Inductivist

Based on 185 studies (43k men), this meta-analysis documents the 1972-2011 drop in total sperm count among men in North America, Europe, Australia and New Zealand. The decline was almost 60%.

The authors do not speculate about causes, but a GQ writer thinks it's due to an increase in plasticizers which are known to disrupt fetal testosterone (T). Perhaps it's due to increasing obesity which lowers T. The authors controlled for increasing age, so that doesn't appear to be the reason.

Anyway, I'm interested in the consequences. Assuming that a sperm count is a proxy for prenatal and adult T, young men strike me as being less masculine than in previous generations. They are certainly not shorter or smaller, but they seem more effeminate. And I'm not talking about dress or tastes. I mean in their faces and in their mannerisms.

According to the General Social Survey, the percent of men reporting they have sex exclusively with other men rose from 2.2% in the 1980s to 3.2% in this decade. This, of course, could be due to a greater willingness to admit the behavior, but there is a theory of homosexuality that claims it is due to inadequate prenatal T.

Subtracting out the 1984-94 gang wars and crack epidemic, the US homicide has declined since the late 1970s. Declining T? I'm just thinking out loud -- I might be crazy -- but it's an interesting idea.

UPDATE: By the way, the GQ author thinks the collapse in sperm count points to the end of the human race.

National Geographic reports on a study of proboscis monkeys:

Here's a new study on the impact of testosterone (T). In a placebo-controlled experiment of 243 men, giving a dose of T increases preference for status brands over brands of similar perceived quality but lower status. T also makes men have more positive attitudes toward high-status goods, but does not affect how they feel about power-enhancing or high-quality goods.

Interesting how T makes us like status, not power. I guess the difference is that power is not necessarily socially-approved, but status is. 

This study did not include women, but it appears that T makes men more concerned with rising in the social hierarchy, and we signal our position through status goods. This has gotten to be a more subtle game as elites have embraced the t-shirts and shabby jeans of the working man, but our nature cannot escape hierarchy. 

A retired researcher friend asked for my help. He has been linking male sex hormones to behavior for more than three decades. Since he is retired, he has no access to students to volunteer as research participants. I can't help him because there is no way the IRB committee at my university will approve this study.  He needs volunteers to complete this 5 minute survey. Please help if you can, and invite others. We need the broadest sample we can get. Warning: you will need to measure a body part!  https://www.surveymonkey.com/r/NKBRYYR

UPDATE: Of course, this study is very exploratory. He wants to see if it looks promising. 

Question of the day: Is penis length correlated with hand size?  The truth is that I don't know, but I would guess it is.  If I'm not mistaken, some of the same genes that control limb growth also influence genitalia growth. The 2D:4D finger ratio is not really relevant because it measures the relative size of fingers, and is of questionable validity. 

Lee Ellis published a fascinating paper which lists traits that are positively associated with penis length: masculine mannerisms, masculine body build, physical strength, strength of sex drive, low-deep voice, upper body strength, lower body strength, and amount of body hair. The argument is that all these traits are influenced by testosterone. The main weakness of the study is that the data are self-reported. Rating your own penis is like asking students to grade themselves. 

I can't recall the paper, but I do remember reading about a positive correlation between height and penis length as well. Again, the idea was testosterone.

Why haven't we heard more about the trial of black serial killer Lonnie Franklin who murdered several black prostitutes?  Americans love serial killer stories.  The media seems to want us to believe that blacks are small-time crooks who are sympathetic victims of the ghetto, while white criminals kill on a massive scale, motivated by pure evil.

Wrong. According to the serial killer expert Eric Hickey, 20% of American serial killers are black even though African Americans are only 13% of the population. Even worse, Hickey says they are half of recent cases.

A clear difference between blacks and whites is that blacks have shorter CAG repeats on the androgen receptor gene which makes people more sensitive to testosterone. Androgen levels and sensitivity might help explain the fact that more than 90% of serial killers are male and that they are disproportionately black.

I doubt that many Inductivist readers want to know how to predict which men have big penises, but what the hell. In a study of 3,762 college males, a list of characteristics reflecting the level of one's masculinity was found to be positively correlated with self-reported criminality. All these factors were also intercorrelated. Here are the correlations with penis length:

Correlations

Lower body strength      .386
Upper body strength      .378
Amount of body hair      .312
Strength of sex drive     .248
Physical strength           .248 
Masculine mannerisms   .231
Masculine body build      .222
Low-deep voice             .148 

So forget the stuff about big hands or big feet: Look for the strong hairy dude with the deep voice. But don't forget he might be a criminal, too.

In a new study of 280 people, researchers found that a measure of feminized brain structure (i.e., 2D:4D digit ratio) was associated with less distress at the hypothetical scenario of sexual as opposed to emotional infidelity by an intimate partner. The relationship was observed for men and women together, but not for each group individually. This relationship for the combined groups disappeared when gender was controlled. This supports the conclusion that males's higher level of prenatal testosterone masculinizes their brains making them more focused than females on sexual infidelity.  Men are thought to be more sensitive than women to cues of sexual infidelity to prevent cuckoldry, while females are more sensitive than males to cues of emotional infidelity to prevent loss of parental investment.

The evidence keeps pouring out that gender is not a social construction (as if any reasonable person would think it is).

This study of Senegalese men from the December 2010 issue of Personality and Individual Differences shows that extraversion predicts mating effort and that extraverted men have higher levels of testosterone. By contrast, other Big 5 personality traits (i.e., neuroticism, openness and agreeableness) are unrelated to mating effort and testosterone levels. It looks like the dominance component of extraversion--linked in other studies to testosterone--is crucial.

Only a small percent of engineers are women.  Feminists claim that misogynist forces keep females out of the profession. Once again, the data show that biology is implicated. A new study by John Manning and colleagues shows that levels of testosterone, both during prenatal development as well as adulthood, predict having a job in a male-dominated field.  High testosterone individuals, male or female, are more likely to work as engineers, IT dudes, or skilled laborers, while low T people are more likely to work in education or as homemakers. At least part of workplace sex segregation is due to gender differences in this very important hormone.

Note to feminists: get over it.     

Studies show that blacks don't have markedly higher levels of testosterone than whites, but recent research suggests that they might be more sensitive to it.

A difference has been found in androgen receptors which vary in the their number of glutamines (an amino acid). The length of the glutamine chain is important in determining a person's sensitivity to testosterone. The shorter the chain, the more sensitive. 

Black men have shorter glutamine chains than white men, and this difference might help explain the higher rate of prostate cancer among blacks.

Having short chains is also linked to ADHD, conduct disorder, and oppositional defiant disorder--disorders which are more prevalent among blacks (in symptoms, but not diagnosis).

These disorders strongly predict a lifecourse-persistent pattern of criminality, a pattern also seen more frequently in blacks compared to whites.