Die Vorteile der Einsicht, dass wir biologische Grundlagen haben

Noch eine interessante Stelle von dem Buch „Genome: The Autobiography of a Species in 23 Chapters“ (PDF) (S. 160). Diesmal deutlich kürzer:

Meanwhile, the discovery that personality has a strong genetic component can be used in some very non-genetic therapy. When naturally shy baby monkeys are fostered to confident monkey mothers, they quickly outgrow their shyness. It is almost certainly the same with people – the right kind of parenting can alter an innate personality. Curiously, understanding that it is innate seems to help to cure it. One trio of therapists, reading about the new  results emerging from genetics, switched from trying to treat their clients‘ shyness to trying to make them content with whatever their innate predispositions were. They found that it worked. The clients felt relieved to be told that their personality was a real, innate part of them and not just a bad habit they had got into. ‚Paradoxically,depathologising people’s fundamental inclinations and giving group members permission to be the way they are seemed to constitute the best insurance that their self-esteem and interpersonal effectiveness would improve.‘ In other words, telling them they were naturally shy helped them overcome that shyness. Marriage counsellors, too, report good results from encouraging their clients to accept that they cannot change their partners‘ irritating habits – because they are probably innate – but must find ways to live with them. The parents of a homosexual are generally more accepting when they believe that homosexuality is an immutable part of nature rather than a result of some aspect of their parenting. Far from being a sentence, the realisation of innate personality is often a release.

Danach ist es also für viele Leute eine Erleichterung und gut für ihr Selbstbewußtsein, wenn sie sich oder andere so akzeptieren können, wie sie sind und dies als Grundlage eröffnet ihnen dann gleichzeitig die Möglichkeit, auch an sich zu arbeiten und so etwas wie Schüchternheit eher zu verbessern. Weil es einem eine Grundlage bietet und auch eine Erklärung: Man muss sich keine Vorwürfe mehr machen und kann daher leichter mit der Sache umgehen.

Ein ähnliches Phänomen hatte ich schon einmal bezüglich der Geschlechterrollen dargestellt:

Eine interessante Beobachtung machte Trautner bei Längsschnittstudien mit anfangs auffällig streng einteilenden Kindern: Wer als Kleinkind seine Welt besonders klar in männlich/weiblich aufteilte, konnte später lockerer mit den Kategorien umgehen. Das entspricht der Alltagswahrnehmung. Männer und Frauen, die früh in eine sichere Geschlechtsrolle gefunden haben, müssen sich nicht mehr ständig ihrer sexuellen Identität durch präpotentes oder püppchenhaftes Gebaren versichern. Sie können sich auch vom Rollenklischee abweichendes Verhalten erlauben.

Die klare Vorstellung von der Geschlechterdifferenz und der eigenen Zugehörigkeit ist offenbar eine gute Basis für einen späteren freien Umgang mit Stereotypen. Man kann sich dann Interesse und sogar Freude und Spaß an der Differenz leisten. Und man kann dann auch Unterschiede ertragen. Denn Differenz, darauf weist der Sozialwissenschaftler Amendt hin, macht eben nicht nur stolz. Sie erzeugt auch Neid. Penisneid ist da bloß ein Beispiel. Nur starke Menschen halten die Unterschiede zwischen den Geschlechtern aus.

Auch hier sind also Menschen, die meinen, sich selbst gefunden zu haben, sicherer. Und auch dabei kann einem dann vielleicht das Wissen, dass man eben auf eine bestimmte Weise ist, helfen.

Ich vermute, dass es auch durchaus Nachteile geben kann, wenn man ohne Grund annimmt, wegen bestimmter angeblich bestehender Geschlechterunterschiede etwas nicht zu können, zB eine Frau, die meint, sie kann keine Bohrmaschine bedienen oder ein Mann, der meint, dass er nicht kochen kann. Allerdings wären das eben auch Vorstellungen, die sehr essentialistisch sind und den Rahmen der Biologie stark überziehen.

Des weiteren vermute ich, dass genau dieser Umstand, dass man sich gern in einer Rolle sicher ist, bestimmte Leute, die in die normalen Rollen und Muster nicht passen, eher motiviert, sich mit Queertheorie und Genderfeminismus zu beschäftigen. Denn dort ist man eben auch plötzlich „richtig“, alle anderen sind falsch. Ich vermute allerdings, dass dort des häufigeren die kognitiven Dissonanzen größer werden, weil man dort ja darauf achten muss, dass man nicht doch ein falsches verhalten, etwas zu stereotyp, zeigt. Da bieten aus meiner Sicht die biologischen Theorien, wenn sie richtig verstanden werden, mehr halt.

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Matt Ridley zu genetischen Konflikten zwischen den Geschlechtern

Hier ein Auszug aus dem Buch „Genome: The Autobiography of a Species in 23 Chapters“  (PDF). Er ist etwas länger, aber er lohnt sich aus meiner Sicht, weil er sehr viele interessante Punkte behandelt:

  • Die Vorteile der Zweigeschlechtlichkeit aus Sicht des egoistischen Gens
  • Der Gedanke, dass innerhalb des Genoms ein Kampf zwischen den Genen der Geschlechter stattfindet, der ebenfalls nur aus der Sicht egoistischer Gene zu verstehen ist
  • Der Gedanke, dass solche Konflikte zwischen den Geschlechtern auf genetischer Ebene überhaupt ausgetragen werden
  • Warum es kein Fehler ist, dass das Y-Genom klein ist, sondern ein Feature
  • Die Ausprägung der Geschlechter über Hormone
  • Die Darlegung, dass ein „Doppel Y“ nicht einfach ein mehr an Männlichkeit ist und deswegen nicht funktioniert (so früher im Feminismus), sondern schlicht eine fehlende Kompatibilität vorliegt.
  • Der Gedanke, dass der Wettkampf über die Schönheit auch als Abstumpfung geführt werden kann (was erklärt, warum Frauen weit weniger an nackten Männern interessiert sind als Männer an nackten Frauen).
  • Der Gedanke, dass der Wettkampf auf genetischer Ebene heftiger wird, wenn eine Spezies besonders viel Kommunikation und soziale Interaktion hat, da dann mehr Manipulationsmöglichkeiten bestehen, was ein Arms Race eröffnet. Das demnach auch gerade beim Menschen bzw- zwischen den menschlichen Geschlechtern mit erheblichen Selektionen gerade in Hinblick auf Kommunikation und soziale Interaktion zu rechnen ist.
  • Die Idee, dass unser Gehirn genau aus diesem Konflikt heraus entstanden ist.

Hier also der Text:

At some point in our past, our ancestors switched from the common reptilian habit of determining sex by the temperature of the egg to determining it genetically. The probable reason for the switch was so that each sex could start training for its special roleat conception. In our case, the sex-determining gene made us male and the lack of it left us female, whereas in birds it happened theother way round. The gene soon attracted to its side other genes that benefited males: genes for big muscles, say, or aggressive tendencies.But because these were not wanted in females — wasting energy they would prefer to spend on offspring – these secondary genes found themselves at an advantage in one sex and at a disadvantage in theother. They are known in the trade as sexually antagonistic genes.The dilemma was solved when another mutant gene suppressed the normal process of swapping of genetic material between thetwo paired chromosomes. Now the sexually antagonistic genes could diverge and go their different ways.

The version on the Y chromosome could use calcium to make antlers; the version on the Xchromosome could use calcium to make milk. Thus, a pair of middlesized chromosomes, once home to all sorts of ’normal‘ genes, was hijacked by the process of sex determination and became the sexchromosomes, each attracting different sets of genes. On the Y chromosome, genes accumulate that benefit males but are often bad for females; on the X accumulate genes that are good for females and deleterious in males.

For instance, there is a newly discovered gene called DAX, found on the X chromosome. A few rare people are born with one X and one Y chromosome, but with two copies of the DAX gene on the X chromosome. The result is, that although such people are genetically male, they develop into normal females. The reason, it transpires, is that DAX and SKY — the gene on theY chromosome that makes men into men — are antagonistic to each other. One SRY defeats one DAX, but two DAXes defeat one SRY.

This outbreak of antagonism between genes is a dangerous situation.Lurching into metaphor, one might begin to discern that the two chromosomes no longer have each other’s interests at heart, let alone those of the species as a whole. Or, to put it more correctly,something can be good for the spread of a gene on the X chromosomethat actually damages the Y chromosome or vice versa.Suppose, for instance, that a gene appeared on the X chromosome that specified the recipe for a lethal poison that killed only sperm carrying Y chromosomes. A man with such a gene would have no fewer children than another man. But he would have all daughters and no sons. All of those daughters would carry the new gene,whereas if he had had sons as well, none of them would have carried it. Therefore, the gene is twice as common in the next generationas it would otherwise be. It would spread very rapidly. Such a gene would only cease to spread when it had exterminated so many males that the very survival of the species was in jeopardy and males were at a high premium.

Far-fetched? Not at all. In the butterfly Acrea encedon, that is exactly what has happened. The sex ratio is ninety-seven per cent femaleas a result. This is just one of many cases known of this form of evolutionary conflict, known as sex-chromosome drive. Most known instances are confined to insects, but only because scientists have looked more closely at insects. The strange language of conflict usedin the remarks I quoted above now begins to make more sense. A piece of simple statistics: because females have two X chromosomes while males have an X and a Y, three-quarters of all sex chromosomes are Xs; one-quarter are Ys. Or, to put it another way, an X chromosome spends two-thirds of its time in females, and onlyone-third in males.Therefore, the X chromosome is three times aslikely to evolve the ability to take pot shots at the Y as the Y is to evolve the ability to take pot shots at the X. Any gene on the Ychromosome is vulnerable to attack by a newly evolved driving X gene.

The result has been that the Y chromosome has shed as many genes as possible and shut down the rest, to ‚run away and hide‘ (in the technical jargon used by William Amos of Cambridge University).So effectively has the human Y chromosome shut down most ofits genes that the great bulk of its length consists of non-codingDNA , serving no purpose at all – but giving few targets for the Xchromosome genes to aim at.

There is a small region that seems to have slipped across from the X chromosome fairly recently, theso-called pseudo-autosomal region, and then there is one immensely important gene, the SRY gene mentioned above. This gene begins the whole cascade of events that leads to the masculinisation of the embryo. Rarely can a single gene have acquired such power.Although it only throws a switch, much else follows from that. The genitals grow to look like a penis and testes, the shape and constitutionof the body are altered from female (the default in our species,though not in birds and butterflies), and various hormones go towork on the brain. There was a spoof map of the Y chromosomepublished in the journal Science a few years ago, which purported to have located genes for such stereotypically male traits as flipping between television channels, the ability to remember and tell jokes, an interest in the sports pages of newspapers, an addiction to death and destruction movies and an inability to express affection over the phone – among others.

The joke is funny, though, only becausewe recognise these habits as male, and therefore far from mocking the idea that such habits are genetically determined, the jokere inforces the idea. The only thing wrong with the diagram is that these male behaviours come not from specific genes for each of them, but from the general masculinisation of the brain by hormonessuch as testosterone which results in a tendency to behave this wayin the modern environment. Thus, in a sense, many masculine habits are all the products of the SRY gene itself, which sets in train theseries of events that lead to the masculinisation of the brain as wellas the body.

The SRY gene is peculiar. Its sequence is remarkably consistentbetween different men: there are virtually no point mutations (i.e.,one-letter spelling differences) in the human race. SRY is, in that sense, a variation-free gene that has changed almost not at all since the last common ancestor of all people 200,000 years ago or so. Yet our SRY is very different from that of a chimpanzee, and different again from that of a gorilla: there is, between species, ten times asmuch variation in this gene as is typical for other genes. Compared with other active (i.e., expressed) genes, SRY is one of the fastest evolving.

How do we explain this paradox? According to William Amosand John Harwood, the answer lies in the process of fleeing and hiding that they call selective sweeps. From time to time, a driving gene appears on the X chromosome that attacks the Y chromosome by recognising the protein made by SRY. At once there is a selective advantage for any rare SRY mutant that is sufficiently different tobe unrecognised. This mutant begins to spread at the expense of other males. The driving X chromosome distorts the sex ratio infavour of females but the spread of the new mutant SRY restoresthe balance. The end result is a brand new SRY gene sequence shared by all members of the species, with little variation.

The effect of this sudden burst of evolution (which might happen so quickly as to leave few traces in the evolutionary record) would be to produce SRYs that were very different between species, but very similar within species. If Amos and Harwood are right, at least one suchsweep must have occurred since the splitting of chimp ancestors and human ancestors, five to ten million years ago, but before theancestor common to all modern human beings, 200,000 years ago.

You may be feeling a little disappointed. The violence and conflict that I promised at the beginning of the chapter turn out to be little more than a detailed piece of molecular evolution. Fear not. I amnot finished yet, and I plan to link these molecules to real, human conflict soon enough.The leading scholar of sexual antagonism is William Rice of theUniversity of California at Santa Cruz and he has completed a remarkable series of experiments to make the point explicit. Let us go back to our putative ancestral creature that has just acquired a distinct Y chromosome and is in the process of shutting down many of the genes on it to escape driving X genes. This nascent Ychromosome, in Rice’s phrase, is now a hotspot for male-benefitgenes. Because a Y chromosome will never find itself in a female,it is free to acquire genes that are very bad for females so long asthey are at least slightly good for males (if you still thought evolution was about the good of the species, stop thinking so right now).

Infruit flies, and for that matter in human beings, male ejaculate consists of sperm cells suspended in a rich soup called the seminal fluid.Seminal fluid contains proteins, products of genes. Their purpose is entirely unknown, but Rice has a shrewd idea. During fruit-flysex, those proteins enter the bloodstream of the female and migrateto, among other places, her brain. There they have the effect of reducing the female’s sexual appetite and increasing her ovulation rate. Thirty years ago, we would have explained that increase interms of the good of the species. It is time for the female to stopseeking sexual partners and instead seek a nesting site. The male’sseminal fluid redirects her behaviour to that end. You can hear theNational Geographic commentary. Nowadays, this information takeson a more sinister aura. The male is trying to manipulate the femaleinto mating with no other males and into laying more eggs for hissperm and he is doing so at the behest of sexually antagonisticgenes, probably on the Y chromosome (or switched on by geneson the Y chromosome). The female is under selective pressure tobe more and more resistant to such manipulation. The outcome is a stalemate.

Rice did an ingenious experiment to test his idea. For twenty-nine generations, he prevented female flies from evolving resistance: he kept a separate strain of females in which no evolutionary change occurred. Meanwhile, he allowed males to generate more and moreeffective seminal fluid proteins by testing them against more and more resistant females. After twenty-nine generations he brought the two lines together again. The result was a walkover. Male sperm was now so effective at manipulating female behaviour that it was effectively toxic: it could kill the females.

Rice now believes that sexual antagonism is at work in all sorts of environments. It leaves its signature as rapidly evolving genes. In the shellfish the abalone, for instance, the lysin protein that the sperm uses to bore a hole through the glycoprotein matrix of the egg is encoded by a gene that changes very rapidly (the same isprobably true in us), probably because there is an arms race betweenthe lysin and the matrix. Rapid penetration is good for sperm but bad for the egg, because it allows parasites or second sperm through.Coming slightly closer to home, the placenta is controlled by rapidly evolving genes (and paternal ones, at that). Modern evolutionary theorists, led by David Haig, now think of the placenta as more likea parasitic takeover of the mother’s body by paternal genes in the foetus. The placenta tries, against maternal resistance, to control herblood-sugar levels and blood pressure to the benefit of the foetus. More on this in the chapter on chromosome 15.

But what about courtship behaviour? The traditional view of the peacock’s elaborate tail is that it is a device designed to seducefemales and that it is in effect designed by ancestral females‘ preferences.Rice’s colleague, Brett Holland, has a different explanation.He thinks peacocks did indeed evolve long tails to seduce females,but that they did so because females grew more and more resistantto being so seduced. Males in effect use courtship displays as asubstitute for physical coercion and females use discrimination toretain control over their own frequency and timing of mating. Thisexplains a startling result from two species of wolf spiders. Onespecies has tufts of bristles on its forelegs that it uses in courtship.Shown a video of a male spider displaying, the female will indicate by her behaviour whether the display turns her on. If the videos are altered so that the males‘ tufts disappear, the female is still just as likely to find the display arousing. But in another species, where there are no tufts, the artificial addition of tufts to males on the video more than doubled the acceptance rate of females. In otherwords, females gradually evolve so that they are turned off, not on,by the displays of males of their own species. Sexual selection is thus an expression of sexual antagonism between genes for seduction and genes for resistance.

Rice and Holland come to the disturbing conclusion that the more social and communicative a species is, the more likely it is to suffer from sexually antagonistic genes, because communication between the sexes provides the medium in which sexually antagonisticgenes thrive. The most social and communicative species on the planet is humankind.

Suddenly it begins to make sense why relations between the human sexes are such a minefield, and why men have such vastly different interpretations of what constitutes sexual harassment from women. Sexual relations are driven not by what is good, in evolutionary terms, for men or for women, but for their chromosomes. The ability to seduce a woman was good for Y chromosomes in the past; the ability to resist seduction by a man was good for X chromosomes in the past.

This kind of conflict between complexes of genes (the Y chromosome being one such complex), does not just apply to sex. Suppose that there is a version of a gene that increases the telling of lies (not a very realistic proposition, but there might be a large set of genes that affect truthfulness indirectly). Such a gene might thrive by making its possessors into successful con-artists. But then suppose there is also a version of a different gene (or set of genes) that improves the detecting of lies, perhaps on a different chromosome.That gene would thrive to the extent that it enabled its possessors to avoid being taken in by con-artists. The two would evolve antagonistically,each gene encouraging the other, even though it wouldbe quite possible for the same person to possess both. There is between them what Rice and Holland call ‚interlocus contest or ICE.

Exactly such a competitive process probably did indeed drive the growth of human intelligence over the past three million years. The notion that our brains grew big to help us make tools or start fires on the savannah has long since lost favour.Instead, most evolutionists believe in the Machiavellian theory —that bigger brains were needed in an arms race between manipulationand resistance to manipulation. ‚The phenomena we refer to as intelligence may be a byproduct of intergenomic conflict between genes mediating offense and defense in the context of language‘,write Rice and Holland.

Eure Meinung dazu würde mich interessieren.

Mir kommen in dem Text noch ein paar andere Aspekte zu kurz, etwa direkte sexuelle Selektion und ihre Auswirkungen auf die Partnerwahl und den Umstand, dass es nach der Sexy Son Theorie noch eine Ebene gibt, bei der die Fähigkeit das andere Geschlecht auszutricken, selbst sexy sein kann, also negative Umstände unter gewissen Umständen positive werden können, aber in dem Text ist dennoch sehr viel drin.

Pränatale Hormone und Verhalten

Eine Metastudie in der Zeitschrift „Neuroscience and Behavioral Review“ (Impact Factor: 10.284) aus dem Jahr 2004 fasst noch einmal den Stand bezüglich Pränataler Hormone und ihrer Auswirkungen auf Geschlechterunterschiede zusammen:

There is now good evidence that human sex-typed behavior is influenced by sex hormones that are present during prenatal development, confirming studies in other mammalian species. Most of the evidence comes from clinical populations, in which prenatal hormone exposure is atypical for a person’s sex, but there is increasing evidence from the normal population for the importance of prenatal hormones. In this paper, we briefly review the evidence, focusing attention on the methods used to study behavioral effects of prenatal hormones. We discuss the promises and pitfalls of various types of studies, including those using clinical populations (concentrating on those most commonly studied, congenital adrenal hyperplasia, androgen insensitivity syndrome, ablatio penis, and cloacal exstrophy), direct measures of hormones in the general population (assayed through umbilical cord blood, amniotic fluid, and maternal serum during pregnancy), and indirect measures of hormones in the general population (inferred from intrauterine position and biomarkers such as otoacoustic emissions, finger length ratios, and dermatoglyphic asymmetries). We conclude with suggestions for interpreting and conducting studies of the behavioral effects of prenatal hormones.

Quelle: Prenatal sex hormone effects on child and adult sex-typed behavior: methods and findings

In der Einleitung wird bereits noch einmal einiges zusammengefasst:

There is now good evidence from human and nonhumanspecies that events occurring during prenatal developmentcan have life-long effects on an organism. These effects are not limited to physical characteristics, but extend to a variety of behavioral traits. Thus, as described in several papers inthis special issue and elsewhere, physical and emotionalstressors experienced by pregnant rodent, monkey, andhuman females are associated with behavioral problems inoffspring throughout life [1–3]. The physical and behavioral effects of prenatal stress appear to be mediated by hormone induced changes to the developing hypothalamic–pituitary–adrenal axis [3,4].Long-term effects of prenatal events extend beyond exposure to stress hormones. There are also marked physical and behavioral consequences of prenatal exposure to another category of hormones, those produced by thegonads (‘sex hormones’). In all mammalian species studied,sexual differentiation of the reproductive system depends largely on the amount of androgens present during critical periods of prenatal life. In human beings, this critical period begins at about 7–8 weeks of gestation when the testes develop and begin to secrete testosterone [5]. The external genitalia are undifferentiated until then, and the amount of testosterone (or other androgens) determine whether they differentiate into male-typical or female-typical genitalia. With high levels of testosterone, the genitalia become the penis, scrotum, and urogenital sinus, where as low or absent testosterone results in the development of the clitoris, labiamajora, and separate vaginal and urethral canals. Intermediate levels of testosterone result in ambiguous genitalia,e.g. an enlarged clitoris with fused labia, a small penis. Sexhormones also affect the development of the internal reproductive structures. Parallel behavioral studies in nonhuman mammals clearly show that the same prenatal hormones responsible for sexual differentiation of the body are also involved insexual differentiation of behavior [for reviews, see 6–8]. Inrodents, females injected with high doses of androgens inthe newborn period show behavior more typical of malesthan of other females, and males that are castrated or givenanti-androgens show behavior more typical of females thanof other males. The behaviors involved include adult sexual behavior, juvenile rough play, adult aggression and maze performance. These effects are also found in rodents naturally exposed to atypical hormone levels from gestatingnext to opposite-sex littermates, as described below.Behavioral effects of early hormones are also found innonhuman primates: female monkeys exposed to androgensearly in development are masculinized with respect tosexual behavior, rough play, grooming [9], and somelearning abilities [10,11]. Studies in monkeys confirm andextend studies in rodents in two important ways. First, they illustrate the complexity of timing effects and show that there may be several distinct sensitive periods for androgen effects on behavior, even within the prenatal period, so thatsome behaviors are masculinized by exposure early (but notlate) in gestation, whereas other behaviors are masculinized by exposure late (but not early) in gestation [9]. For example, monkeys that received androgens early indevelopment and had masculinized genitals showed increased mounting of peers and mothers and less grooming behavior, where as those exposed later in development had normal-looking genitals but showed increased rough play and mounting of peers, but not mounting of mothers. Second, studies in monkeys show the importance of environmental context in modifying the behavioral effects of hormones. For example, the social environment of juvenile monkeys modifies the expression of behavior that is influenced by hormones [12]. The behaviors that are the least variable across social contexts are the most affected by prenatal hormones.

Hier wird also noch einmal einiges dargelegt, was ich hier schon häufiger dargestellt habe: Der Mechanismus zeigt sich bei den Säugetieren an sich, was stark dafür spricht, dass er auch bei Menschen besteht. Und weitere Untersuchungen zeigen, dass dies auch tatsächlich der Fall ist.

Hier eine Tabelle zu den Unterschieden zwischen Männern und Frauen:

Männer Frauen Unterschiede

Männer Frauen Unterschiede

 Hier zeigen sich also einige Unterschiede, Mädchen sind besser im einigen sprachlichen Bereichen, Erinnerung und Auffassungsgabe und interessieren sich sehr deutlich mehr für mädchentypische Aktivitäten, Jungs sind besser in bestimmten Bereichen des räumlichen Denkens, sind aggressiver, Suchen eher nach neuen Erlebnissen und Erfahrungen und interessieren sich eher für typische Jungenaktivitäten. Beide Geschlechter bevorzugen ihre eigenen Geschlechtsgenossen als Spielgefährten und werden von dem anderen Geschlechts stark sexuell angesprochen.

Insgesamt eine interessante Studie.

Werte von Testosteron bei Mann und Frau über verschiedene Lebensphasen

Das Testosteron in biologischen Theorien zu Geschlecht und Geschlechterunterschieden eine wichtige Rolle spielt sollte den meisten Lesern dieses Blogs inzwischen deutlich geworden sein. Es lohnt sich daher einmal die unterschiedlichen Testosteronstände – pränatal und postnatal – näher zu betrachten. Hier also eine Grafik dazu:

 

Testosteron Maenner Frauen
Testosteron Maenner Frauen

Hier sieht man gut, wie unterschiedlich die Werte für Männer und Frauen sind und das bereits vor der Geburt und mit einiger Bewegung. Auch kurz nach der Geburt steigt der Testosteronspiegel bei männlichen Babies noch einmal deutlich an.  Das passt natürlich gut zu den Theorien, wie Geschlechterunterschiede durch pränatales Testosteron entstehen. Gut zu erklären wäre damit auch, wie in der Pubertät mit dem ansteigenden Testosteronspiegel das Interesse an Sex entsteht.

Zudem hatte Roslin auch noch einmal auf Zahlen hingewiesen:

Childhood

Testosterone levels are relatively low during infancy, averaging less than 30 nanograms/deciliter, or ng/dL, in male babies and below 10 ng/dL in female infants, according to the University of Michigan Health System. By 10 to 13 years of age, boys should have between 1 and 619 ng/dL of testosterone in their blood, while girls will run somewhere between 2 and 33 ng/dL.

Adolescence

Testosterone is a major trigger for puberty in boys, and normal blood levels in adolescent males surge as high as 970 ng/dL by the age of 17. A 17-year-old female, on the other hand, usually has only 8 to 53 ng/dL in her blood.

Adulthood

According to MayoClinic.com, testosterone levels in men peak during the teen and early adult years, then decrease about 1 percent a year after age 30. Men in their 20s or 30s generally score testosterone levels of 270 to 1,080 ng/dL, but women in that age bracket run between 10 and 70 ng/dL.

Senior Years

Testosterone drops down to 350 to 890 ng/dL in men between the ages of 40 to 59 years, and then stays between 350 and 720 ng/dL after the age of 60. Adult women run between 10 and 70 ng/dL before menopause, but see a big drop to 7 to 40 ng/dL with the onset of menopause.

Man sieht also auch noch mal in den Zahlen und üblichen Schwankungen, dass der Testosteronspiegel von Männern und Frauen sehr unterschiedlich sind.

Zu den Auswirkungen:

Hormone und Politik

Eine interessante Übersicht, wie Hormone die politische Meinung beeinflussen könnten:

Cortisol: This stress hormone may also influence us politically, according to recent research by Hibbing and his collaborators. „You can see people’s cortisol levels go up dramatically when you stress them out,“ Hibbing says—for instance, by requiring them to prepare to give a speech that is going to be videotaped. „We are finding there are relationships between cortisol and not voting. Those people who don’t vote are the people who tend to have fairly high cortisol levels. Because politics is pretty stressful.“

Wer also eh schon zu gestresst ist, der hat für solche „Nebensächlichkeiten“ wie Wählen oder Politik keine Zeit mehr und blendet es eher aus.

Testosterone. „There is genetic variance in how much testosterone someone has at birth, and there are certain things that can enhance or diminish that,“ explains Brown University political scientist Rose McDermott, a prominent researcher on the science of ideology who authored a recent book chapter on hormones and politics. „One of those things that enhance that is muscle mass—if you build muscle mass, you enhance“ your testosterone levels.

What might this have to do with politics? While direct research linking testosterone to ideology is lacking, researchers have recently published data tying muscle mass to political preferences. One study shows that rich men with large biceps are more opposed to wealth redistribution than rich men with small biceps. Another study finds that weightlifting ability correlates with support for, er, a more muscular foreign policy. Plus, get this: Men with wider faces (an indicator of testosterone levels) have been found to be more willing to outwardly expressprejudicial beliefs than their thin-faced counterparts.

Das Männer, die gerne viel Muskeln aufbauen auch eher solche mit mehr Testosteron sind kann ich mir vorstellen. Allerdings eben auch, dass sie gerne einen auf „starker Mann“ machen und, weil sie selbst nicht vor einer Konfrontation zurückschrecken und sich viel aus Stärke machen, eben auch eher für eine entsprechende Politik sind. Und das mehr Testosteron auch eher mal dazu führt, dass man direkt seine Meinung sagt und nicht vor einer Konfrontation zurückschreckt kann ich mir, da es sich auf die Risikobereitschaft auswirkt, ebenfalls vorstellen. Wäre aus meiner Sicht aber eher ein indirekter Zusammenhang

Oxytocin: Often dubbed the „love hormone“ because of its role in forging ties between lovers (and parents and children), oxytocin may also have a role in politics. Paul Zak, a neuroeconomist at Claremont Graduate University, describes research in which a nasal spray containing oxytocin made research subjects more generous in sharing money with one another. But before you jump to the conclusion that oxytocin simply fuels generosity, consideranother study, in which the hormone seemed to promote cooperation with your in-group or tribe, but quite the opposite with an outside group or tribe that threatens you. Clearly there are strong political implications here—and not entirely cuddly ones

Das alte Porblem – Ingroup-Förderung scheint immer in einem Konflikt mit Outgroup-Abgrenzung zu verlaufen. Was so gesehen schon logisch ist – wer sich seiner Gruppe verbundener fühlt und dort mehr Wohltaten verteilt, der muss eben eher aufpassen, dass man diese nicht ausnutzt und auch das diese Vorteile in der Gruppe bleiben.

Dopamine: This neurotransmitter shapes our need for pleasure, rewards, and novel sensations. Indeed, „sensation seeking“ has been associated with particular dopamine receptors in the brain whose numbers vary, for genetic reasons, from individual to individual. A particular variant of the gene that codes for these receptors has, in turn, been associated with political liberalism; one study found that people who had the key gene variant in question were more likely to be political liberals.

Leuchtet schon ein, dass Leute, die immer auf der Suche nach dem neuesten Kick sind und ihren Vergnügen nachgehen wollen eher für eine liberale Gesellschaft sind, in der man diesen Vergnügungen möglichst ungehindert nachgehen kann

Basha Mika über die freiwillige Unterordnung der Frau

In einem bereits etwas älteren Interview mit Basha Mika nimmt diese zur Geschlechterdebatte Stellung:

Frauen verbauen sich viele Chancen, weil sie sich freiwillig unterordnen. Das geht schon sehr früh los, bereits zu Beginn einer Liebesbeziehung übernehmen sie häufig die Prioritäten ihrer Männer. Beispielsweise indem sie fast immer die größere Verantwortung für den gemeinsamen Haushalt schultern. Oder dass es Frauen sind, die ihren Männern folgen, wenn die in einer anderen Stadt einen Job bekommen.

Ich finde es ja faszinierend zu sehen, dass sie das ganze Interview über nicht einmal den Gedanken hat, dass es gar keine Unterordnung ist. Dass Geldverdienen nicht immer bedeutet, dass man derjenige ist, der es besser hat, sondern derjenige, der dies nicht machen muss, durchaus darin auch einen Vorteil sehen kann. Wenn eben der Mann den besseren Job bekommt und die Frau ihren Schwerpunkt eher auf Familie legen möchte und eh nur einen Nebenjob haben will, dann setzt sie ihre Ziele durchaus um. Sie hat nur nicht die Ziele, die Frau Mika gut findet.

Entlassen Sie die Männer aus ihrer Verantwortung?

Quatsch! Wenn sich Frauen in ihrem persönlichen Umfeld der traditionellen Rolle verweigern, werden sich Männer noch umsehen.

Als ob dies nicht durchaus bereits der Fall wäre und teilweise auch durchaus von den Männern gefordert wird. Ich kenne durchaus Schilderungen von Männern, die meinten, dass sie sich mit ihren Frauen gestritten haben, weil diese eben nicht so schnell wieder anfangen wollen, der Erwerbsarbeit nachzugehen. Dass einige Frauen das gar nicht wollen, dass sie diejenigen sein wollen, die aussetzen, dass sie „nicht schwanger sind um dann nichts von dem Kind zu haben“ oder selbst der Auffassung sind, dass der Mann das Geld heranschafft und die Frau die Kinder versorgt, dass muss nichts damit zu tun haben, dass sich die Frau nicht durchsetzen kann.

Die eigentlichen Probleme beginnen, wenn Kinder kommen.

Ja. Aber warum stecken denn immer die Frauen zurück? Warum sagen sie nicht: So, Schatz, jetzt reduzieren wir beide von Vollzeit auf Teilzeit?

Weil dann das Geld nicht reicht? Weil sie meinen, dass beide besser leben, wenn einer Vollzeit arbeitet? Weil er sein Studium bereits darauf ausgerichtet hat, gutes Geld zu verdienen und sie darauf, dass sie es gut mit der Kindererziehung vereinbaren kann? Weil es ihr zu stressig ist? Weil es schwierig sein kann, die Zeiten abzustimmen? Weil sie dann die gleiche Verantwortung dafür haben würde, dass alles finanziell passt? Weil Östrogene eine stärkere Reaktion auf das Kindchenschema auslösen?

Warum machen Frauen das nicht?

Aus Angst vor Konflikten. Konflikte stören die Harmonie, möglicherweise die Versorgung und die Liebesbeziehung. Das alles könnten Frauen im Ernstfall verlieren.

Sie waren elf Jahre lang Chefredakteurin der taz und stehen damit für einen anderen Lebensentwurf.

Ich war nie ausschließlich auf den Beruf konzentriert. Zwar habe ich immer viel gearbeitet, aber meine Beziehungen waren mir sehr wichtig.

Können Sie uns ein Beispiel geben?

Ich habe nicht laut „Hier!“ geschrien, als es um die Besetzung der taz-Chefredaktion ging. Sondern gewartet, bis ich gefragt wurde. Obwohl ich davon überzeugt war, dass ich es konnte.

Waren Sie feige?

Ja. Nicht über den eigenen Schatten springen zu können ist für mich Feigheit. Ich dachte damals, ich mache mich angreifbar, wenn ich mich hinstelle und sage: Ich will!

Warum?

Wer sich in den Ring begibt, fordert auch die Gegner heraus. Ich kann nur sagen: Mein Verhalten war typisch weiblich. Und typisch weiblich reagiere ich auch an anderen Stellen.

Es ist immerhin ein löblicher Ansatz, wenn sie der Meinung ist, dass Frauen ihre eigene Angst überwinden müssen. Allerdings führt sie diese ja wohl auf die männlichen Strukturen zurück, von denen man sich freimachen muss. Dabei gibt es genug biologische Zusammenhänge, die man da ebenso mitberücksichtigen könnte. Etwa Testosteron und Risikobereitschaft. Oder die stärkere Ausrichtung auf intrasexuelle Konkurrenz bei Männern oder ihr stärkerer Bezug zu Statusberufen.

Ich habe keinen Ratgeber geschrieben, ich kann also auch keine Tipps geben. Aber es würde mich sehr freuen, wenn eine Frau sagt: Ich will eine gleichberechtigte Beziehung auf Augenhöhe führen. Und wenn es um Entscheidungen geht – selbst bei so alltäglichen Dingen wie Hausarbeit -, versuche ich, so zu handeln, dass ich meinen Ansprüchen gerecht werde. So was ganz Schlichtes.

Was ja durchaus eine positive Aussage ist. Es wäre dennoch schön, wenn der Feminismus neben der Unterdrückung noch einmal in eine andere Richtung denken würde.

Das Verhältnis von Versorgen und Statusaufbau in Bezug auf weiblichen Fortpflanzungserfolg

Über „Mein Naturwissenschaftsblog“ bin ich auf einen interessanten Text zu dem Verhältnis von Versorgen und Statusaufbau bei Frauen gestoßen:

Unlike men, women cannot generally enhance their reproductive success by acquiring wealth or accumulating mates, and in some cases it appears that women undermine their reproductive success by acquiring political status. As primatologist Barbara Smuts has suggested, competition among females is at a low level because „the outcome of a single interaction rarely leads to large variations in reproductive success because female reproductive performance depends mainly on the ability to sustain investment in offspring over long periods of time.“ In contrast to men, then, women have increased their reproductive success by devoting the bulk of their energies to investment in children, through provision of milk and other forms of direct caretaking, rather than through acquisition of resources.

Hier muss man bedenken, dass Frauen evolutionär auch über lange Zeit es sehr schwer hatten, mit vielen Ressourcen Männer zu locken. Denn aufgrund von Schwangerschaft etc sind sie in entscheidenden Phasen unter steinzeitlichen Bedingungen auch erheblich eingeschränkt darin, größere Ressourcen anzusammeln. Gerade Nahrung als eine der wichtigsten Ressourcen konnte in dieser Zeit nur sehr eingeschränkt besorgt werden.

There is reason to believe that the closer connection of women to their infants is an evolved response, as a general tendency in an mammalian mother to be indifferent to be indifferent to separation from her infant would have been highly disadvantageous. An intriguing line of evidence implying sex differences in the factors that activate parental feelings and behaviors are studies finding that among non-genetic parents, women’s attachment may suffer more than men’s. For example, stepfathers tend to have better relationships with their stepchildren than stepmothers do and are more likely to report parental feelings. Similarly, the relationship of adoptive mothers to their adoptive children seems to resemble the genetic mother-child relationship less than the relationship of adoptive fathers resembles the genetic father-child relationship. A study by psychologist Irwin Silverman and colleagues examined perception of parental solicitude among adults who had been raised either by birth parents or adoptive parents. Not surprisingly, birth children tended to perceive their mothers as the more solicitous parent. However, adoptees reported substantially less parental solicitude from their mothers than birth children did, but there was no such decline in solicitude between birth and adoptive fathers. Indeed, adoptive fathers tended to be rated higher in solicitude than adoptive mothers. These findings can plausibly be interpreted to mean that experience of carrying and giving birth to a child predisposes women toward later nurturing feelings and behavior toward their children, while for fathers other factors trigger these feelings. Psychologist Geoffrey Miller has suggested that in our ancestral environment women commonly had children by successive males and that an evolved willingness to invest somewhat in stepchildren (although less than in their own biological offspring) may has been selected for as mating tactic.

Ein guter Kontakt zu den Stiefkindern könnte insofern eher zu Männern passen, weil sie dann quasi Werbungskosten um die Frau sind. Frauen bringt das hingegen weniger, wenn es ihnen nur um Befruchtung ginge, dann müssten sie nicht so viel werben.

Substantial reproductive tradeoffs for female competition and aggressiveness may limit the development of dominance in females. Among baboons, for example, high-ranking females obtain some clear reproductive benefits as a consequence of enhanced access to nutritional resources: they have higher infant survival, shorter interbirth intervals, and daughters who usually give birth at a younger age. Their lifetime reproductive success, however, may not substantially exceed that of less-dominant females. Dominant females have greater miscarriage rates and may show signs of reduced fertility. Thus, the same causal factors that lead to high dominance may also carry reproductive costs that have acted as a constraint on selection for competitiveness among females. That common factor is likely to be testosterone.

Hier zeigt sich auch, warum es sich häufig nicht lohnt, sich in die Richtung des anderen Geschlechts zu entwickeln. Der kürzeste Weg dahin sind die Hormone, gleichzeitig wirken diese im Körper aber auch ansonsten eher in die Richtung des anderen Geschlechts, was meist der Fruchtbarkeit abträglich ist

The same effect may occur in humans. It is often reported that female executives have fewer children than male executives and fewer than the average woman. A study of law school graduates found that 40 percent of women remained childless fifteen years after graduation. The usual implication of these findings is that women must choose between work and family and that these women chose work. There is another possible explanation, however. Women who succeed in business tend to be relatively high in testosterone, which can result in lower female fertility, whether because of ovulatory irregularities or reduced interest in having children. Thus, rather than the high-powered career being responsible for the high rate of childlessness, it may be that high testosterone levels be responsible for both.

Ein schönes Beispiel dafür, dass die „Möglichkeit biologoscher Kausalität“ gerne übersehen wird. Ein höherer Tesosterongehalt kann einiges bewirken, eben beispielsweise ein eher Karriereorientiertes Leben über eine höhere Bereitschaft in Konkurrenzsituationen zu stehen oder eben nicht so erpicht auf Kinder zu sein.