The claim is that: “Genetic variation tends to be weeded out by natural selection in the case of traits that are essential to survival. Here it is the opposite; selection is maintaining variation.” My question is: how? “Selection” implies that individuals without a particular trait have less reproductive success. But what “trait” would that be in this case, and how would its absence disadvantage them? (I can understand how it came to be that there’s a high number of variants for facial shape, but wonder whether this is actually now being “maintained” by selection, since it’s hard to see how that would work. Maybe it’s just that departures from a genetic recipe enabling small variations are more likely to result in significant deformities).

>Human faces have evolved to be unique because we recognise one another by sight, according to scientists.

Unlike animals, humans do not recognise each other by smell, according to a study by researchers at the University of California, Berkeley, on how our bodies have evolved.

The scientists assessed human facial variability using a US Army database of body measurements compiled from male and female personnel in 1988. A comparison of the facial traits of European Americans and African Americans, such as forehead-chin distance, ear height, nose width and distance between pupils, with other body traits such as forearm length or height at waist, showed that facial traits are more varied than the others. The most variable traits are situated within the triangle of the eyes, mouth and nose.

The research team also had access to data collected by the 1000 Genome project, which has sequenced more than 1,000 human genomes since 2008 and catalogued nearly 40m genetic variations among humans worldwide. Looking at regions of the human genome that have been identified as determining the shape of the face, they found a much higher number of variants than for traits, such as height, not involving the face.

The authors asked whether the distance between the eyes or width of the nose was variable just by chance, or whether there has there been evolutionary selection to be more variable than they would be otherwise.

They found that people with longer arms typically have longer legs, while people with wider noses or widely spaced eyes don’t have longer noses. Both findings suggest that facial variation has been enhanced through evolution.

Behavioural ecologist Michael Sheehan, co-author of the study published today in the online journal Nature Communications, said many animals use smell or sound to identify individuals, making distinctive facial features unimportant, especially for animals that roam after dark, but humans are different.

He said: “Humans are phenomenally good at recognising faces; there is a part of the brain specialized for that. Our study now shows that humans have been selected to be unique and easily recognisable. It is clearly beneficial for me to recognise others, but also beneficial for me to be recognisable. Otherwise, we would all look more similar.”

Full report: http://www.independent.co.uk/news/science/human-faces-evolved-to-be-recognisable-scientists-say-9736384.html

Bubblecar said:

The claim is that: “Genetic variation tends to be weeded out by natural selection in the case of traits that are essential to survival. Here it is the opposite; selection is maintaining variation.” My question is: how? “Selection” implies that individuals without a particular trait have less reproductive success. But what “trait” would that be in this case, and how would its absence disadvantage them? (I can understand how it came to be that there’s a high number of variants for facial shape, but wonder whether this is actually now being “maintained” by selection, since it’s hard to see how that would work. Maybe it’s just that departures from a genetic recipe enabling small variations are more likely to result in significant deformities).

>Human faces have evolved to be unique because we recognise one another by sight, according to scientists.

Unlike animals, humans do not recognise each other by smell, according to a study by researchers at the University of California, Berkeley, on how our bodies have evolved.

The scientists assessed human facial variability using a US Army database of body measurements compiled from male and female personnel in 1988. A comparison of the facial traits of European Americans and African Americans, such as forehead-chin distance, ear height, nose width and distance between pupils, with other body traits such as forearm length or height at waist, showed that facial traits are more varied than the others. The most variable traits are situated within the triangle of the eyes, mouth and nose.

The research team also had access to data collected by the 1000 Genome project, which has sequenced more than 1,000 human genomes since 2008 and catalogued nearly 40m genetic variations among humans worldwide. Looking at regions of the human genome that have been identified as determining the shape of the face, they found a much higher number of variants than for traits, such as height, not involving the face.

The authors asked whether the distance between the eyes or width of the nose was variable just by chance, or whether there has there been evolutionary selection to be more variable than they would be otherwise.

They found that people with longer arms typically have longer legs, while people with wider noses or widely spaced eyes don’t have longer noses. Both findings suggest that facial variation has been enhanced through evolution.

Behavioural ecologist Michael Sheehan, co-author of the study published today in the online journal Nature Communications, said many animals use smell or sound to identify individuals, making distinctive facial features unimportant, especially for animals that roam after dark, but humans are different.

He said: “Humans are phenomenally good at recognising faces; there is a part of the brain specialized for that. Our study now shows that humans have been selected to be unique and easily recognisable. It is clearly beneficial for me to recognise others, but also beneficial for me to be recognisable. Otherwise, we would all look more similar.”

Full report: http://www.independent.co.uk/news/science/human-faces-evolved-to-be-recognisable-scientists-say-9736384.html

I hope they didn’t get paid for that heap of garbage.

If you group the/se (three) senses of, eyes, nose and ears (and add vocalizations, and body movement and orientation), you have an active sensing system which has some similarities to radar.

Given humans have consciousness, which to me appears to require some special notion of “1” and uniqueness (makes ‘individual’), it doesn’t surprise me the sensor array (face) is quite varied. I note also nature rolls the dice with considerable spread regards cognitive tendencies (I wont say ‘abilities’, though feel free to substitute).

Bubblecar said:

The claim is that: “Genetic variation tends to be weeded out by natural selection in the case of traits that are essential to survival. Here it is the opposite; selection is maintaining variation.” My question is: how? “Selection” implies that individuals without a particular trait have less reproductive success. But what “trait” would that be in this case, and how would its absence disadvantage them? (I can understand how it came to be that there’s a high number of variants for facial shape, but wonder whether this is actually now being “maintained” by selection, since it’s hard to see how that would work. Maybe it’s just that departures from a genetic recipe enabling small variations are more likely to result in significant deformities).

There are probably many ways in which this works, but one possibility is that genes for recognising close relatives combined with genes for not mating with close relatives would have a survival advantage, and if the recognition was done primarily through facial features this beneficial trait would work best in groups that had varied facial features.

except for the fact that all racians look the same

The Rev Dodgson said:

There are probably many ways in which this works, but one possibility is that genes for recognising close relatives combined with genes for not mating with close relatives would have a survival advantage, and if the recognition was done primarily through facial features this beneficial trait would work best in groups that had varied facial features.

While this may have contributed to the development of a certain degree of facial variability in populations, it’s hard to see how “natural selection is maintaining variation” as they claim, unless it doesn’t really have anything to do with facial recognition but with individuals being disadvantaged by features too strongly departing from what’s regarded as “normal” (and therefore in fact being all-too recognisable). People who are merely the “spitting image” of someone else (e.g., identical twins) are not actually reproductively disadvantaged by that fact.

Bubblecar said:

The Rev Dodgson said:

There are probably many ways in which this works, but one possibility is that genes for recognising close relatives combined with genes for not mating with close relatives would have a survival advantage, and if the recognition was done primarily through facial features this beneficial trait would work best in groups that had varied facial features.

While this may have contributed to the development of a certain degree of facial variability in populations, it’s hard to see how “natural selection is maintaining variation” as they claim, unless it doesn’t really have anything to do with facial recognition but with individuals being disadvantaged by features too strongly departing from what’s regarded as “normal” (and therefore in fact being all-too recognisable). People who are merely the “spitting image” of someone else (e.g., identical twins) are not actually reproductively disadvantaged by that fact.

I have often wondered how “Spitting image” came about

bob(from black rock) said:

Bubblecar said:

The Rev Dodgson said:

There are probably many ways in which this works, but one possibility is that genes for recognising close relatives combined with genes for not mating with close relatives would have a survival advantage, and if the recognition was done primarily through facial features this beneficial trait would work best in groups that had varied facial features.

While this may have contributed to the development of a certain degree of facial variability in populations, it’s hard to see how “natural selection is maintaining variation” as they claim, unless it doesn’t really have anything to do with facial recognition but with individuals being disadvantaged by features too strongly departing from what’s regarded as “normal” (and therefore in fact being all-too recognisable). People who are merely the “spitting image” of someone else (e.g., identical twins) are not actually reproductively disadvantaged by that fact.

I have often wondered how “Spitting image” came about

People spitting into heir hands and doing their hair?

mothers doing it to their toddlers?

spitting image
n.
A perfect likeness or counterpart.

Try again

The Rev Dodgson said:

spitting image
n.
A perfect likeness or counterpart.

(Probably from alteration of spitten, dialectal past participle of spit, the close resemblance of one person to another being likened in folk sayings to the former person having been spat out of the latter’s mouth; see spit1.)

The original phrase was apparently “spit and image”, i.e., the two don’t just look identical, they’re so alike they basically share the same spit, or one was spat out by the other. This soon became “spitting image”.