Boy or girl? It's in the father's genes

Boy or girl? It's in the father's genes

A Newcastle University study involving thousands of families is helping prospective parents work out whether they are likely to have sons or daughters.

The work by Corry Gellatly, a research scientist at the university, has shown that men inherit a tendency to have more sons or more daughters from their parents. This means that a man with many brothers is more likely to have sons, while a man with many sisters is more likely to have daughters.

The research involved a study of 927 family trees containing information on 556,387 people from North America and Europe going back to 1600.

"The family tree study showed that whether you’re likely to have a boy or a girl is inherited. We now know that men are more likely to have sons if they have more brothers but are more likely to have daughters if they have more sisters. However, in women, you just can’t predict it," Mr Gellatly explains.

Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother’s X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother’s to make a boy (XY).

The Newcastle University study suggests that an as-yet undiscovered gene controls whether a man’s sperm contains more X or more Y chromosomes, which affects the sex of his children. On a larger scale, the number of men with more X sperm compared to the number of men with more Y sperm affects the sex ratio of children born each year.

Sons or daughters?

A gene consists of two parts, known as alleles, one inherited from each parent. In his paper, Mr Gellatly demonstrates that it is likely 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, known as mf, produce a roughly equal number of X and Y sperm and have an approximately equal number of sons and daughters.
• The third, known as ff produce more X sperm and have more daughters.

“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. If there are too many males in the population, for example, females will more easily find a mate, so men who have more daughters will pass on more of their genes, causing more females to be born in later generations,” says Newcastle University researcher Mr Gellatly.

More boys born after the wars

In many of the countries that fought in the World Wars, there was a sudden increase in the number of boys born afterwards. The year after World War I ended, an extra two boys were born for every 100 girls in the UK, compared to the year before the war started. The gene, which Mr Gellatly has described in his research, could explain why this happened.

As the odds were in favour of men with more sons seeing a son return from the war, those sons were more likely to father boys themselves because they inherited that tendency from their fathers. In contrast, men with more daughters may have lost their only sons in the war and those sons would have been more likely to father girls. This would explain why the men that survived the war were more likely to have male children, which resulted in the boy-baby boom.

In most countries, for as long as records have been kept, more boys than girls have been born. In the UK and US, for example, there are currently about 105 males born for every 100 females.

It is well-documented that more males die in childhood and before they are old enough to have children. So in the same way that the gene may cause more boys to be born after wars, it may also cause more boys to be born each year.

How does the gene work?

The trees (above) illustrate how the gene works. It is a simplified example, in which men either have only sons, only daughters, or equal numbers of each, though in reality it is less clear cut. It shows that although the gene has no effect in females, they also carry the gene and pass it to their children.

In the first family tree (A) the grandfather is mm, so all his children are male. He only passes on the m allele, so his children are more likely to have the mm combination of alleles themselves. As a result, those sons may also have only sons (as shown). The grandsons have the mf combination of alleles, because they inherited an m from their father and an f from their mother. As a result, they have an equal number of sons and daughters (the great grandchildren).

In the second tree (B) the grandfather is ff, so all his children are female, they have the ff combination of alleles because their father and mother were both ff. One of the female children has her own children with a male who has the mm combination of alleles. That male determines the sex of the children, so the grandchildren are all male. The grandsons have the mf combination of alleles, because they inherited an m from their father and f from their mother. As a result, they have an equal number of sons and daughters (the great-grandchildren).

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Story Source:

Materials provided by Newcastle University. Note: Content may be edited for style and length.

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Journal Reference:

1. Gellatly et al. Trends in Population Sex Ratios May be Explained by Changes in the Frequencies of Polymorphic Alleles of a Sex Ratio Gene. Evolutionary Biology, Dec 11, 2008; DOI: 10.1007/s11692-008-9046-3

Black holes – to be or not to be?

Those enigmatic black holes that lead to places unknown may not be what we thought they were – or at least that’s what some scientists think.

Since first proposed in 1784 by John Mitchell and their prediction in 1915 by Einstein’s theory of general relativity, evidence supporting the idea of black holes has continued to be found.

Described as infinitely dense points in space time – where not even light can escape – the presence of a black hole is thus inferred from the gravitational effects on the surrounding material. But what if something else – other than a black hole – could produce these same effects?

Such a question was addressed in two recent papers by a team of scientists at the University of Hawaii. They consider the consequences of replacing all black holes with a class of objects with ‘dark energy’ interiors known as Generic Objects of Dark Energy (GEODEs).

GEODEs, as they are now referred to, were first postulated in 1966 by Russian physicist Erast Gliner who suggested such objects as viable stellar remnants – the end point of stars.

The current understanding of stellar evolution states that for stars massive enough, the stellar remnants would be black holes. However, there are alternative models in which black hole interiors are described by a ‘dark energy’ equation of state – an equation describing the state of matter in terms of its pressure, temperature and volume, for example. Gliner thus proposed that instead of the end stage of stars gravitationally collapsing into black hole singularities, they would collapse into non-singular ‘dark energy’ objects (GEODEs) that only appear to be black holes from the outside.

Fifty years later, the Hawaiian team led by Kevin Croker and Joel Weiner started to look at the Friedman equations – the equations derived in 1922 that describe the expansion of the universe where ultra-dense regions of space such as neutron stars and black holes were treated in the same way as all other regions of space. The current understanding of a black hole is that of a singularity, which is a mathematical construct, and the physicality of such is yet to be understood. What Croker and Weiner found is that in order to incorporate black holes into the framework of an expanding universe, they can’t be singularities. When treated as non-singular GEODEs, they found that if only a fraction of the oldest stars collapsed in this way their averaged contribution would naturally produce the dark energy responsible for the accelerated expansion of the universe.

“If what we thought were black holes are actually objects without singularities, then the accelerated expansion of our universe is a natural consequence of Einstein’s theory of general relativity” – Dr Kevin Croker

The assumption made by cosmologists that the Universe is insensitive to the details of the objects it contains now it seems no longer stands. Not only does this give us a new way of looking at black holes, but also how we look at the Universe and its interconnectedness.

Further support of black holes being more like these GEODEs comes from the binary black hole merger mass found when assuming the colliding binary black holes were instead GEODEs. The resultant mass was greater than if the objects were black holes, and thus more in agreement with the 2016 LIGO-Virgo observations. Of course, this doesn’t confirm the existence of GEODEs just yet and, unfortunately, although observational signatures have been developed, there does not yet seem to be a way to distinguish between the different models.

As well, the GEODEs as proposed by Gliner and described by the team at the University of Hawaii are not the only description of such objects. In 2015, the Gravastar was described by physicists Pawel Mazur and Emil Mottola, and more than 80 years ago George McVittie proposed such a solution in which he describes a mass-particle in an expanding universe.

RSF in perspective

These ideas of objects where the interior region is made of the quantum vacuum – rather than a singularity – is very much in agreement with the unified physics perspective which sees all matter as emerging from the granular Planck scale structure of spacetime, otherwise known as the quantum vacuum. Furthermore, this quantized view of the Universe, as offered by the unified perspective in the form of the generalized holographic approach, similarly describes the expansion of the universe. Notably, the expansion of the Universe as originally proposed by George Lemaitre starts from a primeval super atom, not a singularity. Similarly, when we consider the vacuum energy of a Planck particle as it expands to the size of the Universe, we can explain the expansion of the Universe without the need for dark energy and as well resolving the vacuum catastrophe.

Article: https://bgr.com/2019/10/02/black-hole-theory-geode-study/

Boy or girl? It's in the father's genes

A Newcastle University study involving thousands of families is helping prospective parents work out whether they are likely to have sons or daughters.

The work by Corry Gellatly, a research scientist at the university, has shown that men inherit a tendency to have more sons or more daughters from their parents. This means that a man with many brothers is more likely to have sons, while a man with many sisters is more likely to have daughters.

The research involved a study of 927 family trees containing information on 556,387 people from North America and Europe going back to 1600.

"The family tree study showed that whether you’re likely to have a boy or a girl is inherited. We now know that men are more likely to have sons if they have more brothers but are more likely to have daughters if they have more sisters. However, in women, you just can’t predict it," Mr Gellatly explains.

Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother’s X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother’s to make a boy (XY).

The Newcastle University study suggests that an as-yet undiscovered gene controls whether a man’s sperm contains more X or more Y chromosomes, which affects the sex of his children. On a larger scale, the number of men with more X sperm compared to the number of men with more Y sperm affects the sex ratio of children born each year.

Sons or daughters?

A gene consists of two parts, known as alleles, one inherited from each parent. In his paper, Mr Gellatly demonstrates that it is likely 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, known as mf, produce a roughly equal number of X and Y sperm and have an approximately equal number of sons and daughters.
• The third, known as ff produce more X sperm and have more daughters.

“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. If there are too many males in the population, for example, females will more easily find a mate, so men who have more daughters will pass on more of their genes, causing more females to be born in later generations,” says Newcastle University researcher Mr Gellatly.

More boys born after the wars

In many of the countries that fought in the World Wars, there was a sudden increase in the number of boys born afterwards. The year after World War I ended, an extra two boys were born for every 100 girls in the UK, compared to the year before the war started. The gene, which Mr Gellatly has described in his research, could explain why this happened.

As the odds were in favour of men with more sons seeing a son return from the war, those sons were more likely to father boys themselves because they inherited that tendency from their fathers. In contrast, men with more daughters may have lost their only sons in the war and those sons would have been more likely to father girls. This would explain why the men that survived the war were more likely to have male children, which resulted in the boy-baby boom.

In most countries, for as long as records have been kept, more boys than girls have been born. In the UK and US, for example, there are currently about 105 males born for every 100 females.

It is well-documented that more males die in childhood and before they are old enough to have children. So in the same way that the gene may cause more boys to be born after wars, it may also cause more boys to be born each year.

How does the gene work?

The trees (above) illustrate how the gene works. It is a simplified example, in which men either have only sons, only daughters, or equal numbers of each, though in reality it is less clear cut. It shows that although the gene has no effect in females, they also carry the gene and pass it to their children.

In the first family tree (A) the grandfather is mm, so all his children are male. He only passes on the m allele, so his children are more likely to have the mm combination of alleles themselves. As a result, those sons may also have only sons (as shown). The grandsons have the mf combination of alleles, because they inherited an m from their father and an f from their mother. As a result, they have an equal number of sons and daughters (the great grandchildren).

In the second tree (B) the grandfather is ff, so all his children are female, they have the ff combination of alleles because their father and mother were both ff. One of the female children has her own children with a male who has the mm combination of alleles. That male determines the sex of the children, so the grandchildren are all male. The grandsons have the mf combination of alleles, because they inherited an m from their father and f from their mother. As a result, they have an equal number of sons and daughters (the great-grandchildren).

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Story Source:

Materials provided by Newcastle University. Note: Content may be edited for style and length.