The amazing variety of human faces — far greater than that of most other animals — is the result of evolutionary pressure to make each of us unique and easily recognizable, according to a new study by University of California, Berkeley, scientists.
Okay, so no other life form needs to recognize others of its kind? See also: Dogs recognize familiar faces from images and Dogs pick out faces of other dogs, irrespective of breeds. Clearly, there is more to this:
Our highly visual social interactions are almost certainly the driver of this evolutionary trend, said behavioral ecologist Michael J. Sheehan, a postdoctoral fellow in UC Berkeley’s Museum of Vertebrate Zoology. Many animals use smell or vocalization to identify individuals, making distinctive facial features unimportant, especially for animals that roam after dark, he said. But humans are different.
Yes. In addition to our deficiencies in everything except sight, we walk upright. Here is what I said in some recent notes on bipedalism:
Ah yes, walking. There is a “uniquely human” way of walking upright and there’s no shortage of theses as to why: carrying infants or scarce resources, and saving energy strut the stage. Or it is due to climate change or rough terrain? Don’t assume a “chimpanzee starting point,” counsels one expert. Talk about advice that peers would be reluctant to heed…
These explanations tell us that bipedalism offers considerable advantages. Yet humans were the only creatures to adopt it with no backward glance. If we ask why that is, we will be rewarded only with announcements of the discovery of further ancient advantages. And on that point, we are already convinced. More.
Bipedalism and heavy reliance on sight make facial recognition an easy and obvious form of recognition. Now more from ScienceDaily:
“Humans are phenomenally good at recognizing faces; there is a part of the brain specialized for that,” Sheehan said. “Our study now shows that humans have been selected to be unique and easily recognizable. It is clearly beneficial for me to recognize others, but also beneficial for me to be recognizable. Otherwise, we would all look more similar.”
Maybe we’d all look more alike, but a question nags. Is it true that, say, a cat would not recognize another cat by its face, deprived of data from smell or hearing? That is, is it true that other mammals do not have unique faces? Or is it more that most members of other species would use a different recognition system, given a choice?
Just for example, it has always been assumed that cats are colourblind. Actually, they do see some colours. But in any event, the cat prefers other methods for getting information, and must be patiently prompted to use colours it can in fact recognize. ScienceDaily again:
As predicted, the researchers found that facial traits are much more variable than other bodily traits, such as the length of the hand, and that facial traits are independent of other facial traits, unlike most body measures. People with longer arms, for example, 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.
But do we know that the variation is selected for, as opposed to just not being selected against ? A person with long arms but short legs might have problems working, just to survive. By contrast, a person with a wide but not long nose may not have any problem passing on their genes if the trait is not culturally forbidden. ScienceDaily:
“All three predictions were met: facial traits are more variable and less correlated than other traits, and the genes that underlie them show higher levels of variation,” Nachman said. “Lots of regions of the genome contribute to facial features, so you would expect the genetic variation to be subtle, and it is. But it is consistent and statistically significant.”
Right. But that is consistent with the hypothesis that facial variation does not matter very much to reproductive success, as opposed to it being selected in some way. We read:
“Genetic variation tends to be weeded out by natural selection in the case of traits that are essential to survival,” Nachman said. “Here it is the opposite; selection is maintaining variation. All of this is consistent with the idea that there has been selection for variation to facilitate recognition of individuals.”
No. The finding is more consistent with no selection. People just learn to recognize whatever facial features turn up in the genetic lottery, and accept them if they are not obviously abnormal.
Note: Of course people considered beautiful in a given culture are more sought after as mates. But beauty is no guarantee that they will produce more or more fruitful offspring. And in any event, all others who marry and have children must settle for the runners up. Hence variation is maintained.
So is this UC Berkeley study what claims for natural selection have come to?
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