Why Do I Keep Having Girl Babies?

What does it mean when you keep having girls?

How Dad’s Genes Affect Baby’s Gender – A gene, explains Dr. Langdon, consists of two parts, known as “alleles,” one inherited from each parent. “Newcastle researcher Corry Gellatly demonstrates that it is likely that men carry two different types of allele, which results in three possible combinations in a gene that controls the ratio of X and Y sperm.” Men with the first combination, known as mm, produce more Y sperm and have more sons.

• The second combination, known as mf, produces a roughly equal number of X and Y sperm, and have an approximately equal number of sons and daughters.
• The third combination, known as ff, produce more X sperm and have more daughters.” According to Dr.
• Langdon, “The gene that is passed on from both parents, which causes some men to have more sons and some to have more daughters, may explain why we see the number of men and women roughly balanced in a population.” As we can tell from a variety of studies, more research needs to be done into why women only give birth to boys or girls.

Much of the research has been focused on men because they have the deciding chromosome, but more studies can be done to look at women’s family trees to see if any type of pattern can be determined.

Why are there more girl babies?

Climate change will affect gender ratio among newborns, scientists say Global warming will have a variety of effects on our planet, yet it may also directly impact our human biology, research suggests. Specifically, climate change could alter the proportion of male and female newborns, with more boys born in places where temperatures rise and fewer boys born in places with other environmental changes, such as drought or wildfire caused by global warming.

A in Japan found a link between temperature fluctuations and a lower male-to-female sex ratio at birth, with conceptions of boys especially vulnerable to external stress factors, wrote Dr. Misao Fukuda, lead study author and founder of the M&K Health Institute in Hyogo. Last summer, Fukuda and his colleagues published a separate looking at births in areas hit by environmental events that caused extreme stress.

They included Hyogo Prefecture after the Kobe earthquake of 1995; Tohoku after the Great East Japan Earthquake of 2011 (and subsequent nuclear disaster at the Fukushima Daichii power plant); and Kumamoto Prefecture after the 2016 earthquakes. Nine months after these disasters, the proportion of male babies born in these prefectures declined by between 6% and 14% from the previous year.

1. This data supports the idea that major stress affects gestation, which in turn alters the newborn sex ratio, Fukuda and his co-authors wrote.
2. Stress stemming directly from “climate events caused by global warming” might also affect the sex ratio, Fukuda wrote in an email.
3. Though scientists do not know how stress affects gestation, Fukuda theorizes that the vulnerability of Y-bearing sperm cells, male embryos and/or male fetuses to stress is why “subtle significant changes in sex ratios” occur.

Scientists believe that the sex ratio is equal at conception, explained Steven Orzack, president and senior research scientist of the Fresh Pond Research Institute in Cambridge, Massachusetts. But more than half of all human conceptions die during gestation, and this results in a sex imbalance at birth.

1. Overall, more females die during pregnancy than do males.
2. So that’s why there’s an excess number of males at birth,” said Orzack, who has,
3. Ray Catalano, a professor in the school of public health at the University of California, Berkeley, explained that the process of natural selection in utero is why deaths occur during gestation.

A mother’s biology spontaneously aborts some conceptions in utero but not others. The factors that filter out who “gets through” from conception to birth include chromosomal or genetic abnormalities of the fetus or the mother’s stress response to changes in her environment, Catalano said.

Because the ovaries of a female fetus carry all the eggs she will ever possess, the possibility of genetic defects being found in a female (and her eggs, which represent her potential children) are greater than the possibility of defects in a male fetus, which carries only his own genes. Worldwide, the newborn sex ratio averages 103 to 106 males born for every 100 females, Catalano explained.

In part, this is a result of the fact that a male infant are “a relatively frail organism,” he said. “For every society, for every year, the human being most likely to die is male infants. And that’s true for every society that we have data for,” Catalano said,

• The reasons why are not understood, but some scientists believe that boys are and more susceptible to diseases and premature death.
• The general theory as to why the sex ratio is not equal at birth is that if you want the sex ratio to be 50:50 by reproductive age, you want a few more males than females at birth because more males than females will probably die in early childhood, Catalano said.

What Catalano found when studying populations of Danes, Finns, Norwegians and Swedes born between 1878 and 1914 is that colder years meant, Yet years of fewer males meant hardier baby boys, who were less likely to die in infancy, he found. These boys grew into men who had a larger-than-expected number of children.

This is evidence of selection in utero at work, he said. Effects of global warming will also shape the selection process in utero, Catalano said. The Earth is undergoing a process of rapid change. “If you start to change the environment relatively quickly – within 100, 150 years; in evolutionary time, that’s a blink of the eye – what that means is that you’re going to change the environment in which human gestations occur,” Catalano said.

Add to that the fact that climate change models don’t just predict that Earth will become warmer. “What they predict is that things will get less predictable,” he said: We’ll have greater swings of temperatures with higher highs, lower lows and faster oscillations between the two extremes.

Extreme weather and subsequent environmental effects, such as droughts, will probably lead to human stress. That stress is likely to affect the birth sex ratio, and there will then be human adaptation – the natural evolutionary response, Catalano said. “When you change the climate the way we’re changing it, you will change, profoundly, the characteristics of the population.” Samuli Helle, a senior researcher in the Section of Ecology, Department of Biology at the University of Turku in Finland, also found that “warmer temperatures bring sons.” In his study of the Sami people of Northern Finland he was also able to quantify the effect: For every 1 degree Celsius (1.8 degrees Fahrenheit) rise in temperature, there was a 0.06% increase in the ratio of newborn boys compared with girls.

For example, he said, an annual increase of 3 degrees Celsius (5.4 degrees Fahrenheit) would translate to a 0.18% higher ratio of male-to-female newborns. “Not a dramatic influence at first sight but it should be remembered that in large populations such effect size might mean thousands of ‘extra’ boys annually,” Helle wrote in an email.

Helle also said events caused by global warming, such as forest fires and floods, might also impact the sex ratio, though the scale would not necessarily be global. “Such influences are more likely to be local, since the climate is warming up differently in different parts of the world. Likewise, environmental hazards are also likely to have spatially rather limited influences on human reproduction,” he wrote.

Helle said there are also, potentially, several factors that influence the human birth sex ratio (and in both directions), so he doesn’t expect to see global scale effects just due to climate change in the near future. Orzack does not believe there’s enough evidence to definitively state that climate change affects the newborn sex ratio.

• There is a trend in a number of countries towards a less male-biased sex ratio at birth.
• Orzack said, though he does not know whether this trend is a direct consequence of global climate change.
• However, this trend may be due to the effects of pollution, he said, and this “may be a secondary consequence of global climate change.” Fukuda believes that any potential effects of climate change on the newborn sex ratio “may not be uniform” around the globe.

“It may depend on different environmental factors of each place,” he wrote. “Extremely hot or cold weather” most markedly influenced the birth sex ratio, while more moderate shifts did not always show an effect. Weak or strong, any effects probably would not be long-lasting, Fukuda said.

• His earthquake study found that the newborn sex ratio returned to normal within a few months.
• The “Kobe earthquake took one month, Tohoku earthquake two months, and Kumamoto one month,” he said.
• Ultimately, for Fukuda, the importance of the newborn sex ratio is less societal, more medical.
• The importance of the newborn sex ratio is as a “sensitive reproductive health indicator,” he said.

“Extreme temperature fluctuation affects birth weight.” Catalano’s concern, though, is evolution. “Humans are incredibly adaptable, we got through the Great Ice Age,” he said, so he has no fears that we will adapt to climate change. “What will we be after that adaption? We will be different,” he said.

How do I increase my chance of having a boy?

Deep penetration, for example doggy style, means the male sperm that can swim faster start their race closer to the cervix and are more likely to reach the egg first, resulting in a boy. To try and conceive a girl, Shettles suggested avoiding deep penetration, favoring the missionary position.

Is it more common to have a baby girl?

How does sex ratio at birth vary across the world? We might expect that naturally an equal number of boys and girls are born, but this is not the case. There are biological reasons why more boys than girls are born each year: around 105 boys per 100 girls.

• But in countries with a strong son preference, the sex ratio is even more skewed.
• August 06, 2019 Across the world there are differences in the sex ratio at different life stages.
• This imbalance in the male and female population can in some cases be traced back to birth: in some countries the number of boys and girls born each year is significantly skewed.

In the map we see the differences in sex ratio at birth across the world. Here the sex ratio is measured as the number of male births for every 100 female births; a value greater than 100 indicates there are more boys than girls born that year. A figure of 110 would indicate that there are 110 male births for every 100 female births.

The first striking point is that in every single country of the world there are more boys born than girls. This has been true for all years for which we have data (as far back as 1950) in all countries of the world, as you can when you move the timeslider below the map further back. Does this mean every country selects for boys prior to birth; for example, through induced abortion practices which preferentially select for boys? Not necessarily.

In the absence of selective abortion practices, births in a given population are typically male-biased – the chances of having a boy are very slightly higher than having a girl.

What causes more girls than boys?

The equatorial enigma: Why are more girls than boys born in the Aristotle once suggested that the sex of a child was determined by the ardour of the man at the time of insemination, whereas other ancient Greek philosophers thought that it had something to do with the left and right sides of the body.

Two millennia later, an 18th-century French surgeon writing under the pseudonym of Procope Couteau took up the idea and advised men wishing to have baby boys to cut off their left testicle – a procedure no more painful than extracting a tooth, he said. In more recent times, prospective parents wishing for either a boy or a girl have been offered all manner of remedies and food supplements to affect the sex of a baby.

But none of these folk recipes – even those involving crystals under the bed – has been able to alter the fundamental biology that determines the 50:50 sex ratio. A study published yesterday, however, has revealed a new twist to an ancient story. Scientists have found that the probability of giving birth to a baby girl rather than a baby boy increases significantly the nearer the mother lives to the equator.

• Conversely, the higher the latitude – and the further away from the equator – the greater the chances of a woman having a baby boy.
• Risten Navara of the University of Georgia in Athens studied the sex ratio of newborn boys to girls in 202 countries, from northern Europe to equatorial Africa, and found a clear link between latitude and a skewed sex ratio.

The nearer to the equator the greater the probability of baby girls, according to the study published in the journal Biology Letters. The natural sex ratio at birth is, in fact, slightly biased towards males in humans, with about 106 boys being born to every 100 girls.

• This sex ratio of 51.5 per cent in favour of boys is believed to be nature’s way of balancing the slightly increased risk of premature death in young males, and so bringing the overall sex ratio in the child-rearing age groups nearer to the natural balance of 50:50.
• Dr Navara, however, found that this average sex ratio at birth masks an underlying geographical trend.

Using data on global birth rates compiled by the Central Intelligence Agency, Dr Navara found that countries in tropical latitudes produced significantly fewer boys – 51.1 per cent males – compared to countries in temperate and subarctic regions, where the sex ratio is 51.3 per cent in favour of boys.

• The difference may seem small, but it is nevertheless statistically significant, Dr Navara said.
• It was even larger between some of the countries in the study.
• In tropical Central African Republic, for instance, the sex ratio was 49 per cent boys, whereas in more temperate China it was 53 per cent in favour of baby boys, she said.

“We found that this difference was independent of other cultural variables, including socio-economic status. It was an over-arching pattern and this effect remained despite enormous cultural variations between the countries we looked at,” she said. Access unlimited streaming of movies and TV shows with Amazon Prime Video Sign up now for a 30-day free trial Access unlimited streaming of movies and TV shows with Amazon Prime Video Sign up now for a 30-day free trial The sex ratio is an important biological factor in evolution and any shift away from the 50:50 norm provokes fierce debate among evolutionists.

1. But the determination of sex itself is not controversial.
2. Sex in mammals is determined by the type of sperm that fertilises the egg.
3. A sperm carrying the X chromosome of the man will become a female embryo whereas a sperm carrying the Y chromosome will produce a female embryo at conception.
4. In theory, men produce equal numbers of X and Y sperm which means that the sex ratio at birth should be 50:50.

Evolutionary biologists have shown using mathematical models that any movement away from the 50:50 ratio should become unstable, which is why there should be equal numbers of baby boys and baby girls being born in the population. However, there are possible exceptions to this rule.

One exception is if male embryos and newborn boys are more likely to die prematurely. As a result of this increased risk for males, nature has compensated by skewing the birth rate in favour of boys, or so it was believed. Another could come about if food is at risk of being in short supply. In hard times, it should in theory be more advantageous to give birth to males rather than females because females need more energy than males because of the effort of producing eggs and being pregnant.

A study in Italy has, for instance, found that couples are more likely to conceive a boy in autumn, while those who want a girl should conceive in spring. It was thought that nature favours conception of boys from September to November and girls from March to May.

1. One explanation may be the evolutionary necessity of keeping the overall sex ratio close to the 50:50 norm.
2. Another could be due to seasonal variations in the availability of food.
3. This underlying biological trend may now be showing itself up more clearly in the latest study on latitude.
4. Dr Navara said that the difference in the birth sex ratio between higher and lower latitudes may reflect an ancient evolutionary mechanism reflecting the fact that food resources in more northerly regions are more varied than in the tropics.

“This study really reminds us of our evolutionary roots. Despite enormous cultural and socio-economic variability, we continue to adjust reproductive patterns in response to environmental cues, just as we were originally programmed to do,” she said. This biological trend works independently of cultural factors that may work in favour of one sex over another.

• In some societies in Asia and Africa, for instance, baby boys are favoured over girls and the rise in selective abortions and infanticide has skewed the overall sex ratio in favour of males.
• Dr Navara said she took this into account in her study by taking out those countries where selective abortions based on the sex of the foetus are known to occur.

“I eliminated some Asian and African countries to get rid of any sex-specific abortion,” she said. The trend in favour of women giving birth to girls the nearer they are to the equator was still significant, she said. But the research does not suggest that simply having a romantic holiday in a tropical country could increase a woman’s chances of ending up with a baby girl.

Why are baby girls more than boys?

Typically, there are more male babies born than females, with the global average lying at 105 boys born for every 100 girls. Although more males are born almost universally, there are some incidences of higher number of females being born too. But why is this, and how does it happen? Some places in the world seem to have a particularly high share of girls.

Although more boys are still born in places, there are significantly more girls than average. Rwanda for example, is the country with the lowest male-female birth ratio, with just 101 boys born for every girl. Similar figures also exist in other Sub-Saharan countries such as the Ivory Coast (102) and Togo (102) (Livingston: 2013).

But why is this? One reason for more females being born than males in these countries may be related to the practice of polygamy, or having multiple wives. With fewer women being sexually available for men, a more practical way to ensure the passing on of genes would be to produce more female offspring than male. Another theory is that women living in harsh conditions with fewer resources suppress the survival of boys in the womb. As male fetuses are more likely to be miscarried or stillborn than female fetuses and, once born, tend to suffer from more fatal diseases, and take more mortal risks than females, their chance of making it to breeding age is less (MinuteEarth: 2014).

This means that a more secure way to ensure the passing of genes to future generations would again be via producing girls, and not boys. However, there may be other explanations for a higher likelihood of bearing female. In industrialised countries for example, the ratio of males to females being born has been decreasing since the 1950’s.

For a time, it was presumed that older parents had reduced chances of producing sons. Although there may be some relationship between age and the sex of children born, a study conducted in Denmark found that 51.6% of children born to fathers younger than 25 were male, whereas 51% of children born to fathers over 40 were male.

Thus, it is unlikely that the declining male-female ratio of births in industrialized countries is solely reliant on this factor (Weisskopf: 2004). Perhaps a larger factor influencing the birth ratio of males to females in these countries are chemicals. For example, studies have found that prospective mothers taking clomiphene citrate (Clomid) for infertility bore male babies only 48.5% of the time.

Meanwhile, a study looking at workers producing 1,2-dibromo-3-chloropropane (DBCP), a chemical that kills worms in agriculture, saw even larger decreases in the number of male babies born. While exposure to the chemical suppressed sperm quality to the point of being unable to pass offspring, after exposure to the substance ended, 36 children were born to 44 of the workers. Such incidences of chemical exposures seem to have affected the birth of boys on larger scales too. For example, similar decreases in the male-female birth ratio occurred from fathers’ exposure to dioxin and dioxin-like chemicals after an explosion in an herbicide factory in Seveso, Italy, in 1976, and a contamination of rice oil used in Taiwan.

For fathers who were under 19 during the incident in Seveso, their male-female birth ratio decreased to just 38.2%, while for fathers exposed to the rice oil contamination aged under 20, experienced a male-female birth ratio of just 45.8%. This means that chemical exposure, especially at a young age, seems to have a large influence on the incidence of boys or girls being born.

The reasons for this however require further research. To conclude, many factors influence whether male or female babies are born. Although the natural bias may be towards more males being born, under certain environmental conditions, such as strained resources or chemical interference with male gonads, more females may be born as they are more likely to survive to breeding age than males.

Is it easier to conceive a girl than boy?

Increasing your chance of Conceiving a Girl Are you longing for a girl? Do you already have a one boy or more and now want to see if you can tip the gender balance in your household? There are lots of theories and claims made about influencing the chances of having either a boy or a girl baby, but the scientific facts are absolutely clear.

Is it genetic to have more girls than boys?

Century-old theories that having girls or boys ‘runs in families’ have been upended by a University of Queensland study, proving parents’ genes do not determine their child’s gender. Dr Brendan Zietsch from UQ’s School of Psychology said the study was the largest conducted on the often-debated question, and concluded the sex of offspring is essentially random.

“We found individuals don’t have an innate tendency to have offspring of one or the other gender,” Dr Zietsch said. “The chances are more like 51 to 49 of having a boy, but the genes of the mother and father don’t play any role. “These findings have crucial implications for biological and evolutionary theories of offspring sex ratios.” The study used data from Swedish population registers, which includes every Swede born since 1932, equating to 3,543,243 individuals and their 4,753,269 children.

The research team linked all family members and tested whether the sex of a person’s children was associated with the sex of their brother or sister’s children. Dr Zietsch said the large body of scientific theory around what influences whether someone has boys or girls had been proven to be wrong.

It was thought that rich or tall parents should have more boys and beautiful parents should have more girls. “It was also thought that parents’ hormone levels at the time of conception were important. “Our results rule out all these possibilities and suggest a rethink of offspring sex ratio theory is necessary to properly understand why offspring sex ratios appear to vary, for example, across countries.” The study was published in the scientific journal Proceedings of the Royal Society B (https://doi.org/10.1098/rspb.2019.2849).

Media: Dr Brendan Zietsch, [email protected]; Kirsten O’Leary, UQ Communications, [email protected], +61 73365 7436.

What month are babies born the most?

Why are these the most popular birth months? – “Of course, the first thing we do when we see a full labor and delivery floor is count back nine months to see what was going on! Terms like ‘polar vortex’ strike a little bit of fear in anyone who helps deliver babies.” “We do see many women who try planning what month to get pregnant, with a hopeful due date in mind.

Is it a 50% chance of having a boy?

Is it a boy or a girl? The father’s family might provide a clue | Your Pregnancy Matters | UT Southwestern Medical Center Everyone wonders: Is it a boy or a girl? The answer is in the genes, and the father’s family history. Is it a boy or a girl? That’s the most common question I hear during ultrasounds. Many couples want to know, And there are plenty of that patients reference when guessing the sex of their baby.

1. My general response is that it’s a 50/50 chance that a woman will have a boy or a girl.
2. But that’s not exactly true – there’s actually a slight bias toward male births.
3. The ratio of male to female births, called the sex ratio, is about, according to the World Health Organization (WHO).
4. This means about 51% of deliveries result in a baby boy.

While the sex ratio can be distorted by populations that selectively value male over female births, there could be another explanation. Research suggests the slight natural skew of the sex ratio could be nature’s way of adjusting for higher death rates in males due to injuries, accidents, and war.

For example, in England around 1900, 50.8% of births were boys. Following World Wars I and II, the rate of male births increased to 51.6%. This may not seem like a big difference, but it resulted in 32 more boys than girls born for every thousand births. Similar changes were seen in other European countries as well following these wars.

It seems like sex ratio shifts should be a random phenomenon. But from a medical standpoint, perhaps there’s a genetic explanation to changes in the numbers of boy and girl babies at different times in history. : Is it a boy or a girl? The father’s family might provide a clue | Your Pregnancy Matters | UT Southwestern Medical Center

Is it more rare to have a boy?

Research over hundreds of years has consistently found that boys naturally outnumber girls at birth. The speculation is that this is nature’s way of countering the relatively high mortality rates of males, and creating more of a gender balance in the population. This increase in the sex ratio is driven largely by births in China, where sex ratios have declined slightly in recent years but remain the highest in the world. The world’s most populous country has 118 boys for every 100 girls, and accounts for 12% of births worldwide.

1. However, disproportionately large shares of baby boys are found in other countries scattered throughout Asia and the Caucasus, as well.
2. Azerbaijan, Armenia, Georgia, South Korea, and the Solomon Islands round out the list of places with the highest sex ratios.
3. India is tied with Macedonia, Montenegro, Papua New Guinea, Samoa, Serbia and Suriname for 7th place, with a ratio of 108 boys born for every 100 girls.

Even while some countries seem to have a disproportionate share of boys, others have particularly high shares of baby girls. While there are still slightly more boys born than girls in these places — which are centered in sub-Saharan Africa — the sex ratios are nonetheless much lower than average.

1. The six countries with the lowest sex ratios include: Rwanda, Sierra Leone, Togo, Zimbabwe, Ivory Coast, and Madagascar.
2. So what explains these differences in the shares of baby boys and girls? Perhaps the best-known reason relates to the practice of sex-selective abortion, which has been identified in Asia, and in the Caucasus, as well.

The ability to determine fetal sex, along with strong son preferences, accounts in large part for the high shares of boys in many countries in these regions. The desire to limit family size, either due to government regulations as in China, or due to global social and economic changes that have reduced the need for large families, seems to further contribute to sex-selective abortion and a dearth of baby girls.

• But this is only one of myriad factors that may be affecting the sex ratio at birth.
• Some research suggests that the share of newborn boys declines with older parents, and that the high share of girls in Sub-Saharan Africa may be linked to the practice of polygamy (multiple wives).
• What do these two phenomena have in common? Researchers hypothesize that both situations are associated with less frequent intercourse,

(For possible explanations of this association, see this article from the academic journal Human Reproduction,) On the opposite end of the spectrum, most research shows that the share of baby boys increases during and after wartime, And once again, frequency of intercourse is cited as the likely reason, at least in the case of post-war reunions. Gretchen Livingston is a former senior researcher focusing on fertility and family demographics at Pew Research Center.

Which month is best to conceive for a boy?

Seasons affect sex of babies, study reveals

• Some try crystals under the bed, others a Harley Street doctor but scientists have found the best way of improving the chances of conceiving either a boy or a girl.
• Some try crystals under the bed, others a Harley Street doctor but scientists have found the best way of improving the chances of conceiving either a boy or a girl.
• Couples who want a boy should try to conceive in autumn and those who want a girl have a better chance if they can conceive in spring, a study has found.
• Nature is designed to favour the conception of boys from September to November and girls from March to May because of an evolutionary mechanism aimed at keeping the overall sex ratio as near to 50:50 as possible, the scientists said.
• A team led by Angelo Cagnacci, a gynaecologist at the Policlinico of Modena in Italy, investigated the conception dates of 14,310 births at his clinic between 1995 and 2001 to see if the sex ratio varied substantially.

The normal balance of the sexes is tilted in favour of girls because of a higher mortality of males in the womb and at birth. That was why nature had tried to level the playing field by favouring boys in the best months for conception, Professor Cagnacci said.

1. Research in the journal Human Reproduction shows that 535 males were conceived in the most fertile month of autumn as opposed to 464 females, while only 487 males were conceived, compared with 513 females, in the worst month of spring.
2. “What is fascinating is the degree of disparity in the sex ratio, that the numbers of boys conceived compared with girls was so much higher in the favourable months when overall conception rates were high and so much lower in the unfavourable months when overall conception rates were low,” Dr Cagnacci said.
3. The scientists could not explain the mechanism, but Dr Cagnacci suggested it occurred early in pregnancy.

: Seasons affect sex of babies, study reveals

Which gender is born early?

Indirect data – If x correlates with y, and y correlates with z, then (unless countervailing factors operate), x correlates with z, In such a case, Occam’s Razor suggests that the possibility of such countervailing factors be provisionally ignored.

The sex of a zygote is associated with parental hormone concentrations around the time of conception, high concentrations of oestrogen and testosterone being associated with the subsequent births of boys, and high concentrations of progesterone and gonadotrophins with girls. There is a U-shaped regression of human offspring sex ratio (proportion male) on time of formation of the zygote within the fruitful cycle. There is a positive association between parental coital rate around the time of conception and offspring sex ratio. There is a-shaped regression of human sex ratio on duration of gestation (reported LMP to delivery). In some species of polytocous mammals, the variances of the distributions of the combinations of the sexes within litters is sub-binomial, i.e. there are more litters with equal numbers of males and females than would be expected under binomial sampling.

Using Occam’s Razor in the sense above, if A were true, then B must be true. And if B were true, then C, D and E must all be true. In the rest of this note, it will be shown how proposition B is dependent on A, and how C, D and E may be derived from B. The strength of the relevant direct data on all five propositions will be indicated.

What are the odds of having the same gender again?

It’s still just 50/50 probability, no matter how many children you have. How do mothers who only have boys deal with the sadness of knowing they’ll never have a baby girl?

What are the chances of having a boy after a girl?

50%. The gender of previous children doesn’t influence the chances of either gender of subsequent pregnancies. Each pregnancy is independent of all others. This is based on an analysis of the real numbers, not theoretical speculation.

Do all babies start out as a boy?

ABSTRACT – Sex differences of importance to health and human disease occur throughout the life span, although the specific expression of these differences varies at different stages of life. Some differences originate in events occurring in the intrauterine environment, where developmental processes differentially organize tissues for later activation in the male or female.

• In the prenatal period, sex determination and differentiation occur in a series of sequential processes governed by genetic and environmental factors.
• During the pubertal period, behavioral and hormonal changes manifest the secondary sexual characteristics that reinforce the sexual identity of the individual through adolescence and into adulthood.

Hormonal events occurring in puberty lay a framework for biological differences that persist through life and that contribute to variable onset and progression of disease in males and females. It is important to study sex differences at all stages of the life cycle, relying on animal models of disease and including sex as a variable in basic and clinical research designs.

All human individuals—whether they have an XX, an XY, or an atypical sex chromosome combination—begin development from the same starting point. During early development the gonads of the fetus remain undifferentiated; that is, all fetal genitalia are the same and are phenotypically female. After approximately 6 to 7 weeks of gestation, however, the expression of a gene on the Y chromosome induces changes that result in the development of the testes.

Thus, this gene is singularly important in inducing testis development. The production of testosterone at about 9 weeks of gestation results in the development of the reproductive tract and the masculinization (the normal development of male sex characteristics) of the brain and genitalia.

In contrast to the role of the fetal testis in differentiation of a male genital tract and external genitalia in utero, fetal ovarian secretions are not required for female sex differentiation. As these details point out, the basic differences between the sexes begin in the womb, and this chapter examines how sex differences develop and change across the lifetime.

The committee examined both normal and abnormal routes of development that lead individuals to become males and females and the changes during childhood, reproductive adulthood, and the later stages of life.

What is the scientific reason for baby boy?

Biological sex in healthy humans is determined by the presence of the sex chromosomes in the genetic code: two X chromosomes (XX) makes a girl, whereas an X and a Y chromosome (XY) makes a boy.

How many more girls than boys are there?

Are There More Boys or Girls? Our fan Aliza W. just asked us a great question: are there more girls or boys in the world? At birth, : for every 100 baby girls, there are 106 baby boys. If you look at people of all ages, though, it evens out to about 1 boy for every girl, partly because women live longer than men.

In fact, if you look only at people 65 years or older, there are only 3/4 as many men as women! Wee ones: Do you have more girls than boys in your family, or more boys than girls? How many of each? Little kids: If a boy swings on the monkey bars, then a girl, then a boydoes a girl or a boy go 6th? Bonus: If there are 7 kids on the jungle gym and there’s 1 more boy than girl, how many of each are there? Big kids: If 106 boys and 100 girls line up for tug-of-war, how many kids would that be in total? Bonus: If 19 more boys show up, how many more girls do we need to have equal numbers of each? The sky’s the limit: If 800 200-pound men do tug of war against 1,000 women, how much do the women have to weigh to match the men’s total weight? Answers: Wee ones: Different for everyonecount up your family! Little kids: A girl goes 6 th,

Bonus: 4 boys, 3 girls. Big kids: 206 kids. Bonus: 25 girls. The sky’s the limit: 160 pounds each, since the men weigh 160,000 total. : Are There More Boys or Girls?

Why do some families have all girls?

– Source: CNN ” data-fave-thumbnails=”, “small”: }” data-vr-video=”” data-show-html=”” data-byline-html=”” data-check-event-based-preview=”” data-network-id=”” data-details=””> After 14 sons, couple welcomes a baby girl 00:55 – Source: CNN CNN — My mother was one of four sisters. I have a younger sister, and between the two of us, we have four daughters. We’re not the only ones who appear to have one sex run in the family. Everyone knows a family who has a boy and a boy and then another, all in a row. But are some families really prone to giving birth to one sex over the other? Some scientists think whether you’re likely to have a girl or boy is inherited through the father, although nobody has identified a gene. Others have suggested that it comes down to heritable traits that could confer an evolutionary advantage on one sex, but not the other, when it’s time for offspring to reproduce. For example, studies have speculated that t all parents have more boys, or beautiful parents have more girls, although the theory has been criticized. Another hypothesis is that parents’ hormones at the moment of conception have an influence. However, a new study that examines the entire population of Sweden since 1932 says that the sex of offspring is purely down to chance. “We found individuals don’t have an innate tendency to have offspring of one or the other gender – instead, the sex of their offspring is essentially random,” said Dr. Brendan Zietsch, a fellow at the University of Queensland’s School of Psychology and the lead author of the study, which published Tuesday in the journal Proceedings of the Royal Society B. “If you have a lot of boys or girls in your family, it’s just a lucky coincidence,” Zietsch said. Using information from Swedish birth registries, the researchers compared whether siblings tended to have offspring of the same sex. Their statistical analysis ruled out the possibility that characteristics of the parents influence the likelihood of having boys or girls. “Because siblings share 50% of their genetics, if there was a genetic underpinning of offspring sex determination we would see an association between siblings with regard to offspring sex,” said Zietsch. “However, siblings did not tend to have offspring of the same sex – the probability of having, say, a girl, did not depend on whether one’s siblings had a girl or a boy.” Zietsch said the enormous size and accuracy of the data they used – 4.7 million births – meant they were “very confident” of the findings: “We analyzed all Swedes born after 1932.” Other research on the topic had used much smaller samples, which could have produced a false positive, said Zietsch. For example, a 2008 study of 927 family trees covering 556,387 people going back to the year 1600 found that if a man produced more sons than daughters, those sons were likely to have more sons. The study suggested that an as-yet undiscovered gene controlled whether a man’s sperm contains more X or more Y chromosomes, which affects the sex of his children. Boys generally have an X and Y chromosome and girls have two X chromosomes. Other researchers have found that when food is in short supply women are more likely to bear daughters than sons. A 2012 study analyzed the Great Leap Forward famine in China, one of the most disastrous in history, and found a sharp dip in the number of boys being born, although the reason for the dip was not clear. And some scientists think climate change could alter the proportion of male and female newborns, with more boys born in places where temperatures rise. “We can’t rule out the possibility that extreme environmental events, like famine, could affect offspring sex ratios. But we can say for sure that the variability of environments that Swedes born after 1932 experienced did not affect their having boys or girls,” Zietsch said.

What are the odds of having two daughters in a row?

If you have no children, there is a 25% chance your fist two will be girls. A 50% chance the first will be a girl and a 50% chance the second will be a girl, 0.5 x 0.5 = 0.25. If you already HAVE one girl, then with a 50% chance your next will be a girl, you have a 50% chance you will have two girls in a row.

Do older fathers have more daughters?

Why Are Older Parents More Likely to Have Daughters? One of the consistent findings in the field of reproductive medicine is that older parents are more likely to have daughters. Why? Previous studies have repeatedly found that one of the reliable predictors of the sex of the offspring is the age of the parent. Older parents are significantly more likely to have daughters than younger parents. The National Study replicates these findings from earlier studies. As the following graph shows, the association between the age of the parent and the sex of the first child is not monotonic, but there is a general decline in the proportion of sons as the parents get older. Teenage parents are particularly likely to have sons, with the proportion of sons at,5327, and older parents over the age of 40 are significantly less likely to have sons, with the proportion of sons at,3557. Two-thirds of children born to parents over 40 are girls! The bivariate correlation between the probability of having a son and the age of the parent is significantly negative ( r = -.030, p <,001, n = 9,301). Each year in the parent's age decreases the odds of having a son as the first child by 1%. As you can see in the following two graphs, the association between the age of the parents and the sex of the first child is stronger among women than among men. In fact, the bivariate correlation between the probability of having a son and the age of the parent is only statistically significantly negative among women ( r = -.34, p <,05, n = 4,864), not among men ( r = -.024, ns, n = 4,437). Among women, each year in age decreases the odds of having a son as the first child by 1.2%. However, the graph below clearly shows that fathers over the age of 40 are significantly less likely to have sons, with the proportion of sons at,3592. Given the prevalence of age homogamy, where the age of the mother and the age of the father are generally positively correlated such that younger women are typically married to younger men and older women are typically married to older men, the slight sex difference in the pattern is not important.

• The overall picture is that the older the parents (both the mother and the father), the more likely they are to have a daughter.
• The question is: why? Because both the quality of the eggs and the quality of the sperm decrease with age, it is tempting to explain the declining likelihood of having a son among older parents potentially in terms of such quality of gametes (although I’m not aware of any argument that suggests that lower-quality gametes are more likely to produce girls).

However, such explanations, even when correct, are proximate, not ultimate. They answer the question of how ; they don’t answer the question of why, The lower quality of gametes, if it indeed lowers the probability of producing boys, is the mechanism that evolution employs to make sure that older parents are more likely to have daughters.

But such a proximate mechanism does not explain why evolution “wanted” to make sure that older parents are more likely to have daughters, in other words, why it is adaptive for older parents to have daughters, not sons. That requires an ultimate evolutionary explanation. As I explain in an earlier, parental investment is much more crucial for the future reproductive success of sons than for that of daughters.

Sons’ reproductive success largely hinges on the status and resources that they inherit from their parents, particularly, their fathers. Sons therefore need parents to invest in them, to make sure that they inherit the status and the resources of the family.

In sharp contrast, daughters’ future reproductive success is largely determined by their youth and physical, Once they are conceived with particular that influence their physical attractiveness, there is very little that parents can do to increase their daughters’ future reproductive success, beyond keeping them alive and healthy.

There is absolutely nothing that parents can do to affect the progression of time that determines the daughters’ age, nor is there anything they can do after the conception to influence the daughters’ physical appearance (once again, beyond keeping them healthy).

The problem with older parents, of course, is that they are more likely to die sooner. If the parents die before the children reach maturity, it will have a greater negative impact on sons’ future reproductive success than on daughters’. This may be one evolutionary, ultimate reason why older parents are more likely to have daughters.

Parents may be evolutionarily designed to have more daughters when they are older, so that, when they die, they are less likely to leave sons who have not sexually matured. Being orphaned young is bad both for boys and girls, but it’s much worse for boys than for girls. : Why Are Older Parents More Likely to Have Daughters?

Who genes are stronger male or female when having a baby?

Womb Wars – As anyone who took Biology 101 remembers, we’re all composites of our parents. Mom gives us 50 percent of our DNA and our dad fills in the other half. But only the students who were really paying attention are likely to recall that not all genes are expressed equally.

In many mammals, the scales seem to be tipped toward fathers, whose genes often win the war underway in the womb. This is due in part to the perplexing puzzle known as epigenetics. Basically, epigenetics influence the way your DNA is actually expressed, This can alter your dad’s sperm, which in turn may affect you.

It can also affect the way the genes you have are read — and the proteins they produce — across your lifetime. Take, for example, a 2015 study in Nature Genetics that showed the expression of thousands of different genes in mice varied depending on whether they came from a mom or a dad.

• While each parent technically contributed half of an offspring’s genome, approximately 60 percent of the dad’s genes were more expressive than the mom’s.
• These epigenetic factors can play a role in numerous parts of your life, but they aren’t just about quirks like eye color or whether or not you can roll your tongue.

Researchers think differential expression can also change your mental and physical wellbeing, If mom has a predisposition toward a given disease, you may still inherit it. But if your dad passes on genes that pass on an illness or a mutation of some kind, you may be more likely to be sick yourself, simply because his genes are more likely to be expressed.

Which parent determines gender?

How is gender determined? – Besides the pressing question of what the sex of your child will be, you may be asking yourself which parent ultimately determines the baby’s sex. Female eggs can only transfer X chromosomes, while sperm cells transfer both X and Y chromosomes.

The sex of the child is determined by the father, as a sperm cells transmit either the Y or X chromosome. A subsequent question is whether sperm cells transmit Y and X chromosomes to the same extent. Y chromosomal sperm are proportionally biased and the sex ratio in newborns can vary. So, assuming their chances are even of being one sex or the other is an old wives’ tale that does not always hold true.

Different genes can regulate whether a man’s sperm contains more Y chromosomes or more X chromosomes, and this determines the sex. If a man has mostly or only brothers, he is likely to have sons of his own. If the man himself has one or more sisters, he is likely to have daughters.

If a man has 2 ‘m’ genes, he is likely to have Y chromosome sperm and have sons. If a man has 1 ‘m’ and 1 ‘f’ none, he is likely to produce both X and Y chromosomes. If a man has 2 ‘f’ genes, he is likely to have X chromosomes in his sperm and have daughters.