Questions tagged [sex]

Questions involving the study of sex and reproduction, mating systems, sexuality, sex determination, gender, the evolution of sex, and other topics in the context of sex.

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2 votes
0 answers
38 views

Are humans unusual, compared to other animals, in not understanding the mechanics of sex instinctively?

To begin with a personal anecdote: there was a period in my childhood, which I can remember clearly, in which I was aware of sexual reproduction as a fact, but the mechanics of it remained a ...
0 votes
1 answer
96 views

Is “random arousal” in humans still caused by/connected to “background” sex drive?

I’m not sure if the title is the best way to word the concept but I don’t know how else to put it briefly; though honestly this question itself might be a bit hard for me to communicate concisely in ...
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1 answer
50 views

How does positional memory in fibroblast cells work?

I have a question regarding how positional memory in fibroblasts work, specifically, where the memory comes from/how its made. For example, the Salamander & other amphibians are able to regenerate ...
0 votes
1 answer
171 views

What is the evidence that women experience a larger cortisol spike than men, when they see domestic clutter?

I'm reading a book "The Organized Mind: Thinking Straight in the Age of Information Overload" by Daniel Levitin. At the beginning of chapter "Organizing our homes" he says that ...
5 votes
3 answers
5k views

Is sex a spectrum?

At the moment I'm especially interested in the question of whether biological sex is really a spectrum. Unfortunately I could not find any good answers on the Internet. Therefore I hope that some of ...
0 votes
0 answers
43 views

What is the origin of mammals X/Y sex determination system and what/when was the last common ancestor to possess these chromosomes?

I know many animals use an X/Y sex determination system, but not all of these animals use the same X/Y genes. That is to say the X/Y sex determination system has convergently evolved in many species, ...
12 votes
1 answer
844 views

Genetic expression in interspecific hybrids

Referring to interspecific hybrids, I have the following two questions:- Quoting from wikipedia:- The offspring of an interspecific cross are very often sterile; thus, hybrid sterility prevents ...
4 votes
1 answer
142 views

Is there any evolutionary reason why male traits appear in the heterogametic sex and female traits in the homogametic sex?

If you define male as the heterogametic sex, and female as the homogametic sex, then my question sounds like a tautology. But, what I'm trying to get at is why is it that the traits we associate with &...
12 votes
1 answer
3k views

Evolutionary reasons why you cannot tickle yourself but you can masturbate

There are obviously good reasons that explain why you cannot tickle yourself (see e.g. here). This got me thinking why it is possible to masturbate... Wouldn't it make more sense to not be able to do ...
35 votes
3 answers
6k views

What's the difference between male and female?

As long as we only look at humans the differences are clear: males have chromosomes XY, produce sperm and don't get pregnant. Females have chromosomes XX, produce egg cells and bear babies. But when ...
0 votes
2 answers
269 views

When is it better for a gene to cause a biased sex ratio?

Because genes are selfish and want to maximise their transmission from generation to generation, if they can distort a population's sex ratio, isn't it always in their interest to cause a biased sex ...
2 votes
2 answers
35k views

What is inside the male’s body in the space where females have the ovaries and the uterus?

The male penis and scrotum are external, whereas the female sex organs are placed "inside" the body. As females have the bladder, rectum etc. just like males, does this mean overall females ...
1 vote
1 answer
90 views

For animals with separate hermaphrodite and non-hermaphrodite populations which is more common, female + herm or male + herm?

I think the question already says it all. I know there exist animals that have both herm and female populations and other's with herm and male populations, I'm not personally aware of any animal that ...
1 vote
3 answers
348 views

Is it possible to fuse DNA from two sperms and can a baby be born from that? [closed]

If this is possible, then isn't there going to be a chance to have a YY child?
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1 answer
513 views

Do reproductive organs function before puberty?

Testis means one of the two male reproductive glands that produce spermatozoa and secrete androgens. Ovary means one of usually two organs that produce oocytes and secrete oestrogen and progesterone. ...
1 vote
1 answer
88 views

higher-order evolutionary adaptations

Most adaptations are what I'd call first-order. Cats evolve better eyesight; redwoods evolve to grow taller; male cardinals evolve attractive bright feathers. All of these changes were selected for ...
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2 answers
192 views

What are the distinct neurochemical components of sexual pleasure?

Sexual activity is usually described as pleasurable. What neurochemical systems does sex activate? Does the presence or absence of a partner make a difference -- say, in the activation of the ...
4 votes
1 answer
556 views

Why do women have less synapses / neurons / brain mass than men despite having the same average IQ?

I don't mean to cause offence or suggest than men and women shouldn't be of the same intelligence — that's not something I'm here to dispute. What I want to understand is how this is possible given ...
16 votes
1 answer
10k views

Is female the default sex in humans?

I was taught in school that female is the default sex in humans based on the following logic: Development into a human male requires the activation of the SRY gene in the foetus. If that doesn't ...
2 votes
1 answer
132 views

Will Fst (inbreeding coefficient) always be a value close or at 0 in asexual populations?

FST is the average inbreeding coefficient of a total population. The equation is: $F_{ST} = \frac{Var(S)}{Var(T)} $ $Var(S)$ = variance in the frequency of the allele between different subpopulations, ...
7 votes
3 answers
1k views

If the haploid prothallium of a fern fertilizes itself into a diploid sporophyte, does this make all ferns clones?

From what I understand in the alternation of generations in ferns, mature spores germinate into a haploid prothallium. But how does this gametophyte produce recombinant gametes if it itself develops ...
7 votes
1 answer
527 views

Can you tell the sex of a white willow when it's not flowering?

Can you tell whether a salix alba tree will produce male flowers or female flowers by looking at it, touching it or generally using your unaided senses? If not, is there any way to do that without ...
-4 votes
1 answer
43 views

Do hormones make it more likely to perceive sexual forms in otherwise non-sexual objects? [closed]

People can see sexual forms in many things. It seems that this varies with age, but this is not enough to claim it is because of sexual hormones. The question is: is it?
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2 answers
149 views

Why do the two sexes have different reproductive costs and capabilities?

Is there an evolutionary explanation that shows why the reproductive costs are mostly on the female sex? And therefore, why do males can potentially have more offspring? Does that happen to create ...
1 vote
0 answers
38 views

Flatworms sexual reproduction; one must be the mother and the other the father?

I watched this. I wonder if both of these flatworms ever end up pregnant. Earthworms are simultaneous hermaphrodites, meaning worms have both male and female reproductive organs, just like flatworms. ...
3 votes
1 answer
575 views

What causes the sound of climaxing bees?

I just saw the funniest video of bumblebees(?) having sex. (mirror) As they were getting it on, there seemed to be an almost audible 'moaning' coming from the pair. From what I presume it was a sexual ...
7 votes
1 answer
725 views

Why are men more susceptible to severe COVID-19?

It seems that globally, men are more susceptible to severe COVID-19 than women: https://www.theguardian.com/world/2020/mar/26/men-are-much-more-likely-to-die-from-coronavirus-but-why This is seen in ...
1 vote
0 answers
60 views

Is it impossible for some female songbirds to sing?

I have read that in northern hemispheres, most female songbirds can't sing (for example, the Blackbird). Things are different in tropical regions. Birdsong is for males in some species; it is utilized ...
-4 votes
1 answer
115 views

are there examples of research harmed by the binary vs. non binary genders discussions? [closed]

As a base for my question, here is a link to an article from nature.com: https://www.nature.com/articles/d41586-020-00502-w In the article, the following paragraph is relevant: The researchers ...
0 votes
0 answers
22 views

Empirical Measurements of Barr Body Ratio

'Both X-chromosomes in a female have an equal chance of becomes a Barr body in each cell.' Every source I can find on Barr bodies claims this and I can think of no reason for why it may be wrong. What ...
1 vote
1 answer
133 views

What exactly is "lateral septum"?

I came across the phrase lateral septum and I can't seem to find the precise definition online. Is it "the areas roughly to the right and the left of the septum pellucidum"? Or is it the ...
0 votes
1 answer
51 views

What are "intrinsic hypothalamic fibers"? (From an article on neuronal mechanisms of sexual desire)

I came across the phrase intrinsic hypothalamic fibers which I cannot understand. What is meant by intrinsic - that these fibers (long myelinated axons?) start in the hypothalamus? Or that they start ...
4 votes
1 answer
897 views

Germ cells vs. gametes

Naively, I thought that germ cells are diploid (in diploid species like human/mouse at least). Then, germ cells undergo meiosis and become haploid. I thought this was the critical change that defined ...
-4 votes
2 answers
522 views

Why are (some) male humans sexually attracted to the breasts of female humans? [closed]

Many male humans are sexually attracted to the breasts of female humans. Is there an evolutionary reason for this?
1 vote
1 answer
121 views

Y chromosome changing sex ratios

Fisher's principle explains why sex ratios in most sexually reproducing species is approximately $1:1$. However, given that in humans and many other animals, males and females differ genetically, it ...
-1 votes
1 answer
74 views

Large study showing that attraction to only the same sex has to do with your genes, published where?

Can someone please help me out and find and link me the study from a couple of years ago that showed how only same sex attraction, when the male cant become attracted to a woman, it has to do with ...
1 vote
1 answer
207 views

If someone with "XO" is one of the identical twins with the other twin as male, then what would the sex chromosome of the other twin be?

A more complete question: If someone with sex chromosome of XO is one of the monozygotic twins with the other twin as phenotypically male, then what would the sex chromosome of the other twin be? I ...
12 votes
4 answers
9k views

Are there lifeforms that have more than 2 sexes?

Are there any lifeforms on earth that have more than male and female biological sexes? If so, are all three mates required for reproduction or is there something else going on? If not, why not? ...
1 vote
0 answers
74 views

What is the developmental and health outcome of an XY individual with an SRY addition on their X chromosome?

I know that "XX male" syndrome occurs through various means, including the addition of an SRY gene in one of the X chromosomes. The developmental and health outcomes of such individuals can be ...
2 votes
0 answers
85 views

Evolution of the unique mating system of the scorpion Androctonus australis

Sperm transfer in the scorpion Androctonus australis involves a sclerotized spermatophore, which is formed in the paraxial organs of the male reproductive system. The right paraxial organ produces the ...
2 votes
0 answers
87 views

How widespread in the Animal Kingdom is Aromatization as the Process that Determines an Animal's Sex?

I shall summarize my lay understanding of my question before going into details. To my lay reading, the sex of a vast diversity of animal kingdom species can be thought of as arising from the extent ...
-1 votes
2 answers
255 views

Can diet, supplementation and/or drugs affect sexual dimorphism?

After puberty, can certain diets, exercise, and/or possible drugs affect masculine/feminine dimorphism in adults? We know dimorphism and/or morphology is a product of genes, but to what extent can ...
2 votes
1 answer
353 views

Is sexual desire stronger in men than women?

Usually in popular culture it's considered men sexual desire is stronger than women. This seems to be congruent with the availability of sexual related items for men and women, such as magazines, ...
0 votes
1 answer
52 views

How does X chromosome monosomy occur

I want to understand how Turner syndrome - monosomy X - occurs at the molecular level. The NIH mentions that there are cases of both complete monosomy and of mosaicism. I’m particularly interested ...
4 votes
1 answer
243 views

Evolution of the haplo-diplontic life cycle

From wikipedia > Biological Life Cycle: haplontic life cycle - the haploid stage is multicellular and the diploid stage is a single cell, meiosis is "zygotic". diplontic life cycle - the diploid ...
2 votes
1 answer
7k views

What is the evolutionary advantage of having pubic hair?

Only humans have pubic hair. What is the evolutionary advantage in having it?
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2 answers
559 views

In men, why do over 80% of sperm have abnormal form? [duplicate]

Here is the percentage of normal forms among fertile mens according to the centile (Source: Cooper et al. 2010): 2.5: 3% 5 (below this is Teratozoospermia): 4% 10: 5.5% 25: 9% 50 (median): 15% 75: ...
2 votes
0 answers
266 views

How many mitotic divisions do haploid cells undergo before fertilization?

Background This question is about human physiology and gametogenesis. A spermatozoid is not necessarily the direct "offspring" of a diploid cell. Stated differently, a spermatozoid cell can be the ...
0 votes
1 answer
271 views

Why is sex hurtful for some animals but pleasurable for others?

Sex seems to be pretty hurtful for feline for example. On the other hand sex is pleasurable for humans. Why is sex pleasurable for some and not for others? How do these things evolve?
17 votes
2 answers
5k views

Do males of all sexual species have Y chromosomes?

I know for instance some cells are sexual, so, this got me wondering, do the males of all species that have distinct sexes have Y chromosomes?