Thursday, January 8, 2009

Mental traits and human variation

An interesting article has come out in Edge by Jonathan Haidt, a University of Virginia psychologist and author of The Happiness Hypothesis. Essentially, he argues that science will soon embrace the idea that human nature evolved not only in the hunter-gatherer environments of the Pleistocene but also in the diverse social environments of the past 10,000 years.

Russian scientists showed in the 1990s that a strong selection pressure (picking out and breeding only the tamest fox pups in each generation) created what was — in behavior as well as body — essentially a new species in just 30 generations. That would correspond to about 750 years for humans. Humans may never have experienced such a strong selection pressure for such a long period, but they surely experienced many weaker selection pressures that lasted far longer, and for which some heritable personality traits were more adaptive than others. It stands to reason that local populations (not continent-wide "races") adapted to local circumstances by a process known as "co-evolution" in which genes and cultural elements change over time and mutually influence each other.

… No new mental modules can be created from scratch in a few millennia, but slight tweaks to existing mechanisms can happen quickly, and small genetic changes can have big behavioral effects, as with those Russian foxes. We must therefore begin looking beyond the Pleistocene and turn our attention to the Holocene era as well - the last 10,000 years. This was the period after the spread of agriculture during which the pace of genetic change sped up in response to the enormous increase in the variety of ways that humans earned their living, formed larger coalitions, fought wars, and competed for resources and mates.

… traits that led to Darwinian success in one of the many new niches and occupations of Holocene life — traits such as collectivism, clannishness, aggressiveness, docility, or the ability to delay gratification — are often seen as virtues or vices. Virtues are acquired slowly, by practice within a cultural context, but the discovery that there might be ethnically-linked genetic variations in the ease with which people can acquire specific virtues is — and this is my prediction — going to be a "game changing" scientific event.

Haidt predicts that the paradigm shift will occur as genome research uncovers evidence that many mental traits differ among human populations. These findings will be unexpected and disturbing to some. “Expectations, after all, are not based purely on current evidence; they are biased, even if only slightly, by the gut feelings of the researchers, and those gut feelings include disgust toward racism.” In making this prediction, Haidt feels some foreboding:

I believe that the "Bell Curve" wars of the 1990s, over race differences in intelligence, will seem genteel and short-lived compared to the coming arguments over ethnic differences in moralized traits. I predict that this "war" will break out between 2012 and 2017.

7 comments:

Tod said...

The style of thinking that would go against its 'gut feeling' and be forced by facts to accept the idea that there have been significantly different results from different selection pressures would be :-

deterministic, objective, universal
concrete, specific, single-minded
coherent, bottom-up,
reductionistic, field-independent.
As epitomized in hard science, engineering, and technology, astronomy, chemistry, natural: factually and genetically determined - Darwinism.


As far as I can see it this style of thinking is not a recipe for the high status and success in PC academia, politics or the media. Moreover if they somehow come to believe it has validity in a scientific sense they are going to have to be convinced that presenting the idea to the public is a good thing before any real debate can take place.

If Europeans are the result of sexual selection with a special focus that shifted certain traits towards the feminine maybe their average mental style has been shifted towards Mentalistic Cognition
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To my way of thinking the following linked page is very telling evidence that sexual selection was responsible for the relatively widespread incidence of blond and red hair in parts of Europe. Dr. Brash had been curious why people with dark hair and fair skin weren't as vulnerable to skin cancer as fair-skinned blondes or redheads. He wondered if their vulnerability was actually related to the type of melanin.

What this tells us is that melanin is not only good for you, it also can be bad,” said Dr. Brash. “It depends on the color of your particular melanin. Even red melanin can vary widely, depending on whether your ancestors were Irish, Swedish or Dutch, and some of these variations are known to be associated with greater risk for skin cancer.”

People with the other type of melanin—eumelanin—have darker hair. Interestingly, while dark-haired people with eumelanin can be fair-skinned, they don't burn as readily as a blonde or a red-head.

To me this means there is no advantage even in the putative marginal UVB environment (which doesn't exist) for redheads over dark haired and fair skinned whites.
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In a (2002)Scientific American article Nina G Jablonski and George Chaplin address the objection that Khoisans are native to sub-Saharan Africa but do not have very dark skin

"A number of the earliest movements of contemporary humans outside equatorial Africa were into southern Africa. The descendants of some of these early colonizers, the Khoisan (previously known as Hottentots), are still found in southern Africa and have significantly lighter skin than indigenous equatorial Africans do -a clear adaptation to the lower levels of LTV radiation that prevail at the southern extremity of the continent


I am afraid I have found this to be rather misleading Worldwide UV SA UV Index
As far as I can see they are simply wrong about the amount of UV at the earths surface in most of South Africa. This next linked page sounds authoritative to me Distribution of UV radiation at the Earth's surface from TOMS-measured UV-backscattered radiances
Even though terrain height is a major factor in increasing the amount of UV exposure compared to sea level, the presence of prolonged clear-sky conditions can lead to UV exposures at sea level rivaling those at cloudier higher altitudes. In the equatorial regions, ±20°, the UV exposures during the March equinox are larger than during the September equinox because of increased cloudiness during September. Extended land areas with the largest erythemal exposure are in Australia and South Africa where there is a larger proportion of clear-sky days

Vertumne said...

@ Tod: the UV chart is updated daily. Do not forget it is actually summer in the southern hemisphere. This is why the UV presence is so strong in S.A. at this moment and why even Southern Europe is very low UV wise.

Tod said...

Thanks for taking he time Vertumne. I was made aware of this by Maju while debating the issue at his wide ranging blog Leherensuge

My response, and the reason I didn't mention it here, is this:-
I wasn't factoring in the southern summer, does it make a difference to the point at issue?
As far as I can see it means that Khoi-San people have evolved where UVB is strong enough to make Vitamin D all year and in their summer, they would, as hunter gatherers, have been exposed for much of the day to the very highest levels of UV radiation

The area of the most extreme erythermal UV is not resticted to the Kalahari it's a huge central area that is actually rather close to Johannesburg . Moreover the close-up map is not just backed up by Extended land areas with the largest erythemal exposure are in Australia and South Africa where there is a larger proportion of clear-sky days here is another site (NASA) saying the same thing Persistent lack of cloud cover in some regions (e.g. Australia and South Africa) increases the danger from UV radiation compared to similar latitudes in the Northern Hemisphere.

Peter Frost said...

In the Kalahari (where most Khoisans live today), the intensity of UV at ground level is comparable to that of West Africa. This is what Jablonski and Chaplin show in their own map of ground-level UV (which is reproduced on my website): http://pages.globetrotter.net/peter_frost61z/European-skin-color.htm


It's hard to tell how things will play out in academia over the next decade. A lot of intellectual change is taking place under the radar, so to speak.

A colleague once told me he was in favor of people reading Marx. "If you learn to read Marx, you can go on to read almost anything."

Tod said...

Low serum 25-hydroxyvitamin D (25-OH-D) levels in African Americans are said to be the result of the reduced synthesis of Vitamin D in darker skin: "Vitamin D insufficiency is more prevalent among African Americans (blacks) than other Americans... This is primarily due to the fact that pigmentation reduces vitamin D production in the skin. Harris 2006
This is increasingly being seen as the main cause of various diseases in African Americans.
An alternative explaination is that both the diseases and low serum 25-hydroxyvitamin D levels are due to the fact that "In 2005, African Americans were 1.4 times as likely to be obese as Non- Hispanic Whites. .../In 2003-2004, African American children between ages 6 -17 were 1.3 times as likely to be overweight than Non-Hispanic Whites.../African American women have the highest rates of being overweight or obese compared to other groups in the U.S. About four out of five African American women are overweight or obese. Office of Minority Health Obesity increases the risk of disease, it also reduces Vitamin D levels.

Precisely measured total body fat is inversely associated with 25-OH-D levels and is positively associated with PTH levels. The associations were weaker if anthropometric measures were used, indicating a specific role of adipose tissue. Regardless of the possible underlying mechanisms, it may be relevant to take adiposity into account when assessing vitamin D requirements. ...In a more recent study by Wortsman et al. (11), the capacity of the skin to produce vitamin D was not altered in obesity. However, the increase in serum vitamin D3 after sun exposure was 57% less in obese compared with nonobese subjects. The increase in serum vitamin D3 after oral supplementation was similar in obese and nonobese subjects. This supports the hypothesis of a decreased release of endogenously produced vitamin D into the circulation due to more storage in sc fat in obese subjects (11). The fact that in our study leg fat was more strongly related to 25-OH-D levels compared with trunk fat supports the idea that endogenously produced vitamin D is particularly stored in the sc fat depot. Snijderet et al 2005
Vitamin D is added to milk, ("oral supplementation"), however obese whites are far more likely to drink milk than obese black Americans.

African American infants have higher levels than white infants in the winter
In a 1986 study in 198 subjects < 18 mo of age, we found that differences in vitamin D status by race were significant in winter but not in summer (3). What was also surprising was that African American infants had significantly higher 1,25-dihydroxyvitamin D concentrations than white infants, both in winter and in summer. The study was uniformly blocked by sex, race, age, season, and diet (formula-fed compared with breast-fed infants Lichtenstein et al 86

Caucasian newborns' vitamin D levels are more reduced when they are born in the low UVB period than African American newborns.
By season, the mean 25-hydroxyvitamin D level at birth in November–March compared to April–October was 11.3 ng/ml lower in Caucasian infants (from 29.0 to 17.7 ng/ml) and 3 ng/ml lower in African-American infants (from 13.1 to 10.1 ng/ml). Neonatal Vitamin D Status at Birth at Latitude 32 Degrees 72': Evidence of Deficiency [sic]

Tod said...

Vitamin D and African Americans,Susan S. Harris states
Vitamin D insufficiency is more prevalent among African Americans (blacks) than other Americans and, in North America, most young, healthy blacks do not achieve optimal 25-hydroxyvitamin D [25(OH)D] concentrations at any time of year. This is primarily due to the fact that pigmentation reduces vitamin D production in the skin

However, lower 25-hydroxyvitamin D [25(OH)D] levels in healthy African Americans may not justify the use of the term "insufficiency" because the active form of the vitamin is not lower in African Americans

"1,25-dihydroxyvitamin D [1,25(OH)2D], the kidney metabolite of 25(OH)D and the most biologically active form of the vitamin. ... Extremely low 25(OH)D may be associated with low 1,25(OH)2D due to lack of substrate (15), but moderately low 25(OH)D (e.g., 20–40 nmol/L) is often associated with increased 1,25(OH)2D,

It would be surprising if African Americans had 'adaptive responses' to a environment they hadn't evolved in, (that is a low UV/vitamin D one) as is suggested here.
"Blacks may have adaptive responses to low 25(OH)D that reduce its harmful skeletal effects.

A more likely outcome of having evolved in the high UVB radiation environment of Africa would be that they lacked such adaptations. That African Americans would have adaptations to low vitamin D synthesis while whites lack any such adaptations is an unreasonable assumption.

Surely it is more likely that the
"moderately low 25(OH)D (e.g., 20–40 nmol/L)" level is not low or in any way unhealthy for African Americans. The fact that their bones are less prone to fractures at all ages supports this.

Although it would seem that their lower 25(OH)D concentrations would put blacks at an increased risk for osteoporosis compared with whites, they actually have much lower rates of osteoporotic fracture (10,11). For example, the actuarial risk that a 65-y-old white woman will have a hip fracture by age 80 is 11% compared with only 4% for a 65-y-old black woman (10).

Tod said...

I'll let these papers speak for themselves.

Association between quantitative measures of skin color and plasma 25-hydroxyvitamin D
Abstract
Summary We examined the relationship between vitamin D and skin color measured by reflectance colorimetry at an exposed and un-exposed site in 321 people. Exposed but not unexposed skin color was associated with better vitamin D status. Sun-exposure was more important than natural skin color in determining vitamin D status in our population.... Plasma 25OHD was determined and sun-induced (outer fore-arm) and constitutive (upper inner-arm) measured by reflectance colorimetry....
Skin color at the forearm but not constitutive skin color was a significant predictor of 25OHD. Each 10° lower skin color value at the forearm (more tanning) was associated with a 5 nmol/L higher 25OHD (P < 0.001).
Conclusions Tanning but not natural skin color was an important determinant of 25OHD. Further study is needed in a population with a higher proportion of darker skin people.


Genetic and Environmental Determinants of 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D Levels in Hispanic and African Americans Yann Klimentidis' Weblog says
This study has a large diverse sample and they look at the association between variants in three vitamin D related genes and vitamin D levels in the blood. They find an association between variants in the DBP (vitamin D Binding Protein gene) and plasma levels of 25(OH)D and 1,25(OH)2D in all three populations.

Characterization of mutants of the vitamin-D-binding protein/group specific component : GC aborigine (1A1) from Australian aborigines and South African blacks, and 2A9 from South Germany
Genomic DNA of the variant 1A1 was obtained from Australian Aborigines and from South African Bantu-speaking Blacks. Amplification and sequencing of exon 11 of 1A1 revealed a point mutation in codon 429 at the second position. It is remarkable that this mutation was found in the Australian 1A1 variant and in the African 1A1 variant, and raises the question whether the mutation in these two ethnic groups has a common origin

Population distribution of the human vitamin D binding protein: Anthropological considerations
Abstract
The polymorphism of the serum vitamin D binding protein (DBP) in humans is based on the existence of three common alleles, Gc1F, Gc1S, and Gc2, and 84 rare alleles. The geographical distribution of Gc1F, Gc1S, and Gc2 alleles shows north to south clines, together with a balanced equilibrium between the Gc1F or Gc1S allele frequency and the Gc2 frequency.
The distribution of the FST values shows high variability within a geographical area. For European and North Asiatic groups, the FST values are the lowest observed, and the reason may be a long process of homogenization. Aboriginal populations from Australia and New Guinea and groups from both North Africa and South America show the greatest heterogeneity of their allele frequencies. Systematic factors such as genetic drift and selection may account for this distribution.
In contrast with the three main DBP alleles, the distribution of the rare alleles corresponds to patterns of human migrations that occurred during prehistoric and historic periods. Thus, the rare mutants are of particular relevance to anthropological and genetical investigations