Race and morphology/physiology

There is long history of research on race and morphology/physiology.

Morphology is the study of the form and structure of organisms and the parts compromising them. Morphological differences between groups were once the primary focus of study in both human taxonomy (also racial taxonomy) and in taxonomy in general. Morphological characteristics could be easily and reliable measured, unlike physiological, mental or genetic characteristics, which previously were much more difficult or impossible to measure.

Human morphological differences are primarily studied within the field of anthropology. Increasing political correctness in anthropology in Western countries as well as the dramatically improved measurement methods of physiological, mental and genetic characteristics have caused recent race research to focus more on non-morphological areas. However, morphological research on race differences are still being done, also in Western countries, in areas such as forensic anthropology.

Physiology is the study of the function of organisms and the parts compromising them. In practice, the form/structure and the function of the parts of organisms are usually discussed together. Also the different functions of different muscle fibers and different enzymes are due to differences regarding form/structure. Physiology is usually seen as limited to "body" functions and does not usually include "mental" or "behavioral" characteristics such as IQ, personality traits, or crime. This article will follow this and such topics are discussed in other articles (except if there are argued direct links to the morphological/physiological characteristics discussed below, such as between "alcohol flush reaction" and alcoholism).

Human racial morphological differences compared to morphological differences in and between non-human species

African Pygmies and a European explorer.

The 2004 book Race: The Reality of Human Differences stated that "The differences in morphology (cranial and facial features) between human races are typically around ten times the corresponding differences between the sexes within a given race, larger even than the comparable differences taxonomists use to distinguish the two chimpanzee species from each other. To the best of our knowledge, human racial differences exceed those for any other non-domesticated species".

"In fact, a comparison of the most widely divergent human groups, such as Norwegians and Australian Aborigines finds physical differences as great as those between chimpanzees and gorillas."

Examples of morphological/physiological differences

Alcohol

"Alcohol flush reaction" is a strong flush and other unpleasant symptoms that appear in some individuals after alcohol consumption. The reaction is due to an unusually large build up of toxic alcohol metabolites.

The distribution of gene variants involved in the metabolism of alcohol and contributing to "alcohol flush reaction" is different in different populations. A high frequency has been reported for some Asian populations, in particular East Asians. An association with rice domestication and expansion of rice farming has been suggested. Evolutionary explanations have included reduced risk of alcoholism or increased resistance against certain infectious diseases. At the same time, there is an increased risk for certain other diseases, such as esophageal cancer.

Racial genetic differences regarding alcohol, such as factors influencing susceptibility to alcohol abuse, have been argued to be an explanation for racial differences regarding alcoholism and various alcohol related problems, including alcohol related criminality, such as drunk driving. For example, Amerindians "who suffer from extremely high alcoholism rates, did not have large supplies of alcohol until approximately 300 years ago. These differences in susceptibility are exactly what we should expect given the fact that alcoholism is a hereditary disease. The implication is that the longer an ethnic group is exposed to alcohol, the lower its members’ susceptibility to alcoholism. This relationship is consistent with the principle of natural selection whereby those people with a high genetic susceptibility are eliminated over many generations, resulting in a lower susceptibility rate for the entire group."

Body odor and earwax

Different populations have different frequencies of gene variants affecting body odor and type of earwax.

Cold adaptations

Some of the other sections in this article describes racial differences that may be adaptations to a cold climate.

In addition, some gene variants that are more frequent in populations living in cold area may be involved in adaptations to the cold climate and the food sources found in this environment. One such adaptation involves helping the body’s fat stores to directly produce heat rather than producing chemical energy for muscle movements or brain functions, a process called "nonshivering thermogenesis". Another involves the contraction of smooth muscle, key to shivering and the constriction of blood vessels to avoid heat loss. Still another involves the metabolism of fats, especially those in meat and dairy products—a staple of the fat-laden diets of Arctic peoples.

Craniometry

See Craniometry.

Diving

The Bajau is a people in parts of Indonesia. They have traveled the Southeast Asian seas in houseboats and collected food by free diving up to 70 meters with spears. They have genetically enlarged spleens, argued to be related to their diving ability.

Epicanthic fold

The epicanthic fold is a skin fold of the upper eyelid that covers the inner corner of the eye. This makes the eyes appear somewhat slanted and is common in certain Asian populations. An evolutionary explanation is that the fold provides protection against cold, but it also appears in the San (Bushmen), who live in a desert. Another evolutionary explanation is that the fold protects against being dazzled by sunlight being reflected from snow or sand.

Flat feet

The Huaorani tribe in the Amazon rainforest spend much time climbing trees in order to hunt monkeys. This has caused their feet to evolve and most have very flat feet, which help them to climb the trees.

Head hair structure

Sub-Saharan Africans often have a head hair structure that has been described as "wooly" and that provides protection against strong sunlight. Pygmies, and some other groups who live or lived in hot and damp rainforests, instead have head hair that has been described as "peppercorn" and that grows in spirals with open spaces between tufts. This allows sweat to evaporate, while at the same time providing some protection against sunlight.

Hair structure can affect behavior and health risk. Hair care and hairstyle maintenance in the African American female population can be a costly and time-consuming process. A 2013 study found that 40% of African American women surveyed avoided exercise at times owing to hair-related issue.

Height

Studies in 2014 found that gene markers associated with height differences differed between different populations in a way that inversely mirrored gene markers associated with intelligence differences. This contrasted to the (very weak) positive correlation found within populations, where taller people on average have a small IQ advantage over shorter people. "This suggests that the environments that selected for higher intelligence were also more advantageous for shorter people. A possible explanation of this phenomenon can be inferred from Allen‟s rule, which posits that endotherms from colder climates usually have shorter limbs than the equivalent animals from warmer climates. This is based on the principle that in cold climates, the greater the exposed surface area, the greater the loss of heat and therefore energy. Animals in cold climates need to conserve as much energy as possible. A low surface area to volume ratio helps to conserve heat as there is a smaller surface area for the heat to pass through. Probably also human populations follow Allen‟s rule".

High altitude adaptations

Some gene variants that are common in Tibetans, Ethiopians, and Amerindians populations living in the Andes, and that have been reported to involved in body oxygenation, have been proposed to be genetic adaptations to the high altitude in the regions where these populations live.

HIV resistance

In some people, mainly of European descent, a genetic mutation delays the disease and in some cases brings about immunity.

A genetic mutation known as CCR5-delta 32 is responsible for the two types of HIV resistance that exist. The gene believed to have mutated about 700 years ago and is linked to the resistance to the Black Death in the 14th century. This mutation makes about 1-2% of people descended from Northern Europeans, particularly Swedes, immune to HIV infection. For about 20% of the population, it takes longer time to get sick and the symptoms of the infection is milder.

This mutation is not found among Africans, Asians or Amerindians.

Human microbiome

The human microbiome is the microorganisms (including bacteria and fungi) that live on human skin, in the gastrointestinal tracts, in the respiratory tracts, as well as in other areas. Some are known to perform tasks useful for their human host, but the majority is poorly researched. They may potentially be involved in many important normal functions and also diseases.

There are racial differences regarding the microbiome. A 2013 study stated that it is even possibly to identify a person's race with an accuracy significantly better than chance by examining the DNA of the bacteria living in the mouth. This was argued to not be caused by environmental differences, but by different genetics in different human groups.

Such differences may have practical significance. For example, a bacterium only found in Japanese individuals is thought to be important for digesting seaweed, which has been an important food source in Japan.

Lactose tolerance

See Indo-Europeans: Possible causes of the Indo-European expansion on genetic adult lactose tolerance being a possible cause of the Indo-European and the Arabic expansions.

Menarche

A 2013 study found support for genetic causes for the racial difference between Black and White females regarding the age when the first menstrual cycle (menarche) occurs.

Genetic racial differences regarding this is one aspect of the differential K theory.

Obesity

The "thrifty gene hypothesis" suggests that the genetic factors that predispose to weight gain might have been selectively advantageous in ancient environments, where food was scarce, but might have become deleterious in modern environments, where food is plentiful and lifestyles are generally sedentary. Based on epidemiologic evidence, specific racial/ethnic groups seem to be particularly susceptible to obesity. Genetic studies have found support for that genetic differences between groups may contribute to such differences.

Penis size

Various race differences in penis size have been claimed and criticized.

Pigmentation

Skin color and other attributes related to pigmentation (eye color and hair color) are the most well-known race differences.

Phrases such as "Race Is Only Skin Deep" reflect the belief that pigmentation itself has nothing to do with "inner" characteristics, such personality. Also many race realists may have previously agreed with this, and seen skin color only as a racial marker, that in itself has no direct genetic connection with "inner" characteristics. However, animal research has found that darker pigmented individuals average higher amounts of aggression and sexual activity than lighter pigmented individuals. Human studies are argued to support that such differences also occur within human populations (such as between siblings) as well as between different human groups (such as between races, nations, and states). One explanation for this is that the genes affecting pigmentation are pleiotropic. Pleiotropy is the phenomenon whereby a single gene has two or more phenotypically different effects. This is argued to be further supported by the neural and the hormonal systems affecting pigmentation also affecting behavior and interacting with testosterone.

A very strong negative correlations between darker skin color and average country IQ has also been reported. Lighter pigmentation is also argued to be associated with lower birth rates, less infant mortality, less violent crime, less HIV/AIDS, higher income, and greater longevity. Therefore, pigmentation and the systems regulating pigmentation have been argued to be closely connected to the differential K theory.

This has also been suggested to support that so called "pigmentocracies" (societies in which status hierarchies are based largely on skin color, with lighter skin denoting higher status and darker skin lower status) arise in part due to genetic pleiotropy.

Research has also found other effects between pigmentation and behavior. Darker pigmented African Americans have been found to use tobacco more frequently, which may be due to nicotine binding to the pigment melanin or precursors.

Some studies suggest an association between hair/eye color and behavioral inhibition, with individuals with lighter pigmentation expressing more inhibited behavior. Studies have found associations between eye color and alcohol dependence risk.

Pigmentation differences may also have other “biological” associations, such as regarding skin diseases.

See also albinism, melanin theory, and race and physical attractiveness.

Preterm births

Genetic differences have been argued to contribute to racial differences regarding preterm births.

Skull thickness

"A particularly instructive example comes from nineteenth-century ethnographic reports of Australian Aboriginal groups, particularly for central and southeastern Australia. Men or women who “had a bone to pick” with another group member followed a code for resolving the conflict. They challenged their adversary to a duel with a combination club and throwing stick called a nulla-nulla. Once the bout began, it continued until one of the combatants won by knock-out or TKO—that is, until the adversary was disabled and could not continue.

Peter Brown, a paleoanthropologist at the University of New England in Armidale, Australia, has investigated skull thickness in modern and historical Australian Aboriginal populations, whose cranial bones are the thickest of any living H. sapiens. In a sample of 430 Aboriginal crania, Brown found evidence of healed depressed fractures on the frontal or parietal bones in 59 percent of the female crania and in 37 percent of male crania. Depressed fractures occurred in these people and they survived; undoubtedly, many others did not. His findings led Brown to hypothesize that the thick skull vaults of the Aboriginals may have evolved as a consequence of the traditional method for settling conflicts."

Steatopygia

Steatopygia is a high degree of fat accumulation in and around the buttocks. It is common among the San (Bushmen) and the adaptive advantage may have been to store food and water in times of famine and shortage.

Taste

Gene variants that affect the ability to sense bitterness differ in frequency between different populations. This may be related to differences regarding available food sources. Researchers have also found that such gene variants have a strong relationship with yearly alcohol consumption which may be related to how pleasant alcohol tastes. Non-dietary proposed explanations include the roles of bitter taste receptors in the gastrointestinal tract and the lungs.

Toxin tolerance

A 2015 study found that inhabitants of the northern Argentinean Andes, an arid region where elevated arsenic concentrations in available drinking water is common, have high arsenic tolerance, linked to genetic differences in arsenic metabolism.

General differences

Differences regarding brain morphology/physiology are not discussed in this article. However, differences in brain size between different species are associated with differences in numerous musculo-skeletal traits. This can partly be explained as adaptations to an increasingly larger brain. The same musculo-skeletal differences are seen between different human races.

The differential K theory predicts some general morphological/physiological differences, such as differences regarding maturation speed, sex characteristics, sex hormone levels, and possibly adaptations to differences regarding aggressiveness and physical violence.

See also the article on race and sports regarding various morphological/physiological characteristics related to sport performance.

Other morphological/physiological differences between races

In particular in earlier and less politically correct anthropological literature, there are extensive descriptions of the morphological differences between different races.

See the "External links" section below for some online compilations of racial morphological/physiological differences.

External links

• Erectus Walks Amongst Us: Hard Tissue
• Erectus Walks Amongst Us: Soft Tissue