ghazi52
PDF THINK TANK: ANALYST
- Joined
- Mar 21, 2007
- Messages
- 104,047
- Reaction score
- 106
- Country
- Location
Why do we have lips?
Jason G Goldman
Human beings are unusual in that our mouths are surrounded by hypersensitive, easily-hurt pink tissue – why? Jason G Goldman investigates.
Animals know the importance of kissing and making up after a fight, an audience will be told at a Scottish university.
They kind of flap around on the front of your face, get dried out and chapped in the winter, and occasionally get caught up between your teeth and mistaken for food. Seriously, what good are lips? Birds get on just fine without them, turtles' lips have hardened into beaks as well, and while most mammals have lips, we humans are in a class all our own having lips that are permanently turned outwards.
It turns out that lips are quite important; so important, even, that it seems worth the risk of having your bottom lip caught in between your chompers. Even though that can really hurt.
Using our lips to suck is one of the very first skills we have after we're born. In fact, it's so fundamental to our survival that it's known as a "primitive reflex"; we're born knowing how to suck and no learning is necessary. That's true for nearly all mammals.
Babies have an instinct to suck anything that brushes their lips .
It's the sucking reflex combined with another primitive response, the rooting reflex, that allows infants to breastfeed. The rooting reflex works by turning the infant's head to face anything that strokes its mouth or cheek. As soon as something grazes the newborn's lips, the sucking reflex is activated. While the tongue then does a lot of the work, the lips are vital to maintain a tight seal so that the infant can swallow.
That means feeding, whether from breast or from bottle, is not a passive behaviour on the part of a newborn infant. It's more like a conversation, with each side doing his or her part in a dance elaborately choreographed by evolution. At the centre of that dance are the lips.
Read my lips
The lips are of course also important in the act of eating other foods, and in speech. In linguistics, the lips are two of many places of articulation, or spots in the mouth and throat that aid in blockage of air moving out from the lungs. Bring your two lips together and you can form the sounds p, b, and m. To make the sounds f or v, bring your lower lip to your upper teeth. To make a w sound, move the back of your tongue towards the roof of your mouth while also moving your lips closer together.
Speech is arguably a critical part of human life, but it's not quite as much fun as kissing. Kissing isn't universal, though it does pop up in some 90% of cultures. Darwin himself noted that there are cultures in which kissing is conspicuously absent. "We Europeans are so accustomed to kissing as a mark of affection that it might be thought to be innate in mankind," he wrote in The Expression of Emotion in Man and Animals, "but this is not the case…[it is] unknown with the [Maori] New Zealanders, Tahitians, Papuans, Australians, Somals of Africa, and the Esquimaux [Eskimo]."
Lip service
Lips are exquisitely sensitive (if sometimes slimy) bits of tissue. The part of the brain responsible for detecting touch is called the somatosensory cortex, and is found on the top of the brain in an area called the postcentral gyrus. Touch sensations from all over the body get sent there to be processed, with each part of the body getting its own little sub-division along the postcentral gyrus, and the size reflects the density of receptors rather than the amount of skin available to touch. For example, the part devoted to sensations from the chest and stomach is fairly small. Meanwhile, the parts that process sensations from the hands and lips are enormous. Just as the hands are a central conduit with which we experience the world, so too are the lips.
............................................
BBC - Future - Evolution: Why do we have lips?
Jason G Goldman
Human beings are unusual in that our mouths are surrounded by hypersensitive, easily-hurt pink tissue – why? Jason G Goldman investigates.
Animals know the importance of kissing and making up after a fight, an audience will be told at a Scottish university.
They kind of flap around on the front of your face, get dried out and chapped in the winter, and occasionally get caught up between your teeth and mistaken for food. Seriously, what good are lips? Birds get on just fine without them, turtles' lips have hardened into beaks as well, and while most mammals have lips, we humans are in a class all our own having lips that are permanently turned outwards.
It turns out that lips are quite important; so important, even, that it seems worth the risk of having your bottom lip caught in between your chompers. Even though that can really hurt.
Using our lips to suck is one of the very first skills we have after we're born. In fact, it's so fundamental to our survival that it's known as a "primitive reflex"; we're born knowing how to suck and no learning is necessary. That's true for nearly all mammals.
Babies have an instinct to suck anything that brushes their lips .
It's the sucking reflex combined with another primitive response, the rooting reflex, that allows infants to breastfeed. The rooting reflex works by turning the infant's head to face anything that strokes its mouth or cheek. As soon as something grazes the newborn's lips, the sucking reflex is activated. While the tongue then does a lot of the work, the lips are vital to maintain a tight seal so that the infant can swallow.
That means feeding, whether from breast or from bottle, is not a passive behaviour on the part of a newborn infant. It's more like a conversation, with each side doing his or her part in a dance elaborately choreographed by evolution. At the centre of that dance are the lips.
Read my lips
The lips are of course also important in the act of eating other foods, and in speech. In linguistics, the lips are two of many places of articulation, or spots in the mouth and throat that aid in blockage of air moving out from the lungs. Bring your two lips together and you can form the sounds p, b, and m. To make the sounds f or v, bring your lower lip to your upper teeth. To make a w sound, move the back of your tongue towards the roof of your mouth while also moving your lips closer together.
Speech is arguably a critical part of human life, but it's not quite as much fun as kissing. Kissing isn't universal, though it does pop up in some 90% of cultures. Darwin himself noted that there are cultures in which kissing is conspicuously absent. "We Europeans are so accustomed to kissing as a mark of affection that it might be thought to be innate in mankind," he wrote in The Expression of Emotion in Man and Animals, "but this is not the case…[it is] unknown with the [Maori] New Zealanders, Tahitians, Papuans, Australians, Somals of Africa, and the Esquimaux [Eskimo]."
Lip service
Lips are exquisitely sensitive (if sometimes slimy) bits of tissue. The part of the brain responsible for detecting touch is called the somatosensory cortex, and is found on the top of the brain in an area called the postcentral gyrus. Touch sensations from all over the body get sent there to be processed, with each part of the body getting its own little sub-division along the postcentral gyrus, and the size reflects the density of receptors rather than the amount of skin available to touch. For example, the part devoted to sensations from the chest and stomach is fairly small. Meanwhile, the parts that process sensations from the hands and lips are enormous. Just as the hands are a central conduit with which we experience the world, so too are the lips.
............................................
BBC - Future - Evolution: Why do we have lips?
