Why the Victorian era saw a surge in female births and war begets boys

There is empirical evidence that heavy sexual activity increases the chances that conception will occur before the most fertile time of the female cycle, as the woman may be pregnant by then. And the data also suggest that, possibly for hormonal reasons, such conceptions are slightly more likely to be boys. “It doesn’t take much imagination to suppose that the ends of wars, with servicemen home on leave or returning home, are associated with fairly intense sex – more babies were born in the UK in 1919 than any other year in history. Put all these together and you get the conclusion – frantic fornication breeds boys.”

[…]

Which brings us back to the mysterious surge of female births in the late Victorian period. Could it be that, in the same vein in which heavy sexual activity increases the sex ratio, a  trend towards sexual inactivity lowers it? “Victorian morality” distinguished itself through a set of values that espoused sexual restraint, with an increased condemnation of masturbation and sexual activity in general, repressing any form of sexuality other than penetrative intercourse. And indeed, statistics reflect a steady decline of sexual activity throughout the Victorian period, reaching its lowest point in the year 1898. But as there was less sex going on, conception tended to occur around the most fertile time of the months, bestowing a (relative) excess of baby girls on the Victorians.

{ Rolf Degen | Continue reading }

Hypothesis 1

Up to circa two decades age, it was generally supposed – but without hard supporting evidence – that pregnant women exposed to adverse environmental circumstances were at increased risk of foetal loss, and that male foetuses were at greater risk than female foetuses; and that therefore the liveborn infants produced by stressed women contained a higher proportion of daughters. That hard evidence has now been accumulated in a series of papers by Catalano and colleagues, and others.

Using time-series analysis, it has been shown that the Sex ratios at birth (SRB) briefly declined, slightly but significantly, some three to five months after many catastrophic and other adverse events e.g. the terrorist attacks on September 11th, 2001; the Troubles in Northern Ireland (1969–1998), the Breivik shooting in 2011 in Norway, the Sandy Hook shooting in 2012 in Connecticut; the assassination of President Kennedy [though the effect in this case was more marked in non-White than White births]. […]

Thus there is overwhelming evidence that sex ratios at birth are partially controlled by maternal stress-induced selective culling of frail males in utero, resulting in a conception cohort with a low sex ratio at birth. It has also been postulated that the ratio may be skewed because of fertilization of non-optimally matured oocytes under these circumstances. Moreover, it has also been hypothesized that higher coital rates will lead to ejaculation of newly formed spermatozoa cells, possibly leading to a preponderance of Y-sperm since it is also hypothesized that X-sperm age faster and are eliminated earlier.

However, it will be appreciated that selective culling of frail males during pregnancy cannot explain some of the established variations of SRB. First, it cannot explain why some reported sex ratios are higher than prevailing norms. Second, it cannot explain why these norms almost always exceed 0.5 (equal numbers of males and females).

Hypothesis 2

It has been hypothesized that human sex ratios at birth are partially controlled by the parental hormone levels of both parents around the time of conception. Ex hypothesi, high levels of testosterone (in either parent) and/or of oestrogen (in the mother), are associated with subsequent male births. And high levels of gonadotrophins (in either parent) are associated with subsequent female births. Most of this evidence is observational and correlational, and is in accordance with the hypothesis of Trivers & Willard.

{ Early Human Development | Continue reading }

lithograph { Ellsworth Kelly, Small Blue Curve, 2013 }

Sperm competition theory can be used to generate the hypothesis that men alter the quality of their ejaculates as a function of sperm competition risk.

We investigated whether men produce a higher-quality ejaculate when primed with cues to sperm competition (i.e., imagined partner infidelity), relative to a control prime. Men (n = 45) submitted two masturbatory ejaculates—one ejaculate sample for each condition (i.e., sperm competition and control conditions). Ejaculates were assessed on 17 clinical parameters. The results did not support the hypothesis: Men did not produce higher-quality ejaculates in the sperm competition condition relative to the control condition.

{ Evolutionary Psychology | Continue reading }

C-print { Trevor Paglen, PAN (Unknown, USA-207), 2010 }

Energetic vampirism is the process whereby one person, through manipulation, essentially steals some life energy from another. […]

Vampirism is all around you.  In fact, most of us have done it a little, at least.  […]

According to Roy Masters and some other authorities on this subject, women who are not well enough developed spiritually vampirize others more than men.  This may occur because such women, whom Roy Masters calls “females”, have their energy centers reversed, and they tend to absorb energy rather than radiate energy.  Also, they may steal some energy from others, particularly men, in an effort to correct their energy centers. […]

We find that most successful vampires are fast oxidizers on hair tests. This is a higher amperage state, electrically speaking, and this may be necessary to extract energy from another person. It could also just be a result of the vampirism, but it is an interesting observation.

{ Dr. Lawrence Wilson | Continue reading }

When making trust decisions in economic games, people have some accuracy in detecting trustworthiness from the facial features of unknown partners. […] We observed that trustworthiness detection remained better than chance for exposure times as short as 100 ms, although it disappeared with an exposure time of 33 ms.

{ Experimental Psychology | Continue reading }

photo { Miles Alridge }

Eye movements of 105 heterosexual undergraduate students (36 males) were monitored while viewing photographs of men and women identified as a potential mate or a potential friend. Results showed that people looked at the head and chest more when assessing potential mates and looked at the legs and feet more when assessing potential friends.

{ Archives of Sexual Behavior | Continue reading }

photo { Michelle Pfeiffer photographed by Jim Britt, 1979 }

Whereas women of all ages prefer slightly older sexual partners, men—regardless of their age—have a preference for women in their 20s. Earlier research has suggested that this difference between the sexes’ age preferences is resolved according to women’s preferences. This research has not, however, sufficiently considered that the age range of considered partners might change over the life span.

Here we investigated the age limits (youngest and oldest) of considered and actual sex partners in a population-based sample of 2,655 adults (aged 18-50 years). Over the investigated age span, women reported a narrower age range than men and women tended to prefer slightly older men. We also show that men’s age range widens as they get older: While they continue to consider sex with young women, men also consider sex with women of their own age or older.

Contrary to earlier suggestions, men’s sexual activity thus reflects also their own age range, although their potential interest in younger women is not likely converted into sexual activity. Homosexual men are more likely than heterosexual men to convert a preference for young individuals into actual sexual behavior, supporting female-choice theory.

{ Evolutionary Psychology | PDF }

related { Longest ever personality study finds no correlation between measures taken at age 14 and age 77 }

photo { Joan Crawford photographed by George Hurrell, 1932 }

As men are generally more short-term oriented in their sexuality than women, and given that cigarette and alcohol use are still considered masculine behaviors, we explored if female smoking and drinking can function as a short-term mating strategy. […]

The experiment showed that young men perceive women who use cigarettes and alcohol as being more sexually unrestricted. Furthermore, tobacco and (especially) alcohol use brought some short-term attractiveness benefits to women. In short-term mating contexts, drinking enhanced women’s attractiveness, whereas occasional smoking was found equally desirable as not smoking. However, in long-term mating contexts, frequent drinking and all smoking behavior harmed women’s desirability.

{ Evolutionary Psychology | Continue reading }

art { Edvard Munch, Girls on the Bridge, 1902 }

People are often the most aggressive against the people to whom they are closest—intimate partners. Intimate partner violence might be partly a result of poor self-control. Self-control of aggressive impulses requires energy, and much of this energy is provided by glucose derived from the food we eat. We measured glucose levels in 107 married couples over 21 days. To measure aggressive impulses, participants stuck 0–51 pins into a voodoo doll that represented their spouse each night, depending how angry they were with their spouse. To measure aggression, participants blasted their spouse with loud noise through headphones. Participants who had lower glucose levels stuck more pins into the voodoo doll and blasted their spouse with louder and longer noise blasts.

{ PNAS | PDF }

art { Sergei Eisenstein. Untitled, c. 1931 }

We use data from the 2002–2013 National Surveys of Family Growth to examine change across U.S. cohorts born between 1966 and 1995 in whether individuals have had sex with same-sex partners only, or with both men and women, and in whether they have a bisexual or gay identity. Adjusted for age, race/ethnicity, immigrant status, and mother’s education, we find increases across cohorts in the proportion of women who report a bisexual identity, who report ever having had sex with both sexes, or who report having had sex with women only. By contrast, we find no cohort trend for men; roughly 5 percent of men in every cohort have ever had sex with a man, and the proportion claiming a gay or bisexual attraction changed little. We speculate that this gender difference is rooted in a broader pattern of asymmetry in gender change in which departures from traditional gender norms are more acceptable for women than men.

{ Sociological Science | PDF }

photo { Inez Van Lamsweerde and Vinoodh Matadin }

Marriage is a risky undertaking that people enter with incomplete information about their partner and their future life circumstances. A large literature has shown how new information gained from unforeseen but long-lasting or permanent changes in life circumstances may trigger a divorce.

We extend this literature by considering how information gained from a temporary change in life circumstances - in our case, a couple having a child with infantile colic - may affect divorce behavior. Although persistent life changes are known to induce divorce, we argue that a temporary stressful situation allows couples more quickly to discern the quality of their relationship, in some cases leading them to divorce sooner than they otherwise would have.

{ Demography | Continue reading }

Recently, experimental psychologists at Oxford University explored the function of kissing in romantic relationships.

Surprise! It’s complicated.

After conducting an online survey with 308 men and 594 women, mostly from North America and Europe, who ranged in age from 18 to 63, the researchers have concluded that kissing may help people assess potential mates and then maintain those relationships.

“The repurposing of the behavior is very efficient,” said Rafael Wlodarski, a doctoral candidate and lead author of the study, published in Archives of Sexual Behavior.

But another hypothesis about kissing — that its function is to elevate sexual arousal and ready a couple for coitus — didn’t hold up. While that might be an outcome, researchers did not find sexual arousal to be the primary driver for kissing. […]

The participants generally rated kissing in casual relationships as most important before sex, less important during sex, even less important after sex and least important “at other times.” (To clarify: researchers defined kissing as “on the lips or open-mouth (French).”)

{ NY Times | Continue reading }

Revisiting Depression Contagion […] A Speed-Dating Study.

After four minutes of interaction with partners with high levels of depressive symptoms, participants did not experience increased negative affect; instead, they experienced reduced positive affect, which led to the rejection of these partners.

{ Clinical Psychological Science | Continue reading }

{ Apple consumption is related to better sexual quality of life in young women | PDF }

photo { Carla van de Puttelaar }

Many laboratory experiments show that people are often altruistic or care for fairness. We present data that reveal a darker side of human nature. We introduce the joy-of-destruction game. Two players each receive an endowment and simultaneously decide on how much of the other player’s endowment to destroy. Subjects play this game repeatedly. In one treatment, subjects can hide their destruction behind random destruction. In this treatment, money is destroyed in almost 40% of all decisions. We attribute this behavior to a visceral pleasure of being nasty. Under full information destruction is also observed, but rare. In this treatment, acts of destruction are followed by immediate retaliation.

{ Faculty of Economics and Management Magdeburg | PDF }

We found that women experience more jealousy toward women with cosmetics, and view these women as more attractive to men and more promiscuous.

{ Perception | Continue reading }

photo { Bon Jane }

Age and gender are two important factors that play crucial roles in the way organisms allocate their social effort. In this study, we analyse a large mobile phone dataset to explore the way life history influences human sociality and the way social networks are structured. Our results indicate that these aspects of human behaviour are strongly related to age and gender such that younger individuals have more contacts and, among them, males more than females. However, the rate of decrease in the number of contacts with age differs between males and females, such that there is a reversal in the number of contacts around the late 30s. […]

The maximum number of connections for both males and females occurs at the age of around 25. During this early phase, males appear to be more connected than females. After this, the number of alters decreases steadily for both genders, although the decrease is faster for males than for females. The different rates of decrease result in a crossover around the age of 39 such that after 39 females become more connected than males.

{ Royal Society Open Science | Continue reading }

To fall in love feels like such a personal and spontaneous process, it is strange — and a bit insulting — to suggest that we’re only copying what the novels and the movies tell us to do. However, the differences in how people have loved throughout history suggest that our style of loving is to a significant extent determined by what the prevailing environment dictates. In certain eras, we’ll swoon at the sight of the beloved’s ankle; in others, we’ll coldly put romanticism aside for the sake of dynastic or practical concerns. We learn how to love by copying a range of more or less subtle cues emitted by our culture. Or, as that brilliant observer of human foibles, François de La Rochefoucauld, wickedly put it: “There are some people who would never have fallen in love if they had not heard there was such a thing.”

Crucially, over the centuries, the most important factor to have shaped how we love is art. It is through novels, poems, songs and, latterly, films that we have acquired our ideas about what aspects of our feelings we should value and where our emotional emphases should fall.

This is unfortunate. […]

We may break up with our partners or feel romantically cursed because we have been systematically exposed to the wrong sorts of love stories.

{ FT | Continue reading }

In two studies, the authors examined the projection of romantic and sexual desire in opposite-sex friendships. In both studies, perceivers who strongly desired their friends projected this desire onto their friends, believing that their desire was more reciprocated than was actually the case.

{ Personality and Social Psychology Bulletin | Continue reading }

Most of us think that friendship is a two-way street — but that’s true only half the time, according to research from Tel Aviv University and the Massachusetts Institute of Technology.

Their new joint study says only half of your friends would consider you their own friend. People have a very poor perception of friendship ties, and this limits their ability to influence their “friends,” according to the research, published in PLoS One on March 22, 2016.

If researchers can understand this limitation, companies and social groups that depend on social influence for collective action, information dissemination and product promotion could improve their strategies and interventions.

“It turns out that we’re very bad at judging who our friends are,” says Dr. Erez Shmueli, who conducted the study with Dr. Laura Radaelli, both of TAU’s Department of Industrial Engineering, in collaboration with Prof. Alex Pentland and Abdullah Almatouq of MIT. “And our difficulty determining the reciprocity of friendship significantly limits our ability to engage in cooperative arrangements.”

{ Tel Aviv University | Continue reading }

oil on canvas { Kei Imazu, Berlin 1943-1945, 2014 }

The tendency of people to forge friendships with people of a similar appearance has been noted since the time of Plato. But now there is research suggesting that, to a striking degree, we tend to pick friends who are genetically similar to us in ways that go beyond superficial features.

For example, you and your friends are likely to share certain genes associated with the sense of smell.

Our friends are as similar to us genetically as you’d expect fourth cousins to be, according to the study published Monday in the Proceedings of the National Academy of Sciences. This means that the number of genetic markers shared by two friends is akin to what would be expected if they had the same great-great-great-grandparents. […]

The resemblance is slight, just about 1 percent of the genetic markers, but that has huge implications for evolutionary theory.

{ Washington Post | Continue reading }

polyvinyl chloride, colored with oil, mixed technique and accessories { Duane Hanson, Children Playing Game, 1979 }

Stressful, busy days have been linked with increases in angry and withdrawn marital behavior. The process by which stressors in one domain, such as work, affect an individual’s behavior in another domain, such as the marital relationship, is known as spillover.

{ Journal of Family Psychology | Continue reading }