Gender distribution

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The gender distribution is the numerical ratio of the male to the female members of a population . According to Fisher's rule, it tends to have an even distribution of M (askulin): F (eminin) = 1: 1, but can vary depending on the species, such as with some species of bees or ants ; temporal fluctuations are also possible.

For the gender distribution in humans , natural as well as cultural influences are important (age of the mother, gender-related abortion , environmental influences), which is of interest to anthropologists and demographers . In 2018 the ratio M: F = 1.01: 1.

Individuals that cannot be assigned sexually (in botany, for example, sub-dioceses ) are not taken into account in this consideration.

Classification

Gender distribution of the total population: average worldwide 1.01 men / women; reddish - more men, bluish - more women.
Gender distribution of the under 15 year olds. For example, there is a clear predominance of male children in China due to gender-selective birth prevention.
Gender distribution of people over 65. The significantly lower life expectancy of the male population is noticeable in Russia, for example.

According to the developmental age of the individual, a distinction is made between primary, secondary and tertiary sex ratio.

Primary Sex Ratio : The sex ratio at the time of conception is unknown in humans. It cannot be determined directly, but can only be inferred indirectly from the gender distribution of the individuals born and those lost in the prenatal development phases. According to an estimate of a recent study, half of the male sex (proportion 0.5) after fertilization, the ratio M: F = 1: 1 (= 1.0). In older literature, a higher proportion of male zygotes is often assumed.

Secondary sex ratio : The sex ratio at birth in humans is around 1.05 male to 1 female, unless it is changed by gender-selective birth prevention . The higher proportion of male newborns of M: F = 1.05: 1 is the result of different prenatal mortality rates for embryos and fetuses of different sexes. Spontaneous abortion of male embryos is more common in the first week pc , and early miscarriage of female embryos or fetuses in the following 10–15 weeks ; Late miscarriages affect both sexes roughly equally, while intrauterine fetal death after the 25th week or stillbirths are more common in men.

Hunger periods can lead to fluctuations in the secondary sex ratio. Inadequate nutrition in pregnant women has an impact on the length of pregnancy, with a gender-different course in terms of nidation and fetal loss.

Tertiary sex ratio : The sex ratio in reproductive age is highly dependent on historical and social influences. Wars with high losses cause a shift in the relationship, because mostly only young men are drafted and killed in the war.

Germany and Austria

War dead

In Germany and Austria, as a result of the military losses of the First and, even more, the Second World War , which were mostly men, there was a sharp shift in the gender ratio for some age groups. After the war, this led to a large number of women who remained unintentionally single, which in turn had a negative impact on the birth rate under the social conditions prevailing at the time until the 1950s .

present

Gender distribution of the age group 18 to 29 years in Germany according to data from the 2011 census

The migration behavior of young men and women differs; a significant imbalance can be seen in the age group of 18 to 29 year olds. Young women are increasingly moving to large metropolitan areas, while young men are more likely to stay in their homeland (including in rural areas). As a result, almost all large cities (with the exception of the locations of technical universities such as Aachen , Karlsruhe or Dresden ) have a surplus of women in this age group, while almost all rural regions have a corresponding surplus of men in this age group. This is problematic if the imbalance is too great, which can have a negative effect on finding a partner and starting a family and thus leads to a tendency towards falling birth rates. In individual rural districts of Brandenburg and Mecklenburg-Western Pomerania, there are arithmetically fewer than 8 women for 10 men. It can be foreseen that a traditional normal biography with work and starting a family will be very difficult for these men. The Ilm district has the highest surplus of men in this age group with a ratio of 133 to 100, whereby this is mainly caused by the Technical University of Ilmenau and its student body. The highest surpluses not caused by male-related educational institutions were recorded in 2011 in the Demmin district and the Elbe-Elster district with 128 men to 100 women each. Heidelberg had the highest surplus of women with 81 men to 100 women and 123 women to 100 men.

Gender distribution of the age group 30 to 39 years in Germany according to data from the 2011 census

In the age group of 30 to 39 year olds in Germany, there is a drastic east-west difference, which was triggered by the migration of a large number of young East German women in the 1990s and early 2000s. As a result, many eastern German districts have a significant shortage of women, while some western German regions such as the Rhineland, Schleswig-Holstein and the Rhine-Main and Rhine-Neckar regions have a surplus of women in this age group. The future will show whether this migration behavior is a one-off effect from reunification or a permanent migration pattern. In any case, the current gender distribution has a negative effect on the number of births in East Germany.

When comparing the two age groups, it is noticeable that many large cities have a surplus among 18 to 29 year old women, while a deficit occurs among 30 to 39 year olds (e.g. Halle (Saale) with 89 men to 100 women between 18 and 29 and 112 men to 100 women between 30 and 39 or Trier with 88 to 100 against 110 to 100). Here the future will show whether this generation, in times of demographic change and reurbanisation tendencies , will stay in the big cities even after completing their training and starting a family or (as before) will migrate back to the rural areas.

Worldwide: life expectancy, migration and perinatal femicide

The gender ratio of men to women in industrialized nations is generally around 0.9 to 1.0, which is due to the lower life expectancy of men. The higher mortality of men means that the surplus of men present at birth turns into a surplus of women from around the age of 57.

The relationship is additionally shifted by external influences. Gender-specific health hazards, wars, work and marriage migration as well as legal or illegal influencing of the sex of one's own offspring can shift the gender distribution in one direction or the other.

In many of the successor states of the former Soviet Union , the life expectancy of men is significantly lower than that of women. Of the over 65-year-old residents of Ukraine, only 32% are men (Germany / Austria / Switzerland: 42% each). Reasons for this can still be unhealthy working conditions or the alcoholism, which is widespread in these countries, especially among men .

In the Arab Gulf States, due to considerable labor migration (in Qatar , for example, 81% of the population are foreigners), who predominantly bring men into the country without their families, there is the world's most unequal gender. In Qatar and the United Arab Emirates , only about 32% of the population is female.

In some cultures, killing female babies after birth can affect the gender balance. In East Asia , for cultural reasons, sons are seen as the support and inheritance of the family, while daughters are seen as a risk of poverty. In addition, there are additional influences such as the former, now abandoned one-child policy in the People's Republic of China , which denies parents of girls the “second chance” for a son, or the tradition of dowry in India , which means that a daughter is married for families threatening existence. In China there are 1133 newborn boys for every 1000 girls (DE / AT / CH: around 1055), and for children under 15 there are even 1170 boys for every 1000 girls in China.

Regulation theories

Ronald Aylmer Fisher , in his 1930 book The Genetical Theory of Natural Selection, outlined a model that explains the approximately 1: 1 gender distribution that typically occurs. Fisher postulated that the gender distribution is genetic . As a simple example, imagine that there is a relevant gene with two possible alleles A and B: Individuals who carry the allele A have on average more male offspring than female, and individuals who carry the allele B have im Cut more female offspring than males. If, for example, fewer males than females are born in the general population, then males have a greater chance of reproducing than females. That is why individuals who carry the A allele will have more grandchildren on average than individuals who carry the B allele. As a result, the proportion of allele A in the population increases over time. The result is a stable balance with a gender distribution of 1: 1. Bill Hamilton explained a possible mechanism for the theory in his 1967 publication Extraordinary sex ratios : If one sex is born less frequently, then in monogamous societies the reproductive chances of the rarer sex are higher. This results in a higher number of offspring.

Fisher's theory, however, was based on alleles that have a beneficial effect on the development of one's own sex during meiosis. The equal distribution of the sex chromosomes on the germ cells is due, among other things, to the lack of preference for the individual sex chromosomes during meiosis. The equal distribution represents an evolutionarily stable strategy .

See also

literature

  • Heinrich Zankl: The phenomenon of sexuality . Scientific Book Society 1999, ISBN 3-534-13313-7 .
  • Ronald Aylmer Fisher: The Genetical Theory of Natural Selection . Dover Publications Inc., ISBN 978-0-486-60466-4 .

Web links

  • CIA World Factbook 2011: Sex Ratio List of States by Gender Ratio
  • Statement with scientific justification of the Radiation Protection Commission: Influential factors on the sex ratio of newborns with special consideration of the effects of ionizing radiation from July 17, 2014 ( BAnz AT April 17, 2015 B2 )

Individual evidence

  1. ↑ Fisher's Rule. Retrieved April 5, 2019 .
  2. ↑ M. Neuhauser: HARDY, ICW (editor). Sex Ratios: Concepts and Research Methods. Cambridge University Press, Cambridge, 2002. xiii + 424 pp. £ 32.95 / $ 48.00. ISBN 0-521-66578-7 . In: Biometrics . tape 59 , no. 1 , March 2003, ISSN  0006-341X , p. 207-208 , doi : 10.1111 / 1541-0420.02611 .
  3. ↑ Field Listing :: Sex ratio - The World Factbook - Central Intelligence Agency. Retrieved April 5, 2019 . (under keyword "World").
  4. ↑ a b Orzack SH et al .: The human sex ratio from conception to birth . In: PNAS . 112, No. 16, April 21, 2015, pp. E2102-E2111. doi : 10.1073 / pnas.1416546112 . PMID 25825766 .
  5. ↑ The World Factbook - Sex Ratio. Central Intelligence Agency, January 15, 2013, accessed January 15, 2013 .
  6. ↑ Shige Song: Does famine influence sex ratio at birth? Evidence from the 1959–1961 Great Leap Forward Famine in China . In: Proc Biol Sci . 279, July 2012, pp. 2883-2890. doi : 10.1073 / pnas.1416546112 . PMC 25825766 (free full text).
  7. ↑ S. Song: Malnutrition, sex ratio, and selection: a study based on the great leap forward famine . In: Hum Nat . 25, No. 4, December 2014, pp. 580-595. doi : 10.1007 / s12110-014-9208-1 . PMID 25129431 .
  8. ↑ According to the results of the 1950 census, there were 100 men and 114.2 women in the Federal Republic of Germany including West Berlin; the 1961 census still showed a ratio of 100: 112.7. Calculated according to: Official register of municipalities for the Federal Republic of Germany - Edition 1961 - ed. from the Federal Statistical Office Wiesbaden, W. Kohlhammer, Stuttgart / Mainz 1963, p. 66 f.
  9. ↑ Population by demographic characteristics. Statistics Austria , December 14, 2015, accessed on December 25, 2015 : “The gender ratio of 866 men per 1000 women calculated in the 1951 census has increased to 950 men per 1000 women by 2011. One reason for the excess of women at the time - the fallen men of both world wars - has continuously lost importance, since most of the war widows have now died. "
  10. ↑ Gender distribution in the state of Brandenburg in the age group 18 to under 30 years
  11. ↑ a b c CIA World Factbook 2011: Sex Ratio. 2011, accessed January 24, 2012 .
  12. ↑ Overview in Therese Hesketh & Zhu Wei Xing (2006): Abnormal sex ratios in human populations: Causes and consequences. Proceedings of the National Academy of Sciences USA vol. 103 no. 36: 13271-13275. doi: 10.1073 / pnas.0602203103 (open access)
  13. ↑ Hamilton WD : Extraordinary sex ratios. A sex-ratio theory for sex linkage and inbreeding has new implications in cytogenetics and entomology . In: Science . 156, No. 3774, April 1967, pp. 477-88. bibcode : 1967Sci ... 156..477H . doi : 10.1126 / science.156.3774.477 . PMID 6021675 .
  14. ↑ Maynard Smith, J., Price, GR: The logic of animal conflict . In: Nature . 246, No. 5427, 1973, pp. 15-8. bibcode : 1973Natur.246 ... 15S . doi : 10.1038 / 246015a0 .