lostpunk5545
Bluelighter
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This article had me in stitches. Some humourous fucking stuff. It's all about the purpose for human beings to have evolved hair that grows so much longer than that of any other species, and the reason it happened. It's a great read for next time you're trying to justify the $200 hair cut you just got
Douglas Adams had it right
Tressed to impress: Our love affair with hair
"GET back upstairs and brush your hair before you go to school. You look like some kind of caveman!" Is this a familiar refrain from your youth? If so, perhaps you raged at the injustice of being born into a species with such unruly tresses, wondering why we have hair that needs so much cutting and combing to keep it in check Maybe, in those far-off, pre-Google days, you went to the library to find out more. You would have discovered that, with the exception of the musk ox, humans are the only mammals with almost continuously growing hair. You probably would have wondered why, and after a further search of the shelves you would have been frustrated to discover that nobody had an answer. How times have changed.
The past couple of years have seen growing interest in the science of human head hair. It began with the publication of a short article in Evolutionary Anthropology by Arthur Neufeld, a physiologist at Northwestern University in Chicago and anthropologist Glenn Conroy from Washington University in St Louis, Missouri (vol 13, p 89). They pointed out that while the fur of other mammals just grows to the required length and then stops, the hairs on our heads stick around for years getting longer and longer. "Have you ever seen a chimpanzee getting a haircut?" they asked. "For that matter, have you ever seen any furry mammal (aside from certain competitive canine contestants) in need of tonsorial grooming?" Of course not. So why then have humans evolved this unique adaptation of almost continuously growing head hair, was the question they posed in their article. "The response was enormous," recalls Neufeld.
This much we know. Our hair comes in two types: terminal hair, which occurs on the scalp, eyebrows and eyelashes, and the usually softer vellus hair, which is found everywhere else. Via complex mechanisms of hormonal control, these two give rise to the nine or ten varieties of hair adults have, from pubic and underarm hair to beards. Whether it's glossy shoulder-swishing locks or the tiniest toe-hair, it all grows at the same rate - about 1 to 1.5 centimetres a month - with only a very short dormant spell before it drops out. What differs is the lifetime of the hair on different parts of the body, and this is what determines its maximum length. Leg hairs, for example, last around two months, armpit hairs left to their own devices make it to six months, but head hairs grow nonstop for six years or more.
Things get more uncertain when it comes to exactly how hair growth is regulated. We have yet to untangle the details, but there are probably hundreds of genes involved and we do know that even a single mutation can have a big effect. Angora mice, for example, owe their long hair to a single mutation in FGF5, a gene that codes for a protein involved in halting growth of the hair shaft. Neufeld and Conroy wondered whether human head hair might also keep growing because it has become insensitive to growth inhibitory factors produced by FGF5 or similar genes.
Another possibly lies with the 10 main genes for the keratin from which our hair is constructed. The duo point out that nine of these are almost identical in humans, chimps and gorillas, but the tenth, phi-hHaA, is notably different. In the other primates it codes for a protein, whereas in humans it is a pseudogene - it is transcribed into RNA but no protein is ever synthesised (Human Genetics, vol 108, p 37). Helmelita Winter of the German Cancer Research Centre in Heidelberg, who reported this finding in 2001, has also calculated that the mutation responsible for this change occurred some 240,000 years ago. "Is that when humans acquired head hair that continues to grow?" ask Conroy and Neufeld.
Bernard Thierry from the French national research agency CNRS in Paris thinks it could be. He points out that 240,000 years ago is also when our ancestors started burning fires in hearths (Evolutionary Anthropology, vol 14, p 5). "Cultural evolution first provided an environment with new selective pressures, then genetic mutations were sorted out," he says. In other words, he believes the driving force of change was culture. It was only after our ancestors invented ways to keep warm without being covered in fur that their hair could become adapted to serve new functions.
There are several good reasons to become less furry. One is that it would have helped fight disease, since fur is a prime habitat for parasites. Another is that it was important for thermoregulation, allowing our ancestors to sweat more efficiently following their move from a forest habitat onto the hot savannah. Some even believe it was an adaptation to a more aquatic phase in our history. Darwin, of course, had an explanation, suggesting that sexual selection was the key: the least hairy of our ancestors were considered the most attractive and so produced more offspring, making the species progressively less hirsute.
But none of this explains why the hair on our heads should have evolved in the opposite direction - something that would have been very costly in terms of the energy needed to make it and to keep it free of parasites. Surely there must have been a payoff?
The idea now emerging is that, precisely because our head hair needs so much care, it makes a perfect billboard upon which individuals can advertise their social standing. Good grooming is a social enterprise, and so shows you are part of the in-crowd, that you have friends and the social skills to keep them. If this is correct, then the corollary is clear:head hair grows simply to be cut and coiffed.
You scratch my head
"It makes so much sense," says Alison Jolly, a primatologist from the University of Sussex, UK, who was one of the first to respond to the original paper (Evolutionary Anthropology, vol 14, p 5). "Neat hair shows someone likes you enough to do the bits around the back." She takes the idea a step further. "You must not only be good enough and skilled enough literally to have time on your hands, but also dexterous enough not to make a hash of this delicate operation." So good grooming also requires reciprocity - to trust and to be trusted. This might explain why long, lank, unkempt locks are traditionally the mark of the outcast, the lunatic and the social pariah.
That seems like an awful lot to deduce from a few strands of coiled keratin. "Yes, but primates have done this for a long time," says Jolly, pointing out that grooming is the glue of primate societies. "Many primates have quite complex natural hairstyles that show the individual's health and social status, as well as telling everyone what species they are," says Jolly. She reels off a list of the well-groomed that includes African baboons (magnificent manes), Amazonian cotton-top tamarins (near-punk head-tufts), the emperor tamarin (imperial moustaches) and India's lion-tailed macaque (general chic elegance).
Of course, humans do not need hairstyles to distinguish them from closely related species; since the Neanderthals died out around 24,000 years ago, there haven't been any. Nevertheless, throughout the ages and across cultures, we have used hairstyles to signify membership of particular groups:think Roundheads, punks and Rastafarians. Thierry believes that for our prehistoric ancestors, hair care was not simply a matter of individual belonging but was also about group identity. This notion is clearly very important in tribal societies, he says, pointing to the example of 5300-year-old Ötzi the Iceman, found in the Italian Alps in 1991, whose tribal marks included 57 tattoos - although his hairstyle is unknown. Another example reported earlier this year is the 2300-year-old Cloneycavan Man discovered in a bog in County Meath, Ireland, who was apparently wearing gel to make his hair stand on end.
Thierry believes hairdos have acted as gang membership badges since the evolution of modern humans, around 200,000 years ago. That fits broadly with the timing of the phi-hHaA mutation. Unfortunately there are no fossilised topknots to clinch the argument, and the earliest known combs date back barely 8000 years, but some of the most ancient human figurines do have dressed hair. The 23,000-year-old Willendorf Venus is one. Her creator may have given her no facial features, but she did get a complex hairdo. Similarly the oldest known three-dimensional representation of a person, the 25,000-year-old Brassempouy Lady, an ivory statuette from Aquitane in France, has elegant shoulder-length hair.
Undoubtedly it is a big leap back in time from these cultural artefacts to the dawn of our species. Yet despite the lack of older archaeological evidence, many experts believe our ancestors were braiding hair far further back even than this. By looking at genetic variation in the MC1R gene, which is associated with skin coloration, Alan Rogers from the University of Utah in Salt Lake City concludes that we became furless around 1.7 million years ago (Current Anthropology, vol 45, p 105). Around this time Homo erectus was living on the hot savannah, so this fits with the idea that furlessness is an adaptation to allow better thermoregulation. The heads of these bipeds would have been disproportionately exposed to the sun, and long head hair would have been an effective sunshade. While there is no way of knowing whether the crowning glory of Homo erectus was primped and plaited, the fossil evidence does at least suggest that, even this far back, our ancestors had the dexterity for the job.
Coiffured cavemen
So where does that leave the grubby, hirsute caveman of popular imagination? The very fact that we have this image is evidence of hair's cultural importance, says New York-based anthropologist Judith Berman-Kohn. It dates from the late 19th century, she says, when the notion of what it was to be human and civilised was threatened on many fronts - by the discovery of the first Neanderthal remains, the publication of Darwin's On the Origin of Species, the American civil war and the spread of European imperialism. The hairy, unkempt cavemen depicted by artists such as Charles R. Knight and Fernand Cormon were not based on fact but reflected the influences of their time. "Hair was both a medium and a metaphor," Berman-Kohn says.
Today we know a lot more about how our cave-dwelling ancestors would have lived. They would certainly have had the time to beautify their hair. "Tribal societies are efficient. Hunting and gathering take up only so much time. There are many hours left over for socialisation," says Thierry. They clearly also had a developed aesthetic. "Even the earliest and most mundane artefacts we have seem to have been made with a feeling for style. I see no reason why, even in cultures with few material goods, hair ornamentation should not have been important," he adds.
And if some people were better at it than others, they would surely have been in demand. The unmistakable conclusion is that, along with warrior and prostitute, one of the oldest professions was probably hairdresser.
Adrian Barnett is a primatologist at Roehampton University in London. The name is his own, not a pseudonym adopted for this article.
Hair-raising facts
You have around 5 million hair follicles, which is on a par with other primates.
The number of head hairs varies with natural hair colour. Blondes have around 140,000, brunettes 105,000 and redheads a paltry 90,000.
Left uncut, the average person's hair would grow to waist-length in about four years.
The first blondes appeared only around 11,000 years ago.
About 90 per cent of the hair on your scalp is growing at any one time.
You lose between 50 and 100 head hairs a day.
From issue 2576 of New Scientist magazine, 04 November 2006, page 39-41
Douglas Adams had it right
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