00:00 Everything in the body has some meaning.
00:02 We're gonna take a look, starting at the head
00:04 and going all the way down to the toes
00:06 at some of the most interesting body parts
00:09 that have often been categorized as maybe useless.
00:12 Auricular muscles.
00:15 Some people have muscles where they can
00:18 wiggle their ears a little bit.
00:20 These are rare.
00:21 We have three on the outside.
00:22 So these are remnant auricular muscles
00:25 that originally had great functions,
00:28 particularly with sound, the way your dog or your cat do.
00:32 Even in many of the monkeys, our ancestors' ears
00:37 are able to move a bit with sound,
00:40 but now they've largely lost that function
00:43 and they are usually considered vestigial.
00:46 The term vestigial comes from the Latin meaning footprints.
00:50 So there are structures that were thought
00:52 to be sort of footprints in time,
00:54 giving us little clues to what came before.
00:57 So we, when we hear a sound,
00:59 do not necessarily move our ears in that direction.
01:04 We tend to move our entire head towards the sound.
01:07 What's interesting to show that it's still hooked up,
01:10 studies have shown that when we hear a sound,
01:13 the brain areas that deal with these muscles
01:17 have some activity.
01:19 Flicca semilunaris.
01:21 When you look at the medial side of the eye area,
01:24 you're going to see a vertical line.
01:26 Here is the location.
01:28 Next time you look at a dog or a cat or a reptile,
01:32 you'll notice that they don't have two,
01:34 but they have three eyelids.
01:36 We have an up, we have a down.
01:37 They have one that goes side to side.
01:39 That's the nictitating membrane.
01:41 And this little fold is the remnant.
01:44 We know we don't have it in our closest relative,
01:47 the chimp, and we don't have it in ourselves.
01:49 It's a moistener.
01:50 And apparently we have sufficient moistening
01:53 without needing that.
01:56 Wisdom teeth, technically known as our third molars.
01:59 You can see here they're largely problematic
02:02 in which they bend or twist,
02:04 and you have to go to the oral surgeon
02:07 to have them removed.
02:08 Over the eons of our evolutionary changes,
02:13 our diet became very varied.
02:15 The molars are grinding teeth
02:18 for eating leaves and vegetable type things.
02:21 We became more omnivorous.
02:23 This is a gorilla.
02:24 And you can see how the face is very forward in a gorilla.
02:29 In the course of human evolution,
02:32 our face became very flattened in.
02:36 Our molar teeth became shoved all the way back.
02:40 The molars became squished in.
02:43 We developed a very, very pronounced chin
02:48 found only in Homo sapiens.
02:50 It's a distinguishing feature of our species.
02:54 And we're not exactly clear what made it come about.
02:58 It's a byproduct.
02:59 It's called a spandrel.
03:01 Sometimes things occur in our body
03:05 that had no discrete meaning or function.
03:08 Male nipples.
03:12 Nipples are extremely important structures.
03:14 They're important for breastfeeding.
03:17 But why do I have a nipple?
03:18 The male nipple is not useless.
03:21 It's highly stimulatable.
03:22 It is an erogenous zone.
03:24 And these are not unimportant things.
03:26 By the way, for example, dogs and cats,
03:29 they have multiple nipples.
03:31 There's a developmental ridge where nipples appear.
03:34 That's called the nipple line.
03:37 Nipples can appear all along a series of lines.
03:42 And you may find, for example,
03:44 that somebody has a nipple all the way down in the pelvis
03:47 or frequently in the armpit.
03:50 It's a bit of a throwback.
03:51 We sometimes call it an atavism.
03:54 And that term is usually used for something
03:56 that has missed a few generations
03:58 or something that pops up
04:00 due to an interesting recombination of genes.
04:04 Body hair.
04:07 We have hair, but our hair is not densely packed all over
04:12 like our closest relatives.
04:14 Hair's prime function is for thermoregulation.
04:18 And it played a very vital part
04:20 when our ancestors came from forest-like environments,
04:25 helping to keep heat in.
04:27 When it got too hot, it kept heat away.
04:30 We lost our hair.
04:31 The weather was changing.
04:33 Things were shifting on the plains of Africa.
04:36 And our ancestors started to go to savannas.
04:39 We were starting to be bipedal.
04:41 We were starting to be hunters.
04:43 We were starting to learn to run.
04:46 And the loss of hair helped us
04:49 in our active lifestyles with sweating.
04:53 The glands involved in sweatings are much greater in us.
04:57 And it allows us to maintain our temperatures better.
05:02 Hair in our furry relatives had a purpose
05:05 with little babies being able to hang onto it.
05:08 We think we still maintain
05:09 the little grasp reflex of newborns.
05:11 And that has been related back to it.
05:13 Certain areas in primates, particularly apes,
05:17 became hairless early on, the face.
05:19 We do a lot of signaling with our face.
05:23 So do chimps.
05:24 So do gorillas.
05:25 We do retain some hair on the top of our head,
05:29 in our anogenital area, and in our armpit area.
05:33 The brain has to be kept somewhat cool.
05:36 Hair up there aids in cooling the area and protecting it.
05:41 And that's why they seem to be retained.
05:44 Erector pili muscles produce the effect of goosebumps.
05:49 Here's a hair.
05:50 Here's an erector pili.
05:51 What they do when they're stimulated is they contract.
05:55 They force the hair to stand erect.
05:58 It'll aid in the skin responding to some type of threat.
06:02 You'll get the hair stand up in the back of your neck.
06:05 When this occurs in our ancestors, or your cat,
06:09 the hair will become puffed up.
06:11 What does that puffiness do?
06:13 It increases the appearance of your size,
06:17 so it's a display feature as well.
06:19 Appendix.
06:21 This is called the cecum,
06:24 and this worm-like structure coming off of it
06:27 is known as the appendix.
06:29 It's not useless, it's very useful,
06:34 because it was removable.
06:36 The appendix was thought to be vestigial,
06:38 and worse, bad, because it can swell.
06:42 What we've learned over the last few years
06:45 is that the appendix has healthful bacteria
06:48 and assists the gut when there are
06:51 different problems and diseases.
06:53 Coccyx.
06:55 The coccyx was our primitive tail.
07:00 Here we can look and see the vertebral column.
07:04 The last three to five vertebrae
07:07 that comprise the little funky thing
07:10 that looks like a cuckoo's beak
07:12 that's known as the coccyx.
07:14 This is a vestigial structure.
07:16 A distinguishing difference between great apes
07:19 and monkeys is that none of the apes have tails.
07:23 Our ape ancestors do not locomote
07:27 the same way a monkey does.
07:28 Swinging through a tree, they locomote differently.
07:31 The more these animals started to walk on all fours,
07:35 and then with us, to walk bipedally,
07:38 the tails were not useful any longer.
07:41 And so, it was pushed to the side.
07:44 It became a vestige.
07:45 Every once in a while, pretty rare,
07:48 due to an interesting recombination of genes,
07:51 somebody's born with a tail.
07:53 Pyramidalis muscle.
07:57 If you look in the mirror, you will notice your six pack.
08:00 I don't have a six pack anymore.
08:02 I never had a six pack.
08:03 This forms what's called the rectus sheath.
08:06 We have a muscle called the pyramidalis
08:09 because of its shape.
08:10 At one time, it was thought to give support to the abdomen.
08:13 Various monkeys are shown to have it.
08:16 In us, it's become very small,
08:18 and we're not really certain what it does.
08:20 We might have lost it because of our unique mode
08:23 of bipedal locomotion.
08:25 Every time we've modified our locomotor behavior,
08:29 certain muscles enlarge, certain muscles become less.
08:33 We have a number of muscles in the body
08:37 that have become largely vestigial.
08:40 They've shrunk.
08:41 Their function has shifted.
08:43 Plantaris muscle.
08:46 We have a muscle in the leg
08:49 which has become largely vestigial.
08:51 It's become just a tendon.
08:54 The plantaris comes from the area of the knee,
08:57 comes from the femur,
08:58 and goes all the way down to have a separate tendon.
09:01 They are larger in the apes.
09:03 We have a number of muscles in the body
09:06 that have become largely vestigial.
09:09 They've shrunk.
09:10 Their function has shifted.
09:13 Flat feet.
09:14 The human foot has been modified
09:19 solely for the purposes of ambulation for running.
09:23 In order to do that, we have a double arch system.
09:27 One arch goes from front to back.
09:30 We call this a longitudinal arch.
09:32 And another goes side to side to reduce muscle usage.
09:37 This is one reason why a chimp or a gorilla
09:40 cannot ambulate or run the way we can.
09:44 They don't have double arches.
09:46 Their feet tend to be flatter.
09:49 And every once in a while,
09:51 we'll have somebody who genetically born with flat feet.
09:55 Here's an individual who is showing
09:58 what we call pes planus, or flat feet.
10:01 The arches sink.
10:03 When the arches sink,
10:04 the muscles that go underneath it must fire.
10:08 So anybody with flat feet has to use muscles
10:12 to try to pull those arches up,
10:15 and that's very expensive.
10:18 I'll also tell you how you can damage your arches.
10:22 Nobody ever anticipated something like high-heeled shoes.
10:27 They're dangerous, they're hurtful,
10:29 and they work to destroy
10:31 what nature has taken millions of years to create.
10:36 There have been body parts
10:38 that have diminished greatly in function.
10:41 We have things that we thought may have been useless
10:43 that we've discovered are very useful.
10:46 So our body is the culmination of our history.
10:51 (upbeat music)
10:53 (upbeat music)
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