This Transfusion: Parachutes and death from gravitational challenge | Hawthorn and heart disease | Blood group A and ovarian hyperstimulation syndrome | Rh blood group and hearing loss | Epigenetics, diet and super oxide dismutase (SOD)
Welcome to The Weekly Transfusion, 1.5 for the week of April 13, 2009.
Insufficient evidence for parachute use to prevent death and major trauma related to gravitational challenge
As with many interventions intended to prevent ill health, the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised controlled trials. Advocates of evidence based medicine have criticised the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute.
Evidence based medicine is the buzz-phrase of the moment, the idea being that you scour the medical literature on a particular association,for example using the herb Hawthorn to treat chronic heart failure. You set the selection criteria, such as the type of study (placebo controlled, etc.) and the amalgamate the data. Evidence Basis has some very important advantages, namely that it gives the most accurate current assessment of a treatment or strategy since you are pooling all the available data.
One problem with evidence based medicine is the simple reality that evidence and benefit are not always the same thing. As shown by this slightly tongue in cheek study, there is still an insufficient evidence basis to conclude that parachutes are effective in preventing major trauma related to gravitational challenge. The researchers failed to find suitable studies showing the effects of using a parachute during free fall, despite setting logical criteria (death or major trauma, defined as an injury severity score > 15) and scouring he available literature.
Setting artificial standards can also impeded the workings of common sense: Edward Murphy put it best in his classic The Logic of Medicine: 'Only a fool would require a double-blind study to see if it was raining outside.'
Lack of evidence is not evidence of lack.
Evidence based medicine has potential to revolutionize day to day health care. However I think an even bigger revolution lurks under the surface: The reinterpretation and reorganization of medical facts derived under the older 'disease-care paradigm' by evolving paradigms that better fit new real-world circumstances.
A common argument against the need for heterodoxy in medicine is that 'when facts are proven, they stop being alternative.' This may well be true, but it neglects that facts themselves are forever open to reevaluation, deconstruction and recycling. Much of my work with the ABO polymorphisms was the simple reappraisal and restructuring of the conventional biomedical literature on the subject --but done with an eye to its ulterior benefits in naturopathic circumstances. Had they not been subjected to the 'naturopathic lens' these facts may well still be floating in their own splendid isolation.
Hawthorn extract for treating chronic heart failure
For the physiologic outcome of maximal workload, treatment with hawthorn extract was more beneficial than placebo... Exercise tolerance were significantly increased by hawthorn extract... The pressure-heart rate product, an index of cardiac oxygen consumption, also showed a beneficial decrease with hawthorn treatment... Symptoms such as shortness of breath and fatigue improved significantly with hawthorn treatment as compared with placebo...These results suggest that there is a significant benefit in symptom control and physiologic outcomes from hawthorn extract as an adjunctive treatment for chronic heart failure.
I first wrote about Hawthorn (Crataegus spp.) in my book Eat Right For Your Type over thirteen years ago, making specific reference to its benefit for blood group A individuals with cardiovascular problems. In general the plant has a good track record, especially, if used in quite low doses for extended periods of time. The herb seems to allow cardiac patients to derive extra benefit from exercise (link), has some very nice effects on the artery lining (link) and has been shown to lower blood pressure in patients taking diabetic medication. (link)
Hawthorn was shown to be well tolerated and safe. However, it should not be used as a substitute medication in circumstances of active heart disease or concurrently with other cardiac medicines unless under the supervision of a physician trained in its use. In one study, it actually seemed that the hawthorn group had a worse outcome than the placebo group. (link) Hawthorn also does produce occasional side-effects, though they appear uncommon and rather mild.(link) Perhaps this is the darker side of the biochemical individuality revolution; it's no longer acceptable to claim that all natural products are safe in every person. Anything that can add to the personalization of herbal recommendations can only help to increase their safety profile.
Blood type A women get more complications from fertility treatment
Ovarian hyperstimulation syndrome is a potentially life-threatening complication during controlled ovarian stimulation for fertility treatment. Since no association of this condition with ABO blood groups was known, we compared ABO antigens with severity and onset of symptoms in a case-control study...The odds ratio for patients undergoing controlled ovarian stimulation with blood group A versus O to develop the early-onset form of this condition was 2.171 (p-value 0.002). Blood group A may be associated with early-onset ovarian hyper-stimulation syndrome in Caucasians...This possible association may be considered for an individualized hormone dosing in controlled ovarian stimulation.
Ovarian hyperstimulation syndrome (OHSS) is a complication from some forms of fertility medication. Most cases are mild, but a small proportion is severe. Symptoms can range from a more mild form that includes abdominal bloating and feeling of fullness, nausea, diarrhea, and slight weight gain to a more severe form that includes and fullness/bloating above the waist, shortness of breath, urination significantly darker or cessation of urination altogether, calf and chest pains, marked abdominal bloating or distention, and lower abdominal pains. This study looked at 127 Caucasian patients hospitalized because of ovarian hyperstimulation syndrome after receiving in vitro fertilization, in the period from January 2000 to February 2007 and found that blood group A was markedly more frequent and blood group O less frequent in patients with ovarian hyperstimulation syndrome.
Other studies have found a slightly greater incidence of ovarian cancer in women who are blood group A (link) and blood group antigens (as mucins or 'blood group substances') are known to be richly deposited on ovarian tissue. (link) Hopefully fertility specialists will consider individualizing hormonal treatment by blood group when working with fertility patients.
Four patients developed thrombosis (clots) in the jugular or subclavian vein, none of whom had blood group O; this correlates with earlier studies linking blood groups other that type O with an increased risk of thrombosis (link) at some of this clotting may in fact be due to enhanced sensitivity to estrogen, at least in women who are not blood group O.(link)
What was that? Being Rh positive may increase your risk of hearing loss
Noise-induced hearing loss (NIHL) is one of the most common occupational problems and is one of the main causes of deafness. Many factors cause NIHL. Individual susceptibility is one of them. Rhesus (Rh) antigens and ABO blood groups can be factors in determining individual susceptibility. In conclusion, we suggest that the people with Rh-positive blood group are more prone to develop NIHL.
The researchers looked at factory workers who had been exposed to a noise level more than 85 dB for 8 hours a day for a period of over 15 years. Two hundred and nineteen (55.4%) of Rh-positive workers and seventeen (39.5%) of Rh-negative workers have noise-induced hearing loss, and the difference between the two groups was statistically significant (P < 0.05). There was no link between hearing loss and ABO blood type.
If you are a rabid reader of this blog, you'd immediately notice that these results are just ever-so-slightly statistically significant (and not be much of a discovery) since given enough noise, virtually anyone will develop hearing loss. However we could speculate that something in being Rh positive influences the structure of the ear anatomy to make these people more likely to get hearing damage. Or on the other hand, what is it about being Rh negative that makes these people less likely to get hearing loss?
An earlier study with infants and adults also showed a higher incidence of hearing loss in Rh positive people, with a slightly better level of significance (0.01) if the mother was Rh negative blood type (which might support the idea that the problem would then be seen in the incompatible Rh-positive children). Another maternal influence via blood group!
Diet influences epigenetic regulation of super oxide dismutase (SOD) gene
The impact of nutrition on the epigenetic machinery has increasingly attracted interest. The aim of the present study was to demonstrate the effects of various diets on methylation and gene expression. The antioxidative enzyme mitochondrial superoxide dismutase (MnSOD) was chosen as the model system because epigenetic regulation has been previously shown in cell lines for this gene. A 3-fold increase in the expression of the MnSOD gene was associated with decreased CpG methylation of the analyzed promoter region in the vegetarian group compared with the age-matched omnivores group. These results indicate that diet affects the epigenetic regulation of human MnSOD.
The super oxide dismutases are a class of enzymes that catalyze the conversion of free radical superoxide molecules into oxygen and hydrogen peroxide. They are an important antioxidant defense in nearly all cells exposed to oxygen. SODs 'outcompete' healthy tissue for the damaging free radical molecules. They protect the cell in a way reminiscent of a common scene in the the old Laurel and Hardy movies where two soldiers in a trench hoist a helmet on a stick above their heads and then retrieve it having been shot full of bullet holes. Although SOD supplements are a common item on health food store shelves, oral SOD products are completely destroyed in the gut, so methods to increase the native (endogenous) production in our own cells would be optimal.
Epigenetics is best explained as the 'non-genomic' or 'post-genomic' control of gene expression, mechanisms such as DNA methylation, or histone acetylation, which act a 'volume controls' on the ability of the cell to read the section of DNA that contains that gene. In the case of this study, the vegetarian group has less methylation on the CpG section of promoter region of the SOD gene.
In English, what they are saying is that diet removed some of the restrictions (methyl groups) on the part of the gene that activates it (the promoter region). Removing methyl groups usually takes the brakes off a gene, especially when they are in the gene's cystine-rich 'front.'
Exciting stuff. Now we'll need to see exactly which specific foods have the maximum epigenetic effects on SOD.
Until next week.
Note to readers: By mistake I had uploaded an earlier, non-spell-checked version of this entry on Monday. I beg your indulgence on this matter. Although I am a reasonably good speller, if truth be told I am a terrible typist.
It would be nice if all the type O’s lived in one part of the world, and all the type A’s in another. However, this does not happen --much. The various blood groups are found pretty much all over the world. However they are not found in the same frequency everywhere. It was this difference in the frequency of the different blood types that gave the early blood type detectives their first insights into human individuality.
Soon after the ABO blood groups were discovered by Karl Landsteiner in the early 1900’s, scientists began to think about using them as a tool to help study the differences between populations. One of the first to begin using blood type in this manner was a husband and wife team, Ludwik and Hanka Hirszfeld. During World War I, they took blood samples from the soldiers of three continents then assembled in the area of Greece called Macedonia as “The Allied Army of the East.” In reality this army was a hodgepodge of battered contingents and survivors from various Allied nations which did little more than stay put in camp and suffer from constant epidemics. However the Hirszfelds realized that the international nature of this army presented opportunities of examining the serological properties of the blood of a large number of soldiers or civilians belonging to very different races.
They established three categories: One marked by a high percentage of subjects of blood type A and a low percentage of blood type B and which seemed to include the majority of European races (European type); A second showing on the contrary a high percentage of blood type B and a low one of blood type A, comprising Asians and Ethiopians (Asian-African type); and a last category containing approximately equal quantities of blood types A and B made up of Russians, Turks, Arabs and Jews, which they called an intermediate type.
The Hirszfelds invented an interesting and useful tool called the Hirszfeld Biochemical Index and which conveniently lets us express the ratio of blood group A to B in any population. The formula is very simple; you add up the number of blood type A and AB individuals in a population and then divide it by the number of blood type B and AB individuals. As so:
Hirszfeld Biochemical Index = [A + AB] /[B + AB]
Thus, the higher the Hirszfeld Biochemical Index of a population, the more blood type A people in that population over blood type B people in it; the lower, the more blood type B over A. The highest number in the Hirszfeld Biochemical Index (most As, least Bs) was found among the English troops (4.5); the lowest (most Bs, least As) were found in the Indian (0.5) and Vietnamese troops (0.8).
The work of the Hirszfelds would look crude in comparison to later, more sophisticated methods, and it suffers from the problems of all single-gene examinations of human diversity, that is there a no “pure races” to be identified by a single marker. But their discovery, published in 1919, did give rise to a considerable number of subsequent investigations, producing an enormous mass of documents of varying merit.
The arrival of blood typing signaled a new era in physical anthropology, since up to now the field had been limited to many of the physical measurements that I’ve previously described. Here now was a serologic, or blood marker, simple and easy to perform.
One of the first to begin using blood types as an anthropological tool was none other than William Boyd, who I’ve mentioned early in connection with the debunking of racism. In the years after the First World War, Boyd compiled the abundant blood group data coming from transfusion centers throughout the world. With his wife Lyle, during the 1930's, Boyd made a worldwide survey of the distribution of blood types. On this basis, he divided the world population into 13 geographically distinct races with different blood group genetic profiles. He also studied the blood groups of Egyptian and Amerindian mummies.
William Boyd appears to be one of those fascinating people who go on to dominate an entire area of research for a generation. It seems as if his creativity knew no bounds: I’ve already mentioned of his important work with Isaac Asimov used his work with blood types in Races and People to demolish the racist notions then commonly believed in this country during the 1950's; and here we are discussing his work on blood types and anthropology. But William Boyd accomplished much, much more than that. In the 1940’s Boyd noticed that the protein agglutinin in lima bean would agglutinate red cells of human blood type A but not those of O or B; he had in fact discovered that many of the of these blood agglutinins were actually specific to one blood type or another. With Elizabeth Shapely he coined their modern-day name; lectins which is Latin for “to pick or choose.”
Boyd wrote some excellent science fiction (under the name Boyd Ellanby) including two well-known books, 'Category Phoenix' in 1952 and 'Chain Reaction' in 1956. He also authored the Fundamentals of Immunology, one of the first Immunology textbooks for medical students.
By 1950 Boyd had determined about 20 genes for outward appearance traits that are recessive for typical Asians and/or Europeans but homozygous dominant for Africans. These recessive genes include the 6 to 8 genes for light skin color, the genes for blue eyes, gray eyes, blond hair, red hair, thin lips, straight hair, sacral spot, lack of facial hair (beards), narrow nose shape, and some others.
After the Second World War, William Boyd's baton as compiler of blood group data from around the world passed to the Englishman Arthur E. Mourant.
A native of Jersey in the Channel Islands, Mourant received a degree in geology, but as this was Depression-Era Britain, he was unable to find a job. His very strict Methodist upbringing had caused him considerable emotional unhappiness, which he hoped to resolve by becoming a psychoanalyst. To that end he decided to begin by first study medicine.
To avoid the German bombing raids on the capital, his medical school was moved from London to Cambridge, and it was here that he met Ronald Fisher, the most influential geneticist of his day. Fisher, a brilliant eccentric who we will meet again, had been working out the genetics of the new blood groups which were being discovered, and he had become fascinated by the particularly convoluted inheritance of one of them – the Rhesus blood group. Fisher found him a job at once, and the meticulous Mourant spent the rest of his working life compiling and interpreting the most detailed blood group frequency distribution maps ever produced. He never did become a psychoanalyst.
In the early 1600’s Pierre De Lancre, a French witch hunter, speculated why the Basque area seemed to harbor so many witches. He thought the problem stemmed from their great numbers in the various Jesuit missionaries, with all their evangelizing, which had affected them with demons from far-off places that they had carried back to Spain. De Lancre also thought that there early adoption of tobacco use may also be working on their minds. He held Basque women in special contempt, saying that they produced only undersized and cursed children who died.
As Mark Kurlansky recounts in The Basque History Of The World, this last accusation may have had a ring of truth to it, since Basques are renowned among anthropologists for their strikingly high percentage of individuals who have the Rhesus Negative (Rh-) blood type genotype (dd): 60% compared to an average of 16% for the rest of Europe. When a mother is Rh- and she gives birth to Rh+ children, an immune reaction can occur which gives rise to a hemolytic (“blood destroying”) anemia, and often would lead to the death of the child.
Mourant suggested that modern day Basques have other characteristics which may mark them as descendants of the late Paleolithic population of Western Europe: They share a skeletal resemblance to Cro-Magnon man and they are the only Western European people who do not speak a Indo-European language.
One way to truly screw up the truth is to subject it to public debate; since our minds want some sort of resolution, but out of inbred nicety we often want consensus as well. Problem is, as Winston Churchill so accurately pinned it, consensus is often “the sum total of everyone’s fears.”
People seem to have a love-hate relationship with genetics, or perhaps more accurately, an “awe-hate” relationship. Ask the average person what genetics means to them, and they will typically respond with a litany of dread, largely courtesy of the news media. Cloning. Stem cells. Genetically modified “Frankenfoods.” Yet ask that same person where they envision science will find the cure for cancer, or aging, or diabetes, and they will probably answer genetic research as well.
There are indeed aspects of genetics that are potentially disturbing. Consider the genetic modification of our foods. To a certain degree we are becoming one big uncontrolled experiment, as biotechnology inserts genes from one species into another, often for supercilious reasons. Do we need pesticide-resistant plants, courtesy of genetic engineering, or do we need more pesticide-free organic gardening?
It is precisely when biotechnology becomes the enabler of our existing bad habits that we lead ourselves into uncharted territory. It is also the time when the counter argument in favor of genetic modification of foods, that “nature does it all the time” rings hollow. “Nature” is a vast, living breathing mega-structure. To me Nature might more likely try to destroy pesticide manufacturers rather than re-engineer everything to be able to withstand their wares. It would certainly be easier.
In addition, we have the problem of the politically correct scientific conclusion. Scientists are human beings just like anyone else (stupider actually, if DNA pioneer James Watson were to be believed) and the pressure to conform or arrive at conclusions that are not socially distasteful (and hence not publicly fundable) is great.
But here’s what should be the goal: Take the gobs of generalized information out there, filter and analyze it, then let it guide our actions through the process of making the sort of useful decisions and actions that can produce positive change in public health. Our goal is not Eugenics (getting rid of genetic undesirables, like what the Nazis tried to do), but rather Yougenics --the science of studying yourself. As long as our fact-finding is based on the results that pertain only to you, the individual reading this blog, we will always remain on a strong, fair and firm ethical base.
I would go so far as to say that the absence of Yougenics is the main problem with nutrition as it is practiced today. All too often we read studies done on large groups of individuals and can only be left wondering if these results apply to us. Since nutrition began its meteoric rise in the public consciousness thirty years ago, we’ve been barraged with studies that have lead to sweeping conclusions and have then seen these same conclusions laid to rest, one after the other.
A lot of this is the result of nutrition being largely disease-based, a legacy of its years of discovery centered on finding the cause of deficiencies. Conventional nutritional wisdom came to define health as the absence of nutritional deficiency. Some of this is probably a ripple effect from the major developments that have taken place in the field of pharmaceutical drugs. But foods work differently than drugs. For example, we don’t make energy out of drugs; they don’t fuel or cellular processes. Foods are functional entities in our bodies, not drugs that prevent deficiencies, and our reactions to food are much more individualized than those we have to drugs.
Since nutritional science has such a rudimentary approach to food, it is not surprising that most nutrition research yields results that typically conflict with other results. And although it will eventually be yanked, no doubt kicking and screaming, into the genomic age, nutritionists still clamor for the next “one size fits all approach”, substituting one fad for another, each with its own army of disciples and detractors, the cycle to be repeated again and again.
An interesting observation on the Autism website points to the possibility that The Blood Type Diets can be helpful in managing kids with autism. We've seen some indication of this in the Clinic, and I've speculated in at least one book (Live Right For Your Type) that lectin avoidance may be the mechanism by which this occurs. Would be nice to see a good independent study on this. We can at least hope!
Although I’m probably only one of five people on the planet who have not read it, the blockbuster success The DaVinci Code is just another indication that we humans have an innate curiosity about codes and their relationships and meanings. This blog will take us into the ultimate code of them all: The Code of Life.
By general agreement, a code is a rule for converting a piece of information into another form or representation, not necessarily of the same type. For example, I often write computer programs, most often to do some particular job or another on my website. Most programmers refer to this a “writing code.” Computer programming code appears to the non-programmer as a series of arcane jottings and numbers, but to both the programmer and computer, this code is in reality a series of highly specific instructions, executed step by step, that result in the computer performing some real world action; perhaps posting a message to an internet bulletin board or sending along an email.
Since computer programs are often rather large affairs with many loops and computations, writing good computer code is a daunting -if at other times stimulating- pursuit. It can be reassuring to remember that at any moment in time only very simple, rather dumb things are happening. What makes the computer program so powerful is that all these simple dumb things are happening extremely fast with a tremendous degree of accuracy.
Very few computer programmers can ever claim to have written a perfect program straight off. There are too many places that things can go wrong, computers being the terribly literal creatures that they are. For example, a command that tells a computer to print Hello World! to the screen might look like this:
23. PRINT “Hello World!”;
Simple enough, eh? Like the way we humans typically read books (from front to back and top to bottom) computers execute code from the top down. Thus, our line of computer code is numbered 23, so we can assume that there are twenty odd lines of computer code in front that will be executed before our screen lights up with the words “Hello World!” Perhaps line 22 tells the computer to make the screen font red, in which case our “Hello World!” would be rendered in red colored type. If we remove that line and run the program again, our font color goes back to black.
Look at our line 23 again and you will notice that the phrase you see -- Hello World! -- is in quotes, because in our simple computer language putting a phrase in quotes tells the computer where is the beginning and end of what you want sent to the screen is located. Without this type of instruction, computers are actually quite dumb, and have to rely on us to tell them where the beginning and end of various human things lie. Also notice that at the end of the line is a semi-colon, which in our little computer language tells the computer that this is the end of that particular line of code, so move down one line and execute that command next.
Computers are so literal that a mistake of even one character can cause a program to malfunction. For example, if you saw this line:
23. PRIINT “Hello World!”;
You’d probably guess that something is supposed to be printed. However the computer does not see PRIINT as the equivalent of PRINT. On the other hand if your code looked like this:
23. PRINT “Hello Wurld!”;
The program would probably still execute, since as far as the computer is concerned the command is correct and it’s in quotes, so it assumes that this is probably what you wanted. Once the command is correct, the computer doesn’t care if you tell it to write “Hello Wurld” or “Kick Me”. As long as its own language is correct, the computer will chug happily along, performing its assigned tasks.
Like computers, first impressions, and that light switch on the bathroom wall, genetics is remarkably digit business: On-Off; Yes-No; Love-Hate. So even if it looks complicated at times, don’t be fooled: It’s not. Just remember, like computers, genetics is simply a lot of small things happening in a clear-cut manner and if you get perplexed or lost, just take a step or two backwards and start again.
The mechanism of the genome is surprisingly similar to our simple line of computer code; so simple in fact that I will provide you with an “executive summary” of the whole affair in just two paragraphs.
A molecule called DNA periodically assembles copies of various parts of itself that are called RNA. RNA then travels to other parts of the cell where it is read as an instruction template, assembling chains of amino acids into something very useful: protein molecules of delightfully complex three dimensional shapes that are most often a class of proteins called enzymes.
Enzymes are special speed-up molecules that greatly foster the production and metabolism of the body’s tissues and secretions. Without them many biochemical reactions would occur so slowly as effectively negate their value. Just think about the difference between soaking a dirt stain in plain water for four days, versus soaking it for four minutes in a solution of water and laundry detergent and you’ll get an appreciation for the action of enzymes.
Enzymes catalyze many of the reactions involving proteins, fats, carbohydrates and minerals. Hormones, mucus, neurotransmitters, you name it; they are all made from enzymes.
It sobering and a bit humbling, to ponder the fact that when we eat any kind of protein, we’re actually consuming the results of something’s DNA and some of their DNA as well. However we usually break down dietary proteins to their amino acid building blocks and start all over again.
Occasionally, wild molecular gyrations occur as the incredibly DNA long molecule prepares to replicate by winding itself up tighter and tighter on a tubular scaffold of its own creation. Splitting from the ends much like an old Manila hemp rope would, each of the two unraveling single strands then begins to assemble a copy of its missing partner, producing two unique strands of DNA and creating two daughter replicas from one original.
What happens is surprisingly simple. Good things are like that; a strong underpinning of fact and analysis, and a veneer of simplicity and common sense. Now why, on the other hand, is quite a different story.
Eye color is far more complex than is generally appreciated, ranging from blue, gray, green, green/blue, brown, and others, varying with different populations. As with skin pigmentation, eye and hair color results from the degree of melanin pigment deposited in the tissue. Humans have several eye color genes. Two best understood are named BEY2 (brown eye) located on chromosome 15 and GEY (green/blue eye) located on chromosome 19. Interestingly, the human “secretor” blood type gene is linked to the GEY gene, since they are both found on chromosome 19. This may explain why the percentage of secretors in the population rises as one heads further north, since the percentage of green and blue eyes increases as well.
There is one peculiarity of eye structure which has been used in making racial distinctions called the epicanthic eye-fold, a fold of flesh that covers the upper eyelid, and sometimes even the upper eyelashes, when the eyes are wide open. It gives the eyes a narrower appearance. It may be an evolutionary defense against both the extreme cold as well as the extreme light that occurs in the Eurasian arctic and north. It has also been suggested that the fold provides some protection against dust in areas of desert such as that found in the deserts of northern China and Mongolia as well as parts of Africa.
Although almost universal amongst Central and Northern Asians, there is a wide distribution of the epicanthic fold across the world. It is also found in significant numbers amongst Amerindians, the Khoisan of Southern Africa and some people of Sami (Lapp) origin. The presence of epicanthic folds is common in many, though not all, groups of East Asian and Southeast Asian descent. Due to classic genetics children of a parent with a pronounced epicanthic fold and one without an epicanthic fold will have varying degrees of epicanthic folds as a result. On the other hand, high orbits, with no folds, are characteristic of certain Balkan populations and of most Near Eastern peoples.
Hair texture is measured by the degree of fineness or coarseness, which varies according to the diameter of each individual hair. There are four major types of hair texture, which are fine, medium, coarse and wiry (sometimes referred to as wooly). Head hair grows at the rate of approximately 1.25 centimeters, or about 0.5 inches, per month, and it has been speculated that the significance of long head hair may be adornment leading to what evolutionary biologists call “Fisherian Runaway Sexual Selection”, in which an prospective mate’s health is gauged by lustrous hair, leading to a greater rate of selection for those individuals with the gene –the same mechanism that probably led to those beautiful peacock feathers.
Scalp hair varies tremendously between races; the scalp hair of most Asians has the greatest thickness and the roundest cross-section, which produces a thick, straight hair. In Europeans the hair is more oval and finer; in Negroes it is flattened, resulting in small wiry, or “kinky” curls. There are at least three kinds of kinky hair. There is short kinky hair that covers the whole scalp evenly, as with most African peoples. There is short kinky hair that grows in tufts with seemingly bare spaces between, as in some East African groups. Then there is the longer kinky hair of the peoples of the Southwest Pacific islands. The hair of the Australian Aborigines is curly or wavy, except for one small group in Queensland who have what is called "frizzy" hair, or hair that is slightly kinky. It has been speculated that wiry hair texture has an advantage in being difficult to penetrate by stinging insects and tends to wick sweat effectively, keeping it away from the face, two distinct benefits in hot, humid environments. Only persons of African descent usually have this type of hair, although some Europeans can have extremely curly or frizzy hair.
Blonde hair is produced by an absence of melanin and may be attempt to optimize UV penetration of the scalp (maximizing vitamin D levels in the northern climes)
Having red hair is associated with the recessive version of the MC1R gene on chromosome 16, which also codes for fair skin and freckles. Four out of five redheads have this gene variant, which is found at its greatest frequency in Scotland and Ireland. Some authorities suggest that red-haired people may be descendents of a blending of Neanderthal and Cro-Magnon peoples while others suggest that the gene is more recent, well after the human migration from Africa, so that the geographical distribution of red hair would be due to post-glacial expansions from Europe.
The tendency of the two eyebrows to blend over the nose, called “concurrency” is found in its highest frequency in the Middle East, but is also common among Southern Europeans.