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20200621 – Human Diversity



The main idea of this book is to provide review of the most recent scientific research into human biology and humanities related to variation between individuals belonging to three different types of groups: by sex, by race, and by class. The objective is to provide hard data on intrinsic differences between groups within each type: male vs. female; one race vs. another; one class vs. another.


The introduction is mainly about author’s intention to present scientific data that contradict currently dominant orthodoxy and support 10 propositions presented by author. Here is author’s description of orthodoxy:” The core doctrine of the orthodoxy in the social sciences is a particular understanding of human equality. I don’t mean equality in the sense of America’s traditional ideal—all are equal in the eyes of God, have equal inherent dignity, and should be treated equally under the law—but equality in the sense of sameness. Call it the sameness premise: In a properly run society, people of all human groupings will have similar life outcomes. Individuals might have differences in abilities, the orthodoxy (usually) acknowledges, but groups do not have inborn differences in the distributions of those abilities, except for undeniable ones such as height, upper body strength, and skin color. Inside the cranium, all groups are the same. The sameness premise theoretically applies to any method of grouping people, but three of them have dominated the discussion for a long time: gender, race, and socioeconomic class. Rephrased in terms of those groups, the sameness premise holds that whatever their gender, race, or the class they are born into, people in every group should become electrical engineers, nurture toddlers, win chess tournaments, and write sci-fi novels in roughly equal proportions. They should have similar distributions of family income, mental health, and life expectancy. Large group differences in these life outcomes are prima facie evidence of social, cultural, and governmental defects that can be corrected by appropriate public policy.”

The 10 propositions that author supports are:

1. Sex differences in personality are consistent worldwide and tend to widen in more gender-egalitarian cultures.

2. On average, females worldwide have advantages in verbal ability and social cognition while males have advantages in visuospatial abilities and the extremes of mathematical ability.

3. On average, women worldwide are more attracted to vocations centered on people and men to vocations centered on things.

4. Many sex differences in the brain are coordinate with sex differences in personality, abilities, and social behavior.

5. Human populations are genetically distinctive in ways that correspond to self-identified race and ethnicity.

6. Evolutionary selection pressure since humans left Africa has been extensive and mostly local.

7. Continental population differences in variants associated with personality, abilities, and social behavior are common.

8. The shared environment usually plays a minor role in explaining personality, abilities, and social behavior.

9. Class structure is importantly based on differences in abilities that have a substantial genetic component.

10. Outside interventions are inherently constrained in the effects they can have on personality, abilities, and social behavior.

Part I: “Gender Is a Social Construct”
Here author retells the story of development of feminist idea that sex is social construct and attempts to separate it from human biology. He states that last 20 years of scientific development left no doubt that this idea is completely detached from reality and then proceeds to discuss details.

1. A Framework for Thinking About Sex Differences
First author is trying to establish dimensions of discussion about male/female differences:

  • The People-Thigs Dimension
  • Height as example of statistical differences illustrated by graph below:
  • Which Effect Size is Big Enough
  • Inedividual vs. Aggregated Aproach

2. Sex Differences in Personality
In this chapter author looks at differences in personality disorders and differences within normal range. Author looks at this issue as it occurs in USA, worldwide, and especially how it depends on cultural environment: levels of equality.  

3. Sex Differences in Neurocognitive Functioning
Here author provides a long list of differences defined as result of multiple empirical studies:

  • Females tend to be better than males at detecting pure tones. 
  • Adult females tend to have more sensitive hearing for high frequencies than males. 
  • Females tend to have better auditory perception of binaural beats and otoacoustic emissions.
  • Females tend to detect faint smells better than males. 
  • Females tend to identify smells more accurately than males.
  • Males under 40 tend to detect small movements in their visual field better than females. 
  • Age-related loss of vision tends to occur about ten years earlier for females than for males. 
  • Males are many times more likely to be color-blind than females (the ratio varies by ethnic group).  
  • The balance of evidence indicates that females are more accurate than males in recognizing the basic tastes (sweet, sour, salty, bitter), though some studies find no difference. 
  • Females tend to be better than males at perceiving fine surface details by touch. This holds true for blind people as well as sighted ones.
  • Females tend to be better than males at remembering faces and names. 
  • Females tend to be better than males at recognizing facial emotions. 
  • Females tend to be better at remembering the minutiae of an event (labeled peripheral detail), while males tend to be better at remembering the core events (labeled gist)
  • Females tend to remember speech they have heard better than males, particularly when it relates to emotionally laden events in their past. 
  • Females tend to retain memories from earlier childhood better than males do. 
  • Females tend to have better short-term memory than males (e.g., given a list of single-digit numbers, they remember longer lists than males do). 
  • Females tend to have better verbal working memory (e.g., remembering a list of numbers while answering questions about an unrelated topic). 
  • Females tend to have better memory for locations of objects (e.g., remembering where the car keys were left). 
  • Males tend to have better visuospatial memory (e.g., navigating on the basis of a combination of landscape features).

4. Sex Differences in Educational and Vocational Choices
In this chapter author reviews results of multiple studies; stresses increase in female educational achievement and provides summary results of difference:

5. Sex Differences in the Brain
Here author discussesProposition #4: Many sex differences in the brain are coordinate with sex differences in personality, abilities, and social behavior.” He looks at difference in genotype and phenotype, and provides analysis of brain scans results. He summarizes it the following way:

  • Circulating sex hormones produce easily observable differences in the phenotype. Those hormones have specific, documented effects that match up with some of the differences in personality and neurocognitive functioning discussed in chapters 2 and 3. 
  • The underreported news about sex hormones is the permanent effect that prenatal and infant surges of testosterone have on masculinizing the male brain. Those effects also match up with the earlier discussions of personality and neurocognitive functioning. 
  • The greater lateralization of the male brain has been documented by a variety of evidence about sex differences in structural connectivity and functional connectivity. These findings bear on phenotypic sex differences in visuospatial and verbal skills. 
  • Differences in the functioning of the amygdala, hypothalamus, and other regions of the limbic

Part II: “Race Is a Social Construct”
This part is about another source of division – race. Author reviews history of development of idea that race is a social construct and looks at couple of famous people who promoted this idea.

6. A Framework for Thinking About Race Differences

In this chapter author is stresses that his approach in no way is supporting ideas about superior and inferior races and similar staff. His point is that science should look at genetics to define what is different in people of different races and not get beyond its area of competence. Therefore, author provides some minimal data and terminology related to genetics.

7. Genetic Distinctiveness Among Ancestral Populations
Here author looks at decoded human genome and discusses what databases are available, evolution of hominins, expansion of our species all around the world, and how genetic differences analyzed. Here is his summary: “The material here does not support the existence of the classically defined races, nor does it deny the many ways in which race is a social construct. Rather, it communicates a truth that geneticists expected theoretically more than half a century ago and that has been confirmed by repeated empirical tests: Genetic differentiation among populations is an inherent part of the process of peopling the Earth. It is what happens when populations successively split off from parent populations and are subsequently (mostly) separated geographically.”

8. Evolution Since Humans Left Africa
The next proposition author discusses is: “Evolutionary selection pressure since humans left Africa has been extensive and mostly local.” Author discusses recent findings in genetics, which move it away from relatively simple model of random and rare mutations to much more complex understanding in which diverse mechanisms impact organism in such way that evolution becomes a lot more dynamic, allowing for huge decrease in time is requires to make material changes in organisms.

9. The Landscape of Ancestral Population Differences
The final chapter of this part is designed to demonstrate that “Continental population differences in variants associated with personality, abilities, and social behavior are common.” Author going through multiple comparisons among subpopulations from the same continent and then at different continents demonstrating genetic diversity much higher between races than between subpopulations. Author’s recapitulation is:” The story of the raw material for studying continental population differences applies to SNPs related to physiological parameters, diseases, and cognitive repertoires. Substantial between-continent differences in target allele frequencies are common. Around a third of all differences meet a plausible definition of “large.” The limited amount of sophisticated genetic analysis of between-continent differences done to date suggests that these extensive differences observed in the raw material will frequently yield productive results about genuine continental population differences.”

Part III: “Class Is a Function of Privilege”
The final part of the book is about class difference. Author makes point that this difference comes not that much from formal privileges as from diversity of cognitive abilities that make individuals more or less capable to succeed in any given circumstances and that these abilities to large extent come from genotype and transferred from generation to generation. Author describes IQ role in three steps:

  • Establishing the heritability of cognitive repertoires and the relative unimportance of family background. 
  • Demonstrating that those cognitive repertoires are important causes of success. 
  • Examining the potential ways to mitigate the role of genes in determining success.

10. A Framework for Thinking About Heritability and Class
Here author discusses heritability: the process of transfer of features across generation and uses twins’ studies to demonstrate that it is valid in relation to genotype only, regardless of other forms of inheritance such as wealth, culture, and so on.

11. The Ubiquity of Heritability and the Small Role of the Shared Environment
Here author presents what he calls three laws of genetics:

  • First Law. All human behavioral traits are heritable. 
  • Second Law. The effect of being raised in the same family is smaller than the effect of genes. 
  • Third Law. A substantial portion of the variation in complex human behavioral traits is not accounted for by the effects of genes or families.

After that once again he refers to twins’ studies to support the proposition:” The shared environment usually plays a minor role in explaining personality, abilities, and social behavior.”

 Author summarizes this in quite interesting graphic form:

12. Abilities, Personality, and Success
This chapter argues that “Class structure is importantly based on differences in abilities that have a substantial genetic component.” Author uses Herrnstein syllogism:

1. If differences in mental abilities are inherited, and

2. If success requires those abilities, and

3. If earnings and prestige depend upon success,

4. Then social standing (which reflects earnings and prestige) will be based to some extent on inherited differences among people.

To support this idea author provides results of comparative studies of IQ in childhood with adult outcomes.

13. Constraints and Potentials
The final chapter of this part argues that “Outside interventions are inherently constrained in the effects they can have on personality, abilities, and social behavior.”

Author uses here another syllogism:

1. If the shared environment explains little of the variance in cognitive repertoires, and

2. If the only environmental factors that can be affected by outside interventions are part of the shared environment,

3. Then outside interventions are inherently constrained in the effects they can have on cognitive repertoires.

Then he analyses veracity of each premise based on research results, looking at specific areas:

  • Role of outside interventions
  • How genes shape environment
  • Heritability and Socioeconomic status
  • Empirical record for early childhood interventions

Author also looks at various attempts to achieve improvements:

  • The Self-esteem Movement
  • Stereotyping Threat
  • The Growth Mindset Movement

The result of analysis is conclusion that effects are minimal.

The final part of chapter is discussion of epigenetics.

Part IV: Looking Ahead
Here author refers to E.O. Wilson’s idea of Consilience: merge of all areas of human knowledge into one seamless entity in order to present a coherent vision of the future.

14. The Shape of the Revolution
In this chapter author “focuses on the problem of establishing causation with genomic material and describes a great debate about the role of genomics in social science that is already well under way. Its resolution will determine whether the social science revolution is upon us or will be deferred indefinitely.” Author presents variety of schools of thought in this area and discuss ongoing debates.

15. Reflections and Speculations
The final chapter presents author’s key conclusions:

  • Human beings can be biologically classified into groups by sex and by ancestral population. Like most biological classifications, these groups have fuzzy edges. This complicates things analytically, but no more than that. 
  • Many phenotypic differences in personality, abilities, and social behavior that we observe between the sexes, among ancestral populations, and among social classes have a biological component. 
  • Growing knowledge about human diversity will inevitably shape the future of the social sciences.

After that he discusses how it would impact understanding of human nature:


I think that results of research and analysis presented in this book demonstrate quite convincingly that men are somewhat different from women, smart people from stupid, successful from unsuccessful, and that a lot of this difference is intrinsic, coming from genetic makeup of individuals. The funny thing about all these is that I do not think that on the reasonably long run it has any relevance to human lives whatsoever. The origin of interest in differences between humans comes from the period in history when role of family origin become much less important in defining quality of individual life, while personal qualities much more important. It used to be if one born duke, he is duke to the end so IQ would not matter. When born poor got opportunity become rich then IQ become important. However, while opportunity to move up opened, the places up there remained scarce, and road there went via selection by others. For example, IQ test came from US army, which needed easy to use tool that would provide good prediction for which conscript is smart enough to become artillery calculator, which one is better fit to learn tactics and weapons to be a good infantry soldier, and which is best fit to load and unload trucks. Same for deciding if women can do this or that job and whether class position defined by robbery and banditry or by superior intellectual abilities and grit. All this is losing relevance as soon as most of necessary for production activities moves to AI and machines, so people are free to do whatever they want and do not need to compete for place in some hierarchy in order to satisfy their material and psychological needs. They just need resources to pursue their own unique type of happiness.  

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