Articles tagged with Sex Ratios
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A recent study found associations between air and water pollutants and changes in the human sex ratio at birth. Pollutants such as PCBs, iron, lead, and chromium were linked to an increased or decreased ratio of baby boys to girls.
The analysis found that nearly 40 million referrals to surgeons showed a greater proportion of patients referred to male surgeons by male physicians. In contrast, female physicians were less influenced by surgeon sex when making referral decisions.
A recent study investigated sex disparity in living donor liver transplant access, revealing a significant inequity between men and women. The research suggests that male donors have better access to liver transplants than female donors, highlighting the need for gender-specific solutions to address this disparity.
Researchers project a further decline in excess male births in countries like China and India, but warn of a surplus of young men globally, posing social and economic challenges. A global loss of 22 million female births could occur by 2100 if all at-risk countries are included in projections.
Researchers identified a novel lncRNA, Teshl, which plays a crucial role in the development of Y-bearing sperm and regulates sex chromosome gene expression. The study provides new insights into sex ratio variations and suggests that genetics may be a key factor in human male infertility.
A Finnish study analyzed the reproductive histories of women who moved from rural to urban areas during WWII and found that urban women were 15% less likely to reproduce than their rural counterparts. The study suggests that women may be delaying childbearing due to increased competition for spouses in urban environments.
A new study projects that India will experience a significant shortage of female births between 2017 and 2030, with an estimated 6.8 million fewer female births recorded due to sex-selective abortions. The country's regional diversity and cultural preferences for male babies have contributed to this imbalance.
Researchers found that approximately 3.3% of families engage in 'coupon-collection behavior', where they have children of both sexes except for the last-born child, reducing sex-ratio variation. The trend is more pronounced in recent decades and suggests a growing desire for gender equality.
Researchers found a seasonal bias in the sex ratio of brown-headed cowbird offspring, with more female hatchlings emerging in May and July. The study suggests that male and female cowbirds may have different developmental trajectories, influencing their survival and breeding success.
Researchers at Florida Atlantic University have created a minimally invasive technique to determine the sex of sea turtle hatchlings using small blood samples. This method is more reliable and efficient than existing methods, providing valuable insights into the impact of climate change on imperiled turtle species.
A new FSU study suggests that competition for mates leads to increased risk-taking and aggression in men, but also reveals a lesser-known female response: settling down quickly to avoid competition. The study found that when women outnumber men, they become more open to casual relationships and less likely to get married.
Research found a short-term drop in the proportion of boys born in Ontario, Canada's most populated province, following the 2016 US presidential election. This effect was observed only in politically liberal areas, not in conservative ones, suggesting a potential impact of societal stressors on birth ratios.
A new discovery reveals that mouse X and Y chromosomes compete to produce female versus male offspring, with genes on the X favoring daughters and genes on the Y favoring sons. IVF fertilization can reverse this imbalance.
Researchers from the University of Bath and UCL will study the effect of skewed sex ratios on social behavior in birds and mammals. The team aims to understand how variations in sex ratios impact human populations, including mating behavior, parenting roles, and violence.
A four-year study will investigate how green sea turtles' reproductive behaviors influence the effects of climate change. The research team, led by Lisa Komoroske, will use genetic samples and satellite telemetry to estimate sex ratios and predict population viability under different climate scenarios.
A study analyzing 21 years of data on Darwin's finches found that environmental perturbations can strongly bias the adult sex ratio, particularly among females. Females that changed mates gained a clear fitness advantage in terms of numbers of offspring that survived to the following year.
A new estimation method for assessing natural variations in the sex ratio at birth was developed by an international team of researchers. The study found regional baseline SRB imbalances and identified 12 countries with strong evidence of sex ratio inflation, leading to fewer female births than expected.
A study analyzing vital registration, census, and survey data from 202 countries estimates sex ratio at birth for all countries between 1950 and 2017. The study reveals significant regional variations and findings a total of 23.1 million missing female births worldwide.
A study of messaging patterns on an online dating platform reveals geographic distance as the strongest driver of reciprocal interactions. Researchers found 19 distinct communities that closely mirrored geographic regions across the US, with age and race also influencing dating markets.
Wild bees experiencing widespread declines due to urbanization may be more male-dominated as females decline in numbers, impacting pollination and reproduction rates. This study suggests considering sex-specific differences in bee behavior when analyzing environmental change effects on populations.
A study by University of Washington researchers reveals that rising single male Magellanic penguins are a result of higher juvenile female mortality and population decline. The data suggests that protecting the penguins' food supply during non-breeding seasons is crucial for conservation.
A new study from an international team of researchers found that an imbalance of the sexes leads to single parenting in birds. The researchers discovered that when there are more males than females or vice versa, the parenting roles shift, leaving the males to care for the chicks.
A Florida Atlantic University study found that 70% of loggerhead sea turtle nests and hatchlings had different fathers, with no repeat males detected. This research provides insight into the reproductive behavior of male sea turtles and suggests a breeding sex ratio of approximately 1 female for every 2.5 males.
A study by Florida Atlantic University researchers found that moisture conditions inside sea turtle nests significantly affect the development and sex ratios of turtle embryos. The coolest and wettest substrates produce 100% males, while warmer and drier ones produce fewer males.
A new study shows people accurately extract social category information from groups of faces, perceiving the sex ratio in half a second. The researchers found that as the number of men in the group increases, so does the perceived threat level, impacting group cohesion.
Researchers found that male woolly mammoth specimens were more common in the fossil record due to their tendency to travel alone and fall into natural traps. The discovery highlights the utility of fossil remains for studying extinct animal behavior and social structures.
A study found that atrazine exposure increases feminization in male Blanchard's cricket frogs, altering their sex ratio. The species is highly sensitive to atrazine, which disrupts gonadal development and impacts ecological trajectories.
Research found that population growth in birds is sensitive to male-to-female ratio, affecting mating behavior and survival rates. A male-biased population can lead to increased aggression, while a female-biased population can result in lower parental investment.
A new method to identify baby sea turtles' sex has been developed using an immunohistochemical approach, increasing the accuracy of sex determination for leatherback turtles. The technique, which uses a RNA-binding protein, achieved 100% success agreement with established methods in leatherbacks and 93% in loggerheads.
A University of Utah study contradicts traditional expectations by finding that surpluses of men are associated with higher levels of marriage, relationship commitment and paternal involvement. This challenges the prevailing notion that an abundance of single men lead to outcomes of crime, violence and broken homes.
Researchers from UEA's School of Biological Sciences found that female birds are choosing busier breeding locations with more abundant males, leading to skewed sex ratios in small populations. These findings suggest that conservation efforts should focus on maintaining large populations with equal sex ratios.
A UCI study reveals that climate change is altering the growth patterns of male and female Valeriana edulis over elevation in the Colorado Rockies. The shift in sex ratios allows female plants to successfully produce more seeds, while males become more common at higher elevations.
A male-killing bacterium has been identified as the cause of female-biased sex ratios in green lacewings. The bacterium is closely related to plant pathogens and may have jumped hosts to infect lacewings. Further research is needed to investigate possible host suppressors against male-killing.
A study in GENETICS identifies the first gene associated with temperature-dependent sex determination in reptiles, highlighting the role of genetic variation and climate change. The research found that a specific DNA sequence variation at the CIRBP gene influences sex ratio in snapping turtles.
Research shows that people who face uncertain outcomes may prioritize high-risk options even when unrelated to romance. This study found that exposure to unfavorable sex ratios led participants to make riskier financial decisions, such as investing more in a single high-stakes option.
A large study in CMAJ found that Indian-born women living in Ontario, Canada, who already have two daughters are more likely to have a boy. The likelihood of male births increases if women had an induced abortion before the birth. Birth ratios fell within natural ranges for Canadian-born and immigrant women from most other countries.
Scientists have determined a female bias of 2.83 females to each male among 69 green turtles sampled in San Diego Bay, revealing potential feminization due to climate change. The study provides a safe and effective method for determining the sex of immature turtles using enzyme-linked immunosorbent assay (ELISA).
Researchers found dramatic differences in pond ecosystems depending on the ratio of males to females in mosquitofish populations. Female-dominated ponds exhibited fewer zooplankton and a greater abundance of algae.
Researchers analyzed 640 pregnancies in 142 mares to understand the impact of maternal lineage on gestation length and foal characteristics. The study found that certain maternal lineages produce more female foals, with young and older mares contributing to this trend. These findings have implications for horse breeding practices.
A study by University of Sheffield and University of Bath found that female-biased populations have higher divorce rates, while male-dominated environments lead to increased short-term infidelity. The research also discovered that both sexes become more polygamous when the sex ratio is skewed towards the opposite sex.
A University of Calgary study found that earlier spring births result in a higher female-to-male sex ratio among big brown bats. This skewed sex ratio may be due to natural selection favoring females' reproductive success.
A study from the University of Minnesota's Carlson School of Management found that when men perceive women as scarce, they become more impulsive, save less, and increase borrowing. This effect is seen in both laboratory experiments and archival data from over 120 US cities.
A study found that stress in the second and third months of pregnancy can shorten pregnancies, increase the risk of pre-term births, and affect the ratio of male to female births. Exposure to stress itself, rather than other factors accompanying it, appears to have this impact.
A team of evolutionary biologists found that when mothers control offspring sex ratios, sexual selection collapses, and males lose their elaborate courtship displays to attract females. This twist adds unexpected complexity to Darwin's theory of sexual selection, suggesting that motherly control can override the need for showy males.
New research reveals that Indian families are selectively aborting girls if their first child is also a girl, leading to a widening imbalance in the child sex ratio. The study estimates that millions of selective abortions have occurred over the past few decades, contributing to the problem.
Research from the University of Arizona found that bacteria in the genus Rickettsia can rapidly evolve whiteflies, making them more likely to survive and reproduce. The bacteria manipulate sex ratios, causing more female offspring to be born, which is unusual for such a short period.
The sex ratio at birth is skewed due to son preference and easy access to sex-selective abortions, leading to a significant imbalance between males and females in China, India, and South Korea. The number of males under 20 exceeds the number of females by around 32 million in China.
Researchers found that male rats raised with lots of sisters spent less time mounting female rats, but still ejaculated equally. The males may be compensating for reduced attractiveness, suggesting families play a role in shaping personality and behavior.
Researchers found that rainfall affects sex ratios in African buffalo, with more males born during rainy seasons. The study suggests the presence of sex ratio genes influencing semen quality and female-biased sex ratios during dry periods.
A new study published in Current Biology found that a parasite killing male butterflies caused a rapid shift in the sex ratio of a tropical butterfly species, from 2:1 to 10:1. The researchers used museum specimens and modern tools to analyze the changes, providing insight into evolutionary processes.
A study found that fish with temperature-dependent sex determination are more vulnerable to climate change, with increasing temperatures leading to a shift towards males. Small changes in temperature can significantly alter the sex ratio, compromising the viability of some fish populations.
Researchers have identified a sex-ratio meiotic drive system in Drosophila simulans, with an X-linked distorter gene that creates skewed female litters and an autosomal suppressor gene that counteracts this effect. The findings provide insights into the molecular mechanisms underlying sex ratio distortion.
A study found that mothers who gained weight between their first and second pregnancies were more likely to have a baby boy. The researchers analyzed data from over 220,000 women and discovered a significant association between increased maternal weight gain and an increased male-to-female sex ratio in the second pregnancy.
New research reveals that shorebirds' breeding systems are shaped by the battle over childcare responsibilities. The study found that parents with demanding young are more likely to stay together to help rear their offspring, while those with harder-to-raise young are more likely to fight for mating opportunities.
Researchers found that female domesticated canaries varied the size of their eggs in response to the attractiveness of the male's song. The study highlights the importance of behavioral stimuli for reproductive physiology. In this experiment, attractive songs led to larger eggs, but no difference was observed in brood sex ratio.
Researchers at Cornell University found that higher-than-normal progesterone levels in female chickens during the first meiosis significantly produce more females. The study suggests that female birds manipulate sex ratios to adapt to their environment and ensure the next generation has enough females to care for.
Researchers found a significant decline in female water voles at a Norfolk site, with radio-collars potentially linked to the change. The study suggests that local resource competition may drive sex-ratio shifts in stressed females.
Researchers investigate the impact of partnership status on human sex ratios at birth, shedding new light on this complex topic. The study reveals intriguing findings about the dynamics between relationships and sex ratios, with potential implications for our understanding of human behavior.
A new study found that many fig wasp species are cryptic, meaning they are genetically identical but belong to different host fig species. This challenges current ideas about the stability and evolution of mutualisms, strengthening other critical parts of modern evolutionary theory.
Researchers from Italy studied over 14,000 births and found a significant disparity in sex ratios between optimal and sub-optimal reproductive conditions. The study suggests that nature tries to compensate for the vulnerability of male babies by favoring them in favorable months.