Does the Y-haplogroup influence the appearance of the genitalia?

[Groninger]

There has been a discussion on this forum about the influence of the Y-haplogroup on a man's looks. Now the genitalia are, as far as I can see, the one part of the body whose appearance is most likely to be influenced by the Y-haplogroup. Has there ever been any research on this? I'm sorry to bring up a bit of an awkward topic, but I think it is relevant in this discussion.

 

[Angela]

There has been a discussion on this forum about the influence of the Y-haplogroup on a man's looks. Now the genitalia are, as far as I can see, the one part of the body whose appearance is most likely to be influenced by the Y-haplogroup. Has there ever been any research on this? I'm sorry to bring up a bit of an awkward topic, but I think it is relevant in this discussion.

I've seen references here and there about studies on size, but they're presented by country, not by haplogroup. Plus, some of the results were self-reported, so not likely to be entirely reliable.

 

[MOESAN]

what do you mean by 'genitalia'?: male and female sexual organs with/without their pilous environment?
concerning male sex size (a big question for a small part of the body, obsession of males!) I think that for the most the global autosomal background accounts for a big part of the result - chromosom Y principally chooses the sex quality and the concerned hormones respective dosis/proportions - it can have some other effects, but my first impression stays the same - autosomal background -
we have not the penis of our papa or the vagina of our mum! they are multigenic interactions I think - no government agreement, no proof!

 

[Expredel]

I remember once reading some "ask the doctor" site where a guy claimed to have insecurities because he was white but had a very dark penis. This may be an Y-linked trait as it's difficult to otherwise explain. There's also statistical evidence that men are more likely to have light eyes than women which suggests the Y chromosome influences pigmentation.

I think a "micropenis" can be Y-linked, not sure if it's common enough to suspect a specific Y haplogroup.

 

[ngc598]

...and again the question - 'Can I blame the Y on his ... (whatever)?'

The size of the testicles: Gorillas have harems, no sexual competition and there balls are really small. Chimpanzees have extreme competition and theirs are 10 time bigger than those from the gorillas (compared to their body mass). Those of humans, by the way, are right in the middle of the two extremes. So, does the Y determine the size? Obiously it's the social circumstances and not the genes.

To determine what the Y-chromosome can and cannot, we should know what's on it. There are 4 kinds of genes there.:
1. The pseudoautosomal genes (regions PAR1,2,3), which lie on positions, where the X and the Y can pair and segregate. They are therefore not male specific, so we can forget them.
2. X-degenerate genes: those are genes which come from the precursor of the X and Y chromosome. Most of them are already deleted, some exist as defunct pseudogenes and just a few of them (a dozen or so) are still functional. They are usually cell housekeeping genes with no pronounced functions which we can relate to ANY 'visible' attributes of a person, but a few of them indeed have special functions. Just a handful of them is currently known. AMELY is related to the enamel production, NGLN4Y binds to the nerve cell synapses and can be blamed for several neural dysfunctions, TBL1Y is involved in cell signalling processes and finally SRY, THE male-defining gene, which is highly variable, except for a strictly conserved motif, which is necessary for sex definition. This gene initiates the forming of the male gonads. Mutations can lead to reduced size of the testes, but also to complete sex reversal. It interacts with the Androgen receptor, which can cause androgen insensitivity and therefore turn an otherwise normal male into a person with reduced male expression, both somatically and psychologically.
3. Amplicon genes: those are housekeeping genes for germ cell development transposed from the autosomal gene pool to the Y chromosome. There they were duplicated or multiplied (therefore - amplicons) to enhance or make their abilities more specifically. In reality they are less than a dozen genes, but with amplification there are about 60 of them around, accounting for about 80% of the protein coding genes. Their effect is almost exclusively on the sperm cells themselves and have no somatic consequences.
4. X-transposed genes: When God created Adam about 4 Mio years ago , he shuffled some genes from the X-chromosome to the Y. From the two, which have survived, one - TGIF2L - is a transcription factor, a housekeeping gene, that is targeted mainly at the testes (perhaps at the brain and the prostate as well). The other gene is PCDH11Y, which is one of the important genes for the development of brain lateralisation, so it is involved in the mental sex difference of male and female, and plays a role in the handedness of a person.

That's all about the functional genes on the Y genome, hardly more than 20 different genes. As you can see, there are less than a handful of genes, which can be responsible for physical appearance, and the mutations, defining the different haplogroups, have to be exactly inside these genes, and the mutations must have the capacity to change the molecules, they encode, sufficently for a recognizable variation in a person.

 

[Expredel]

That's all about the functional genes on the Y genome, hardly more than 20 different genes. As you can see, there are less than a handful of genes, which can be responsible for physical appearance, and the mutations, defining the different haplogroups, have to be exactly inside these genes, and the mutations must have the capacity to change the molecules, they encode, sufficently for a recognizable variation in a person.

The Y chromosome does not need to encode genes, it only needs to regulate gene expression, which can take place outside the gene itself in the so called "junk DNA".

There are many cases of XX-males (men without an Y chromosome) with a fully functional penis, it was noted however they all have smaller testicles. So it appears the Y chromosome plays a role here. There are observed racial differences as well.

According to an article published in Nature, Japanese and Chinese men’s testicles tend to be smaller than those of Caucasian men, on average. The authors of the study concluded that “differences in body size make only a slight contribution to these values.” Other researches have confirmed these general trends, finding average combined testes weights of 24 grams for Asians, 29 to 33 grams for Caucasians, and 50 grams for Africans.

 

[ngc598]

The Y chromosome does not need to encode genes, it only needs to regulate gene expression, which can take place outside the gene itself in the so called "junk DNA".

Junk DNA is such a bad word for this part of the genome. I like the expression 'functional wasteland', which some scientist once called it... From the 57 Mio. basepairs of the Y genome about 40 Mio. are coated in heterochromatine, which normally inhibits gene expression, and indeed so far there hasn't been reported gene activity in this region. From the euchromatic part of the genome there are over 100 genes which will turn into several kinds of RNA and functioning as gene regulators. Unfortunately the research concentrates on diseases related to these genes , and so far the RNA genes were all targeted at the protein coding genes of the Y-chromosomes causing neural dysfunctions, cancer and infertility issues, as I described before. Effects on autosomal genes are therefore still speculation. My personal opinion on such a possibility is, that it looks pretty dangerous to let a gene, which is not controlled by gene recombination, intervene with genes of the whole genome instead of (theoretically) no more than two or three genes of the Y-chromosome given the fact that any micro RNA can possibly target a hundred or more genes of the whole genome. A defective one would seriously compromise the survival of the individuum. So I don't believe this is going to happen (more from my understanding than from knowledge, I admit).

There are many cases of XX-males (men without an Y chromosome) with a fully functional penis, it was noted however they all have smaller testicles. So it appears the Y chromosome plays a role here. There are observed racial differences as well.

In most cases the SRY gene is the culprit, which erranously landed on the X-chromosome.

Other researches have confirmed these general trends, finding average combined testes weights of 24 grams for Asians, 29 to 33 grams for Caucasians, and 50 grams for Africans.

I smell competition related causes, as I explained above. Although we have some genes on the Y-chromosome targetting at the testes I am still not completely convinced that Y-chromosome genetics is the (only) reason.

 

[MOESAN]

I remember once reading some "ask the doctor" site where a guy claimed to have insecurities because he was white but had a very dark penis. This may be an Y-linked trait as it's difficult to otherwise explain. There's also statistical evidence that men are more likely to have light eyes than women which suggests the Y chromosome influences pigmentation.

I think a "micropenis" can be Y-linked, not sure if it's common enough to suspect a specific Y haplogroup.

males and females are almost the same thing at first; the bigger role of the Y chromosom is to change the sexual hormones proportions; it's these proportions which determine external and internal sexual differenciation, spite some outside not genetically inherited influences can come to put disorder in the game. Even testosterone density is not by force responsible for the penis size once the "floor-level" is reached: some men have a very viril aspect and body hair along with small sexual organs and the contrary is true too; nothing simple - Comparating Gorillas and Chimps, the testicles size is one aspect but the sperm richness/density is other thing.
I have to learn on this matter but I think the Y chroms role is an indirect one more than a direct one.
I think if you give oestrogens to a male he would have the tits like his mum's tits or like his father's sister (or father's grand'ma) or between, according to the bunch of autosomals he has from his diverse ascendants lineages; if the group he pertains is very homogenous this 'poor) male would have tits like the tits of his sisters. specie/race(s) Background. I think it would be the same concerning penis and clitoris and vagina, or testicles and vulva/"lips".

@ngc598:you said:
The size of the testicles: Gorillas have harems, no sexual competition and there balls are really small. Chimpanzees have extreme competition and theirs are 10 time bigger than those from the gorillas (compared to their body mass). Those of humans, by the way, are right in the middle of the two extremes. So, does the Y determine the size? Obiously it's the social circumstances and not the genes.

you seem knowing more than me on this very matter (it's not too difficult; here I give opinion, not knowledge). But you cannot say the genes does not determine the size; you can say: it's not only the genes present on the Y chroms which determine size; because the social circumstances you allegue here (are their invocated effects proved?) act by genetic selection, whatever the chroms concerned, not by direct effect on live beings after birth. Just an hair splitting, I suppose your explanation was a "raccourci". Thanks for your post all the way.

 

[ngc598]

... But you cannot say the genes does not determine the size; you can say: it's not only the genes present on the Y chroms which determine size; because the social circumstances you allegue here (are their invocated effects proved?) act by genetic selection, whatever the chroms concerned, not by direct effect on live beings after birth. Just an hair splitting, I suppose your explanation was a "raccourci".

You are right. My explanation was quite a stub. The lengthier version would be like...social circumstances influence the genes, and those genes produce the physical, somatical expressions, but it's not primarily the genes on the Y-chromosome which are affected and cause the variants.

There are not enough mutations at the positions, which define the various haplogroups, that can possibly explain a connection between haplogroups and some physical or psychological trait, the relations are therefore either more complex (involving more components) or the relationship between haplogroups and attributes is an indirect one, meaning that other things play a role, which are in relationship both to haplogroups and the properties.

A simple thought may help to understand such a relationship. Let's assume we have a region with almost exclusively one haplogroup, like R1a. The people there have the arctic tundra to the north, the Ural mountains to the east, the R1b-cowboys to the south and the I-group Europeans to the west. So they are pretty much confined. Within this group there is genetic exchange and over time the gene pool is pretty much mixed up and all people in the region share a great amount of autosomal genes with each other. Because part of the autosomal genes show in physical traits as well, they become more and more similar over time. When they leave their confinement this similarity doesn't disappear all of a sudden, it just slowly diminishes, when they merge with other populations, and you can still find a correlation between this haplogroup and some physical and psychological attributes.

The strength of the similarity depends on the factors confinement (how strong is it at the margins), the mobility within the confinement (hunter-gatherer groups are far more mobile than agriculturists, more mixing means more shared attributes) and the length of time (the longer the confinement, the better the mixing), they were confined. The mixing velocity in their new environment decides, how long this group will be distinguishable from other ethnic groups.

Altogether, yes, you can sometimes see a relation between a certain haplogroup and physical traits, but it's mostly because they shared their autosomal genes as well, not only the Y-chromosome, and their autosomal genes define their appearance almost exclusively (mind you: I said almost, because a tiny bit is of course brought in by the few Y-chromosome genes, they are a part of their genome after all).

 

[Thismare89]

I agree with you.

 

[Alpenjager]

What about this? https://en.wikipedia.org/wiki/Hirsuties_coronae_glandis