Aufgrund der Möglichkeit, das Geschlecht vor der Geburt zu bestimmen, haben sich neue Möglichkeiten entwickelt, das Geschlecht der Kinder, die man tatsächlich bekommt über geschlechts-selektive Abtreibungen zu bestimmen.
Zunächst erst einmal zu der Frage, warum es überhaupt eine ungefähr gleiche Anzahl von Männern und Frauen gibt: Fishers Prinzip:
W.D. Hamilton gave the following basic explanation in his 1967 paper on „Extraordinary sex ratios“,[4] given the condition that males and females cost equal amounts to produce:
- Suppose male births are less common than female.
- A newborn male then has better mating prospects than a newborn female, and therefore can expect to have more offspring.
- Therefore parents genetically disposed to produce males tend to have more than average numbers of grandchildren born to them.
- Therefore the genes for male-producing tendencies spread, and male births become more common. As the 1:1 sex ratio is approached, the advantage associated with producing males dies away. The same reasoning holds if females are substituted for males throughout.
- Therefore 1:1 is the equilibrium ratio.
In modern language, the 1:1 ratio is the evolutionarily stable strategy (ESS).[5] The claim previously made here that „all strategies have equal fitness when the sex ratio is 1:1 (i.e. an individual who produces strictly sons has just as many offspring as an individual producing sons and daughters with equal probability), and thus can invade the population“ is incorrect because it does not consider that the fitness of the sons is reduced due to an excess of males, and therefore the strategy cannot invade the population.
Demnach sollte sich normalerweise ein ungefähres Gleichgewicht einstellen.
Allerdings können bestimmte Umstände dazu führen, dass es günstiger ist, Mädchen oder Jungen zu bekommen: Das Trivars-Willard-Prinzip:
Das Trivers-Willard-Prinzip wurde 1973[1] von Robert Trivers und Dan Willard als soziobiologischer Effekt beschrieben. Das Prinzip besagt, dass aus Gründen der genetischen Fitnessmaximierung statushöhere Eltern eher in die Aufzucht von Jungen investieren, statusniedrigere dagegen eher in die Aufzucht von Mädchen.
Der Grund hierfür ist vermutlich, dass im Rahmen der sexuellen Selektion, das heißt im weitesten Sinne der Partnerwahl, Männer mit guten (materiellen) Ressourcen bessere Chancen bei Frauen haben, da diese Väter für ihre Kinder bevorzugen, die deren Überleben sichern können. Wenn eine statusniedrige Mutter in die Aufzucht ihres männlichen Nachwuchses investiert, muss sie davon ausgehen, dass dieser bei der Partnersuche keine oder eine geringe Chance hat, eine geeignete Partnerin zu finden. Für Mädchen gilt dies nicht.
Ihre Chancen werden durch Jugendlichkeit und Gesundheit maximiert, was durch eine gute Pflege gegeben werden kann, unabhängig von anderen Ressourcen wie Status, Geld und Einfluss. Andersherum kann eine statushohe Mutter davon ausgehen, dass ihr männlicher Nachwuchs mit an Sicherheit grenzender Wahrscheinlichkeit eine geeignete Partnerin finden wird. Die Investition in dessen Aufzucht lohnt sich somit. Andererseits stellt die Aufzucht eines Mädchens für diese Mutter ein gewisses Risiko dar, da der weibliche Nachwuchs auch mit Mädchen aus niedrigeren Statusklassen konkurrieren muss und darum keine so hohe Sicherung des Reproduktionserfolges darstellt. Einer Untersuchung britischer und US-amerikanischer Daten zufolge haben misshandelte Frauen, die mit gewalttätigen Männern zusammen sind, signifikant mehr Söhne als Töchter. Diese Beobachtungen sind konsistent mit dem Trivers-Willard-Prinzip
Diese evolutionären Prinzipien spielen aber als biologische Prozesse bei der Abtreibung keine Rolle, wenn die dahinterstehenden Erwägungen andererseits auch mit in die Abtreibungsdebatte mit reinspielen.
Beispielsweise kann bei einer Ein-Kind-Politik wie in China ein Grund sein, dass man als relativ gut gestelltes chinesisches Paar der Mittelschicht einen Sohn wesentlich besser fördern kann, weil bei ihm eben Status einen wesentlich höheren Effekt hat.
Auf Wikipedia finden sich die folgenden Gründe für eine selektive Abtreibung nach Geschlecht:
Cultural preference
The reason for intensifying sex-selection abortion in China and India can be seen through history and cultural background. Generally, before the information era, male babies were preferred because they provided manual labor and success the family lineage. Labor is still important in developing nations as China and India, but when it comes to family lineage, it is of great importance. The selective abortion of female fetuses is most common in areas where cultural norms value male children over female children.[1] A son is often preferred as an „asset“ since he can earn and support the family; a daughter is a „liability“ since she will be married off to another family, and so will not contribute financially to her parents. The patriarchal structure of a society is the single most important factor skewing the sex ratio in favor of males, accentuated in some cultures by the burden of raising a dowry for a daughter’s marriage. Openness to the very concept of sex selection is a significant factor: among societies which practice selective female abortion nowadays, many were systematically practicing female infanticide (either directly or by withholding postnatal care from children of undesirable sex) long before abortion became a viable option.[32] Furthermore, in some cultures sons are expected to take care of their parents in their old age.[33] In modern East Asia, a large part of the pattern of preferences leading to this practice can be condensed simply as a desire to have a male heir. Monica Das Gupta (2005) observes that, in late 1980s to early 1990s China, there was no evidence of selective abortion of female fetuses among firstborn children, or in families with one or more existing sons (in fact, families with multiple sons were, if anything, more likely to abort a boy than a girl). But, at the same time, families with existing daughters appeared very likely to abort any further female fetuses, resulting in heavily skewed sex ratios.[32]
Sexual discrimination
The role of many women in nations that are prone to sex-selection abortion is to stay home, do house chores, and raise children. She is mutely banned to work in the society, pressured by family and discouraged by society. Lower salary, working in temporary or non-regular jobs, and lower status at work is often the case even for women who do work. In these societies, mothers are compelled to assist their husbands and raise their children, sparing no time for self-development. All in all, in cultures that practice sex-selective abortion, women are prone to sexual discrimination and are viewed as inferior to men.[citation needed]
One-child Policy
The 1960s scare for overpopulation led governments to implement laws to control birth rate such as the one-child policy. Accordingly, it led to consequence where parents highly value boys over girls; even to a point were words such as „infanticide“ come into existence. Infanticide has come to be known as the „Holocaust for baby girls“. What’s more, her child will follow the husband’s surname and is restricted to visit her parents whenever she wishes. These kinds of cultural practice mixed with the government implications of one-child policy have caused one-daughter parents to become ‘’childless’’ after the marriage. As a result, these parent no longer have a financially supporting or lineage successor. Thus, for parents to ensure financial dependence and hereditary successor, a boy must be born. In this regard, the pervasion of male dominant culture and one-child policy heightens the sex-selective abortion.
Trivers–Willard hypothesis
The Trivers–Willard hypothesis argues that available resources affect male reproductive success more than female and that consequently parents should prefer males when resources are plentiful and females when resources are scarce. This has been applied to resource differences between individuals in a society and also to resource differences between societies. Empirical evidence is mixed with higher support in better studies according to Cronk in a 2007 review. One example, in a 1997 study, of a group with a preference for females was Romani in Hungary, a low status group. They „had a female-biased sex ratio at birth, were more likely to abort a fetus after having had one or more daughters, nursed their daughters longer, and sent their daughters to school for longer.“[34]
Genetic
Gender-linked genetic abnormalities, such as several forms of colorblindness, are linked to recessive genes on the X chromosome. Pre-implantation genetic diagnosis can identify some life-threatening genetic abnormalities in embryo. The easiest way to select against embryos which may have a gender-linked genetic abnormality is to choose only female embryos. Embryos which are not implanted are usually discarded.
Die Gründe für die Bevorzugung von Jungs werden auch in diesem Artikel behandelt:
In many countries, however, the sex ratio deviates from these norms because of the tradition of son preference. Son preference is most prevalent in an arc of countries from East Asia through South Asia to the Middle East and North Africa (23).
Sons are preferred because
(i) they have a higher wage-earning capacity, especially in agrarian economies (24);
(ii) they continue the family line; and
(iii) they are generally recipients of inheritance (25, 26). Girls are often considered an economic burden because of the dowry system; after marriage they typically become members of the husband’s family, ceasing to have responsibility for their parents in illness and old age (27).
Son preference is manifest prenatally, through sex determination and sex-selective abortion, and postnatally through neglect and abandonment of female children, which leads to higher female mortality (28). Since prenatal sex determination became available in the mid-1980s it has made a major contribution to imbalances in the sex ratio seen in many Asian countries (29). However, it is the combination of sex-selective technology and a small-family culture that has caused the highest sex ratios (29, 30). When large family size is the norm and access to contraception is limited, son preference has little influence on sex ratio because couples continue bearing children, largely irrespective of the gender of the children (31). Female infanticide, abandonment of newborn girls, and neglect of daughters have been used in such societies to increase the male-to-female ratio in families, especially in situations where poverty has limited the number of desired children (25). When the family size norm is moderate and only contraceptive methods are available, couples may consider the sex distribution of their existing children and decide whether or not to use family planning, weighing the need for a son against their desired family size (31). However, when fertility rates are low, by choice or coercion, female births must be prevented to allow for the desired number of sons within the family size norm.
Postnatally, discrimination against daughters leads to neglect of their health care or nutrition, resulting in higher female mortality. A number of studies have shown that unequal access to health care is the most important factor (32, 33). This is especially the case in societies where health care costs have to be borne by the family (34–36). In 1990, Sen (21) estimated that differential female mortality had resulted in ≈100 million “missing females” across the developing world. Klasen (30) and Coale (5) arrived at figures of ≈93 million and ≈90 million, respectively, with the highest percentages of missing females occurring in the Indian subcontinent: Pakistan (11% of all missing females), India (9.4%), and Bangladesh (8.9%).
Since the mid-1980s, female disadvantage in mortality has declined substantially, only to be replaced by a different type of disadvantage: sex-selective abortion (28). The combination of widespread access to noninvasive sex-selective technology (ultrasound) and the advent of the small-family culture happened to coincide in some Asian countries in the mid-1980s and has led to a greatly increased sex ratio at birth (25, 31, 37). Realization of the potentially disastrous effects of this distortion has led many Asian governments, including those of India and China, to outlaw prenatal sex determination and sex-selective abortion, yet these techniques are still being carried out on a large scale, with virtual impunity (38, 39).
Es sind also aus der Sicht der jeweiligen Familie durchaus wirtschaftliche Gründe, die dazu führen, dass sie lieber Söhne hätten. Das macht die Praxis nicht richtig, wer sie allerdings ändern will, der muss sich mit diesen Gründen auseinandersetzen.
Gegen das Recht je nach Geschlecht abzutreiben regen sich allerdings auch unerwartete Stimmen: Einige Feministinnen meinen, dass ein Eingriff in das Recht zur Abtreibung schwerer wiegt als der Umstand, dass überwiegend Frauen abgetrieben werden:
An even more compelling argument against sex-selective abortion bans is that restrictions on access to prenatal technologies and to abortions can create barriers to health care for women with legitimate medical needs; scare health care providers from providing safe, otherwise legal abortion services; and force women who want to terminate their pregnancies into sidestepping the regulated health care system and undergoing unsafe procedures. Accordingly, the joint UN statement stresses that “States have an obligation to ensure that these injustices are addressed without exposing women to the risk of death or serious injury by denying them access to needed services such as safe abortion to the full extent of the law. Such an outcome would represent a further violation of their rights to life and health.”
Oder hier:
As women, when we decide whether or not to continue our pregnancies, we deal with what is, not with what should be or what is theoretically palatable. This woman knows she cannot provide for this child in some way that matters, in some way that matters to her.
Is it any different than knowing one cannot provide economically for a child and choosing an abortion for this reason? No. Will we tell the woman of no economic means that this is not a good reason to have an abortion? No. We all know we wish it weren’t so, that in a perfect world all women would be capable of supporting their families, but in our world, the imperfect world, they are not. Women still earn much less than men and have less steady work, work in lower paid part time jobs and without benefits. We lack affordable and decent child care. These are issues we all know about. (…)
Ultimately, when we factor out all the “reasons” for abortion, whether they be economic or social, there will still be abortions. What happens when we only have women left who choose abortion because they simply don’t want to have a child? Do we tell these women that this is not a good reason? That this is selfish? No. We would not do this.
The whole line of thinking that some abortions are done for reasons that are more valid than others, because someone was raped, for example, is problematic. Any woman can choose an abortion for any reason, and she doesn’t have to tell us what it is. It’s none of our business.
Meanwhile, we do not stop striving to make the world a place where little girls are as wanted as little boys, where the systemic discrimination of women is a thing of the past. As we all know, taking away a woman’s right to control her own body, to be fully informed and make fully informed choices, is not a way to do this.
Demanding a woman give birth to an unwanted girl to make some sort of anti-sexist point is to sacrifice her will for ideology. It is as coercive as demanding she abort the girl, also a demand that sacrifices her will for ideology.
We assume, and I think we assume wrongly, that women who have an abortion for reasons of sex selection do so unwillingly. To impose our ideas on another woman’s life is patronizing. We can’t know. We don’t need to know. Again, it’s none of our business. As always, the pregnant woman is the best person to make this choice about her own body and her own family. No one can take this away from her. To do so would be truly sexist.
Eine Nation, in der der Trend zur selektiven Abtreibung von Frauen gestoppt wurde ist wohl Südkorea. Dort ist die Geschlechterrate wohl inzwischen wieder normalisiert. Grund waren soziale Änderungen, die die Kostenrechnung veränderten:
The preference for boys here is centuries old and was rooted in part in an agrarian society that relied on sons to do the hard work on family farms. But in Asia’s Confucian societies, men were also accorded special status because they were considered the carriers of the family’s all-important bloodline.
That elevated status came with certain perquisites — men received their families’ inheritance — but also responsibilities. Once the eldest son married, he and his wife went to live with his family; he was expected to support his parents financially while his wife was expected to care for them in their old age.
The wife’s lowly role in her new family was constantly reinforced by customs that included requiring a daughter-in-law to serve her father-in-law food while on her knees.
“In the old days, when there was no adequate social safety net, Korean parents regarded having a son as kind of making an investment for old age security,” Professor Chung said. It was common for married Korean men to feel ashamed if they had no sons. Some went so far as to divorce wives who did not bear boys.
Then in the 1970s and ’80s, the country threw itself into an industrial revolution that would remake society in ways few South Koreans could have imagined.
Sons drifted away to higher-paying jobs in the cities, leaving their parents behind. And older Koreans found their own incomes rising, allowing them to save money for retirement rather than relying on their sons for support.
Married daughters, no longer shackled to their husbands’ families, returned to provide emotional or financial support for their own elderly parents.
“Daughters are much better at emotional contact with their parents, visiting them more often, while Korean sons tend to be distant,” said Kim Seung-kwon, a demographer at the government’s Korea Institute for Health and Social Affairs.
Ms. Park, the newspaper executive, said such changes forced people to rethink their old biases. “In restaurants and parks, when you see a large family out for a dinner or picnic, 9 out of 10, it’s the wife who brings the family together with her parents, not the husband with his parents,” she said. “To be practical, for an old Korean parent, having a daughter sometimes is much better than having a son.”
Inzwischen kann es also wohl sogar vorteilhaft sein, wenn man eine Tochter bekommt.
Insgesamt ist es denke ich gut, wenn der Trend gebrochen wird. Ein hoher Männerüberschuß bedeutet auch hohe intrasexuelle Konkurrenz unter Männern und das wiederum begünstigt nicht unbedingt eine friedliche Welt.
Alles Evolution 