Why Do We Have An Internal Skeleton?

If you think about it, skeletons aren't awesome. Instead of the super strong shells or exoskeletons so many other animals have, we have these internal skeletons. That leaves or fragile bodies highly vulnerable to all kinds of serious injury. But as Trace explains, our internal skeletons are actually an evolutionary advantage.

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What if people had exoskeletons?
"Human beings are like reptiles, amphibians, birds, and fish in the fact that we all have internal skeletons. Muscles connect to the skeleton to provide motion, and we have soft skin on the outside."

Why Exoskeletons Exist
We've learned that all arthropods have a tough outer covering called an exoskeleton. However, we have also learned that some arthropods, such as "honey-pot" ants and ticks actually expand as they collect honey or blood in their body. Is the exoskeleton able to expand? Do these organisms have a different type of exoskeleton that other arthropods?

Where did bone come from?
"Bone is specific to vertebrates, and originated as mineralization around the basal membrane of the throat or skin, giving rise to tooth-like structures and protective shields in animals with a soft cartilage-like endoskeleton."

Exoskeleton Evolution
"Less than three inches long, it has nonetheless made quite an impression. Diania cactiformis, more affectionately known as the "walking cactus," has given scientists new clues to the evolution of arthropods."

Skeletal System
"Your Skeletal system is all of the bones in the body and the tissues such as tendons, ligaments and cartilage that connect them.
Your teeth are also considered part of your skeletal system but they are not counted as bones. Your teeth are made of enamel and dentin. Enamel is the strongest substance in your body."

The problem with giant exoskeletons
"Last week we looked into a problem most fantasy worlds have, and this week we're looking at a related, but more specific, problem endemic to science fiction. The Ender series. Starship Troopers. Them! (and dozens of other horror classics)."

Oldest human skeleton offers new clues to evolution
"The oldest-known hominid skeleton was a 4-foot-tall female who walked upright more than 4 million years ago and offers new clues to how humans may have evolved, scientists say."

Invertebrate vs Vertebrate
"Animals can be classified into two main groups: Vertebrates and invertebrates. The main difference between vertebrates and invertebrates is that invertebrates do not have a backbone or a spinal column."

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[JanetStarChild]

Turtles have the best of both worlds. Internal skeleton for flexible limbs, and exoskeleton to protect the torso. Seems to work very well for the Teenage Mutant Ninja Turtles.

[IcariiPriestess]

Oh my gosh, Trace is my favorite LMAO "You'll never make it as a dancer, Crab!"

[spaceagequice]

Seeker: you'll never be a dancer crab!

Crab rave:

[truckshackley]

I think I'll stick with my ol' reliable internal skeleton...I've grown rather attached to it over the years.

[sirwilliam]

Hey Trace, thanks now iv got to feed my futurama addiction. I've been trying to decrease my bender/ hermes intake. Good ole inspector 5 may he rest in Tijuana peace.

[llVIU]

I think the bad guys in horror movies have exo-skeletons... they are tough as fuck but also damn slow

[lubricatedgoat]

@1:29 "But they just couldn't quite hit the sizes... of their vertebrate cousins."

That was a totally accidental, but awesome, Christopher Walken!

[bobrulerofall]

and the gap in the rib cage enables us to pick things up off the ground. you cant just fill it in, you have to balance like he said flexibility with protection.

[eventhorizon]

The ribcage is mostly for breathing. Muscles bend the ribs outward so the lungs can inflate. To deflate they do the outher thing around....

[DearestClaudio]

It doesn't completely protect it. Our stomachs are a lot higher up than we tend to think; the majority of the abdominal area of our torso is just a pile of intestines with a few other organs smooshed into the mix, like your liver and kidneys (the kidneys are also slightly protected, as the ribcage extends far enough on the back to give them some coverage).

[brianasanders]

The way I see it, as long as the internal is strong the more damage the external can take and survive. Like if you squashed a bug ( we've all done it at some point) it's exoskeleton is toast, and so is its life. Now things with an endoskeleton can be squashed and survive with their live while their skeleton mends.

[rorrt]

S: Support, so y'can walk and jump. And swim, and do fun stuff.
P: Protection, bones protect you, and that.
A: Anchorage, muscles and tendons are anchored in your bone. Muscles aren't strong enough to support themselves.
M: Movement, joints help you move and stuff.

Thats what we learnt in school. I got a 10/10 on that test :D

[Yesiani.]

I usually don't find your jokes funny, but 2:25 caught me off guard.

[raymondfake]

Well, define "vital" organs as heart, brain, lungs. Yes there is the rib cage for some protection. However some may say our stomach or intestine are non-immediate vital organs. Still, your question is valid, why no bone structures to protect other important organs such as our kidneys? Maybe too many bones also have their disadvantages?

[DarthBiomech]

Well, why not both? Exoskeletal shell supporting with vertebrate bones. Former can replace itself piece by piece, instead molding all at once.

[IanAtkinson]

Because we have a primate skeleton that originally evolved to be lightweight for leaping about in trees. That's why our feet are actually modified fingered hands instead of tough clawed running pads like dogs, for instance.

[darkdracha]

Immediate thought after the Dr. Zoidberg comment was Dr. Zoidberg jiggling without his shell, I lol'd so hard.

[killer]

why not have a combination of a natural exoskeleton and an internal one? the exoskeleton in a flexible plate-armor like arrangement on our chest, side back, and stomach for protection of vitals hard exoskeleton on our forearms and shins to protect the 2 thinner bones and these armored parts be as soft as our skin until our bodies stop growing and then harden within a couple of weeks. with our internal frame we could support it and we'd gain muscle strength and high metabolism to help keep us fit

[lightningeyes]

Our skeleton actually can and does protect our most vital organs, lungs, heart, brain, bone marrow, spine and more. As for other organs there are two main reasons why our skeletons don't protect them.
1. Muscles: these organs allows the body to move, fight, react, survive and defend, often using bones as an anchor. It's how Paleontologists can tell how muscular a dino was.
2. Weight: If we had bones protecting other organs, we would be heavier. Thus meaning we had a disadvantage in survival.

[jevonmcpherson]

1:58 This isn't completely true you can mislead people with that. an animals size depends entirely on how well it is able to collect energy sources (without photosynthesis this would be food and oxygen).

1. tetrapods have a sack (called lungs) that sucks up oxygen directly from the air, this is the most effective compared to filtering it from water and the other ways animals breathe.

2. The only endoskeletal animals in this world have bones and consequently a great body plan for catching food. a large mouth, teeth to bite and hold onto the food as well as better locomotion the exoskeletal animals.

so in some ways your right about the effect that an exoskeleton has on body structure but it was said so vaguely that people might think that its not simply about how effective an animal is at collecting energy (in this context food and oxygen). Their body plan doesn't limit their sizes, it just makes it harder for them to compete against vertebrates so they are better off not getting too large.