Latitude
Skin Color and Political-Religious Disposition
by Charles Brack
What is the strange biological relationship between skin color and political orientation?
One of the great stories of the human behavior may ultimately involve molecular chirality, or the mirror-like structure of chemically identical molecules. Chirality came under public scrutiny in the 1960s, when a drug called thalidomide was prescribed for morning sickness. Thalidomide consists of two chemically identical mirror-image molecules, much like human hands.
The left-handed version of thalidomide was a tranquilizer that quelled the symptoms of nausea. Unfortunately, the right-handed version was not removed during synthesis, and due to its chemical similarity to guanine, would bind into the guanine-rich regions of the DNA molecule, where it would block the proteins that promoted limb formation. Approximately 10,000 children were born with severe birth defects, including phocomelia, or the attachment of the hands and feet directly to the torso.
The human body, while looking relatively symmetrical on the outside, is not so symmetric on the inside. The heart is shifted to the left, the liver to the right, the stomach to the left, the appendix to the right, etc. Even the lungs, while symmetrically distributed on each side of the body, are morphologically different.
How does embryogenesis position all these organs so precisely within the body? How does it know left is left and right is right? The mysterious positioning and development of our internal organs is not perfect, and results in some interesting abnormalities. One of these is situs inversus, or organ juxtaposition across the left-right axis, resulting in a jumbled mirror image of our internal organs.
Molecular chirality at work: two chemically identical mirror-image molecules, like human hands, have completely different physiological impacts. Brown and Wolpert have proposed that molecular chirality has been adapted into left-right asymmetry at the cellular level. Does molecular chirality start the chain of events that ultimately result in the left and right brains?
How did this complete reversal of the arrangement of internal organs get accomplished in such a precise manner? Is there a simple embryological mechanism behind this? Further, why isn't the human brain impacted by this juxtaposition, while all the other internal organs are? The human brain is mysteriously exempt from situs inversus.
Recent evidence has implicated cascades of asymmetrically expressed genes, which are initiated by a first embryonic event that distinguishes left from right, and is the start of all subsequent embryonic events that propagate laterality in the developing embryo. That event, according to ingenious model of Brown and Wolpert (1990), is the conversion of molecular handedness, or chirality, into handedness at the cellular level.
It is interesting to note that homozygous human twins conserve chirality, that is, they exhibit opposite directionality in hair whorl direction, tooth patterns, and a variety of birth defects. This implies that the daughter cells of mitosis may be involved in a sort of reverse chirality, analogous to the conservation of spin and electric charge when an electron and positron are created from a heavy photon.
Mitosis is notable by the asymmetry of intracellular ion distribution, and while the early human embryo looks like a tightly bound sphere, its dalliance with spherical symmetry is short lived. The embryo soon develops a midline, defined by the asymmetric membrane voltage and pH of the cells on the contralateral sides. This pH/voltage gradient is possibly driven by the chiral movement of motor proteins with respect to the cytoskeleton.
The asymmetric electrical charge distribution in the embryo sets up the action of the "time-released" genes, which guide the positioning and formation of the various cell groups in the early embryo. With every round of mitosis, the young embryo propagates the specialization of cell groups asymmetrically along the anteroposterior, dorsoventral, and left-right axes.
The subsequent development of the human embryo would now center around three germ layers, the ectoderm, mesoderm, and endoderm, which, along with the neural crest, would provide the wide variety of cell phenotypes that eventually construct the wide variety of human tissues and organs.
The many biological faces of serotonin: a key monoamine neurotransmitter implicated in political-religious affiliation, also functions in the embryological positioning of internal organs across the left-right axis. In this frog embryo, the red arrow indicates the presence of serotonin, while the white arrow indicates its absence. In Drosophilia, serotonin reduces body size in high population densities. How serotonin impacts human body size is speculative.
The endoderm would form many of the energy processing organs, such as the stomach, liver, colon, intestine, and parts of the lungs and trachea. The mesoderm would go on to form the locomotive and structural components of the body, such as the skeleton and muscles, along with the dermis, spleen, and heart.
But it was the ectoderm and neural crest that were given the unusually difficult task of forming the nervous system, and interestingly, several side tasks, such as the formation of the epidermis and hair. Thus the unusually close relationship between the brain and the skin, which makes sense, given the skin's key roles in the detection of temperature, pressure, touch, vibration, and pain.
Further, neurons related to chemosensation and olfaction were among the earliest to evolve, laying the foundation for the complex embryological process of neuronal migration and axonal projection to the central nervous system. The relationship between the central nervous system and the skin is highlighted by the relationship between stress and skin disorders such as shingles, herpes, and psoriasis.
The darker the skin, the more liberal the political preferences?
But it is skin pigmentation which is of particular political interest, in that there is indeed a strong correlation with liberal voting trends. In the most recent US presidential election, 66% of Latinos, 61% of Asians, and 95% of Blacks voted for Obama, compared to 43% of Caucasians. It is indeed interesting that in the United States, voting trends by race follow the general tendency: the darker the skin, the more liberal the political preferences.
This phenomenon is seen not just in the United States, but also occurs in nations like England, India, and Australia. However, identifying the specific reason is indeed tricky, given the many diverse environmental and genetic influences on political-religious disposition, not to mention the multiple ways in which skin color interacts with political preferences.
But our argument for a link between skin color and liberalism starts with serotonin and its close relationship to both liberalism and melanin. We have previously proposed a monoamine hypothesis of conservatism and liberalism, with the dopaminergic system being more responsible for those attitudes and behaviors associated with conservatism, while the noradrenergic and serotonergic systems are more responsible for liberalism.
Interestingly, the dopaminergic system is expressed predominately in the left hemisphere, while the noradrenergic and serotonergic systems are expressed mainly in the right hemisphere (Davidson, 1998), which is why we sometimes refer to "left-brain" conservatism and "right-brain" liberalism.
Serotonin and Race
The detection of variations in serotonin levels by racial group was by accident, and subsequently introduced as a control for studies on autism (Cuccaro et al., 1993; McBride et al., 1998), suicidal tendencies (Pfeffer et al., 1998), and mood-behavioral disorders (Hughes et al., 1996).
Cuccaro found that black and Hispanic subjects had higher levels of platelet serotonin than whites; McBride found whites with significantly lower levels of platelet serotonin than blacks or Hispanics; Pfeffer found that whites had significantly lower levels of platelet serotonin than blacks or Latinos, and further, blacks had significantly higher levels of whole blood tryptophan (a serotonin precursor) than the other racial groups. Finally, the Hughes study found that blacks had higher levels of platelet serotonin than whites.
Further, racial variations in the frequencies of long and short alleles of the serotonin transporter gene (5HTTLPR) were reported by Gelernter et al. (1999) and Williams et al. (2003). The Gelernter study found that the frequency of the long allele was more than 70% in Africa and black Americans, compared to 50% in Europeans, and less than 30% in Japan.
Williams had similar results, with black Americans having 72% long alleles and 28% short alleles, compared to 60% long and 40% short alleles for whites. However, it is interesting to note that in the Williams study, the behavioral impact of allele combinations was not consistent across racial groups.
Serotonin and Liberalism
The evidence for a link between serotonin and liberalism, to date, is indirect, and comes from studies involving serotonin and a variety of behaviors more likely to be found among liberals. The first such behavior is greater tolerance for population density, which had long been inferred by the liberal voting patterns of urban populations. Further, liberals report a much greater tolerance for urban environments than conservatives. The conservative intolerance for high population density is closely associated with the conservative's higher reproductive rates.
The facilitating impact of serotonin on population density has been found in many species, including desert locusts (Anstey, 2009), rhesus macaques (Mehlman, 1995), crickets (Iba, 1995), and implied with humans via MDMA-induced serotonin release (Parrott, 2004).
However, the relationship between serotonin and tolerance for population density is equivocal, and seems to be nonlinear, that is, different levels of crowding induce different responses of the serotonin system, depending on the species. Further, population density response varies from individual to individual, which has been linked to specific allele combinations for the genes responsible for the functioning of the serotonin system.
The evidence for a relationship between population density tolerance and serotonin is particularly strong with humans, and is implied by the success of SSRIs and SNRIs in treating social anxiety disorder. Further, the voluntary crowding behavior (rave parties) associated with MDMA use operate by enhancing serotonin release. It is interesting to note that liberals report less discomfort while standing closer to people than do conservatives.
Would Caucasians in Texas crowd into a train like the Japanese? Conservatives are more likely to drive and less likely to use mass transit than liberals. They also feel more discomfort in crowded places, and their lack of serotonergic tone is a primary suspect for this phenomenon.
Another indicator of a serotonin connection to liberalism involves the preference for delayed rewards. Compared to conservatives, liberals are more likely to prefer delayed rewards. The evidence for the serotonergic modulation of this phenomenon is growing (Doya, 2002; Schweighofer, 2008), and provides another indirect link between the serotonin system and liberalism.
One of the most interesting variations between conservatives and liberals is their divergence in gaze direction while walking. The conservatives tend to walk with their gaze fixed parallel to the ground, while the liberals are more likely to look towards the ground. This is interesting in light of the monoamine theory of conservatism and liberalism, as the dopamine system is more orientated towards the upper visual field, while the noradrenergic and serotonergic systems are more oriented towards the lower visual field (Previc, 2006).
However, we must note that not all evidence is consistent with the liberalism-serotonin connection. Liberals are more likely to report social anxiety disorder than conservatives, which has been linked to the hypofunctioning of the serotonin system. However, social anxiety disorder has also been linked to the hypofunctioning of the dopamine system (Schneier, 2000), which is indeed the most "conservative" of the monoamine transmitter systems. Therefore, liberal social anxiety disorder may be more related to a deficit in dopamine tone, rather than serotonergic deficits. Further, the serotonin system is not the only contributor to liberalism, as we believe the noradrenergic system also contributes, but in different ways, to liberalistic attitudes and behaviors.
Serotonin and Skin Color
Serotonin is located in three major areas of the body: the intestines, the blood, and the central nervous system. The presence of serotonin in the intestines is particularly interesting, in that it is part of the "digestive brain", which manages digestion in the esophagus, stomach, small intestine, and colon. This digestive brain is a nearly self-contained neural network, located along the digestive organs, using serotonin and several types of serotonin receptors to trigger enzyme release, and further, communicating these activities to the central nervous system.
Blood platelet serotonin also assists in both vasoconstriction and vasodilation, but its curious relationship to melanin takes us down the pathway of a possible connection between skin color and political disposition. Melanin is the primary determinant of skin color, and is produced by melanocytes located in the basal epidermis.
This is interesting, since melanocytes originate from the neural crest and subsequently migrate to the epidermis during fetal development, they are therefore associated with the nervous system. This evolutionary connection should be expected, as many species rapidly modulate skin color in the presence of both prey and predators. However, humans have only one class of pigment cell, the melanocyte, which manufactures melanin that is subsequently released and transported to the keratinocytes, which constitute about 95% of the epidermis.
Melanocyte stimulating hormone (MSH) stimulates the production and release of melanin, which itself has been stimulated by injections of serotonin into eels and some amphibian species, producing a strong darkening in the skin (Olivereau, 1978). Further, injectons of serotonin stimulated the melanin dispersion in amphibian skin, while serotonin synthesis inhibitor inhibited melanin dispersion (Olivereau et al., 1980; Miller, 1989).
Serotonin was proposed to be manufactured in the cutaneous melanocytes (Johansson, 1998), and indeed, this has been verified (Nordlind, 2008). Further, not only is serotonin being manufactured in melanocytes, skin cells also express serotonin receptors, implicating the skin as a target of bioregulation by serotonin. Interestingly, increases in UV exposure result in increases in serotonin concentration in skin cells (Iyengar, 1998).
Skin and Brain
Even if serotonin promotes the darkening of human skin and the brain's serotonin system contributes to political-religious disposition, we have yet to establish a connection between skin and brain serotonin. The fact that melanocytes develop from the neural crest, manufacture serotonin, and contain serotonin receptors is certainly suspicious.
The complementary activity of brain and skin serotonin in humans has never been the direct target of scientific analysis, and therefore, direct evidence is quite sparse. Further, skin serotonin is rarely studied at all, and only recently detected in humans. However, there are a handful of experiments that indicate a mild correlation between brain and platelet serotonin. Note that the major source of skin serotonin comes from platelets (Nordlind, 2008).
Unlike skin, the brain does not directly absorb serotonin from the blood. However, tryptophan and 5-HTP are, from which serotonin is subsequently manufactured in the brain. There are a number of experiments that indicate a correlation between blood and brain serotonin. One such experiment found a mild correlation between high levels of platelet serotonin and serotonin mRNA in the midbrain of rats (Bordukalo-Niksic, 2004).
Among humans, there is a correlation between low platelet serotonin levels and depression (Sarrias, 1991; Maurer-Spurej, 2004), perhaps indicating a common genetic substrate between blood and brain serotonin. It is interesting that human platelet serotonin uptake site and brain serotonin transporter are coded from the same single-copy gene, located on chromosome 17 (Lesch, 2006). The multiple duties of this gene may ultimately be contributing to the relationship between skin and brain serotonin.
While the causes of the correlation between skin and brain serotonergic tone are very speculative, and may be working via a variety of physiological mechanisms, the evolutionary pressure for skin melanin levels to match sunlight exposure has been great. It is indeed possible that this pressure could spill over into human cognitive styles, and ultimately impacting political disposition. This viewpoint is bolstered by the opposite impact on melanin of another politically-active neurochemical: dopamine.
Dopamine, Conservatism, and White Skin
While we suspect a biological connection between dark skin color and liberalistic attitudes, and further, this connection works primarily through the dual role of serotonin in skin color and cognition, there is evidence that at least one other politically-salient neurotransmitter may also contribute to this phenomenon: dopamine.
The dopamine system has been implicated in both religiosity (Previc, 2006) and conservative political attitudes. There is also evidence that it contributes to the lightening of skin via its negative influence on the expression of melanin. Dopamine was the only monoamine that contributed to melanocyte cytotoxicity in the Chu study (2006) of dopamine, norepinephrine, epinephrine, and serotonin. It seems that dopamine induces melanocyte apoptosis, and may even contribute to vitiligo (depigmentation of the skin).
However, linking white skin to conservatism has the same issues as does serotonin and dark skin. But it is an interesting coincidence that serotonin and dopamine have opposite effects on both political-religious disposition and skin color.
The Political Sun
The ability of melanin to regulate the sunlight-mediated conversion of 7-dehydrocholesterol into vitamin D3 and subsequently modulate calcium metabolism is just one of the growing list of functions of the photobiology of the human skin. Melanin absorbs ultraviolet radiation, reducing the incidence of skin cancers, and further, facilitating the skin's immune response.
As such, melanin physiology has been under extreme selective pressure in the human species, which is why the genetics of melanin physiology are highly variant across the human genome, and correlate closely with latitude. Given the strong selective pressure of latitude on melanin physiology, there indeed may be evolutionary side-effects, such as with cognitive styles.
Serotonin and dopamine, both contributors to melanin physiology, have diverse impacts on human cognitive styles and political-religious orientation. Have the multiple functions of these two monoamine neurotransmitters become genetically intermingled to the extent that political-religious orientation is influenced by skin color?
We must certainly be careful in this assertion, as we believe that skin color, with regards to political orientation, works along two dimensions. One dimension is the resolution of genetic distance, which subsequently influences the altruistic responses and political attitudes between individuals. The other dimension is its covariance with the function of the dopaminergic and serotonergic neuotransmitter systems, which not only have diverse influences on political attitudes, but also on how one organizes and functions in the space around them (see God, Dopamine, and 3-Dimensional Space).
Further, we do not want to confuse this theory with another theory of sunlight and political orientation: the sunlight theory of political preference. This theory proposes that the influence of sunlight on testosterone and estrogen levels ultimately impacts the dopamine system. This effect influences Caucasians in particular, and partially explains the tendencies for lower-latitude Caucasian populations to be more politically conservative, although the conservative tendencies of migrating populations also help to explain this phenomenon.
If skin color is indeed genetically intermingled with political-religious orientation, the long-term implications on the political trends in the United States will be dramatic, and distinctly liberal. While Caucasian conservatives substantially out-reproduce Caucasian liberals, they have been overwhelmed by the immigration of non-Caucasian populations that can reproduce with less energy.
The Republican Party, which has become the de facto Caucasian Party, is now caught between the preservation of Caucasian genetics and the declining percentages of Caucasians. To make matters worse, the American system of government is not conducive to this endeavor.
Charles Brack, June 2009
http://neuropolitics.org/defaultjun09.asp
Skin Color and Political-Religious Disposition
by Charles Brack
What is the strange biological relationship between skin color and political orientation?
One of the great stories of the human behavior may ultimately involve molecular chirality, or the mirror-like structure of chemically identical molecules. Chirality came under public scrutiny in the 1960s, when a drug called thalidomide was prescribed for morning sickness. Thalidomide consists of two chemically identical mirror-image molecules, much like human hands.
The left-handed version of thalidomide was a tranquilizer that quelled the symptoms of nausea. Unfortunately, the right-handed version was not removed during synthesis, and due to its chemical similarity to guanine, would bind into the guanine-rich regions of the DNA molecule, where it would block the proteins that promoted limb formation. Approximately 10,000 children were born with severe birth defects, including phocomelia, or the attachment of the hands and feet directly to the torso.
The human body, while looking relatively symmetrical on the outside, is not so symmetric on the inside. The heart is shifted to the left, the liver to the right, the stomach to the left, the appendix to the right, etc. Even the lungs, while symmetrically distributed on each side of the body, are morphologically different.
How does embryogenesis position all these organs so precisely within the body? How does it know left is left and right is right? The mysterious positioning and development of our internal organs is not perfect, and results in some interesting abnormalities. One of these is situs inversus, or organ juxtaposition across the left-right axis, resulting in a jumbled mirror image of our internal organs.
Molecular chirality at work: two chemically identical mirror-image molecules, like human hands, have completely different physiological impacts. Brown and Wolpert have proposed that molecular chirality has been adapted into left-right asymmetry at the cellular level. Does molecular chirality start the chain of events that ultimately result in the left and right brains?
How did this complete reversal of the arrangement of internal organs get accomplished in such a precise manner? Is there a simple embryological mechanism behind this? Further, why isn't the human brain impacted by this juxtaposition, while all the other internal organs are? The human brain is mysteriously exempt from situs inversus.
Recent evidence has implicated cascades of asymmetrically expressed genes, which are initiated by a first embryonic event that distinguishes left from right, and is the start of all subsequent embryonic events that propagate laterality in the developing embryo. That event, according to ingenious model of Brown and Wolpert (1990), is the conversion of molecular handedness, or chirality, into handedness at the cellular level.
It is interesting to note that homozygous human twins conserve chirality, that is, they exhibit opposite directionality in hair whorl direction, tooth patterns, and a variety of birth defects. This implies that the daughter cells of mitosis may be involved in a sort of reverse chirality, analogous to the conservation of spin and electric charge when an electron and positron are created from a heavy photon.
Mitosis is notable by the asymmetry of intracellular ion distribution, and while the early human embryo looks like a tightly bound sphere, its dalliance with spherical symmetry is short lived. The embryo soon develops a midline, defined by the asymmetric membrane voltage and pH of the cells on the contralateral sides. This pH/voltage gradient is possibly driven by the chiral movement of motor proteins with respect to the cytoskeleton.
The asymmetric electrical charge distribution in the embryo sets up the action of the "time-released" genes, which guide the positioning and formation of the various cell groups in the early embryo. With every round of mitosis, the young embryo propagates the specialization of cell groups asymmetrically along the anteroposterior, dorsoventral, and left-right axes.
The subsequent development of the human embryo would now center around three germ layers, the ectoderm, mesoderm, and endoderm, which, along with the neural crest, would provide the wide variety of cell phenotypes that eventually construct the wide variety of human tissues and organs.
The many biological faces of serotonin: a key monoamine neurotransmitter implicated in political-religious affiliation, also functions in the embryological positioning of internal organs across the left-right axis. In this frog embryo, the red arrow indicates the presence of serotonin, while the white arrow indicates its absence. In Drosophilia, serotonin reduces body size in high population densities. How serotonin impacts human body size is speculative.
The endoderm would form many of the energy processing organs, such as the stomach, liver, colon, intestine, and parts of the lungs and trachea. The mesoderm would go on to form the locomotive and structural components of the body, such as the skeleton and muscles, along with the dermis, spleen, and heart.
But it was the ectoderm and neural crest that were given the unusually difficult task of forming the nervous system, and interestingly, several side tasks, such as the formation of the epidermis and hair. Thus the unusually close relationship between the brain and the skin, which makes sense, given the skin's key roles in the detection of temperature, pressure, touch, vibration, and pain.
Further, neurons related to chemosensation and olfaction were among the earliest to evolve, laying the foundation for the complex embryological process of neuronal migration and axonal projection to the central nervous system. The relationship between the central nervous system and the skin is highlighted by the relationship between stress and skin disorders such as shingles, herpes, and psoriasis.
The darker the skin, the more liberal the political preferences?
But it is skin pigmentation which is of particular political interest, in that there is indeed a strong correlation with liberal voting trends. In the most recent US presidential election, 66% of Latinos, 61% of Asians, and 95% of Blacks voted for Obama, compared to 43% of Caucasians. It is indeed interesting that in the United States, voting trends by race follow the general tendency: the darker the skin, the more liberal the political preferences.
This phenomenon is seen not just in the United States, but also occurs in nations like England, India, and Australia. However, identifying the specific reason is indeed tricky, given the many diverse environmental and genetic influences on political-religious disposition, not to mention the multiple ways in which skin color interacts with political preferences.
But our argument for a link between skin color and liberalism starts with serotonin and its close relationship to both liberalism and melanin. We have previously proposed a monoamine hypothesis of conservatism and liberalism, with the dopaminergic system being more responsible for those attitudes and behaviors associated with conservatism, while the noradrenergic and serotonergic systems are more responsible for liberalism.
Interestingly, the dopaminergic system is expressed predominately in the left hemisphere, while the noradrenergic and serotonergic systems are expressed mainly in the right hemisphere (Davidson, 1998), which is why we sometimes refer to "left-brain" conservatism and "right-brain" liberalism.
Serotonin and Race
The detection of variations in serotonin levels by racial group was by accident, and subsequently introduced as a control for studies on autism (Cuccaro et al., 1993; McBride et al., 1998), suicidal tendencies (Pfeffer et al., 1998), and mood-behavioral disorders (Hughes et al., 1996).
Cuccaro found that black and Hispanic subjects had higher levels of platelet serotonin than whites; McBride found whites with significantly lower levels of platelet serotonin than blacks or Hispanics; Pfeffer found that whites had significantly lower levels of platelet serotonin than blacks or Latinos, and further, blacks had significantly higher levels of whole blood tryptophan (a serotonin precursor) than the other racial groups. Finally, the Hughes study found that blacks had higher levels of platelet serotonin than whites.
Further, racial variations in the frequencies of long and short alleles of the serotonin transporter gene (5HTTLPR) were reported by Gelernter et al. (1999) and Williams et al. (2003). The Gelernter study found that the frequency of the long allele was more than 70% in Africa and black Americans, compared to 50% in Europeans, and less than 30% in Japan.
Williams had similar results, with black Americans having 72% long alleles and 28% short alleles, compared to 60% long and 40% short alleles for whites. However, it is interesting to note that in the Williams study, the behavioral impact of allele combinations was not consistent across racial groups.
Serotonin and Liberalism
The evidence for a link between serotonin and liberalism, to date, is indirect, and comes from studies involving serotonin and a variety of behaviors more likely to be found among liberals. The first such behavior is greater tolerance for population density, which had long been inferred by the liberal voting patterns of urban populations. Further, liberals report a much greater tolerance for urban environments than conservatives. The conservative intolerance for high population density is closely associated with the conservative's higher reproductive rates.
The facilitating impact of serotonin on population density has been found in many species, including desert locusts (Anstey, 2009), rhesus macaques (Mehlman, 1995), crickets (Iba, 1995), and implied with humans via MDMA-induced serotonin release (Parrott, 2004).
However, the relationship between serotonin and tolerance for population density is equivocal, and seems to be nonlinear, that is, different levels of crowding induce different responses of the serotonin system, depending on the species. Further, population density response varies from individual to individual, which has been linked to specific allele combinations for the genes responsible for the functioning of the serotonin system.
The evidence for a relationship between population density tolerance and serotonin is particularly strong with humans, and is implied by the success of SSRIs and SNRIs in treating social anxiety disorder. Further, the voluntary crowding behavior (rave parties) associated with MDMA use operate by enhancing serotonin release. It is interesting to note that liberals report less discomfort while standing closer to people than do conservatives.
Would Caucasians in Texas crowd into a train like the Japanese? Conservatives are more likely to drive and less likely to use mass transit than liberals. They also feel more discomfort in crowded places, and their lack of serotonergic tone is a primary suspect for this phenomenon.
Another indicator of a serotonin connection to liberalism involves the preference for delayed rewards. Compared to conservatives, liberals are more likely to prefer delayed rewards. The evidence for the serotonergic modulation of this phenomenon is growing (Doya, 2002; Schweighofer, 2008), and provides another indirect link between the serotonin system and liberalism.
One of the most interesting variations between conservatives and liberals is their divergence in gaze direction while walking. The conservatives tend to walk with their gaze fixed parallel to the ground, while the liberals are more likely to look towards the ground. This is interesting in light of the monoamine theory of conservatism and liberalism, as the dopamine system is more orientated towards the upper visual field, while the noradrenergic and serotonergic systems are more oriented towards the lower visual field (Previc, 2006).
However, we must note that not all evidence is consistent with the liberalism-serotonin connection. Liberals are more likely to report social anxiety disorder than conservatives, which has been linked to the hypofunctioning of the serotonin system. However, social anxiety disorder has also been linked to the hypofunctioning of the dopamine system (Schneier, 2000), which is indeed the most "conservative" of the monoamine transmitter systems. Therefore, liberal social anxiety disorder may be more related to a deficit in dopamine tone, rather than serotonergic deficits. Further, the serotonin system is not the only contributor to liberalism, as we believe the noradrenergic system also contributes, but in different ways, to liberalistic attitudes and behaviors.
Serotonin and Skin Color
Serotonin is located in three major areas of the body: the intestines, the blood, and the central nervous system. The presence of serotonin in the intestines is particularly interesting, in that it is part of the "digestive brain", which manages digestion in the esophagus, stomach, small intestine, and colon. This digestive brain is a nearly self-contained neural network, located along the digestive organs, using serotonin and several types of serotonin receptors to trigger enzyme release, and further, communicating these activities to the central nervous system.
Blood platelet serotonin also assists in both vasoconstriction and vasodilation, but its curious relationship to melanin takes us down the pathway of a possible connection between skin color and political disposition. Melanin is the primary determinant of skin color, and is produced by melanocytes located in the basal epidermis.
This is interesting, since melanocytes originate from the neural crest and subsequently migrate to the epidermis during fetal development, they are therefore associated with the nervous system. This evolutionary connection should be expected, as many species rapidly modulate skin color in the presence of both prey and predators. However, humans have only one class of pigment cell, the melanocyte, which manufactures melanin that is subsequently released and transported to the keratinocytes, which constitute about 95% of the epidermis.
Melanocyte stimulating hormone (MSH) stimulates the production and release of melanin, which itself has been stimulated by injections of serotonin into eels and some amphibian species, producing a strong darkening in the skin (Olivereau, 1978). Further, injectons of serotonin stimulated the melanin dispersion in amphibian skin, while serotonin synthesis inhibitor inhibited melanin dispersion (Olivereau et al., 1980; Miller, 1989).
Serotonin was proposed to be manufactured in the cutaneous melanocytes (Johansson, 1998), and indeed, this has been verified (Nordlind, 2008). Further, not only is serotonin being manufactured in melanocytes, skin cells also express serotonin receptors, implicating the skin as a target of bioregulation by serotonin. Interestingly, increases in UV exposure result in increases in serotonin concentration in skin cells (Iyengar, 1998).
Skin and Brain
Even if serotonin promotes the darkening of human skin and the brain's serotonin system contributes to political-religious disposition, we have yet to establish a connection between skin and brain serotonin. The fact that melanocytes develop from the neural crest, manufacture serotonin, and contain serotonin receptors is certainly suspicious.
The complementary activity of brain and skin serotonin in humans has never been the direct target of scientific analysis, and therefore, direct evidence is quite sparse. Further, skin serotonin is rarely studied at all, and only recently detected in humans. However, there are a handful of experiments that indicate a mild correlation between brain and platelet serotonin. Note that the major source of skin serotonin comes from platelets (Nordlind, 2008).
Unlike skin, the brain does not directly absorb serotonin from the blood. However, tryptophan and 5-HTP are, from which serotonin is subsequently manufactured in the brain. There are a number of experiments that indicate a correlation between blood and brain serotonin. One such experiment found a mild correlation between high levels of platelet serotonin and serotonin mRNA in the midbrain of rats (Bordukalo-Niksic, 2004).
Among humans, there is a correlation between low platelet serotonin levels and depression (Sarrias, 1991; Maurer-Spurej, 2004), perhaps indicating a common genetic substrate between blood and brain serotonin. It is interesting that human platelet serotonin uptake site and brain serotonin transporter are coded from the same single-copy gene, located on chromosome 17 (Lesch, 2006). The multiple duties of this gene may ultimately be contributing to the relationship between skin and brain serotonin.
While the causes of the correlation between skin and brain serotonergic tone are very speculative, and may be working via a variety of physiological mechanisms, the evolutionary pressure for skin melanin levels to match sunlight exposure has been great. It is indeed possible that this pressure could spill over into human cognitive styles, and ultimately impacting political disposition. This viewpoint is bolstered by the opposite impact on melanin of another politically-active neurochemical: dopamine.
Dopamine, Conservatism, and White Skin
While we suspect a biological connection between dark skin color and liberalistic attitudes, and further, this connection works primarily through the dual role of serotonin in skin color and cognition, there is evidence that at least one other politically-salient neurotransmitter may also contribute to this phenomenon: dopamine.
The dopamine system has been implicated in both religiosity (Previc, 2006) and conservative political attitudes. There is also evidence that it contributes to the lightening of skin via its negative influence on the expression of melanin. Dopamine was the only monoamine that contributed to melanocyte cytotoxicity in the Chu study (2006) of dopamine, norepinephrine, epinephrine, and serotonin. It seems that dopamine induces melanocyte apoptosis, and may even contribute to vitiligo (depigmentation of the skin).
However, linking white skin to conservatism has the same issues as does serotonin and dark skin. But it is an interesting coincidence that serotonin and dopamine have opposite effects on both political-religious disposition and skin color.
The Political Sun
The ability of melanin to regulate the sunlight-mediated conversion of 7-dehydrocholesterol into vitamin D3 and subsequently modulate calcium metabolism is just one of the growing list of functions of the photobiology of the human skin. Melanin absorbs ultraviolet radiation, reducing the incidence of skin cancers, and further, facilitating the skin's immune response.
As such, melanin physiology has been under extreme selective pressure in the human species, which is why the genetics of melanin physiology are highly variant across the human genome, and correlate closely with latitude. Given the strong selective pressure of latitude on melanin physiology, there indeed may be evolutionary side-effects, such as with cognitive styles.
Serotonin and dopamine, both contributors to melanin physiology, have diverse impacts on human cognitive styles and political-religious orientation. Have the multiple functions of these two monoamine neurotransmitters become genetically intermingled to the extent that political-religious orientation is influenced by skin color?
We must certainly be careful in this assertion, as we believe that skin color, with regards to political orientation, works along two dimensions. One dimension is the resolution of genetic distance, which subsequently influences the altruistic responses and political attitudes between individuals. The other dimension is its covariance with the function of the dopaminergic and serotonergic neuotransmitter systems, which not only have diverse influences on political attitudes, but also on how one organizes and functions in the space around them (see God, Dopamine, and 3-Dimensional Space).
Further, we do not want to confuse this theory with another theory of sunlight and political orientation: the sunlight theory of political preference. This theory proposes that the influence of sunlight on testosterone and estrogen levels ultimately impacts the dopamine system. This effect influences Caucasians in particular, and partially explains the tendencies for lower-latitude Caucasian populations to be more politically conservative, although the conservative tendencies of migrating populations also help to explain this phenomenon.
If skin color is indeed genetically intermingled with political-religious orientation, the long-term implications on the political trends in the United States will be dramatic, and distinctly liberal. While Caucasian conservatives substantially out-reproduce Caucasian liberals, they have been overwhelmed by the immigration of non-Caucasian populations that can reproduce with less energy.
The Republican Party, which has become the de facto Caucasian Party, is now caught between the preservation of Caucasian genetics and the declining percentages of Caucasians. To make matters worse, the American system of government is not conducive to this endeavor.
Charles Brack, June 2009
http://neuropolitics.org/defaultjun09.asp
