Date:September 22, 2015
Source:Swiss National Science Foundation (SNSF)
Summary:According to a well-known theory in evolutionary biology healthy females should give birth to more males than females. A study shows why this is not always true.
According to popular belief, whether you have a baby girl or boy is purely a matter of chance. And yet, a study published several years ago shows that mothers in stressful jobs, for instance, give birth to more girls than boys. The correlation between such shifts in the offspring sex ratio and the mother’s overall state is something that evolutionary biologists are familiar with from other animal species. One influential hypothesis puts natural selection as an explanation for the imbalances observed.
Strong males with high reproductive success
The Trivers-Willard hypothesis states that it is beneficial for mothers to be able to adjust the sex of their offspring in response to their own state of health. Accordingly, a female in good condition should give birth to more male offspring. This is because successful males have the potential to produce more children in their lifetime than successful females. By producing strong sons, healthy mothers increase the probability of their own genes being widely distributed. Conversely, low-ranking females who are not in such good shape are more likely to produce daughters, because the chances of giving birth to a future dominant male are poor.
“However, it’s not quite as simple as that,” points out biologist Peter Neuhaus sponsored by the Swiss National Science Foundation, based at the University of Calgary in Canada. Taking the example of a model with data from Columbian ground squirrels and Canadian bighorn sheep, Neuhaus — together with colleagues from the UK, the US, France and South Africa — has demonstrated in an article published in Nature magazine that optimal reproduction also depends on a series of other factors.
Dead before reaching sexual maturity
Bighorn ewes, for instance, give birth to only one lamb a year. Most females mate with the dominant ram, which means many of the other males don’t get a chance. Females in a good state often pass on their condition and so can be expected to “to make supermales,” as Neuhaus explains. Nonetheless, the healthy females do not produce more male than female offspring. As the model demonstrates, other parameters, such as the fact that a large number of males die before reaching sexual maturity, play a central role in assessing reproductive potential.
But what have sheep got to do with mothers in jobs with some degree of stress? Nobody doubts that they have more girls, but Neuhaus advises caution: “Evolution is very complex. To understand how it works, you need to take into account as many factors as possible that could influence reproductive potential.”
- Susanne Schindler, Jean‐Michel Gaillard, André Grüning, Peter Neuhaus, Lochran W. Traill, Shripad Tuljapurkar, Tim Coulson. Sex‐specific demography and generalization of the Trivers–Willard theory. Nature, 2015; DOI: 10.1038/nature14968
Date:September 10, 2015
Source:Taylor & Francis
Summary:Can events you endured as a child really impact your ability to have children yourself? New research examines the mechanism by which adverse experiences in childhood impact female fertility. Researchers explore the hypothesis that negative experiences in childhood can result in menstrual cycle irregularities, which consequently impact fertility. They relate their hypothesis to life-history theory, which talks of balancing the preservation of one’s health and the production of offspring that will survive to reproduce themselves.
Can events you endured as a child really impact your ability to have children yourself? New research in the Journal of Psychosomatic Obstetrics & Gynecology examines the mechanism by which adverse experiences in childhood impact female fertility. In their paper ‘Adverse childhood event experiences, fertility difficulties and menstrual cycle characteristics’, Marni B. Jacobs et al. explore the hypothesis that negative experiences in childhood can result in menstrual cycle irregularities, which consequently impact fertility. They relate their hypothesis to life-history theory, which talks of balancing the preservation of one’s health and the production of offspring that will survive to reproduce themselves, and theorize that “early life stressors may predispose an individual to adaptively suppress fertility when situations are less than optimal, leading to periods of fertility difficulties even following previous births.”
The study examined data from 774 women of reproductive age, 195 of whom were pregnant. It analysed fertility difficulties, menstrual cycle irregularities and adverse childhood experiences, through a mixture of in-person interviews and take-home questionnaires.
Following their research, the team came to the conclusion that those women who had experienced negative events at a young age — such as “abuse, neglect, household dysfunction or parental substance abuse” — were more likely to have faced fertility difficulties and abnormal absences of menstruation lasting three months or more, and also took a longer time to get pregnant. Their research also suggests that certain harmful events in childhood can potentially have a greater impact on fertility than others.
- Marni B. Jacobs, Renee D. Boynton-Jarrett, Emily W. Harville. Adverse childhood event experiences, fertility difficulties and menstrual cycle characteristics. Journal of Psychosomatic Obstetrics & Gynecology, 2015; 36 (2): 46 DOI: 10.3109/0167482X.2015.1026892
Jan. 23, 2013 — New research at the University of Chicago and the University of North Carolina at Chapel Hill shows that children begin to show signs of higher-level thinking skills as young as age 4 ½. Researchers have previously attributed higher-order thinking development to knowledge acquisition and better schooling, but the new longitudinal study shows that other skills, not always connected with knowledge, play a role in the ability of children to reason analytically.
The findings, reported in January in the journal Psychological Science, show for the first time that children’s executive function has a role in the development of complicated analytical thinking. Executive function includes such complex skills as planning, monitoring, task switching, and controlling attention. High, early executive function skills at school entry are related to higher than average reasoning skills in adolescence.
Growing research suggests that executive function may be trainable through pathways, including preschool curriculum, exercise and impulse control training. Parents and teachers may be able to help encourage development of executive function by having youngsters help plan activities, learn to stop, think, and then take action, or engage in pretend play, said lead author of the study, Lindsey Richland, assistant professor in comparative human development at the University of Chicago.
Although important to a child’s education, “little is known about the cognitive mechanisms underlying children’s development of the capacity to engage in complex forms of reasoning,” Richland said.
The new research is reported in the paper “Early Executive Function Predicts Reasoning Development” and follows the development of complex reasoning in children from before the time they go to school until they are 15. Richland’s co-author is Margaret Burchinal, senior scientist at the Frank Porter Graham Child Development Institute at the University of North Carolina at Chapel Hill.
The two studied the acquisition of analogical thinking, one form of complex reasoning. “The ability to see relationships and similarities between disparate phenomena is fundamental to analytical and inductive reasoning, and is closely related to measurements of general fluid intelligence,” said Richland. Developing complex reasoning ability is particularly fundamental to the innovation and adaptive thinking skills necessary for a modern workforce, she pointed out.
Richland and Burchinal studied a database of 1,364 children who were part of the Early Child Care and Youth Development study from birth through age 15. The group was fairly evenly divided between boys and girls and included families from a diverse cross-section of ethnic and income backgrounds.
The current study examined tests children took when they were 4 ½, when they were in first grade, third grade, and when they were 15. Because the study was longitudinal, the same children were tested at each interval. Among the tests they took were ones to measure analytical reasoning, executive function, vocabulary knowledge, short-term memory and sustained attention.
Children were tested at 4 ½ on their ability to monitor and control their automatic responses to stimuli. In first grade they worked on a test that judged their ability to move objects in a “Tower of Hanoi” game, in which they had to move disks between pegs in a specific order.
In third grade and at 15 year olds, they were tested on their ability to understand analogies, asked in third grade for instance to complete the question “dog is to puppy as cat is to__?” At 15 year olds, they were asked to complete written tests of analogies.
The study found a strong relationship between high scores among children who, as preschoolers, had strong vocabularies and were good at monitoring and controlling their responses to later ability on tests of understanding analogies.
“Overall, these results show that knowledge is necessary for using thinking skills, as shown by the importance of early vocabulary, but also inhibitory control and executive function skills are important contributors to children’s analytical reasoning development,” Richland said.
The National Academy of Education/Spencer Foundation, the Office of Naval Research and the National Science Foundation supported the research.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
- L. E. Richland, M. R. Burchinal. Early Executive Function Predicts Reasoning Development. Psychological Science, 2012; 24 (1): 87 DOI:10.1177/0956797612450883
Jan. 23, 2013 — People with color-grapheme synesthesia experience color when viewing written letters or numerals, usually with a particular color evoked by each grapheme (i.e., the letter ‘A’ evokes the color red). In a new study, researchers Nathan Witthoft and Jonathan Winawer of Stanford University present data from 11 color grapheme synesthetes who had startlingly similar color-letter pairings that were traceable to childhood toys containing magnetic colored letters.
Their findings are published inPsychological Science, a journal of the Association for Psychological Science.
Matching data from the 11 participants showed reliably consistent letter-color matches, both within and between testing sessions (data collected online athttp://www.synesthete.org/). Participants’ matches were consistent even after a delay of up to seven years since their first session.
Participants also performed a timed task, in which they were presented with colored letters for 1 second each and required to indicate whether the color was consistent with their synesthetic association. Their data show that they were able to perform the task rapidly and accurately.
Together, these data suggest that the participants’ color-letter associations are specific, automatic, and relatively constant over time, thereby meeting the criteria for true synesthesia.
The degree of similarity in the letter-color pairings across participants, along with the regular repeating pattern in the colors found in each individual’s letter-color pairings, indicates that the pairings were learned from the magnetic colored letters that the participants had been exposed to in childhood.
According to the researchers, these are the first and only data to show learned synesthesia of this kind in more than a single individual.
They point out that this does not mean that exposure to the colored letter magnets was sufficient to induce synesthesia in the participants, though it may have increased the chances. After all, many people who do not have synesthesia played with the same colored letter magnets as kids.
Based on their findings, Witthoft and Winawer conclude that a complete explanation of synesthesia must incorporate a central role for learning and memory.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
- N. Witthoft, J. Winawer. Learning, Memory, and Synesthesia. Psychological Science, 2013; DOI:10.1177/0956797612452573
Jan. 22, 2013 — Using a brain-imaging technique that examines the entire infant brain, researchers have found that the anatomy of certain brain areas – the hippocampus and cerebellum – can predict children’s language abilities at 1 year of age.
The University of Washington study is the first to associate these brain structures with future language skills. The results are published in the January issue of the journal Brain and Language.
“The brain of the baby holds an infinite number of secrets just waiting to be uncovered, and these discoveries will show us why infants learn languages like sponges, far surpassing our skills as adults,” said co-author Patricia Kuhl, co-director of the UW’s Institute for Learning & Brain Sciences.
Children’s language skills soar after they reach their first birthdays, but little is known about how infants’ early brain development seeds that path. Identifying which brain areas are related to early language learning could provide a first glimpse of development going awry, allowing for treatments to begin earlier.
“Infancy may be the most important phase of postnatal brain development in humans,” said Dilara Deniz Can, lead author and a UW postdoctoral researcher. “Our results showing brain structures linked to later language ability in typically developing infants is a first step toward examining links to brain and behavior in young children with linguistic, psychological and social delays.”
In the study, the researchers used magnetic resonance imaging to measure the brain structure of a mix of 19 boys and girls at 7 months of age. The researchers used a measurement called voxel-based morphometry to determine the concentration of gray matter, consisting of nerve cells, and of white matter, which make up the network of connections throughout the brain.
The study is the first to relate the outcomes of this whole-brain imaging technique to predict future ability in infants. The whole-brain approach freed the researchers from having to select a few brain regions for study ahead of time, ones scientists might have expected to be involved based on adult data.
Five months later, when the children were about 1 year old they returned to the lab for a language test. This test included measures of the children’s babbling, recognition of familiar names and words, and their ability to produce different types of sounds.
“At this age, children typically don’t say many words,” Deniz Can said. “So we rely on babbling and the ability to comprehend language as a sign of early language mastery.”
Infants with a greater concentration of gray and white matter in the cerebellum and the hippocampus showed greater language ability at age 1. This is the first study to identify a relationship between language and the cerebellum and hippocampus in infants. Neither brain area is well-known for its role in language: the cerebellum is typically linked to motor learning, while the hippocampus is commonly recognized as a memory processor.
“Looking at the whole brain produced a surprising result and scientists live for surprises. It wasn’t the language areas of the infant brain that predicted their future linguistic skills, but instead brain areas linked to motor abilities and memory processing,” Kuhl said. “Infants have to listen and memorize the sound patterns used by the people in their culture, and then coax their own mouths and tongues to make these sounds in order join the social conversation and get a response from their parents.”
The findings could reflect infants’ abilities to master the motor planning for speech and to develop the memory requirements for keeping the sound patterns in mind.
“The brain uses many general skills to learn language,” Kuhl said. “Knowing which brain regions are linked to this early learning could help identify children with developmental disabilities and provide them with early interventions that will steer them back toward a typical developmental path.”
Todd Richards, a UW professor of radiology, was another co-author. The study was funded by the National Institutes of Health and the Santa Fe Institute Consortium.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
- Dilara Deniz Can, Todd Richards, Patricia K. Kuhl. Early gray-matter and white-matter concentration in infancy predict later language skills: A whole brain voxel-based morphometry study. Brain and Language, 2013; 124 (1): 34 DOI: 10.1016/j.bandl.2012.10.007
an. 7, 2013 — Social practices and cultural beliefs of modern life are preventing healthy brain and emotional development in children, according to an interdisciplinary body of research presented recently at a symposium at the University of Notre Dame.
“Life outcomes for American youth are worsening, especially in comparison to 50 years ago,” says Darcia Narvaez, Notre Dame professor of psychology who specializes in moral development in children and how early life experiences can influence brain development.
“Ill-advised practices and beliefs have become commonplace in our culture, such as the use of infant formula, the isolation of infants in their own rooms or the belief that responding too quickly to a fussing baby will ‘spoil’ it,” Narvaez says.
This new research links certain early, nurturing parenting practices — the kind common in foraging hunter-gatherer societies — to specific, healthy emotional outcomes in adulthood, and has many experts rethinking some of our modern, cultural child-rearing “norms.”
“Breast-feeding infants, responsiveness to crying, almost constant touch and having multiple adult caregivers are some of the nurturing ancestral parenting practices that are shown to positively impact the developing brain, which not only shapes personality, but also helps physical health and moral development,” says Narvaez.
Studies show that responding to a baby’s needs (not letting a baby “cry it out”) has been shown to influence the development of conscience; positive touch affects stress reactivity, impulse control and empathy; free play in nature influences social capacities and aggression; and a set of supportive caregivers (beyond the mother alone) predicts IQ and ego resilience as well as empathy.
The United States has been on a downward trajectory on all of these care characteristics, according to Narvaez. Instead of being held, infants spend much more time in carriers, car seats and strollers than they did in the past. Only about 15 percent of mothers are breast-feeding at all by 12 months, extended families are broken up and free play allowed by parents has decreased dramatically since 1970.
Whether the corollary to these modern practices or the result of other forces, an epidemic of anxiety and depression among all age groups, including young children; rising rates of aggressive behavior and delinquency in young children; and decreasing empathy, the backbone of compassionate, moral behavior, among college students, are shown in research.
According to Narvaez, however, other relatives and teachers also can have a beneficial impact when a child feels safe in their presence. Also, early deficits can be made up later, she says.
“The right brain, which governs much of our self-regulation, creativity and empathy, can grow throughout life. The right brain grows though full-body experience like rough-and-tumble play, dancing or freelance artistic creation. So at any point, a parent can take up a creative activity with a child and they can grow together.”
Further information: http://ccf.nd.edu/symposium/2012-symposium-presentations/
Jan. 4, 2013 — Spanish researchers have traced the bacterial microbiota map in breast milk, which is often the main source of nourishment for newborns. The study has revealed a larger microbial diversity than originally thought: more than 700 species.
The breast milk received from the mother is one of the factors determining how the bacterial flora will develop in the newborn baby. However, the composition and the biological role of these bacteria in infants remain unknown.
A group of Spanish scientists have now used a technique based on massive DNA sequencing to identify the set of bacteria contained within breast milk called microbiome. Thanks to their study, pre- and postnatal variables influencing the micriobial richness of milk can now be determined.
Colostrum is the first secretion of the mammary glands after giving birth. In some of the samples taken of this liquid, more than 700 species of these microorganisms were found, which is more than originally expected by experts. The results have been published in theAmerican Journal of Clinical Nutrition.
“This is one of the first studies to document such diversity using the pyrosequencing technique (a large scale DNA sequencing determination technique) on colostrum samples on the one hand, and breast milk on the other, the latter being collected after one and six months of breastfeeding,” explain the coauthors, María Carmen Collado, researcher at the Institute of Agrochemistry and Food Technology (IATA-CSIC) and Alex Mira, researcher at the Higher Public Health Research Centre (CSISP-GVA).
The most common bacterial genera in the colostrum samples were Weissella, Leuconostoc, Staphylococcus, Streptococcus and Lactococcus. In the fluid developed between the first and sixth month of breastfeeding, bacteria typical of the oral cavity were observed, such as Veillonella, Leptotrichia andPrevotella.
“We are not yet able to determine if these bacteria colonise the mouth of the baby or whether oral bacteria of the breast-fed baby enter the breast milk and thus change its composition,” outline the authors.
The heavier the mother, the fewer the bacteria
The study also reveals that the milk of overweight mothers or those who put on more weight than recommended during pregnancy contains a lesser diversity of species.
The type of labour also affects the microbiome within the breast milk: that of mothers who underwent a planned caesarean is different and not as rich in microorganisms as that of mothers who had a vaginal birth. However, when the caesarean is unplanned (intrapartum), milk composition is very similar to that of mothers who have a vaginal birth.
These results suggest that the hormonal state of the mother at the time of labour also plays a role: “The lack of signals of physiological stress, as well as hormonal signals specific to labour, could influence the microbial composition and diversity of breast milk,” state the authors.
Help for the food industry
Given that the bacteria present in breast milk constitute one of initial instances of contact with microorganisms that colonise the infant’s digestive system, the researchers are now working to determine if their role is metabolic (it helps the breast-fed baby to digest the milk) or immune (it helps to distinguish beneficial or foreign organisms).
For the authors, the results have opened up new doors for the design of child nutrition strategies that improve health. “If the breast milk bacteria discovered in this study were important for the development of the immune system, its addition to infant formula could decrease the risk of allergies, asthma and autoimmune diseases,” conclude the authors.
- R. Cabrera-Rubio, M. C. Collado, K. Laitinen, S. Salminen, E. Isolauri, A. Mira. The human milk microbiome changes over lactation and is shaped by maternal weight and mode of delivery. American Journal of Clinical Nutrition, 2012; 96 (3): 544 DOI:10.3945/ajcn.112.037382
Jan. 2, 2013 — Today, mothers of newborns find themselves confronting a common dilemma: Should they let their babies “cry it out” when they wake up at night? Or should they rush to comfort their crying little one?
In fact, waking up in the middle of the night is the most common concern that parents of infants report to pediatricians. Now, a new study from Temple psychology professor Marsha Weinraub gives parents some scientific facts to help with that decision.
The study, published in Developmental Psychology, supports the idea that a majority of infants are best left to self-soothe and fall back to sleep on their own.
“By six months of age, most babies sleep through the night, awakening their mothers only about once per week. However, not all children follow this pattern of development,” said Weinraub, an expert on child development and parent-child relationships.
For the study, Weinraub and her colleagues measured patterns of nighttime sleep awakenings in infants ages six to 36 months. Her findings revealed two groups: sleepers and transitional sleepers.
“If you measure them while they are sleeping, all babies — like all adults — move through a sleep cycle every 1 1/2 to 2 hours where they wake up and then return to sleep,” said Weinraub. “Some of them do cry and call out when they awaken, and that is called ‘not sleeping through the night.'”
For the study, Weinraub’s team asked parents of more than 1,200 infants to report on their child’s awakenings at 6, 15, 24 and 36 months. They found that by six months of age, 66 percent of babies — the sleepers — did not awaken, or awoke just once per week, following a flat trajectory as they grew. But a full 33 percent woke up seven nights per week at six months, dropping to two nights by 15 months and to one night per week by 24 months.
Of the babies that awoke, the majority were boys. These transitional sleepers also tended to score higher on an assessment of difficult temperament which identified traits such as irritability and distractibility. And, these babies were more likely to be breastfed. Mothers of these babies were more likely to be depressed and have greater maternal sensitivity.
The findings suggest a couple of things, said Weinraub. One is that genetic or constitutional factors such as those that might be reflected in difficult temperaments appear implicated in early sleep problems. “Families who are seeing sleep problems persist past 18 months should seek advice,” Weinraub said.
Another takeaway is that it is important for babies to learn how to fall asleep on their own. “When mothers tune in to these night time awakenings and/or if a baby is in the habit of falling asleep during breastfeeding, then he or she may not be learning to how to self-soothe, something that is critical for regular sleep,” she said.
According to Weinraub, the mechanism by which maternal depression is connected to infant awakenings is an area that would benefit from further research. On the one hand, Weinraub said, it’s possible that mothers who are depressed at six and 36 months may have been depressed during pregnancy and that this prenatal depression could have affected neural development and sleep awakenings. At the same time, it’s important to recognize that sleep deprivation can, of course, exacerbate maternal depression, she said.
“Because the mothers in our study described infants with many awakenings per week as creating problems for themselves and other family members, parents might be encouraged to establish more nuanced and carefully targeted routines to help babies with self-soothing and to seek occasional respite,” said Weinraub.
“The best advice is to put infants to bed at a regular time every night, allow them to fall asleep on their own and resist the urge to respond right away to awakenings.”
- Marsha Weinraub, Randall H. Bender, Sarah L. Friedman, Elizabeth J. Susman, Bonnie Knoke, Robert Bradley, Renate Houts, Jason Williams. Patterns of developmental change in infants’ nighttime sleep awakenings from 6 through 36 months of age..Developmental Psychology, 2012; 48 (6): 1511 DOI:10.1037/a0027680