Genomic data from 1,785 ancient humans who lived in the last 45,000 y: Low rates of first cousin or closer unions & a marked decay in background parental relatedness co-occurring with or shortly after sedentary agriculture

Parental relatedness through time revealed by runs of homozygosity in ancient DNA. Harald Ringbauer, John Novembre & Matthias Steinrücken. Nature Communications volume 12, Article number: 5425. Sep 14 2021. https://www.nature.com/articles/s41467-021-25289-w

Abstract: Parental relatedness of present-day humans varies substantially across the globe, but little is known about the past. Here we analyze ancient DNA, leveraging that parental relatedness leaves genomic traces in the form of runs of homozygosity. We present an approach to identify such runs in low-coverage ancient DNA data aided by haplotype information from a modern phased reference panel. Simulation and experiments show that this method robustly detects runs of homozygosity longer than 4 centimorgan for ancient individuals with at least 0.3 × coverage. Analyzing genomic data from 1,785 ancient humans who lived in the last 45,000 years, we detect low rates of first cousin or closer unions across most ancient populations. Moreover, we find a marked decay in background parental relatedness co-occurring with or shortly after the advent of sedentary agriculture. We observe this signal, likely linked to increasing local population sizes, across several geographic transects worldwide.

Discussion

We developed a method for measuring ROH in low coverage ancient DNA. Our algorithm follows a long line of previous work utilizing HMMs to infer such segments10,40,41,42. A key methodological advantage here is to use hidden states that, within an ROH segment, copy from a reference panel of haplotypes to take advantage of haplotype information. This tool enabled us to screen aDNA data from 1785 individuals for ROH, an order of magnitude more ancient individuals than hitherto amenable for such analysis. We generated evidence for two key aspects of the human past: Identifying long ROH (>20 cM) provided insight into the past prevalence of close kin unions such as cousin matings, whereas short ROH (4–8 cM) revealed changing patterns of past background relatedness that reflect local population sizes.

We found that only 1 out of 1785 ancient individuals have long ROH typical for the offspring of first-degree relatives (e.g., brother–sister or parent–offspring). Historically, matings of first-degree relatives are only documented in royal families of ancient Egypt, Inca, and pre-contact Hawaii, where they were sporadic occurrences7. The only other example of an offspring of first-degree relatives found using aDNA to date is the recently reported case from an elite grave in Neolithic Ireland18. Our findings are in agreement that first-degree unions were generally rare in the human past.

Further, we find that only 54 out of 1785 ancient individuals (3.0%, CI: 2.3–3.9%) have long ROH typical for the offspring of first cousins (88%) and less commonly observed for second cousins (20%). Such long ROH can also arise as a consequence of small mating pools (e.g., 8% in randomly mating populations of size 500, which may explain the long ROH we observed on certain island populations). Therefore, the rate of long ROH is an upper bound for the rate of first-cousin unions. On the other hand, because of incomplete power, some long ROH may be missed in our empirical analysis; however, even if the method would fail to detect half of all ROH > 20 cM, well below the power that we observed in our simulations, we would still detect 60% of first cousins (see Table S5). We conclude that in our ancient sample substantially less than 10% of all parental unions occurred on the level of first cousins.

In two specific regions with high levels of long ROH in the present-day2, the dataset contained a sufficient number of ancient individuals to allow analyzing time transects. For both transects (the Levant and present-day Northwest Pakistan), we observe a substantial shift in the levels of long ROH. In contrast to the high abundance of long ROH typical of close kin unions in the present-day individuals, long ROH was uncommon in the ancient individuals, including up to the Middle Ages. Additional data from these regions and others with high levels of long ROH today, such as North Africa as well as Central, South, and West Asia2, will help resolve with more precision the origin and spread of these well-studied kinship-based mating systems43,44. Overall, our results show how an ROH-based method can be used to inform understanding of shifts in cultural marriage/mating practices.

As a second major finding, we observed that human background relatedness as measured by short ROH (4–8 cM) decreased markedly over time in many geographic transects, with a significant drop occurring during or shortly after the local “Neolithic Transition”, the transition from a lifestyle of hunting and gathering to one of agriculture and settlement45,46,47. Assuming that early farmers had no increased individual mobility compared to foragers, which would agree with observations in present-day forager populations48, the substantial decrease of short ROH evidences markedly increasing local population sizes. This finding adds support to the long-held hypothesis of local population sizes increasing following the Neolithic transition45,46,47. Previous analysis of ancient genomes of foragers and early farmers already identified several lines of genomic evidence for farmers having larger population sizes than earlier hunter–gatherers, such as decreasing genome-wide diversity49,50, decreasing prevalence of ROH11,12,13,14,18 and decreasing coalescent rates estimated from high-coverage genomes27. Our analysis adds a refined level of geographic and temporal resolution by analyzing an order of magnitude of more individuals (1785 ancient humans) and by organizing those individuals into several densely sampled time transects in different geographic regions.

For individuals from early Eurasian Steppe pastoralist groups, we observe an intermediate level of short ROH. These early cultures (e.g., the Yamnaya) have drawn much attention in archeological and ancient DNA studies to date, as archeological, linguistic, and genetic evidence suggest they played an important role in the origin of Indo-European languages and of several populations expansions32,51,52,53,54. The elevated rate of short ROH we observed provides evidence that many matings occurred within and among small, related groups. An alternative interpretation for the abundance of short ROH could be that burial sites (Kurgans) represent a biased sample of societal classes with more short ROH than the general populace51. However, as short ROH probes parental ancestry up to several dozen generations into the past, this signal would require reproductive isolation between societal strata maintained over many generations. Therefore, it is likely that at least part of the signal is due to Steppe populations having comparably low population densities or experienced recent bottlenecks.

Our analysis is limited by several caveats. Importantly, skeletal remains accessible by archeological means often do not constitute a random cross-section of past populations. While levels of background relatedness are expected to be similar within a mixing population, rates of close kin unions can vary substantially because of social structure; e.g., elite dynasties may practice close kin unions despite them being uncommon in the general population. Another limitation is the incomplete sampling of the current aDNA record and that for much of the world, we necessarily make inferences from small numbers and sparse sampling. Future work analyzing the rapidly growing ancient DNA record will help to resolve additional details of social and cultural factors operating at finer scales (e.g., leveraging more precise timings of shifts and more subtle shifts in ROH patterns). In particular, future studies focusing on specific localized questions will increasingly combine archeological and genetic evidence16, in ways that will empower the use of the genetic evidence about the past provided by the methodology presented here.

In addition to denser sampling, there are several ways how our analysis can be improved upon by future work. Here we focused our analysis on long ROH (>20 cM) and short ROH (4–8 cM). While this dichotomy helped us to disentangle more clearly recent and distant parental relatedness, we expect that future work refining the downstream analysis of ROH will be able to extract more subtle signatures by looking across all ROH scales. Furthermore, we note that our application focused on a set of SNPs widely used for human ancient DNA (1240K SNPs). For whole-genome sequencing data (available for a subset of the data analyzed here), using all genome-wide variants would likely lower the requirements for coverage below the current limit of 400,000 of the 1240K SNPs covered at least once (corresponding to ca. 0.3× whole-genome sequencing coverage). Another improvement would be using a reference panel that includes ancient haplotypes. Currently, no long-range phased ancient haplotypes are available, but future work will likely produce such data.

One alternative approach to identify ROH in low coverage ancient genomes could be to use imputation followed by screening for stretches of homozygous markers using standard ROH detection methods. This was recently done for ancient individuals with >10× coverage18. Since imputation of genomes was reported to work well to a coverage similar to the low coverage cutoff used here [55,56ca. 0.5×] and most imputation methods are based on haplotype-copying methods related to the approach utilized here [the Li and Stephens model22, we expect any such approach to perform similar to ours, after appropriate testing and calibration, as conducted for our method. We chose to develop a method utilizing several key advantages of pseudo-haploid data, which is more widely available and requires fewer assumptions about genotype quality, making subsequent analysis less prone to batch effects introduced by various isolation, sequencing, and genotyping protocols.

Identifying ROH can also be a starting point for other powerful applications: ROH consists of only a single haplotype (the main signal of our method), which is therefore perfectly phased, a prerequisite for powerful methods relying on haplotype copying57 or tree reconstruction26,58. Moreover, long ROH could be used to estimate contamination and error rates, an important task in ancient DNA studies20. ROH lacks heterozygotes, allowing one to identify heterozygous reads within ROH that must originate from contamination or genotyping error, similar to estimating contamination from the hemizygous X chromosomes in males59. Another promising future direction is the development of a method to identify long shared sequence blocks in ancient DNA not only within (ROH), but also between individuals, called identity-by-descent (IBD). Calling IBD between individuals would substantially increase power for measuring background relatedness since signals from every pair of individuals could be used. Moreover, a geographic IBD block signal is highly informative about patterns of recent migration35,60,61,62. Extending our method to similarly use haplotype information from a phased reference panel when detecting IBD could enable such analyses in low coverage ancients individuals.

Finally, the analysis of ROH has additional implications beyond human demography and kinship-based mating systems. In many plants and animal species, ROH is more prevalent (due to different mating systems, small population sizes, or domestication), and the study of ROH may be particularly interesting for understanding early plant and animal breeding, as actively controlled mating among domesticates would be expected to alter ROH63. For aDNA from extinct or endangered species, ROH can shed light on the extinction and inbreeding processes, as is observed for example in aDNA from high-coverage Neanderthal individuals17,64,65,66, or modern DNA from Isle Royal wolves67. Finally, as ROH exposes rare deleterious recessive alleles68, the temporal dynamics of ROH are relevant for understanding the evolutionary dynamics of deleterious variants and health outcomes67,69,70,71. We hope that the core ideas of our approach will inspire the analysis of low-coverage data from a wide range of natural populations.

Women with large breasts were rated as more attractive, fertile, reproductively successful, likely to befriend, & threatening (& less likely to be introduced to a current partner)

Garza, R., Pazhoohi, F., & Byrd-Craven, J. (2021). Women’s perceptions of breast size, ptosis, and intermammary distance: Does breast morphology play a role in women’s intrasexual competition? Evolutionary Behavioral Sciences, Sep 2021. https://doi.org/10.1037/ebs0000273

Abstract: Women’s breasts are considered attractive and sexually appealing, perhaps due to their residual reproductive value. However, most research has focused on their intersexual selective display. The current study investigated women’s perceptions of women’s breasts when primed with an intrasexual competition prime. Across two studies, women (N = 467) were randomly assigned to a partner threat condition or control. They were asked to rate women’s breasts that had been manipulated for their size, ptosis (i.e., sagginess), and intermammary distance (i.e., cleavage). Women with large breasts were rated as more attractive, fertile, reproductively successful, likely to befriend, threatening, and they were rated as less likely to be introduced to a current partner. More importantly, these ratings were influenced by the interaction between breast size, intermammary distance, and ptosis. The findings contribute to how women’s breasts may be perceived from an intrasexual competitive perspective.

Gender Differences & the 5 Facets of Conspiracy Theory: Women score higher in all of them (government malfeasance, malevolent global conspiracies, extraterrestrial cover-up, personal well-being, & information control)

Gender Differences and the Five Facets of Conspiracy Theory. Gary Popoli, Angel Longus. International Journal of Psychological Studies Archives Vol. 13, No. 3. Jul 2021. https://ccsenet.org/journal/index.php/ijps/article/view/0/45859

Abstract: Although research examining conspiracy theory beliefs has been examined, there is conflicting literature on the relationship between gender and conspiracy thinking. Before this study, little research has been conducted on the differences between males and females in each of the five facets of conspiracy theory. This study was designed to investigate differences in gender as they pertain to government malfeasance (GM), malevolent global conspiracies (MG), extraterrestrial cover-up (ET), personal well-being (PW), and control of information (CI). It was hypothesized that there are statistically significant differences between females and males when it comes to conspiracy theory beliefs for each of the five facets. Archival data from 2016 containing responses to the Generic Conspiracist Beliefs Scale was analyzed. Results supported the main hypothesis of this investigation that significant differences do, in fact, exist between females and males in all five facets of conspiracy theory: government malfeasance, malevolent global conspiracies, extraterrestrial cover-up, personal well-being, and control of information. In addition, this study revealed that females score higher than males in all facets. In general, a computed total conspiracy belief score demonstrated that females (M = 45.10, SD = 15.07) were significantly higher than males (M = 42.13, SD = 15.90). Nevertheless, some recent research has reported that women were significantly less likely than men to engage in ‘conspiratorial thinking’ and endorse a conspiracy about the COVID-19 pandemic of 2020. These findings may be suggesting a change in direction for gender differences and a need for further research. 

Having a child: You go through all the things you do when you fall in love. You find yourself infatuated. You want to tell everyone about your new love. You can’t wait to be with that person. And you feel like, no matter how many things are going wrong, someone loves you.

The kid option. Alice Dreger. 2009. https://alicedreger.com/child

I often say, honestly, if the woman I was before I had a child could see the woman I am now, there is no way she would have a kid. That woman was so intense about her work, so used to having her schedule at her control, so used to napping, eating, watching a movie, and having sex whenever she felt like it, she would be horrified to see herself as me.

Me, I get the start and the end of each work day lopped off by the school bus. I get sick all the time from the latest germ to hit our elementary school. (And living in an international academic community, we get a lot of well-traveled germs.) I spend my weekends waiting for my son to finish eating his bagel so we can move on with our day. And then we move on to trainspotting out in the cold for several hours. I even (gasp) go to soccer practice—though I do bring something interesting to read, and I drive a little Honda Fit, or the Saturn SL from grad school (a ’95, with a glove compartment held closed by string), not a minivan. (I am way too sexy for a minivan.)

For intellectuals, having a child can be especially challenging. This is particularly true of the time when your children are babies. Babies don’t hold very good conversations. They don’t make good arguments or cite their sources. And children make you dumber, at least in the short term, because not only is it hard to keep up in your discipline when you lose so much time to family needs, it’s also hard to think straight when you are perpetually sleep-deprived.

When I was breast-feeding, I was sure that the ancients were right about the humours, especially about brains and breast-milk both being made of the same stuff (phlegm). Because the more I fed my son, the dumber I got, and the smarter he got. It really seemed like my brain was draining out my nipples into him.

One colleague of mine was considering having a child, and she asked me what it is like. I decided simply to explain the time loss, for starters. I asked her to pull up her calendar so I could show her. She did. “Now,” I said, “cross off one-third of what you currently have scheduled.” Then I suggested she imagine three days a week doing her remaining work while being very low on sleep. After that, I randomly chose three weeks from her calendar, and told her those would be weeks in which her imaginary child was too sick for her to really get any work done.

And then I explained that, from the moment she had a wanted child, she would be worrying about its mortality, no matter how rational she was, no matter how healthy and sensible her child was.

Obesity and compensatory consumption: Evidence from jewelry shopping

Obesity and compensatory consumption: Evidence from jewelry shopping. Didem Kurt. Psychology & Marketing, September 16 2021. https://doi.org/10.1002/mar.21578

Abstract: This article examines the link between obesity and compensatory consumption in the context of jewelry shopping. Study 1 finds that participants with higher body mass indices are willing to pay more for a jewelry item. Study 2 generalizes this finding by documenting that jewelry store sales are higher in places with greater obesity rates. Using Google Trends data, Study 3 shows that the search interest for jewelry stores increases with the obesity rate and that this relationship is mediated by people's dissatisfaction with their current weight as revealed by their search activity. Finally, supporting the self-discrepancy account, Study 4 shows that the use of self-related and discrepancy words together in jewelry-related tweets is more pronounced in places with greater obesity rates. These findings collectively help enhance the field's understanding of the consumption behavior of people who are part of a large stigmatized group.

Rolf Degen summarizing... People believe that they understand complicated things better when they are sure that other people understand them

From 2020... How others drive our sense of understanding of policies. Nathaniel Rabb, John J Han, Steven A Sloman. Behavioural Public Policy, Volume 5 Special Issue 4, September 4 2020. https://www.cambridge.org/core/journals/behavioural-public-policy/article/abs/how-others-drive-our-sense-of-understanding-of-policies/3AC030D64B59647AE1F0DA2321E67B0A

Abstract: Five experiments are reported to compare models of attitude formation about hot-button policy issues like climate change. In broad strokes, the deficit model states that incorrect opinions are a result of a lack of information, while the cultural cognition model states that opinions are formed to maximize congruence with the group that one affiliates with. The community of knowledge hypothesis takes an integrative position. It states that opinions are based on perceived knowledge, but that perceptions are partly determined by the knowledge that sits in the heads of others in the community. We use the fact that people's sense of understanding is affected by knowledge of others’ understanding to arbitrate among these views in the domain of public policy. In all experiments (N = 1767), we find that the contagious sense of understanding is nonpartisan and robust to experimental manipulations intended to eliminate it. While ideology clearly affects people's attitudes, sense of understanding does as well, but level of actual knowledge does not. And the extent to which people overestimate their own knowledge partly determines the extremity of their position. The pattern of results is most consistent with the community of knowledge hypothesis. Implications for climate policy are considered.

Both genders show increase in consumption behaviors & substance use, but women revealed decrease in consumption of wine during pandemic; men showed more TV hours per day; women stand out in the use of mobile phone per day

Health risk behaviors before and during COVID-19 and gender differences. Cátia Branquinho, Teresa Paiva, Fábio Guedes, Tânia Gaspar, Gina Tomé, Margarida Gaspar de Matos. Journal of Community Psychology, September 13 2021. https://doi.org/10.1002/jcop.22705

Abstract: Changes in routines and habits, fear of contamination from the coronavirus disease 2019 (COVID-19) virus, and economic crisis have resulted in significant impacts upon individuals' lives, health, and risk behaviors. The present study aims to analyze health risk behaviors and gender differences of Portuguese adults before and during the COVID-19 pandemic. A quantitative analysis using SPSS v. 26 software presents the evaluation of 5746 responses (M = 48.5 years, SD = 14.3), of which 67.7% were female. t Test was used to study differences in means before and during the pandemic and analysis of variance test to analyze gender differences. In the comparative study before and during the pandemic showed a decrease in the number of meals per day, physical activity and perception of sleep quality; an increase in tobacco use, beer consumption, and media use (TV, mobile phone, social networks, and online games). Gender differences study demonstrated that the number of meals per day suffered a decrease from pre to pandemic in women, while increasing in men, becoming prominent in the second moment under study. Both genders had an increase in consumption behaviors and substance use, but women revealed a decrease in the consumption of wine during the pandemic, while men revealed more consumption behaviors in the variables under study. The use of media also changed, with men showing a higher level in TV hours per day, social networks and online games before the pandemic and in TV hours per day and games/online during the pandemic. Women stand out in the use of mobile phone per day during the pandemic. Daily physical activity decreased during the pandemic, as did sleep quality. Males revealed a higher practice of physical activity at both periods, as well as sleep quality. Based on the results presented, it is expected that considerations and actions in the scope of public health policies and health prevention and promotion, will be rethought and adapted to the specificities of each gender.

4 CONCLUSIONS AND DISCUSSION

The present study was developed to compare gender differences in health risk behaviors before and during the pandemic scenario.

In general, health behaviors such as the number of meals per day, physical activity practice, declined during the pandemic, as did the perception of sleep quality; while tobacco, beer consumption, and media use (TV, mobile phone, social networks, and online games) increased. In the same sample, shorter sleep duration, poorer nutrition, decline in physical activity, greater media use, and more negative attitudes and behaviors during the pandemic were found to be positively associated with poor sleep and awakening quality (Paiva et al., 2021). Also in a literature review conducted by Stockwell et al. (2021), a decrease in physical activity and increase in sedentary behaviors is highlighted.

Gender differences are clear: Women have, both prior and during the pandemic, a higher number of meals per day when compared with men, but this number decreased in women and increased in men during COVID-19. Although negative impacts on diet are highlighted (Martínez-de-Quel et al., 2021; Ramalho et al., 2021; Rodgers et al., 2020), Janssen et al. (2021) reveal different changes in lifestyles and diet during the pandemic. The authors report that the number of meals per day can increase or decrease depending on the person, and be related to restrictions, frequency of shopping, perceived risk of disease, decreased financial capacity, and sociodemographic factors.

Smoking behavior (number of cigarettes per day), intensified during the pandemic, being higher in men in the prepandemic. The consumption of beer per day also showed an increase during the pandemic in both genders, as well as the number of glasses of wine per day in men (decreasing in women). Satre et al. (2020) and Weerakoon et al. (2021) reveal similar results.

Media use increased from prepandemic to pandemic in both genders, especially in males in the prepandemic (hours TV per day, social networks and online games) and postpandemic (hours TV per day and games/online). Women use more the mobile phone per day during the pandemic. A study also developed in Europe and during the current scenario, presents that males are more prone to gambling, while women tend to spend more time on social networks (Lemenager et al., 2020).

The number of hours of daily physical activity decreased during the pandemic scenario (Park et al., 2021) as did the quality of sleep. In both a higher mean in males stands out. Despite the worse perception of prepandemic sleep quality, the literature has reported that the worries and uncertainties of this period have a greater impact on female sleep (Liu et al., 2020; Pinto et al., 2020; Sinha et al., 2020; Voitsidis et al., 2020). As women often report their sleep quality as less positive, and it is not known whether this is a reality or a perception, it is also true that they report and live with a lower perception of well-being (de Matos, 2019).

4.1 Strengths and limitations

As regards limitations, and due to the constraints associated with the pandemic scenario, the present study was conducted exclusively online to reach a larger number of participants and decrease the exposure of the team and participants to the SARS-CoV-2 virus. Although efforts have been made to have an equitable gender distribution, this was not achieved, but other studies developed in the country show this common reality.

In contrast to the identified limitations, the present study reveals several strengths. The first, the total number of responses obtained, which allows us to increase the validity of its conclusions. The second, the diversity of the sample. Lastly, to our knowledge, this is the first study conducted in the country that includes such a complete diversity of themes in studying the impacts of the COVID-19 pandemic, as well as the involvement of a multidisciplinary team in its design and analysis.

Experiences during the epidemic and reproductive motivation yielded the results which are incongruent with life history theory—adverse experiences during the state of emergency were negatively related to the reproductive motivation

Mededovic, Janko (2021). Reproductive motivation in the context of the COVID-19 epidemic: Is there evidence for accelerated life history dynamics? Evolutionary Behavioral Sciences, Sep 2021. https://doi.org/10.1037/ebs0000270

Abstract: One of the key life history assumptions is that mortality rates are positively associated with fast life history dynamics. Since the COVID-19 pandemic has elevated mortality rates throughout the world, we tested this assumption using reproductive motivation (desired number of children and desired age of first reproduction) as a key output measure using a repeated cross-sectional design. We assessed reproductive motivation in Serbian young adults before the pandemic started (N = 362), during the pandemic-caused state of emergency (the peak of the epidemic's first wave: N = 389) and after the state of emergency (i.e., after the first wave: N = 430). Furthermore, in the third time-point we measured experiences during the state of emergency and additional measures of reproductive motivation (reasons for and against parenthood). Subsamples were matched by sex, education, and the sampling procedure. We found the between-group differences which are congruent with life history theory: the desired age of first reproduction was lowest after the state of emergency compared to the 2 previous time-points. However, there were no differences in the desired number of children. Furthermore, the analysis of the links between experiences during the epidemic and reproductive motivation yielded the results which are incongruent with life history theory—adverse experiences during the state of emergency were negatively related to the reproductive motivation. Since the findings were only partially in accordance with life history theory, we discuss possible reasons which may explain the heterogeneity of results.

When dating, men without children (or those who wanted children) rated age as more important & selected a preferred age range that incorporated younger women; women’s age preferences showed little association with having/wanting children

Kramer, R. S. S., & Jones, A. L. (2021). Wanting or having children predicts age preferences in online dating. Evolutionary Behavioral Sciences, Sep 2021. https://doi.org/10.1037/ebs0000274

Abstract: When dating, women seek men slightly older than themselves while men typically prefer younger women. Such patterns reflect differences in parental investment and age-related fertility, which are both concerned with maximizing reproductive outcomes. Using large samples of online daters, we considered whether having or wanting children was associated with the perceived importance of age as a matching criterion when dating (Study 1; N = 119,361), as well as how these two factors related to the preferred age of a match (Study 2; N = 486,382). Men without children (or those who wanted children) rated age as more important than those with children (or those who did not want children), and also selected a preferred age range that incorporated younger women. In contrast, women’s preferences showed little association with having or wanting children. Taken together, these findings demonstrate that age preferences may depend on factors in addition to those previously investigated, and that the relationships with the number of current children and the desire to have children are consistent with evolutionary predictions.

Rolf Degen summarizes... The male attraction to nubile traits in females may reflect an evolved strategy to safeguard a successful first pregnancy

Does Nubility Indicate More Than High Reproductive Value? Nubile Primiparas’ Pregnancy Outcomes in Evolutionary Perspective. William D. Lassek, Steven J. C. Gaulin. Evolutionary Psychology, September 15, 2021. https://doi.org/10.1177/14747049211039506

Abstract: The idea that human males are most strongly attracted to traits that peak in women in the nubile age group raises the question of how well women in that age group contend with the potential hazards of a first pregnancy. Using data for 1.7 million first births from 1990 U.S. natality and mortality records, we compared outcomes for women with first births (primiparas) aged 16–20 years (when first births typically occur in forager and subsistence groups) with those aged 21–25 years. The younger primiparas had a much lower risk of potentially life-threatening complications of labor and delivery and, when evolutionarily novel risk factors were controlled, fetuses which were significantly more likely to survive despite lower birth weights. Thus, nubile primiparas were more likely to have a successful reproductive outcome defined in an evolutionarily relevant way (an infant of normal birth weight and gestation, surviving to one year, and delivered without a medically necessary cesarean delivery). This suggests that prior to the widespread availability of surgical deliveries, men who mated with women in the nubile age group would have reaped the benefit of having a reproductive partner more likely to have a successful first pregnancy.

Keywords: first pregnancy, female attractiveness, nubility, primiparas, pregnancy complications, mating preferences, reproductive timing

Discussion

Nubile Mothers Have Better First-Pregnancy Outcomes

As noted in the Introduction section, recent evidence suggests that heterosexual men are attracted to attributes characteristic of physically and sexually mature women between 15 and 19 years of age, closely corresponding to the 16–20 years age group when first births typically occur in natural-fertility populations (Kramer & Lancaster, 2010; Lassek & Gaulin, 2019; Symons, 1979; Walker, 2019). Relevant to that preference, the current study is consistent with others in a variety of populations indicating that, when surgical deliveries are not available, this is also the age group with the best first-pregnancy outcomes.

In our large sample, primiparas were at much higher risk than multiparas for CPD, critical C-sections, and other complications of labor and delivery that increase the risk of maternal mortality, but primiparas aged 16–20 years had substantially lower risks than those 21–25, experiencing a 30% lower risk of any C-section, a 27% lower risk of a critical C-section, and much lower risks for serious complications of labor and delivery, including CPD, abnormal labor, and fetal distress (Table 4). These findings are consistent with many other studies that show a reduced risk of C-sections in primiparas aged 16–19 years versus older mothers, including studies in many non-Western countries (Conde-Agudelo et al., 2000; Ganchimeg et al., 2013, 2014).

The reduced risk of complications of labor and delivery in primiparas aged 16–20 years is of special importance in a species where the conjunction of bipedalism and very large brains has made vaginal births difficult. Only very recently have these conflicting selection pressures been relieved by the surgical innovation of C-section, an intervention still not available everywhere. Where and when such surgical births are unavailable, it is essential for a first-time mother to produce a child who can successfully pass through her birth canal so that mother and child can survive and continue to augment her fitness.

Our study does not present data on maternal survival, but the lower risk of labor-and-delivery complications for mothers in the nubile age group would likely decrease the risk of maternal deaths in childbirth. In a recent study of maternal mortality in 144 countries (Nove et al., 2014), in a third of countries mortality was lower for mothers aged 15–19 years than those aged 20–24 years; and this included most of the countries with the highest maternal mortality rates.

There may also be survival benefits for the infants of younger mothers. Our study is consistent with others showing comparable survival in the newborns of mothers aged 16–19 years with those aged 20–24 years when social and behavioral risk factors are controlled (Bradford & Giles, 1989; Conde-Agudelo et al., 2000; Gallais et al., 1996; Ganchimeg et al., 2013, 2014; Geist et al., 2006; Geronimus & Korenman, 1992; Phipps-Yonas, 1980; Scholl et al., 1984; Smith & Pell, 2001).

When evolutionarily novel risk factors were controlled, the fetuses and newborns of primiparas aged 16–20 years did as well or better as those of primiparas aged 21–25 years and were more likely to survive to 1 year. Although the 16–20-year old primiparas had significantly more preterm births with normal birth weights (which have good survival rates), their risks for preterm births with low birth weight, overall low birth weight, and neonatal mortality were significantly lower.

These results are also consistent with the finding that in 18th–19th century Germany, when infant and child mortality rates were much higher, the children of mothers aged 15–19 years were more likely to survive to reproductive age than those of older mothers (Knodel & Hermalin, 1984). Such high infant and child mortality rates were also likely in the environment of evolutionary adaptedness (EEA; Tooby and Cosmides, 1992), with almost half of children dying before reaching puberty (Volk & Atkinson, 2013).

Because until quite recently most women gave birth at home with assistance from their relatives, another potential advantage for younger mothers is their greater likelihood of having mothers, grandmothers, and aunts to help with pregnancy and childbirth, especially in groups with shorter life expectancies, where senior kin may have been less common.

Thus, it is not surprising that women's evolved life history seems to schedule first reproduction soon after the attainment of adult size and sexual maturity, as revealed by the demography of subsistence populations. Primiparas aged 16–20 years were likely to have a better newborn outcome than older primiparas and much better labor-and-delivery outcomes, which combine to yield a substantially greater chance for a successful pregnancy outcome (Figure 3).

Evolution of Male Preferences for Nubility

Because first pregnancies are most likely to be successful in women in the 16–20 years age group, we would expect positive selection on male preferences that targeted any reliable phenotypic correlates of this female life stage. Thus, this study, together with others showing the advantages of first births in this age range, when first births typically occur in subsistence populations, supports nubility as a key criterion of female attractiveness.

Men’s preferences for certain female traits associated with nubility—such as low WHRs, low BMIs (in well-nourished populations), and low waist–stature ratios (which may be the best predictor of attractiveness)—have recently been explained in terms of their correlation with female reproductive value (Andrews et al., 2017; Butovskaya et al., 2017; Fessler et al., 2005; Lassek & Gaulin, 2019; Marlowe, 1998; Prokop et al., 2020; Röder et al., 2013; Sugiyama, 2005; Symons, 1979, 1995), an inherently future-oriented parameter (Fisher, 1930). Complementing those findings, this study suggests an additional, more immediate, benefit to preferences for nubility.

If, as our findings suggest, nubile women have had more successful first-pregnancy outcomes than older women (thus enhancing their own reproductive success), men with preferences for traits correlated with nubility would have experienced a parallel fitness advantage. Conscious awareness would not have been required for this preference to evolve (Gaulin & McBurney, 2001; Kenrick, 1995); genetic variance in the preference and a reliable correlation between the preferred trait (e.g., any sign of nubility) and a positive fitness outcome (e.g., a successful first birth) would be sufficient.

The main cost to males who prefer nubile women is the lower frequency of ovulation in younger women (see Lassek and Gaulin, 2018a). However, this can be largely overcome by an increased frequency of coitus, which is usual for this age group (Weinstein et al., 1990). The fact that the typical age at first birth falls in the nubile period in traditional populations suggests that copulatory effort is normally sufficient to overcome the lower probability of conception with women in this age group.

Because of the lower fertility of nubile women, Symons (1979) suggested that males seeking short-term mating with minimal commitment might prefer older women who would have a greater chance of conceiving, as fertility is maximal in the late 20s. However, Symons (1995) changed his view because of studies in modern hunter-gatherers showing most potentially fertile women over 20 are either pregnant or nursing, with small windows of time when conception is possible. In this context, nubile women are likely to have a greater chance of conceiving despite their reduced frequency of ovulation.

Why do Nubile Primiparas Have Better Obstetric Outcomes?

Three factors help to explain the lower risk of critical surgical deliveries in the 16–20-year-old mothers: (a) Younger primiparas had smaller newborns than older primiparas, with more neonates weighing 2.5–3.4 kg, in the lower two-thirds of the normal range (2.5–3.9 kg), and fewer weighing 3.5 kg or more (Table 3). As shown in Figure 1, smaller neonates are less likely to have CPD or require a critical C-section. (b) For newborns of the same birth weight, nubile primiparas had a much lower risk of a critical C-section (Figure 1), and all but one of its associated complications, than those over 20. (c) The fetuses of younger primiparas were less likely to experience complications during labor and delivery, including fetal distress, cord prolapse, placenta previa, and abnormal position (Table 4). In total, younger mothers seem to have an enhanced ability to move their fetus through the birth canal and their fetuses also seem to be more tolerant of the stresses of labor and delivery.

Negative Consequences of Teen Pregnancy Today

It is important to stress that our analysis also documents the disadvantages of teen pregnancy in WEIRD (as defined by Henrich et al., 2010) populations, such as the United States in 1990, especially in younger teens. Where both surgical births and birth control are widely available and where teen pregnancy is usually associated with social and behavioral risk factors, teen pregnancies are very likely to have many negative long-term consequences for the mother and infant (Black et al., 2012). Pregnancies in teens younger than 16 years had much poorer infant outcomes and were more likely to have an operative delivery (forceps or vacuum extraction). Thus, efforts to prevent teen pregnancies are highly desirable and are not in any way contradicted by any of our conclusions concerning past selection on female life history.

Despite the disadvantages of teen pregnancy in contemporary WEIRD societies, we suggest that our findings are relevant to understanding human evolution, in particular women’s life history and men’s mating preferences. Given the obvious evolutionary importance of a successful vaginal delivery, early first pregnancies and a male preference for nubility were probably advantageous in the premodern era. They would have produced the best odds of a successful reproductive outcome—a benefit to mother, father, and infant.

Limitations

The use of data from a modern North American population to gauge probable reproductive outcomes in evolutionarily relevant populations is not ideal; but because of the extremely recent nature of shifts in human reproductive ecology, the relevant underlying biology may be largely unchanged. By controlling for evolutionarily novel risk factors which make “teen pregnancy” disadvantageous in contemporary populations, the results should have some validity for natural-fertility populations where first pregnancies in 16–20 year-olds are normative. Our findings of a much lower risk of critically necessary surgical births and a slightly lower risk of neonatal deaths for mothers in the 16–20 years age group (with controls for social and behavioral risk factors) are consistent with findings from a large variety of non-Western countries (Conde-Agudelo et al., 2000; Ganchimeg et al., 2013, 2014) and from 18th–19th century Germany (Knodel & Hermalin, 1984).

It might be argued that modern American obstetric practices are quite different from those in traditional societies where experienced midwives play a crucial role, but the uniformity of findings in the US and in three different samples of 23, 29, and 18 non-Western countries points to common underlying factors in reproductive biology and suggests that similar biological factors are likely to have been operating in the EEA.

Because all of the many available studies uniformly show a decrease in obstetric complications requiring a C-section in the 16–19 years age group, this is more likely to be species-typical. Limiting the analysis to C-sections associated with complications that would be likely to cause significant harm to the mother or fetus without surgical intervention may give some indication of the risk in natural-fertility populations without access to surgical deliveries.

Traditional populations are also likely to have much higher infant and child mortality: Infant mortality has been estimated at 27% in the EEA (Volk & Atkinson, 2013), compared with 0.8% in the 1990 data set. However, our analysis controlling for contemporary maternal risk factors suggests that the infants of nubile mothers in the past would likely have done as well or better than those of older mothers, as also indicated by findings from 18th to19th century Germany, where the overall infant mortality rate was 23% (Knodel & Hermalin, 1984).

When comparable infant outcomes are combined with the much lower risk of death in childbirth from complications of labor and delivery, it seems likely that nubile women would have been the most successful primiparas, thus suggesting an adaptive explanation for the timing of first births in a wide range of forager and subsistence populations (Kramer & Lancaster, 2010; Lassek & Gaulin, 2019; Symons, 1979; Walker, 2019).

From 2016... Glaciers, gendered knowledge, systems of scientific domination, & alternative representations of glaciers: A feminist glaciology framework for global environmental change research

From 2016... Glaciers, gender, and science: A feminist glaciology framework for global environmental change research. Mark Carey et al. Progress in Human Geography, January 10, 2016. https://doi.org/10.1177/0309132515623368

Abstract: Glaciers are key icons of climate change and global environmental change. However, the relationships among gender, science, and glaciers – particularly related to epistemological questions about the production of glaciological knowledge – remain understudied. This paper thus proposes a feminist glaciology framework with four key components: 1) knowledge producers; (2) gendered science and knowledge; (3) systems of scientific domination; and (4) alternative representations of glaciers. Merging feminist postcolonial science studies and feminist political ecology, the feminist glaciology framework generates robust analysis of gender, power, and epistemologies in dynamic social-ecological systems, thereby leading to more just and equitable science and human-ice interactions.

Keywords: feminist glaciology, feminist political ecology, feminist postcolonial science studies, folk glaciology, glacier impacts, glaciers and society

VII Conclusions

Ice is not just ice. The dominant way Western societies understand it through the science of glaciology is not a neutral representation of nature. The feminist glaciology framework draws attention to those who dominate and frame the production of glaciological knowledge, the gendered discourses of science and knowledge, and the ways in which colonial, military, and geopolitical domination co-constitute glaciological knowledge. Even in a globalized age where the place of women and indigenous people has improved markedly in some parts of the world, masculinist discourses continue to dominate, in subtle and determinative ways. Feminist glaciology advocates for a shift of preoccupations in research, policy, and public perceptions from the physical and seemingly natural, to a broader consideration of ‘cryoscapes’, the human, and the insights and potentials of alternative ice narratives and folk glaciologies. The critique and framework outlined here illuminate experiences and narratives that emerged historically but remain potent today. Public discourse on the cryosphere continues to privilege, quite explicitly, manly endeavours and adventures in the field, and those who conduct their science in the manner of masculinist glaciologists and other field scientists of decades and centuries past. A new documentary by French filmmaker Luc Jacquet (2015) about the preeminent French glaciologist and geochemist Claude Lorius perpetuates narratives of heroic domination of nature, while, in interesting ways, noting that ‘triumphant man’ is responsible for the global problems that make Lorius’ research so necessary. At the same time, in the midst of extensive coverage of the polar regions in the context of climate change, the New York Times has published articles that foreground the dangerous field in Greenland, thereby validating manly, heroic fieldwork while simultaneously relegating work with models and computers to something like ‘armchair glaciology’ (Davenport et al., 2015; Gertner, 2015). Unlike past narratives, there are subtleties and tensions within these public discourses, especially as they often seek to see scientific work in more detail, a detail that can soften or undercut the individual exertions on display. However, they still privilege stereotypical and masculinist practices of glaciology. Other narratives, however, challenge these practices, thereby generating alternative approaches to ice. Emerging from Australia, the Homeward Bound initiative plans a ‘state of the art leadership and strategic program for 78 women in science from around the globe’ to travel to Antarctica in late 2016, one of its aims being to ‘explore how women at the leadership table might give us a more sustainable future’ (Homeward Bound, 2015). The call for a feminist glaciology is not limited to ice and glaciers, but is a larger intervention into global environmental change (and especially climate change) research and policy. As international negotiations remain stalled and governmental commitments to change and reform are fitful and seemingly ineffectual, those studying environmental change and aware of its significant effects and dangerous potentials continue to search for ways of stemming the tides of change as well as forming just and equitable global structures for addressing it. The feminist glaciology framework articulates with these larger quests in at least two ways. First, it repeats the demands for increased presence of humanities and social science perspectives in global environmental change research, policy, and broader public discourse. Many humanities and social science disciplines and sub-disciplines have given significant attention to these issues, but there remain boundaries between these analyses and those considered central to the environmental change question. The natural sciences that drive and undergird environmental change policy are often asked by decision-makers and the media to speak for society or frame research and policy questions for humanity. But the natural sciences are not equipped to understand the complexities and potentialities of human societies, or to recognize the ways in which science and knowledge have historically been linked to imperial and hegemonic capitalist agendas. Feminist glaciology participates in this broader movement by suggesting richer conceptions of humanenvironment relations, and highlighting the disempowering and forestalling qualities of an unexamined and totalizing science. Second, we reiterate the need not only to appreciate the differential impacts of environmental change on different groups of people – men and women, rich and poor, North and South – but to understand how the science that guides attempted solutions may in fact perpetuate differences because they are, essentially, built on and draw their epistemic power from differentiation and marginalization. Struggles over authority and legitimacy play out in many obvious ways in climate change negotiations. Struggles also happen in less obvious ways, such as in the environmental change research underpinning climate politics. Analysts and practitioners must recognize the ways in which more-than-scientific, non-Western, nonmasculinist modes of knowledge, thinking, and action are marginalized. The response to simplistic ‘ice is just ice’ discourse is not merely to foreground or single out women and their experiences – that would simply perpetuate binaries and boundaries and ignore deeper foundations. Rather, it is a larger integration of human approaches and sensibilities with the existing dominant physical sciences. Global environmental change research must pluralize its ontologies, epistemologies, and sensibilities. Though there is ever-increasing evidence to guarantee future temperature increases, what remains uncertain are the human structures and ideas mobilized to cope with environmental changes as well as to forestall potentially worse outcomes. If we constitute glaciological and global environmental change research differently, we can constitute our future, our gender relations, and our international political economic relations more justly and equitably.

The Big Five predict numerous preferences, decisions, and behaviors—but why? To help answer this key question, the present research develops the sociocultural norm perspective

Eck, J., & Gebauer, J. E. (2021). A sociocultural norm perspective on Big Five prediction. Journal of Personality and Social Psychology, Sep 2021. https://doi.org/10.1037/pspp0000387

Abstract: The Big Five predict numerous preferences, decisions, and behaviors—but why? To help answer this key question, the present research develops the sociocultural norm perspective (SNP) on Big Five prediction—a critical revision and extension of the sociocultural motives perspective. The SNP states: Agreeableness, Extraversion, and Conscientiousness predict outcomes positively if those outcomes are socioculturally normative. Openness, by contrast, predicts outcomes negatively if they are socioculturally normative. Moreover, the SNP specifies unique mechanisms that underlie those predictions. Two mechanisms are social (social trust for Agreeableness, social attention for Extraversion) and two are cognitive (rational thought for Conscientiousness, independent thought for Openness). The present research develops the SNP by means of three large-scale experiments (Ntotal = 7,404), which used a new, tailor-made experimental paradigm—the minimal norm paradigm. Overall, the SNP provides norm-based, culture-focused, and mechanism-attentive explanations for why the Big Five predict their outcomes. The SNP also has broader relevance: It helps explain why Big Five effects vary across cultures and, thus, dispels the view that such variation threatens the validity of the Big Five. It suggests that the psychology of norms would benefit from attention to the Big Five. Finally, it helps bridge personality, social, and cross-cultural psychology by integrating their key concepts—the Big Five, conformity, and sociocultural norms.