Woman is the biological default. That’s why women have redundancy on the 23rd chromosomal pair, whereas men have a special “Y” chromosome—leading to much higher rates of genetic disorders in men. That’s why in infant male humans, the testicles have to descend. And so on. Both from an encoding and from a developmental point of view, a man is a woman altered to be masculine. And testosterone is what does that altering.
Yes, it could have been different. We can imagine a species with a neutral default, which then gets altered to be either masculine or feminine by different sex-encoding hormones. But that’s not how humans came about.
We don’t have to imagine. We can look at birds, where the sex chromosomes are the opposite. I haven’t looked at them, so I don’t know how much is a consequence of the chromosomal structure. But, for some reason, I’m skeptical that most people who pontificate their role have looked either. The points about hormones and development are more reasonable.
Are the opposite? I assumed the XX/XY goes back to the very beginnings of gender i.e. fishes… how comes very different chromosomes can make the same hormones i.e. AFAIK birds do have testosterone?
The sheer number of ways sex can be determined amongst vertebrates is amazing, let alone other animals or microbes (there are fungi with 10,000 ‘sexes’/mating types...). I will restrict my examples to vertebrates.
As a rule, in most vertebrates (including humans and other organisms in which it is genetically determined) everything needed to make all the biology of both sexes is present in every individual, but a switch needs to be thrown to pick which processes to initiate.
Many reptiles use temperature during a critical developmental period with no sex chromosomes. Many fish too.
The x y system has evolved independently several times, when an allele of a gene or a new gene appears that when it is present reliably leads to maleness regardless of what else is in the genome. For weird population genetic reasons this nucleates an expanding island of DNA that cannot recombine with the homologous chromosome and which is free to degenerate except for sex determining factors and a few male gamete specific genes that migrate there over evolutionary time, until eventually the entire chromosome degenerates and you get a sex chromosome.
The zw system has evolved multiple times, in which the factor present in one sex and leading to a degenerate sex chromosome leads to femaleness.
In species that are hermaphroditic like some fish all this is superfluous.
In many organisms where sex determination is random or temperature based there are still genetic loci that bias the choice of program one way or another, see my recent comment about zebrafish. These traits are kept in balance in the population because the more males there are the less likely any one of them is to successfully reproduce and vice versa.
Biological sex is ancient but the method of picking which program (or both) to follow has changed frequently.
To echo Salemicus, everyone with a normal endocrine system has testosterone/androgens and estrogens (and other sex hormones too) and indeed both are needed for normal puberty in both sexes, but the ratios and absolute levels vary a lot between the two usual patterns. For example, sealing growth plates in bones to establish adult height requires estrogen for males and females, and androgens are required to establish a lot of hair and skin changes.
One interesting thing I have heard is that amongst hyenas females have more androgens, and this is also visible in size, behavior etc. Must be an interesting kind of puberty.
Yep. While having different developmental payhways to making ova and sperm is ancient, pretty much everything else associated with biological sex is potentially mutable over evolutionary time (and even that can revert to hermaphrodite status).
I am unaware of any examples of normally functionally hermaphroditic mammals, and unaware of but less confident in the same for tetrapods (four limbed vertebrares that came onto land and their descendants). I am aware of tetrapod species that became almost entirely female, reproducing primarily by cloning. I am also aware of tetrapods that switch sex during their lifetimes, though you could call that a form of hermaphroditism. Tetrapods also exhibit all of the above methods of sex determination.
The pattern of hermaphroditism in ray finned fish, a very diverse and old vertebrate lineage, however suggests multiple conversion events back and forth some of which are recent. See http://evolution.berkeley.edu/evolibrary/images/hermaphroditismtree.gif . Of note, cichlid fish are listed as hermaphroditic on there but recently went through a huge evolutionary radiation and several of their sublineages have been caught in the act of reevolving most of the above sex determination systems.
They all contain the same genome and can activate the same pathways. Same way that your skin and airways can make histamine as an inflammitory signal while your midbrain makes it as a sleep suppressing neurotransmitter (which is why most antihistamines make you sleepy). Genes and pathways and enzymes are quite often not organ specific.
People with full androgen insensitivity syndrome (never responding to androgens produced by gonads) or gonadal dysgenesis of various stripes (gonads fail to develop properly and don’t make any hormones) usually wind up more or less externally normally female regardless of the state of their sex-associated karyotypes/genoypes (with the internal plumbing variable depending on the exact details). In this way, the pre-pubescent female state is probably the closest thing we have to a default inasmuch as that means anything.
These people do, however, fail to naturally go through most of puberty (a few androgens are usually made by the adrenal glands in everyone regardless of sex but not much) which is an active switch being thrown regardless of sex. As such, the secondary female sex characteristics of sexual maturity are not exactly ‘default’ themselves in the same way.
Not sure how the following anecdotal observation relates but it seems to me female gender expression is far more fluid. That is, if situation is tough, poverty and all that, and women end up doing hard physical labor and facing similar challenges of deprivation and difficulties, they end up pretty close to becoming tough-guys, even including things like having insults develop into fist-fights.
The opposite does not seem to be true, it is pretty rare that circumstances make men adopt feminine traits, it is more like they either like them on their own or will never pick up.
However the situations are not exactly parallel because any sort of deprivation and difficulty is generating an obvious response to toughen up with moves people naturally towards masculine roles while there is no such similarly compelling force that could force men towards feminine roles.
Or is there? It would be interesting to examine 1) what fathers do if their wives suddenly die, do they manage to simulate the motherly role as well 2) do more or less cis/straight men sometimes adopt gay traits in prisons?
This is a bit of a chaotic comment, I probably need to organize my thoughts better. My thoughts are roughly like, put women into a tough environment and their testosterone goes up and adopt masculine traits. But there is not really such an environment for men that would make their estrogene go up, except xenoestrogens. However it is possible to create testosterone-lowering environments e.g. schools with an anti-competitive ethos.
I don’t think that women doing hard physical labour is a consequence of ” female gender expression” under certain circumstances. If you need to do physical labour to survive, you do physical labour to survive and gender has nothing to do with it.
As to feminization of men, it’s a popular topic (google it up), usually in the context of political correctness / rise of feminism / anti-discrimination policies / SJWs / etc. in the first world countries.
By the way, for feminization you don’t need estrogen to go up, all you need is testosterone to go down. And, hey, look, testosterone seems to be decreasing in late XX century…
Woman is the biological default. That’s why women have redundancy on the 23rd chromosomal pair, whereas men have a special “Y” chromosome—leading to much higher rates of genetic disorders in men. That’s why in infant male humans, the testicles have to descend. And so on. Both from an encoding and from a developmental point of view, a man is a woman altered to be masculine. And testosterone is what does that altering.
Yes, it could have been different. We can imagine a species with a neutral default, which then gets altered to be either masculine or feminine by different sex-encoding hormones. But that’s not how humans came about.
We don’t have to imagine. We can look at birds, where the sex chromosomes are the opposite. I haven’t looked at them, so I don’t know how much is a consequence of the chromosomal structure. But, for some reason, I’m skeptical that most people who pontificate their role have looked either. The points about hormones and development are more reasonable.
Are the opposite? I assumed the XX/XY goes back to the very beginnings of gender i.e. fishes… how comes very different chromosomes can make the same hormones i.e. AFAIK birds do have testosterone?
The sheer number of ways sex can be determined amongst vertebrates is amazing, let alone other animals or microbes (there are fungi with 10,000 ‘sexes’/mating types...). I will restrict my examples to vertebrates.
As a rule, in most vertebrates (including humans and other organisms in which it is genetically determined) everything needed to make all the biology of both sexes is present in every individual, but a switch needs to be thrown to pick which processes to initiate.
Many reptiles use temperature during a critical developmental period with no sex chromosomes. Many fish too.
The x y system has evolved independently several times, when an allele of a gene or a new gene appears that when it is present reliably leads to maleness regardless of what else is in the genome. For weird population genetic reasons this nucleates an expanding island of DNA that cannot recombine with the homologous chromosome and which is free to degenerate except for sex determining factors and a few male gamete specific genes that migrate there over evolutionary time, until eventually the entire chromosome degenerates and you get a sex chromosome.
The zw system has evolved multiple times, in which the factor present in one sex and leading to a degenerate sex chromosome leads to femaleness.
In species that are hermaphroditic like some fish all this is superfluous.
In many organisms where sex determination is random or temperature based there are still genetic loci that bias the choice of program one way or another, see my recent comment about zebrafish. These traits are kept in balance in the population because the more males there are the less likely any one of them is to successfully reproduce and vice versa.
Biological sex is ancient but the method of picking which program (or both) to follow has changed frequently.
To echo Salemicus, everyone with a normal endocrine system has testosterone/androgens and estrogens (and other sex hormones too) and indeed both are needed for normal puberty in both sexes, but the ratios and absolute levels vary a lot between the two usual patterns. For example, sealing growth plates in bones to establish adult height requires estrogen for males and females, and androgens are required to establish a lot of hair and skin changes.
One interesting thing I have heard is that amongst hyenas females have more androgens, and this is also visible in size, behavior etc. Must be an interesting kind of puberty.
Yep. While having different developmental payhways to making ova and sperm is ancient, pretty much everything else associated with biological sex is potentially mutable over evolutionary time (and even that can revert to hermaphrodite status).
Has that actually happened to anything amphibian or above?
I am unaware of any examples of normally functionally hermaphroditic mammals, and unaware of but less confident in the same for tetrapods (four limbed vertebrares that came onto land and their descendants). I am aware of tetrapod species that became almost entirely female, reproducing primarily by cloning. I am also aware of tetrapods that switch sex during their lifetimes, though you could call that a form of hermaphroditism. Tetrapods also exhibit all of the above methods of sex determination.
The pattern of hermaphroditism in ray finned fish, a very diverse and old vertebrate lineage, however suggests multiple conversion events back and forth some of which are recent. See http://evolution.berkeley.edu/evolibrary/images/hermaphroditismtree.gif . Of note, cichlid fish are listed as hermaphroditic on there but recently went through a huge evolutionary radiation and several of their sublineages have been caught in the act of reevolving most of the above sex determination systems.
Birds have a ZZ/ZW system where the male is the homogametic sex.
Yes, birds have testosterone. Mind you, women have testosterone. It’s the elevated quantity of testosterone that leads to masculinity.
How come very different organs in mammals can make the same hormones? ie. testes, ovaries, adrenals all make testosterone
They all contain the same genome and can activate the same pathways. Same way that your skin and airways can make histamine as an inflammitory signal while your midbrain makes it as a sleep suppressing neurotransmitter (which is why most antihistamines make you sleepy). Genes and pathways and enzymes are quite often not organ specific.
You could with equal sense (i.e. very little) summarise the same empirical observations as “a woman is an incompletely developed man.”
No quite because ‘development’ at least suggests that the change happens ‘later’.
I am not convinced that “is the biological default” is a meaningful concept.
If (a) then b else c
is the same thing as if (!a) then c else b
The point is that !a (not testosterone) is just the lack of testosterone, but not the presence of estrogen.
People with full androgen insensitivity syndrome (never responding to androgens produced by gonads) or gonadal dysgenesis of various stripes (gonads fail to develop properly and don’t make any hormones) usually wind up more or less externally normally female regardless of the state of their sex-associated karyotypes/genoypes (with the internal plumbing variable depending on the exact details). In this way, the pre-pubescent female state is probably the closest thing we have to a default inasmuch as that means anything.
These people do, however, fail to naturally go through most of puberty (a few androgens are usually made by the adrenal glands in everyone regardless of sex but not much) which is an active switch being thrown regardless of sex. As such, the secondary female sex characteristics of sexual maturity are not exactly ‘default’ themselves in the same way.
Not sure how the following anecdotal observation relates but it seems to me female gender expression is far more fluid. That is, if situation is tough, poverty and all that, and women end up doing hard physical labor and facing similar challenges of deprivation and difficulties, they end up pretty close to becoming tough-guys, even including things like having insults develop into fist-fights.
The opposite does not seem to be true, it is pretty rare that circumstances make men adopt feminine traits, it is more like they either like them on their own or will never pick up.
However the situations are not exactly parallel because any sort of deprivation and difficulty is generating an obvious response to toughen up with moves people naturally towards masculine roles while there is no such similarly compelling force that could force men towards feminine roles.
Or is there? It would be interesting to examine 1) what fathers do if their wives suddenly die, do they manage to simulate the motherly role as well 2) do more or less cis/straight men sometimes adopt gay traits in prisons?
This is a bit of a chaotic comment, I probably need to organize my thoughts better. My thoughts are roughly like, put women into a tough environment and their testosterone goes up and adopt masculine traits. But there is not really such an environment for men that would make their estrogene go up, except xenoestrogens. However it is possible to create testosterone-lowering environments e.g. schools with an anti-competitive ethos.
I don’t think that women doing hard physical labour is a consequence of ” female gender expression” under certain circumstances. If you need to do physical labour to survive, you do physical labour to survive and gender has nothing to do with it.
As to feminization of men, it’s a popular topic (google it up), usually in the context of political correctness / rise of feminism / anti-discrimination policies / SJWs / etc. in the first world countries.
By the way, for feminization you don’t need estrogen to go up, all you need is testosterone to go down. And, hey, look, testosterone seems to be decreasing in late XX century…