Darwinists: How Did Homosexuality Evolve?

reply to post by AaronTheSpeaker


I think that shows a great respect for reproduction.
It also scares the heck out of those doing the most reproducing.

Originally posted by Grant123
reply to post by AaronTheSpeaker

 

Left handedness is different than sexuality. It has been shown that lefties are at advantage in fighting.


[edit on 26-4-2010 by Grant123]

Apparently you haven't met many angry drag queens.

I will take a stab at it.

There seems to be some statistical correlation between the number of older brothers a boy has & his increasing probability of being homosexual.

The notion of the mother building up some sort of immune response to 'alien' male DNA in her system. [More-so than with female babies, because they are both female?]

These articles would seem to support the notion of the mother's hormones having some effect on fetal brain development, notably those that differentiate a 'male' brain from a 'female' brain.
Essentially an embryo's brain is 'female' unless it gets an unblocked testosterone wash [that breaks down to other chemicals in the process].

Presumably for a female embryo to have a 'male' brain the embryo itself must in virtually all cases create the testosterone [or something that produces similar results] itself at that critical stage,
but i am just making a 'seemingly' logical guess.

It doesn't say so explicitly, but the impression i am getting is perhaps the mother's progesterone 'blocks' the testosterone at that critical stage [or perhaps some male embryos occasionally fail to produce [enough] testosterone at that stage].

Potential role of maternal progesterone in the sexual differentiation of the brain.

In rats, fetal testosterone directs sexual differentiation of the brain. However, fetuses are also exposed to maternal progesterone. Here we report that progestin receptor immunoreactivity in the medial preoptic nucleus (MPN) of fetal and neonatal rats is high in males but virtually absent in females. The MPN is one of the most sexually dimorphic structures in the rat brain and mediates several sexually differentiated behaviors. This suggests that progesterone may play a previously overlooked role in the development of sex differences in the brain and behavior. Henceforth, a novel function of the mother in the sexual differentiation of the CNS must be considered.

www.ncbi.nlm.nih.gov...

24 April 2002
Maternal progesterone influences fetal brain development

Unexpected patterns of progesterone receptor expression in fetal and newborn rats break the rules of sexual differentiation, according to a researcher at the Experimental Biology 2002 conference. Contrary to current dogma, progesterone from maternal circulation binds to progesterone receptors in the fetal cortex.

Christine Wagner, assistant professor of psychology at the University at Albany, explained at the meeting that progesterone receptors clearly influence neuronal development in previously unthought ways.

In the classical brain development paradigm, fetal hormones drive the sexual differentiation of the developing brain. But Wagner now reports that maternal progesterone binds to fetal progesterone receptors.

The results, Wagner says, reveal a novel role of the mother in the development of the fetal central nervous system: A possible source of progesterone receptor ligand.

In males, fetal testosterone aromatises to oestradiol and masculinises the fetal brain. Without testosterone, the fetal brain is female. Wagner and her team previously reported that certain areas of the fetal rat brain, notably the medial preoptic nucleus (MPN) – an area that mediates sexually differentiated behaviours in adulthood – express the progesterone receptor well before birth.

On the day of birth, expression of the progesterone receptor (PR) in the MPN is high in males but virtually absent in females, a difference likely produced by differential exposure to oestradiol.

In contrast, Wagner has found that PR expression in another part of the developing rat brain, the ventral medial nucleus (VMN), is higher in females than males, an observation not readily explained by perinatal exposure to gonadal hormones.

Wagner says she believes the source of fetal PR receptor ligand is maternal ovarian progesterone, which is present in extremely high levels during pregnancy.

To test this hypothesis, Wagner and her colleagues manipulated fetal and postnatal hormonal exposure. They found that prenatal testosterone treatment in females, or castration of males upon birth, abolished the sex difference in PR expression. Sex differences in PR expression were also absent in mice lacking a functional oestrogen receptor-alpha.

In another finding, prenatal treatment with the aromatase inhibitor ATD reduced PR expression in both the male and female MPN. In contrast, prenatal treatment with flutamide, an androgen receptor antagonist, had no apparent effect on PR expression.

Neonatal treatment with the PR antagonist RU486 also abolished subsequent sexual behaviour in most adult males and attenuated the masculinising effects of testosterone on the MPN structure in females.

This surprising finding – the strikingly opposite effects of RU486 in males and females given identical doses – suggests, Wagner explained, that males and females come to the day of birth already substantially differentiated in ways postnatal testosterone cannot counter.

The findings also suggest progesterone is capable of both pro- and anti-apoptotic effects in the developing brain.

BioMedNet
23 April 2002

www.vetscite.org...

Evolution doesn't care how high or cleanly it leaps the hurdle to survival, anything sufficient will do. Sometimes the genetic differentiation is clear & unmistakable, & a clearly superior trait.
Many other times there is a negative balance payback point as is the case with some people having sickle cell anemia because those same genes give resistance to malaria, in mosquito infested regions.

Oysters spew as many as a hundred million of eggs into the same ocean male loose sperm into in hopes that a few of them reach maturity & survival, which might seem horrific to our 'human' standards. We fight over a single early term abortion or RU486 taken after a previous night's sex.

In the case of human sexuality there are a bunch of different pieces to all get on one side or the other of the sexual schism. Because it is multiple part occasionally some things like physical anatomy get one form but the brain may get the opposite.
Adding to that the potential influence from the mother's own hormones & immune system,
& yeah, things get mixed from time to time.

In human populations, we have a distributed kind of child rearing as well as survival systems so those who are usefully integratable may have their differences overlooked.

In the complex web of human survival it is not some simple binary mechanism. [Bi-]Sexual reproduction is itself an almost intentional genetic complicating factor used to evade pathogens, with arguably an increased variety & more rapid species development/'advancement'.

Homosexuality imo is 'noise', sometimes useful 'noise', in the fuzzy, complicated reproduction & genetics of humans, that is quite insufficient to be a problem for successful species generatiation.

The complications of large brains, social structures & abilities to utilize technology has served us very well, . . . thus far.

Arguably our biggest problem now, after starting from populations perhaps as small as 50,000 - 100,000 is over population to the point our small planet can not sustain us & we all go extinct.

Gay & other non-reproductive sexual activity may be the thing that saves the species at this point, although i think we are going to have to get out & push if we are going to survive.

In point of fact with evolution/biology/science there is no right or wrong.
Extinction or never having come into being in the first place are all the same.
It is only our bias to our own personal/species/life survival that has us hooking into emotional attitudes of 'correct' or 'incorrect'.

Correct or Incorrect are functions of some agenda. A cleavage of differentiation. The Universe doesn't appear to have any artificial differentiation, but it does seem to have some organic bias of exists/does-not-exist.

As a gay person, having to 'explain' yourself can be such a pain of torture, lol.

Kiss my gay backside

[edit on 27-4-2010 by slank]

reply to post by Xcalibur254


Evaluating the results of the 1979 Minnesota study were based on observable charecteristics, not statistical probability. As stated that probability as it applies to a random population sample, was used as a base line in evaluating the study group.

reply to post by arbiture


If it was a twin study, then what it was trying to uncover was the heritability of homosexuality. Heritability is used to explain how much of the variability of a trait in the population can be explained by genetics. In fact, all psychological studies deal with statistics. There is no sure thing in psychology, no matter how well designed your study may be.

reply to post by Xcalibur254


The study compared major personality traits, such as chosen profession, between a random population sample and the study group. It compared the observed difference between both group's. To evaluate something, you have to have something to compare it to. That require's a statistical baseline. The goal of the study was to ask, what part of behaviour was controled by genetic's, which was also meant to say anything other then the environment. The study did not identify the biological mechanisim. It just confirmed there was one. Any conclussion is impossible with out the application of statistic's

reply to post by arbiture


Your a bit wrong. To evaluate it you compare two groups. You can use a chi-squared test or a t-test to compare to things. Please look at the study and read how they compared their data. You have two twins, you compare the twins. You don't need to identify the biological mechanism in this case. The fact that two people with the same exact genetics develope the same traits implys a genetic relationship when this is not seen in twins that don't share the same genetics.

...Read the study