens lay square eggs, it is Plain awful to find…….

    Carl and Keno say hi!

  13. I'm a little extra worried that so little people are discussing or apparently are not worried that YouTube is creating an environment where words like "die" and "moist" are censored, and hopefully not filtered entirely in the future, from more reputable channels' vocabulary just because they are more likely to depend on ad revenue.

  14. Why do chickens need to lay eggs when chickens can be made by mixing wood and sugar so they chemically react with each other to form a chicken

  15. Only a man would ask why chickens don't lay square eggs… as a mother I can say why. The question is why can't our kids be born more round-shaped.

  16. Growing up, in the 80s, the local paper (The Oregonian) had a comic on the comics page in which subscribers submitted egg puns. Usually it was "eggs" in place of the "ex" that eggsist in many words.

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