Neonatal Shoulder Width Suggests a Semirotational, Oblique Birth Mechanism in Australopithecus afarensis.

Birth mechanics in early hominins are often reconstructed based on cephalopelvic proportions, with little attention paid to neonatal shoulders. Here, we find that neonatal biacromial breadth can be estimated from adult clavicular length (R2 = 0.80) in primates. Using this relationship and clavicular length from adult Australopithecus afarensis, we estimate biacromial breadth in neonatal australopiths. Combined with neonatal head dimensions, we reconstruct birth in A. afarensis (A.L. 288-1 or Lucy) and find that the most likely mechanism of birth in this early hominin was a semi-rotational oblique birth in which the head engaged and passed through the inlet transversely, but then rotated so that the head and shoulders remained perpendicular and progressed through the midplane and outlet oblique to the main axis of the female pelvis. Any other mechanism of birth, including asynclitic birth, would have resulted in either the head or the shoulders orthogonal to the short anteroposterior dimension of the A.L. 288-1 pelvis, making birth untenable. There is a tight fit between the infant and all planes of the birth canal, perhaps suggesting a difficult labor in australopiths. However, the rotational birth mechanism of large-brained humans today was likely not characteristic of A. afarensis. Thus, the evolution of rotational birth, usually associated with encephalization, may have occurred in two stages: the first appeared with the origin of the australopiths with their platypelloid pelves adapted for bipedalism and their broad-shouldered neonates; the second which resulted in the modern mechanism of rotational birth may be associated with increasing brain size in the genus Homo. Anat Rec, 300:890-899, 2017. © 2017 Wiley Periodicals, Inc.

Daily vasomotor symptoms, sleep problems, and mood: using daily data to evaluate the domino hypothesis in middle-aged women.

OBJECTIVE: The aim of this study was to investigate the relationships among daily reports of vasomotor symptoms (hot flashes and/or sweats), same-day sleep problems, and next-day mood reports in middle-aged women. METHODS: Fifty-five healthy middle-aged women were recruited to keep daily records for up to 5 years or until menopause. For each participant, the first 252 days of contiguous data with the highest weekly frequency of vasomotor symptoms was selected for the current analyses. Multilevel structural equation modeling was used to test whether changes in daily vasomotor symptom occurrence predicted changes in occurrence of same-day sleep problems and changes in next-day positive and negative mood ratings and whether sleep problems mediated any predictive effect of symptoms on next-day mood. RESULTS: Controlling for initial depression, daily vasomotor symptoms predicted same-day sleep problems (b = 0.59, P < 0.001) and next-day positive mood (b = -0.07, P < 0.01), although significant direct relationships between vasomotor symptoms and mood were found primarily in women with initial depression scores in the low to moderate range. Sleep problems predicted next-day positive (b = -0.08, P < 0.01) and negative (b = 0.10, P < 0.001) mood more robustly than vasomotor symptoms did. CONCLUSIONS: Sleep problems predicted worse mood on the following day and accounted for only a small portion of the relationship between vasomotor symptoms and mood. These findings suggest that any effect of vasomotor symptoms on mood may occur largely through a mechanism other than sleep disruption.

Cortisol Reactivity, Maternal Sensitivity, and Infant Preference for Mother's Familiar Face and Rhyme in 6-Month-Old Infants.

This study investigated how cortisol (stress) reactivity and mothers' behavioral sensitivity affect familiarity preferences in 6-month-old infants. Relations between sensitivity and stress were explored using saliva samples taken from mothers and infants before, and 20-min after, two preferential looking experiments. Photographs and voice recordings from infants' mothers were incorporated into standard visual preference tasks. Sensitivity was assessed by determining the degree of behavioral synchrony between mother and infant from a 10-min interaction period preceding the preferential looking experiments. Results showed that decreasing infant cortisol reactivity and greater maternal sensitivity were associated with familiarity preferences for mother's face stimuli. For the experiment with voice stimuli, a sex difference was obtained in the relationship between the directionality of cortisol reactivity and familiarity preferences. Results are related to a parallel study with 3-month-old infants (Thompson & Trevathan, 2008), and issues are discussed in terms of infants' developing emotional independence from mother.

Cortisol reactivity, maternal sensitivity, and learning in 3-month-old infants.

This study investigated the effects of adrenocortical functioning on infant learning during an emotionally challenging event (brief separation from mother). We also explored possible relationships between maternal sensitivity and both infant and maternal cortisol reactivity during the learning/maternal separation episode. Sixty-three 3-month-olds and their mothers were videotaped for a 10 min normal interaction period, and mother-infant behavioral synchrony was measured using Isabella and Belsky's [Isabella, R. A., & Belsky, J. (1991). Interactional synchrony and the origins of infant-mother attachment: A replication study. Child Development, 62, 373-384] coding scheme. The percentage of synchronous behaviors served as a measure of maternal sensitivity. Learning and short-term memory involved relating the infant's mother's voice with a moving colored block in a preferential looking paradigm. Infants whose cortisol increased during the session showed no learning or memory, infants whose cortisol declined appeared to learn and remember the association, while infants whose cortisol did not change evidenced learning, but not memory for the voice/object correspondence. Sensitivity and cortisol reactivity were correlated for mothers, but not for infants. Infant and maternal cortisol values for the first sampling period were highly correlated, but their cortisol reactivity values were uncorrelated, supporting the notion that infants and mothers have coordinated adrenocortical functioning systems when physically together, but become uncoordinated during a separation/learning event.

An anthropological perspective on the evolutionary context of preeclampsia in humans.

Preeclampsia/eclampsia is a dangerous condition unique to humans that is associated with an energetically expensive developing fetal brain and extremely invasive implantation of the trophoblast. We review here the evolutionary history of human pregnancy and childbirth to set a context for evolutionary hypotheses about the origin of preeclampsia. Humans are characterized by having large brains, bipedal locomotion and helpless newborns. These distinctive aspects of our biology arose independently but together constrain pregnancy and childbirth leading to an unusual mechanism of birth, cephalopelvic disproportion, shoulder dystocia, difficult labors, and neonates requiring high levels of parental care. Our cultural adaptation in the form of assistance during childbirth and intensive parental investment make it possible to balance those constraints. Preeclampsia probably arose only after the increase in human brain size and modern human mechanism of birth. Like the other risks of childbirth, preeclampsia also represents a risk associated with these distinctive aspects of human pregnancy and childbirth and is mitigated today by medical intervention. We speculate that, like assistance during childbirth, cultural intervention during pregnancy may extend into the past.

In the mood for love or vice versa? Exploring the relations among sexual activity, physical affection, affect, and stress in the daily lives of mid-aged women.

How do physical affection, sexual activity, mood, and stress influence one another in the daily lives of mid-aged women? Fifty-eight women (M age, 47.6 yrs) recorded physical affection, several different sexual behaviors, stressful events, and mood ratings every morning for 36 weeks. Using multilevel modeling, we determined that physical affection or sexual behavior with a partner on one day significantly predicted lower negative mood and stress and higher positive mood on the following day. The relation did not hold for orgasm without a partner. Additionally, positive mood on one day predicted more physical affection and sexual activity with a partner, but fewer solo orgasms the following day. Negative mood was mostly unrelated to next-day sexual activity or physical affection. Sexual orientation, living with a partner, and duration of relationship moderated some of these effects. Results support a bidirectional causal model in which dyadic sexual interaction and physical affection improve mood and reduce stress, with improved mood and reduced stress in turn increasing the likelihood of future sex and physical affection.

Knowledge and perception of risk for HIV and condom use among male injecting drug users in Cebu City, Philippines.

Injecting drug users (IDU) represent a small fraction of the HIV and AIDS cases in the Philippines. To determine if these people are engaging in behaviors that put them at risk for HIV, interviews were conducted with 360 male IDUs in Cebu City, Philippines, from 1997 to 1999, as part of a national surveillance system. The interviews assessed knowledge about HIV transmission, sources of information about HIV/AIDS, perceived risks of contracting HIV, needle-sharing practices, condom use, self-reported signs and symptoms of STDs and number of sex partners. Although most of the men were able to recognize behaviors accurately that put them at risk for HIV, more than two-thirds claimed that they shared needles and almost two-thirds of those who were sexually active claimed that they never used condoms. Intervention strategies must be developed for this population if the nation is to avoid the dramatic increase in HIV infection among IDUs that has been witnessed in neighboring Southeast Asian nations such as Malaysia and Vietnam.

Sexual behavior in lesbian and heterosexual women: relations with menstrual cycle phase and partner availability.

Using a prospective design over three complete menstrual cycles, 147 heterosexual and 89 lesbian women made daily recordings of their basal body temperature (BBT), cervical mucus status, menses, and completed a daily checklist of various sexual behaviors (including sexual self-stimulation and sexual activity with a partner). They also gave their age, height, weight, age at menarche, number of pregnancies, duration of sleep, tobacco, caffeine, and alcohol use, and whether they had a live-in sexual partner. Using BBT, cervical mucus status, and menses information, cycle days were grouped into five discrete phases: menses, follicular, ovulatory, early luteal, and premenstrual. Daily frequencies of sexual behavior with a partner and autosexual behavior were computed for each phase. Mixed ANOVAs on the resultant proportional data revealed similar patterns for autosexual behavior across the phases for both heterosexuals and lesbians who did not have a live-in partner, in which autosexual behavior was highest during the follicular and ovulatory phases. For those with live-in partners, autosexual behavior did not vary across the phases. Lesbians engaged in more autosexual behavior overall. Allosexual behavior peaked during the follicular phase for both heterosexuals and lesbians, and the phasic pattern was unrelated to live-in partner status. Additional analyses suggest that the observed patterns were unrelated to anticipated changes in sexual activity due to menses. Results are discussed in terms of social variables and hormonal fluctuations associated with the menstrual cycle.