Читать книгу Reversing Your Hair Loss - A Practical Scientific Guide - Robert J. Hall - Страница 9

Any observer taking even the most casual of glances along the concourse of any large international airport would notice that there are at least three distinct racial types of human. Continuing the glance for just a second longer, the observer would also notice three types of human hair, all very clearly distinguishable from one another and each belonging to one of these separate races.

As a determinant, any simple forensic examination of a single hair is more than accurate enough to not only distinguish between animal hair and human hair but also ascertain the racial origin of its donor, if human, or determine which animal produced it, if not. In fact, by using more sophisticated forensic techniques such as DNA matching, even the actual donor of a single strand of hair can be identified. Put simply, every single strand of hair carries with it both the general characteristics and the unique genetic signature of its donor.

The three main types of hair our observer would have noted are as follows:

Ulotrichous (some sources give it as helicotrichous). This first type is black, or Negroid hair. This grows as very black, very tightly-coiled and very springy strands. Compared to the other two types, it never grows very long and is relatively weak and brittle. As an aside it is also much less prone to head lice infestation as well.

Lissotrichous (sometimes given as leiotrichous) is Asian, or oriental hair. This is also black, but differs from the first type in that it is very straight and can grow very long. Relative to the other two types, it is also the thickest. A single strand of this hair can easily have a weight of several ounces suspended from it.

The last main type of hair, cymotrichous (also called cynotrichous) is simply European hair. This falls midway between the other two types in terms of natural length and strength. It is finer and silkier than the other two and has a much wider variation in colour. Rather than being either straight or coiled, it tends to be wavy albeit, again, with a very wide range between very curly and almost dead straight.

The difference between these three major types in their ‘curliness’ is caused by the shape of the follicle and the bulb and, as a result, that of its output; the cross-section of the hair itself, in fact. Ulotrichous hair has a very pronounced oval shape (reaching kidney-shaped proportions in some instances). Lissotrichous hair is virtually circular in cross-section, whilst cymotrichous hair ranges from almost circular to fairly oval.

Ulotrichous, or Negroid, hair is certainly the most functionally evolved. Although never recognised as such, it is probably one of the most functionally evolved structures in the entire primate world. Apart from growing more like a ribbon than a string, the hair itself has a somewhat different lipid coating to it when compared to the other two types of hair. The functional advantage of this shows up when the hair becomes wet through with either rain or sweat. The hair does not stick to the scalp or neck; rather, it stays upright. This is an important feature, the function of which will be seen in a moment.

This hair also has something else not found in other hair types: inbuilt, protein-based torsion bars, as it were. These are found within the individual hairs and prevent them from spiralling around one another too much. As a result of these torsion structures, the entire head of hair remains covered, instead of the individual ribbons simply coiling together eventually forming interwoven clumps.

Why are these two features important? Well, these tight, individual, non-wettable coils create a layer of continually ventilated air between the scalp and the external environment. This acts as a highly effective, yet beautifully simple insulating barrier against the sun’s heat. The British Army had to invent the pith helmet around 1840 to achieve anywhere near the same effect.

Added to these purely mechanical features is the actual colour of ulotrichous hair itself. The very dense black pigmentation absorbs virtually all the incident light falling upon it, the short as well as longer wavelengths. All these wavelengths get converted to heat (very long wavelength, infrared light that is completely invisible to the naked eye). This pigmentation, therefore, not only acts as a further thermal barrier against the strong tropical sun, but also saves the scalp from the extremely damaging ultraviolet wavelengths. The cymotrichous hair of Europeans, and especially that of Nordics (north-west Europeans, roughly speaking) is completely lacking in this respect and, as a result, next to useless.

The colour difference between cymotrichous hair and the other types (and between actual samples within the hair type itself) is accounted for by the ratio of the two colourising materials found deep within the hair itself. These two substances are called eumelanin and pheomelanin and both belong to the melanin group of organic compounds. Black through to light brown hair is determined simply by the amount of eumelanin present, whilst additional reddish shading is provided by the pheomelanin pigment.

Blonde hair is caused by there being very little of either pigment, whilst so-called ‘strawberry blondes’ simply have low levels of eumelanin and a higher proportion of pheomelanin than usual. All Nordics are born with blonde hair, incidentally. Their hair gradually darkens over a number of years in most cases with the increased production of pigmentation. Other races are born with their pigmentation levels already in full production and, consequently, their newborns have hair the same colour as the parents.

Red hair has a much greater proportion of the pheomelanin pigment. This higher ratio of pheomelanin is a genetic rarity that is actually found amongst all races. For this reason, there is no specific red-haired race and the only reason that red-headed individuals are seen so easily amongst Nordics and not other races is simply that the heavier pigmentation of the latter tends to disguise any redness of their hair.

Grey hair is a mixture of both pigmented and unpigmented hair. As the white hairs start to predominate, the head of hair progressively greys. White hair is found where the production of pigmentation material has ceased completely. Nordics, who have less pigment to start with, go grey earlier than the other races and tend to go completely white more easily. This trend is so prevalent, in fact, that white hair (as well as baldness) in old people is seen as just not entirely normal amongst Nordics but any elderly person with a head of hair (especially still-pigmented hair) is assumed not to be from their (Nordic) country at all, but some sort of foreigner.

A second stage of hair development occurs at puberty when, under the influence of sex hormones, the vellus hair in the genital region, the armpits and, in males, the chest and face turns into yet more terminal hair. This type of hair is called androgenic hair because its appearance is triggered by the pubertal production of the male sex hormones, the androgens.

It is at this point, and precisely this point, that the balding process starts its inexorable march.