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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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112 votes
3 answers
26k views

Are male and female brains physically different from birth?

Male and female brains are wired differently according to this article: Maps of neural circuitry showed that on average women's brains were highly connected across the left and right hemispheres, ...
Pablo's user avatar
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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 ...
user15004's user avatar
  • 361
19 votes
1 answer
119k views

What is the female equivalent of the morning erection that some men experience?

There was question about what causes "morning wood." It was answered that the erection in the morning is caused by decline of norepinephrine during REM sleep. Which in part allows to prevent ...
jnovacho's user avatar
  • 363
19 votes
1 answer
2k views

How do porcupines keep from pricking each other while mating?

How do porcupines keep from pricking each other while mating? It seems like they would constantly be scratching each other.
J. Musser's user avatar
  • 3,717
18 votes
2 answers
13k views

Why does sex last so long?

I wonder why (especially human) sex lasts longer than just a few seconds? My thought is that the shorter it takes a man to ejaculate, the lesser is the risk that he gets interrupted by a rival or a ...
MaxD's user avatar
  • 272
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?
Stan Shunpike's user avatar
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 ...
user1205901 - Слава Україні's user avatar
15 votes
1 answer
717 views

How do members of cryptic species know who to mate with?

According to Wikipedia: In biology, a cryptic species complex is a group of species which satisfy the biological definition of species—that is, they are reproductively isolated from each other—...
Douglas S. Stones's user avatar
13 votes
1 answer
40k views

What is the standard deviation of adult human heights for males and females?

The wikipedia article on human height reports mean height for many different countries by sex but it does not report standard deviations. What is the standard deviation of adult human heights within ...
Jeromy Anglim's user avatar
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? ...
ToMakPo's user avatar
  • 249
12 votes
3 answers
5k views

Why do hot water baths affect only males' fertility? Why not females'?

Here is the link where urologists are warning men not to take hot water baths. Why does it affect only males' fertility? Why not females also?
K Sai Harsha's user avatar
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 ...
stochastic13's user avatar
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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 ...
vonjd's user avatar
  • 1,061
9 votes
3 answers
2k views

Is homosexuality an adaptation in humans?

Homo sapiens have menopause - as some other mammals (e.g. some Cetacea) - a phenomenon where older females live for decades after the end of their own reproduction. Perhaps homosexuality, that looks ...
Rodrigo's user avatar
  • 1,300
9 votes
2 answers
985 views

How and when did sex evolve?

As I know evolution comes bit by bit mutation by mutation How sex evolved which requires a major change in at least two individuals one to become male and one to become female ? When that happened ...
George Botros's user avatar
8 votes
2 answers
767 views

Can you tell if a corpse was male or female by only examining its skull?

There are articles that says women have more rounded corner faces than men, than women noses are usually shorter, etc. But are those (and other features) tendencies or deterministic features that ...
Pablo's user avatar
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8 votes
2 answers
984 views

Why are there so many sex determining systems in animals

There are several sex determining systems in animals. In mammals XY = male(except in rare cases where SRY crosses with genes on the X so that it is the reverse) and XX = female. In some birds it is ...
Caters's user avatar
  • 694
8 votes
1 answer
6k views

In males, why it is difficult to control orgasm?

Why it is difficult to control orgasm in male humans? How are orgasms controlled and what is different between males and females? We can control urine for few minutes, but we can't control orgasm for ...
user avatar
8 votes
0 answers
365 views

Why females don't have much sexual desire when compare to males? [closed]

I read this Wikipedia article about Playgirl, It is made especially for females. but Its Spokesman Daniel Nardico revealed subscriptions are generated more from males. In a February 2010 interview ...
Tabbatha Silver's user avatar
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 ...
johnO's user avatar
  • 87
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 ...
BRZA's user avatar
  • 268
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 ...
ymar's user avatar
  • 680
7 votes
1 answer
767 views

When did our ancestors switch to a menstrual cycle instead of the estrous cycle?

The Wikipedia page on the Estrous cycle says: Humans have menstrual cycles instead of estrous cycles. They shed their endometrium instead of reabsorbing it. Unlike animals with estrous cycles, ...
Christian's user avatar
  • 2,616
7 votes
1 answer
507 views

What is most ancestral: isogamy or anisogamy?

Sexual reproduction can be feasible with anisogamy (gametes of different sizes i.e. genders) or isogamy (gametes of same size i.e. mating types) or with undifferentiated gametes (i.e. true random ...
Remi.b's user avatar
  • 68.1k
6 votes
8 answers
8k views

Does any animal species have two sexes and more genders?

Are there any animal species that have two sexes and a kind of different internal diversification in two genders or more? I don't mean something like different-task-based diversity, but something ...
lalessandro's user avatar
6 votes
2 answers
271k views

Teens concerned about impregnation through clothes

Dry Humping, is: dry humping is the process of two people repeatedly moving up and down and back and forth on top of each other fully clothed( or missing various pieces, but the penis must not come ...
TheNotMe's user avatar
  • 249
6 votes
2 answers
4k views

Skin porosity in glans penis when erect

(Apologies if this is a too weird/inappropriate question in this forum. I only thought that I ask it since it happens to be part of human life.) The skin on a human typically blocks many substances ...
x457812's user avatar
  • 463
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 ...
Tetragrammaton's user avatar
5 votes
2 answers
2k views

Why sperm count matter for pregnancy?

In order for a woman to become pregnant, sperm is needed. Why is sperm count so important for pregnancy? http://en.wikipedia.org/wiki/Sperm
ashrad klateus's user avatar
5 votes
1 answer
431 views

How does sex differentiation work in Paracerceis sculpta, the sexually tetramorphic isopod?

Paracerceis sculpta is a marine isopod species known for its unusual reproductive strategy: female: medium-sized; lives in harems run by an α male α male: large; keeps a harem of females β male: ...
Mechanical snail's user avatar
5 votes
1 answer
1k views

Do hormones make men think of sex?

I remember hearing a saying that goes like "men think of sex every 7 minutes (or seconds?)". I take this saying to mean that men have sex related thoughts more often than women. I'm ...
Alex Stone's user avatar
  • 6,515
5 votes
1 answer
153 views

Is there any evolutionary reason for why some organisms (wrasse) change their sex in adult stage?

In San Francisco, I saw this fish: and quoting the aquarium's page: Part of the wrasse family, the California sheephead is a protogynous hermaphrodite. Simply put, all sheepheads are born as ...
gsamaras's user avatar
  • 153
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 &...
Tom888's user avatar
  • 167
4 votes
2 answers
764 views

How to know if a woman is fertile without actually making her pregnant?

How to know if a human female is fertile (can give birth to child in future) without making her pregnant? Any signs, tests?
Santosh Kumar's user avatar
4 votes
1 answer
231 views

Are all non-breeding naked mole rats the same sex?

In many eusocial species, all the non-breeding members are the same sex. Honeybees are a good example, with only female workers. Are naked mole rats that do not breed also all either male or female, ...
Joe's user avatar
  • 215
4 votes
1 answer
3k views

Why do humans masturbate? [closed]

Why does masturbating seem to be like an addiction? What controls or initiates the urge to masturbate? Is it good or bad or both and why is it so? I have heard guys who say that the do it ...
Chloritone_360's user avatar
4 votes
3 answers
125 views

sex limited genome transmission

In general, for dioecious species, a large portion of the genome passed from parents to offspring of both sexes - in mammals the X-chromosomes and autosomes are passed from a mother to both daughters ...
rg255's user avatar
  • 16.1k
4 votes
2 answers
8k views

Do women experience more bonding hormones than men after sex?

Does Oxytocin (or any other bonding hormone) increase more so for women than for men after sex? Someone told me that it increases 4-fold for men and 12-fold for women (unconfirmed). Is there any ...
PAINKILLER's user avatar
4 votes
1 answer
342 views

Is there a theoretical maximum on the number of sexes a given species can have?

Background: To the best of my knowledge, most sexually-reproducing species of organism have two sexes, although there are also sexually-reproducing species of organism (flatworms come to mind) which ...
Chill2Macht's user avatar
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 ...
tay_100's user avatar
  • 41
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 ...
Remi.b's user avatar
  • 68.1k
4 votes
1 answer
1k views

Sexual Differentiation in Monoecious plants with unisexual flowers

In monoecious plants having unisexual flowers (eg Zea Mays, Ricinus Communis etc), there must be some mechanism as to produce two sexually distinct flowers from the same genotype. Since both the type ...
stochastic13's user avatar
  • 4,689
4 votes
1 answer
899 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 ...
Chris_Rands's user avatar
4 votes
1 answer
590 views

Are there animal species with sex of an offspring determined by sex of preceding offspring?

For instance, if an animal's first offspring is male, then all subsequent offsprings will be male too (the sex of first offspring could be determined randomly). Does it happen in any species?
Misha Monahov's user avatar
3 votes
1 answer
122 views

Is the term 'allele' specific to sexual populations?

I had always thought that 'allele' simply meant a variant of a gene and thus could be used in the context of either asexual or sexual populations. With it only being slightly less useful as a concept ...
Artem Kaznatcheev's user avatar
3 votes
1 answer
539 views

Two-fold cost of sex and r/K selection theory

This article cites a bunch of articles (I haven't been through them) that the effect of the two-fold cost of sex is "reduced" in stable environment or in K-selected environment. It says: [..] the ...
Remi.b's user avatar
  • 68.1k
3 votes
1 answer
577 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 ...
Xunie's user avatar
  • 261
3 votes
1 answer
1k views

Sex determination in cephalopod?

I see some source say octopus do not have sex chromosome. So what's the sex determination mechanism for cephalopods?
A.Z.'s user avatar
  • 139
3 votes
1 answer
1k views

Advantages of bisexual reproduction over asexual one toward species promotion? [duplicate]

Are there any advantages of bisexual reproduction over asexual one towards species conservation and promotion? Do animals that have two or more sexes have more chances to reproduce? Does anybody had a ...
lalessandro's user avatar
3 votes
1 answer
212 views

Evolution from Mating types to different sexes

Imagine a lineage of multicellular organisms that had mating types and evolved their mating types into sexes. What are the possible mechanisms that might have brought this lineage to evolve sexes from ...
Remi.b's user avatar
  • 68.1k