Inductivist

A study by John Archer reviewed meta-analyses on psychological sex differences, so we're talking about hundreds of studies. I will highlight the largest differences; those with means that are at least eight-tenths of a standard deviation apart. For the non-stats people among us, that is a very big gap.

Largest sexually dimorphic psychological traits (difference in sd units)

Homicide   2.54
Rape   2.32
Mate choice--Age difference   2.00
Violent computer-game use   1.41
Occupational interests   1.39
Systemizing   1.21
Pain tolerance  1.17
Fear in real-world situations   -1.16
Violent crime   1.11
Engineering interests   1.11
Partner homicide   1.06
People-things distinction   -.93
Empathy   -.91
Weapons use  .88
Sexual v. emotional jealousy  .87
Revenge   .83

Among the traits that Archer included, there is no bigger difference between the sexes than violence. Men are the violent sex and love it much more than women (i.e., violent video game use).

Male superiority in visuospatial ability is talked about a lot, and there is a difference, but it is not large enough to make the list. Interest is where the big gap exists. Men are much more likely to have an interest in engineering, making systems, and working with things over people.

While I've admired my wife's ability to suffer the pains of childbirth repeatedly, experimental research indicates that men can tolerate pain much better than women. Women are much more fearful of being harmed in real-world situations. This might figure into male willingness to get his ass kicked in a fight.

Women are the empathetic sex. They are much less likely to desire revenge. They get jealous about their man having romantic attachments, while men are much more concerned about sexual betrayal. Women desire older, resource-possessing men, while men desire younger women who have lots of reproductive potential.

These sex differences are what evolutionary theory would predict: men compete with each other, sometimes violently and vengefully, for access to mates.

There must have been benefits for women to be more sensitive to the feelings of others--effective childcare comes to mind--and men must have benefitted from a greater orientation to the analysis of systems. Strategic thinking for hunting and war?


UPDATE: Archer neglects to include perhaps the largest psychological sex difference: males are overwhelming attracted to females, while females are overwhelmingly attracted to males. The exceptions are noise. And the evolutionary reason is obvious.

Research indicates that men have more general knowledge than women, and--important for this blog--men know more about science. People like Richard Lynn see this as evidence that men have, on average, higher levels of general intelligence. The idea is that smart people seek out and absorb more information than others.

Perhaps this is relevant to the issue of belief in evolution. Understanding science better, are men more likely than women to accept the theory of evolution?

The General Social Survey asked participants if they believe that man descended from other species. In a sample of 6,375, 59.1% of men and 48.2% of women answered yes. That's roughly an 11 percentage point difference.

Now, let's see if superior knowledge of science helps explain the gender gap. We'll use logistic regression.  Here is the relationship between gender and acceptance of evolution

Belief in evolution--logistic regression coefficients

Male   .44***

***p < .001, two-tailed test

Men are significantly more likely to accept Darwin. Now let's see how much the coefficient shrinks when scores on a science quiz are added:

Male   .38***
Science Quiz   .42***

So some of the gender gap is due to superior male knowledge of science. How about religion? Women are more religious than men, and there is a tension between religious belief and acceptance of evolution.

Male   .14**
Science Quiz   .27**
Belief in God   -.62***
Church attendance   -.18***

**p < .01, two-tailed test

The gap closes even more: Women are less likely to accept evolution, in part, because they are more religious than men.

My last hypothesis goes beyond the sex difference in religiosity--perhaps men are more likely than women to accept ideas that are unpleasant. Most people are not thrilled to think that life has no objective meaning or purpose, or that they have a monkey for a grandfather.

The question was asked if the respondent agreed with this: "Life is only meaningful if you provide the meaning yourself."

Let's add this variable to the model:

Male  -.05
Science Quiz  .15
Belief in God   -.62***
Church attendance   -.14***
Meaning subjective    .32***

Gender and even science knowledge drop to non-significance when the meaning variable is added. The gender gap in belief in evolution seems to be explained by men's harsher, more secular worldview.

The Left dislikes evangelicals as much as they dislike anybody, and one of the reasons they don't like them is because they tend to reject the theory of evolution--which is ironic since the Left rejects the implications of evolution for human nature. But what about Muslims? Don't they reject evolution as well? The Left is usually silent about Muslim fundamentalism.

How many American Muslims don't believe that humans descended from earlier species of animals? General Social Survey (GSS) respondents were asked this question. Here are the percent who answered no listed by religion (sample size = 6,353):

Percent who don't believe humans descended from animals

Muslims  65.6
Christians  65.5
Protestants  63.6
Catholics  36.2
Orthodox Christians  32.1
Jewish   20.1
No religion  19.8
Buddhists   4.5
Hindus   3.2

Muslims are at the top of the list. Compare them to Buddhists and Hindus. An enormous difference.

If fundamentalism is an impediment to a pro-science culture, why isn't it a problem when it's found among Muslims? For the Christian fundamentalists always you have with you, but inviting the growing Muslim world to move to the US is a choice.

UPDATE: My 12-year-old son informs me that Hindus naturally accept evolution because they believe in a God that is an elephant.

This new meta-analysis of 28 studies finds that men are funnier than women. The gap, however, is not large (Cohen's d = .32).  To get specific, 63% of males get more laughter than the average female. 

The authors explain the difference in evolutionary terms: Women are choosier than men when selecting mates, and humor serves as an indicator of mental fitness that is not easy to fake. You're funny or you're not. This pressure has supposedly selected for men who can make people laugh.

It's the 10th anniversary of 10,000 Year Explosion, a fantastic book by Gregory Cochran and the late Henry Harpending.  You MUST read it if you haven't.  I command you.

The book is chock full of provocative hypotheses about humans.  Let's test just one of them with General Social Survey (GSS) data.  The authors explain that hunter-gatherers routinely share resources, in part because it is difficult for mobile people to hold on to things.  It's also advantageous to cement positive ties and to make others feel obligated to you by being generous with them.

By contrast, farming selects for people who are good at holding on to possessions: seed grain, breeding stock, land, etc. A farmer who gives away everything will starve.

So Cochran and Harpending predict that ethnic groups lacking deep histories of agriculture will tend to be quicker to share with others. In the US context, this would be American Indians and blacks.

The GSS asked respondents: "People help other people in ways besides giving money, time, or other things to organized groups. Sometimes people help needy people directly. During the past 12 months, did you or members of your family or household give money, food, or clothing to any of the following types of people: The homeless or street-people."

Here are the percentages who answered yes:

Percent giving to the homeless in the past year

American Indian  55.4
Blacks  45.7
Irish  44.0
East Asian  41.7

Total sample 40.2

Mexican  39.4
Italian  37.7
French  37.0
Russian  36.8
German  34.2
English/Welsh  33.1
Scottish  30.4
Asian Indian  28.6
Norwegian  20.0

Even though American Indians and blacks are poor groups, they are more likely to give to the homeless.  Groups with long agricultural histories are less likely to give, even if they are wealthy like Asian Indians.

And if you argue that giving to the homeless is largely an urban thing, American Indians tend to live in rural areas but are at the top of the list, while urban Asian Indians are at the bottom.

Lance Welton at Unz.com does a nice job of summarizing Richard Lynn's brand new book Race Differences in Psychopathic Personality

I won't repeat Lance's points, but I see in the comments that some people are claiming that the racial differences are explained in terms of the environment. This, of course, is the standard explanation--the only one you will get in sociology class, if the instructor is honest enough to acknowledge that the group differences indeed exist.

There are two obvious reasons to think the racial gaps (psychopathy running from high to low in this order: black, Native American, Hispanic, white, Asian) are at least partially due to genetic differences: 1) the differences are basically universal–found historically (Lynn cites over 700 studies conducted from the 19th century to now) and all around the world, and 2) psychopathy is highly heritable, similar to general intelligence. Therapists find it practically impossible to treat.

As Arthur Jensen explained, it is reasonable to conclude that if genes explain 70% of the variation in a trait, they likely explain 70% of group differences. The only reason why the commonsense belief that “What You See is What You Get” is not popular today but “People Are Not Themselves But Their Surroundings” is assumed to be true is that we have been propagandized by armies of full-time storytellers for more than a century.

I do take issue with conceptualizing psychopathy as a disorder, as if human nature is naturally good, and antisociality suggests a brain that is not working properly. I’m not criticizing Lynn but psychiatry. Exploitativeness is a regrettable but perfectly healthy and natural supertrait.  Psychiatrists want to turn all problematic behaviors into forms of mental illness, which is just silly. Evolution has designed us to thrive and to be strong, not to be burdened on every side by illness and weakness.  Mainstream behavioral science portrays us--the descendants of nature's winners--as naturally frail.  Complete BS.

In a recent post, I critiqued Richard Wrangham's theory of why humans are so much less violent than our cousins, the chimpanzees.  In The Goodness Paradox, he also attempts to explain why we have a strong moral sense.  It's strange for an animal designed to outcompete others through survival and greater reproductive success to care so much about abstract concepts of right and wrong.

He hypothesizes that human society changed fundamentally when men developed the language to coordinate control over other members of the group.  While apes sometimes gang up and beat or kill a single, obnoxious ape, they don't plan it out ahead of time.  Men gained a tremendous tool when they began to conspire as a group of five or six against one.  They could discuss the idea, plan a surprise attack, and kill the offender with little danger to themselves.  Sometimes the murder wasn't necessary: A rumor could be floated and the troublemaker might be convinced to change his ways.

Wrangham claims that men expanded their control to all members of the community so that everybody was were in fear of their ability to conduct a surprise attack against them.  Over evolutionary time, humans were selected for their ability to please the men who had this power over them.  Extremely selfish, exploitative people were weeded out.  A person who treated everyone well was unlikely to displease elders, so prosociality became a more and more common trait.  And while I didn't find Wrangham clear on this point, I think moral values gradually developed as a reflection of the prosocial personalities that were becoming common.

According to Wrangham, selection has been more successful at producing people oriented toward having a good reputation and appearing moral rather than creating humans of deep, genuine integrity and principle.  After all, we are still programmed to care about our own reproductive interests.

I would return to my earlier criticism: In 2019, some groups seem to have much higher rates of prosociality than others.  For example, a quick look at the Corruption Perceptions Index reveals that Denmark has very little public corruption compared to Somalia. How does Wrangham help us explain the enormous gulf between the two countries?  He doesn't.  He presents the image of all human groups across the globe being identical in terms of genes that contribute to cooperativeness.  I suppose he would say that evolutionary biology tells the story up until the day before yesterday, but now it's irrelevant: It's all sociology now.  Not credible. 

I read a tweet quoting Richard Lewontin the other day (can't find the article -- I'd love a copy if someone has one) that suggested that perhaps evolution was coming to an end in modern societies because few people die until they're old, and a model was emerging where everyone has two kids, effectively creating a new generation just like the last.

I hope I read that wrong because it's simply stupid.  It's been more than 40 years since Lewontin presented the idea, so the Two-Child Model should have become even more solidified in US society. Look at this graph to see the current distribution of family size for women ages 40-55:
















Does everyone have two kids? Hardly.  The mean is 2.12, while the standard deviation (SD) is 1.49.  One way to interpret SD is to say that if we randomly grabbed two American women in the 40-55 age range, we would expect them to differ in number of children by 1 1/2 kids. (No jokes about half a kid.)

With a normal distribution (known as the "bell curve"), the standard deviation is about 1/6 of the mean, but with this family size variable, the SD is 70% of the mean.  In plain English, women are all over the map in terms of how many babies they have.

Some women (and their partners) are contributing much more genetically to the next generation, and since most traits are heritable, they are shifting the distribution of traits.  That's called evolution, and it's alive and well.

In Part I, I introduced the idea that blacks and whites differ in how their immune systems react to pathogens, and this is due, in part, to evolution having affected relevant genes.

Here in Part II, I lay out the research evidence summarized in this study. Compared to whites, the immune systems of blacks have a stronger gene response to immune stimulation, especially the genes related to the activation of inflammatory responses. Blacks often have higher frequencies of alleles (i.e., one variety of a gene) associated with stronger proinflammatory responses to infection.

Two studies illustrate this. One tested how macrophages (i.e., a type of large white blood cell) responded to two different types of infections, and the other on monocyte (i.e., another large white blood cell) response to several pathogens such as the human seasonal influenza A virus. On average, 21% of the relevant genes appeared to show different expression between whites and blacks, and 16% of the genes reacting to immune stimulation showed that blacks had a more intense response.

Differences in genes that regulate other genes explain much of the racial difference in immune response. One variant is found in 67% of whites but only 4% of blacks. The authors found that this one difference explained from 27 to 91% of the black-white difference in immune response to various infections.

While the authors write that we have not studied very much the extent to which positive selection has contributed to racial differences in immune response, they cite at least seven studies that report signs that evolutionary pressures have caused the racial differences. Some of the relevant diseases include malaria, African trypanosomiasis (sleeping sickness), celiac disease, lupus, rheumatoid arthritis, ulcerative colitis, and systemic sclerosis.

The researchers suggest the possibility that there is an "evolutionary conflict between mounting a strong inflammatory response to effectively fight pathogens and avoiding the detrimental consequences of acute and chronic inflammation, which can lead to tissue damage and the development of autoinflammatory and autoimmune diseases."

We have recently learned that 2% of the ancestry of humans outside of Africa is Neanderthal. This may help explain the black-white differences in immune response. Higher levels of Neanderthal admixture can be detected in immune system genes in Europeans and Asians. Regulatory gene variants from Neanderthals have been found to affect the immune responses of Europeans, especially the responses to viruses.

All these racial differences in genes and immune systems are really weird since "race experts" tell us that this race stuff is just an hallucination dreamed up by evil white people.

Here's a figure from a new study that reviews research on racial differences in immune system response. Notice how the regions with the highest abundance of pathogens (disease-causing microorganisms) are the northern half of South America, central sub-Saharan Africa (SSA), and southeast Asia.

The graph also traces important moves humans have made over the past 65,000 years, and the right panel shows that people with European ancestry suffer from high rates of death from Parkinson's and Alzheimer's, while those with SSA ancestry experience a high incidence of mortality from cardiovascular disease, surgical complications, meningitis, diabetes, septicemia (blood poisoning), kidney inflammation, perinatal death, asthma, childbirth, and HIV.

In the next post, I'll summarize the evidence presented in the study that immune system genes show signs of evolutionary adaptation to the different pathogen environments that races have lived in.

When people cite stats that seem to show that Americans are dumb, I suspect that many people get a mental image of a redneck.  I discussed in an earlier post that some people think Republicans are dumb even though the data contradicts this. In all probability, white liberals are comparing themselves with white hicks and conveniently forgetting that a big chunk of their party is made up of low IQ blacks and Latinos.  I'm willing to bet that with controversial attitudes that suggest intelligence or the lack of it, non-Asian minorities often have the worst numbers. Let's try belief in evolution as a first try.

General Social Survey respondents were asked in 2012, "According to the theory of evolution, human beings, as we know them today, developed from earlier species of animals. Is that true or false?" Here are the answers for white, blacks and people of Mexican ancestry:

Percent answering false (N = 390)

Black  33.3
Mexican  27.3
White  18.4

Blacks are almost twice as likely as whites to believe we did not develop from earlier species. People of Mexican descent reject science here at 1 1/2 times the rate of whites.

By the way, these percentages are lower than the--what--40 percent number cited as the percent of Americans who reject evolution.

From the Atlantic:

A few decades ago, Darwinians and creationists had a de facto nonaggression pact: Creationists would let Darwinians reign in biology class, and otherwise Darwinians would leave creationists alone. The deal worked. I went to a public high school in a pretty religious part of the country--south-central Texas--and I don't remember anyone complaining about sophomores being taught natural selection. It just wasn't an issue.

A few years ago, such biologists as Richard Dawkins and PZ Myers started violating the nonaggression pact. [Which isn't to say the violation was wholly unprovoked; see my update below.] I don't just mean they professed atheism--many Darwinians had long done that; I mean they started proselytizing, ridiculing the faithful, and talking as if religion was an inherently pernicious thing. They not only highlighted the previously subdued tension between Darwinism and creationism but depicted Darwinism as the enemy of religion more broadly.

If the only thing this Darwinian assault did was amp up resistance to teaching evolution in public schools, the damage, though regrettable, would be limited. My fear is that the damage is broader--that fundamentalist Christians, upon being maligned by know-it-all Darwinians, are starting to see secular scientists more broadly as the enemy; Darwinians, climate scientists, and stem cell researchers start to seem like a single, menacing blur.

I'm not saying that the new, militant Darwinian atheists are the only cause of what is called (with perhaps some hyperbole) "science denialism." But I do think that if somebody wants to convince a fundamentalist Christian that climate scientists aren't to be trusted, the Christian's prior association of scientists like Dawkins with evil makes that job easier.

I reiterate that this theory is conjectural--so conjectural that "hypothesis" is a better word for it than "theory". The jury may remain out on it forever.

Meanwhile, some data to keep your eye on: Check out the extreme right of the graph above. Over the past two years, the portion of respondents who don't believe in evolution has grown by six percentage points. Where did those people come from? The graph suggests they're people who had previously believed in an evolution guided by God--a group whose size dropped by a corresponding six percentage points. It's as if people who had previously seen evolution and religion as compatible were told by the new militant Darwinians, "No, you must choose: Which is it, evolution or religion?"--and pretty much all of them chose religion.

The use of the word "primitive" is revealing. Here is a partial list of things that are labeled primitive as opposed to modern:

Ethnocentrism
Racism
Nativism
Xenophobia
Nepotism
Favoritism
Sexism
Objectification
Patriarchy
Hierarchy
Supernaturalism
Hunting
Violent sports
Fist fighting
Assault
War
Genocide
Anger
Hate
Jealousy

Funny, but you never hear love or compassion or altruism or generosity or cooperation described as primitive even though they are certainly as old as the other items. What people are really saying when they use the word primitive is "old stuff that we don't like but can't seem to get rid of."  All the energy devoted to eradicating these barbarisms, but they never die.  These folks don't know it, but their use of the word primitive is basically making a case for a biological view of man. Show me a behavior dismissed as primitive, and I'll show you a behavior rooted in evolution and biology.    

The table shows that General Social Survey respondents who accept evolution are less likely to think cheating on your spouse is always wrong, and are more likely to have strayed.

We know that correlation does not prove causation, but it doesn't seem unlikely to me that acceptance of evolution might lead some to justify infidelity.  Arguments like the following are easily concocted: "If bonobos are close cousins, can I really expect myself and others to remain monogamous?"   

This is a potential problem for any theory of humans, even if it is true. A theory doesn't just simply stand outside human society, explaining how things work. Theories are brought into a person's worldview and can affect his behavior.  So theories don't merely explain; they influence.

Atheism, evolution, and the death penalty: Speaking of the last post, I'll concede that I picked a conservative version of a barbarism. Let's pick a liberal one this time: the death penalty. The argument was made in the documentary Expelled that belief in atheism and evolution tend to reduce the value of humans, especially unproductive ones. The whole question becomes, does a person improve the population or not? People become economic units, and the door is opened to eliminate those who are a drag on society.

Murderers are certainly undesirable, so do atheism and acceptance of Darwin make us want to get rid of them? I followed the same strategy as in the last post and included a liberal outlook as a control.


Logistic regression coefficients

Acceptance of evolution -.042
Atheism .045
Liberalism -.252**

p < .01, two-tailed test

In analyes not shown, both atheism and acceptance of evolution are significantly related to being against the death penalty, but you can see in the results above that when liberalism is entered in the model, the effects of the other two fall to non-significance. So atheists and Darwinists tend to be against executing criminals, but only because they tend to be liberals. No whiff of Hitler here.

Atheism, acceptance of evolution, and atrocity: When it was in the theaters, I wasn't interested enough in Ben Stein's Expelled to go see it, but I saw that it was available online at Netflix.com. It was more stimulating than I expected, and it made me wonder if there was something to the idea that atheism and belief in Darwin were associated with various forms of barbarism. My sense of the historical record would lead me to say no--I mean, haven't elites in all developed countries accepted the science--but you folks know I like data.

The General Social Survey asked the following questions: 1) confidence in the existence of God, 2) likelihood that humans evolved from animals, 3) political orientation, and 4) favoring abortion for any reason. I chose the last one because it is an attitude in favor of a barbarism. To approve of abortion at any time for any reason would include killing a baby right before birth because at the last minute Mom decided she couldn't afford an iPhone if she had to buy diapers.

I doubted that mere adoption of atheism or acceptance of evolution would lead one to accept any kind of abortion; I suspected that a liberal worldview might explain any correlation. To assess this, I estimated a logistic regression model with abortion attitude as the dependent variable and the other measures as predictors:


Logistic Regression Coefficients, DV = Favoring abortion for any reason

Liberalism .302**
Skepticism about God .294**
Acceptance of evolution .383**

**p < .01, two-tailed test

Atheism and belief in evolution both significantly predict favoring abortion on demand, independent of the influence of a liberal worldview. I don't like to admit it, but some of the people who seem to be most devoted to Darwinism and atheism are neo-Nazis, and many of them have adopted barbaric attitudes. When, in an online debate forum, I was told that an autistic family member of mine should be euthanized, I wanted to reach through the Internet with a switchblade and slit the guy's throat. Some readers, I'm sure, will suggest that I examine the correlates of a real atrocity like denying racial preferences to less qualified minorities--the American equivalent of gassing Jews.

In honor of Darwin's birthday, Gallup conducted a poll and found all sorts of discouraging things, like how only 39% of Americans accept the theory of evolution. I'd rather focus on the positive part that younger people are more likely to believe it than older people. There is an 18 point gap between the youngest and oldest groups.

I can see this in my own family. Despite my best efforts, both parents are skeptical, but all the kids accept it. On the other hand, I get a lot of resistance in the classroom from students. Many students don't deny it's true, but they make yucky faces if you use it to explain human behavior.

God versus Darwin: What is the best predictor of belief in evolution? I guessed education, but I was wrong. The General Social Survey asked a representative sample of Americans in 2006 whether the idea that humans evolved from earlier animals is true or false. Only 49.6% said true. Here is the list of predictors I included in a multivariate model, and the standardized OLS coefficients. (I know, I know--my dependent variable should be normally distributed when estimating OLS coefficients, but the technique is robust enough to handle a dichotomous variable that is evenly distributed between the two categories).


Belief in evolution (standardized OLS regression coefficients)

Age -.07
Sex -.08
Race -.01*
Years of education .17
IQ .14
Informed about sci/tech .07
Liberal politics .14
Church attendance -.34

R-squared .29
Number of valid cases 737

* not significant at .05 level, two-tailed test


Except for race (black v. white) all the effects are statistically significant. Men and younger people are more likely to accept evolution, but the tendency is slight. Being more educated, smarter, or saying that you are informed about science and technology is not particularly predictive--at least not more than being liberal.

It turns out that the bigger winner is religiosity--as church attendance increases, so does skepticism about evolution. Seventy-two percent of people who never go to church believe we evolved from earlier animals: the number for those who attend more than weekly is only 13%! God and Darwin may not necessarily be logically incompatible, but there is a clear sociological divide.