- Everything in the body has some meaning.
We're gonna take a look, starting at the head
and going all the way down to the toes,
at some of the most interesting body parts
that have often been categorized as maybe useless.
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Auricular muscles.
Some people have muscles
where they can wiggle their ears a little bit.
These are rare.
We have three on the outside, so these are remnant
auricular muscles that originally had great functions,
particularly with sound the way your dog or your cat do.
Even in many of the monkeys
our ancestors ears are able to move a bit with sound,
but now they've largely lost that function
and they are usually considered vestigial.
The term vestigial comes from the Latin meaning footprints,
so there are structures that were thought
to be sort of footprints in time,
giving us little clues to what came before.
So we, when we hear a sound
do not necessarily move our ears in that direction.
We tend to move our entire head towards the sound.
What's interesting to show that it's still hooked up,
studies have shown that when we hear a sound,
the brain areas that deal with these muscles
have some activity.
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Pica Semilunaris.
When you look at the medial side of the eye area
you're going to see a vertical line.
Here is the location.
Next time you look at a dog or a cat or a reptile,
you'll notice that they don't have two,
but they have three eyelids.
We have an up, we have a down,
they have one that goes side to side.
That's the nictitating membrane
and this little fold is the remnant.
We know we don't have it in our closest relative, the chimp,
and we don't have it in ourselves.
It's a moister,
and apparently we have sufficient moistening
without needing that.
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Wisdom teeth.
Technically known as our third molars.
You can see here they're largely problematic,
in which they bend or twist,
and you have to go to the oral surgeon to have them removed.
Over the eons of our evolutionary changes,
our diet became very varied.
The molars are grinding teeth for eating leaves
and vegetable type things.
We became more omnivorous.
This is a gorilla,
and you can see how the face is very forward in a gorilla.
In the course of human evolution
our face became very flattened in.
Our molar teeth became shoved all the way back.
The molars became squished in.
We developed a very, very pronounced chin,
found only in homo sapiens.
It's a distinguishing feature of our species
and we're not exactly clear what made it come about.
It's a byproduct.
It's called a spandrel.
Sometimes things occur
in our body that had no discreet meaning or function.
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Male nipples.
Nipples are extremely important structures.
They're important for breastfeeding,
but why do I have a nipple?
The male nipple is not useless.
It's highly stimulatable.
It is an erogenous zone,
and these are not unimportant things.
By the way, for example, dogs and cats,
they have multiple nipples.
There's a developmental ridge where nipples appear.
That's called the nipple line.
Nipples can appear all along a series of lines
and you may find, for example,
that somebody has a nipple all the way down in the pelvis
or frequently in the armpit is a bit of a throwback.
We sometimes call it an atavism,
and that term is usually used
for something that has missed a few generations
or something that pops up
due to an interesting recombination of genes.
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Body hair.
We have hair, but our hair is not densely packed
all over like our closest relatives.
Hair's prime function is for thermo-regulation
and it played a very vital part when our ancestors
came from forest-like environments, helping to keep heat in,
when it got too hot, it kept heat away.
We lost our hair.
The weather was changing,
things were shifting on the planes of Africa
and our ancestors started to go to savannahs.
We were starting to be bipedal.
We were starting to be hunters.
We were starting to learn to run,
and the loss of hair helped us in our active lifestyles
with sweating.
The glands involved in sweating are much greater in us
and it allows us to maintain our temperatures better.
Hair in our furry relatives had a purpose,
with little babies being able to hang onto it.
We think we still maintain the little grasp reflex
of newborns and that has been related back to it.
Certain areas in primates, particularly apes,
became hairless early on, the face.
We do a lot of signaling with our face, so do chimps,
so do gorillas.
We do retain some hair, on the top of our head,
in our anal genital area and in our armpit area.
The brain has to be kept somewhat cool,
hair up there aids in cooling the area and protecting it
and that's why they seem to be retained.
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Arrector pili muscles produce the effect of goosebumps.
Here's a hair, here's an arrector pili.
What they do when they're stimulated is they contract.
They force the hair to stand erect.
It'll aid in the skin responding to some type of threat.
You'll get the hair stand up in the back of your neck.
When this occurs in our ancestors or your cat,
the hair will become puffed up.
What does that puffiness do?
It increases the appearance of your size
so it's a display feature as well.
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Appendix.
This is called the cecum
and this worm-like structure coming off of it
is known as the appendix.
It's not useless, it's very useful.
Because it was removable
the appendix was thought to be vestigial,
and worse, bad, because it can swell.
What we've learned over the last few years is
that the appendix has helpful bacteria
and assists the gut when there are different problems
and diseases.
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Coccyx.
The coccyx was our primitive tale.
Here we can look
and see the vertebral column,
the last three to five vertebrae that comprise
the little funky thing that looks
like a cuckoo's beak that's known as the coccyx.
This is a vestigial structure.
A distinguishing difference between great apes
and monkeys is that none of the apes have tails.
Our ape ancestors do not locomote
the same way a monkey does, swinging through a tree,
they locomote differently.
The more these animals started to walk on all fours
and then with us to walk bipedally,
the tails were not useful any longer,
and so it was pushed to the side, it became a vestige.
Every once in a while,
pretty rare, due to an interesting recombination of genes,
somebody is born with a tail.
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Pyramidalis muscle.
If you look in the mirror, you will notice your six pack.
I don't have a six pack anymore.
I never had a six pack.
This forms what's called the rectus sheath.
We have a muscle called the pyramidalis
because of its shape.
At one time it was thought to give support to the abdomen.
Various monkeys are shown to have it,
in us it's become very small
and we're not really certain what it does.
We might have lost it
because of our unique mode of bipedal locomotion.
Every time we've modified our locomotor behavior
certain muscles enlarge, certain muscles become less.
We have a number of muscles
in the body that have become largely vestigial.
They've shrunk.
Their function has shifted.
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Plantaris muscle.
We have a muscle in the leg
which has become largely vestigial.
It's become just a tendon.
The plantaris comes from the area of the knee,
comes from the femur
and goes all the way down to have a separate tendon.
They are larger in the apes.
We have a number of muscles
in the body that have become largely vestigial,
they've shrunk.
Their function has shifted.
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Flat feet.
The human foot has been modified solely
for the purposes of ambulation for running.
In order to do that, we have a double arch system.
One arch goes from front to back.
We call this a longitudinal arc
and another go side to side to reduce muscle usage.
This is one reason why a chimp
or a gorilla cannot ambulate or run the way we can.
They don't have double arches.
Their feet tend to be flatter
and every once in a while we'll have somebody
who genetically born with flat feet.
Here's an individual who is showing
what we call pes planus, or flat feet.
The arches sink.
When the arches sink
the muscles that go underneath it must fire
so anybody with flat feet has to use muscles
to try to pull those arches up, and that's very expensive.
I'll also tell you how you can damage your arches.
Nobody ever anticipated something like high heeled shoes.
They're dangerous, they're hurtful,
and they work to destroy
what nature has taken millions of years to create.
There have been body parts
that have diminished greatly in function.
We have things that we thought may have been useless
that we've discovered are very useful,
so our body is the culmination of our history.
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