Loki
02-20-2009, 02:25 AM
From NewScientist article (http://www.newscientist.com/article/mg20126952.200-valentines-day-special-kissing.html).
AS NATURAL as kissing seems, it also means swapping mucus, bacteria and who knows what else, so how and why would such a behaviour evolve?
Science has been seeking answers for decades. Neuroscientists point to the way it unleashes a flood of neurotransmitters and hormones associated with social bonding and sex. Anthropologists explain it as a relic of mouth-to-mouth feeding from mothers to infants. Others have suggested that kissing conveys important information about prospective mates and so evolved as a guide to mate selection. It has even been passed off as a purely cultural phenomenon since some groups refrain from it entirely. Despite this, we still do not have a complete answer: the latest proposal is that we kiss because our lips are reminiscent of ripe fruit.
Neuroscientist V. S. Ramachandran of the University of California, San Diego, points out that since our ancestors needed to find ripe fruit, they would have been attracted to the colour red. Red thus became an indicator of food reward.
Then something called "evolutionary co-option" happened, turning red into a general signal for attraction. "The attraction [for red] may have been transferred to the labial region during oestrous to make it conspicuous for males to locate a potential mate," says Ramachandran. Chimpanzees and baboons continue to respond to the red posterior display in females; the "ripeness" cue may also account for the origins of oral sex. When humans became bipedal and no longer advertised their fertility, their upright posture resulted in a different alignment of both visually attractive signals and comfortable mating positions. "Despite these changes, the swollen labia still remain powerfully attractive to males because of an atavistic persistence of evolutionary memory for attraction to red," suggests Ramachandran. Hence the "come-hither" colour cue along with our oral propensity for fruit may have been transferred to our lips, resulting in the intensely arousing nature of a kiss.
This hypothesis is supported by the fact that bonobos share our pink lips, as well as our inclination toward kissing, face-to-face mating and oral sex - much more so than pale-lipped chimpanzees. A fuller pout has also been linked to increased levels of oestrogen in women, suggesting that plump rosy lips may indeed serve as a reliable indicator of fertility.
Romance and bacteria aside, the kiss may be a modern vestige of a love of fruit and sex inherited from our herbivore ancestors.
AS NATURAL as kissing seems, it also means swapping mucus, bacteria and who knows what else, so how and why would such a behaviour evolve?
Science has been seeking answers for decades. Neuroscientists point to the way it unleashes a flood of neurotransmitters and hormones associated with social bonding and sex. Anthropologists explain it as a relic of mouth-to-mouth feeding from mothers to infants. Others have suggested that kissing conveys important information about prospective mates and so evolved as a guide to mate selection. It has even been passed off as a purely cultural phenomenon since some groups refrain from it entirely. Despite this, we still do not have a complete answer: the latest proposal is that we kiss because our lips are reminiscent of ripe fruit.
Neuroscientist V. S. Ramachandran of the University of California, San Diego, points out that since our ancestors needed to find ripe fruit, they would have been attracted to the colour red. Red thus became an indicator of food reward.
Then something called "evolutionary co-option" happened, turning red into a general signal for attraction. "The attraction [for red] may have been transferred to the labial region during oestrous to make it conspicuous for males to locate a potential mate," says Ramachandran. Chimpanzees and baboons continue to respond to the red posterior display in females; the "ripeness" cue may also account for the origins of oral sex. When humans became bipedal and no longer advertised their fertility, their upright posture resulted in a different alignment of both visually attractive signals and comfortable mating positions. "Despite these changes, the swollen labia still remain powerfully attractive to males because of an atavistic persistence of evolutionary memory for attraction to red," suggests Ramachandran. Hence the "come-hither" colour cue along with our oral propensity for fruit may have been transferred to our lips, resulting in the intensely arousing nature of a kiss.
This hypothesis is supported by the fact that bonobos share our pink lips, as well as our inclination toward kissing, face-to-face mating and oral sex - much more so than pale-lipped chimpanzees. A fuller pout has also been linked to increased levels of oestrogen in women, suggesting that plump rosy lips may indeed serve as a reliable indicator of fertility.
Romance and bacteria aside, the kiss may be a modern vestige of a love of fruit and sex inherited from our herbivore ancestors.