人為什麼要有智齒、闌尾？生物學教授解釋從頭到腳各種「無用處」人體器官｜科普長知識｜GQ Taiwan

everything in the body has some meaning we're going to 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 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 that brain areas that deal with these muscles have some activity Plica semilunaris when you look at the medial side of the eye area you're going to see the 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 in 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 moistener and apparently we have sufficient moistening without needing that 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 discrete meaning or function 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 body hair we have hair but our hair is not densely packed it's all over like our closest relatives hair's Prime function is for thermoregulation 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 plains of Africa and our ancestors started to go to Savannah's 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 sweatings 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 on to it we think we still maintain the little grass 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 erector peeling muscles produce the effect of Goosebumps here's the hair here's an erector 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 hairs stand up in the back of your neck when this occurs in our ancestors or your cat the hair will become puffed up what is that puffiness do it increases the appearance of your size so it's a display feature as well appendix [Music] 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 coccyx [Music] coccyx was our primitive tail 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 are 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 by penally 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 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 very 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 [Music] plantaris muscle we have a muscle in the leg which has become largely vestigial and 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 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 launch it to nalark and another goes side to side to reduce muscle usage this is one reason why a chimp or a gorilla cannot emulate or run the way we can they don't have double arches their feet tend to be flatter and every once in a while will 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 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 ports that have diminished greatly in function we have things that we thought may have been useless that we've discovered are very useful our body is the culmination of our history [Music]

Channel: GQ Taiwan

Views: 1,359,671

Keywords: arched foot vs flat foot, cne-us, currents, evolution, gq, gq 科普, gq 醫師, gq 醫生, gqtaiwan, human evolution, nictitating membrane, tail bone, useless organs, vestigial, vestigial body parts, vestigial muscle, vestigial organs, wired, wired currents, wired taiwan, wired 中文, 器官, 器官介紹, 尾骨, 扁平足, 智齒, 智齒要拔嗎, 無用身體部位, 科普長知識, 耳肌, 身體器官, 身體器官介紹, 身體部位, 退化肌肉, 闌尾, 闌尾炎

Id: cwS2mSLFX1g

Length: 10min 59sec (659 seconds)

Published: Thu Aug 10 2023