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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108
votes
3answers
24k 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, ...
32
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2answers
5k 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 ...
19
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1answer
78k 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 ...
19
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1answer
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.
17
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2answers
4k 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?
16
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2answers
10k 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 ...
14
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1answer
634 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—...
13
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1answer
8k 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 ...
13
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1answer
36k 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 ...
12
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3answers
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?
11
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4answers
1k 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? ...
10
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1answer
2k views

Evolutionary reasons why you cannot tickle yourself but 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 being able to ...
8
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3answers
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 ...
8
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2answers
608 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 ...
8
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2answers
709 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 ...
8
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1answer
5k 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 ...
8
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2answers
690 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 ...
8
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0answers
342 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 ...
8
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0answers
779 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 ...
7
votes
1answer
676 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 ...
7
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3answers
964 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
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1answer
459 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 ...
7
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1answer
687 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, ...
7
votes
1answer
491 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 ...
6
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2answers
226k 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 ...
6
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2answers
3k 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 ...
5
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8answers
6k 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 ...
5
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2answers
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
5
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1answer
417 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: ...
5
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1answer
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 ...
5
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1answer
135 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 ...
4
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2answers
717 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?
4
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3answers
4k 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 ...
4
votes
1answer
219 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, ...
4
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1answer
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 ...
4
votes
3answers
115 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 ...
4
votes
1answer
78 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 ...
4
votes
1answer
223 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 ...
4
votes
1answer
169 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 ...
4
votes
1answer
942 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 ...
4
votes
1answer
129 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
1answer
572 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?
3
votes
1answer
72 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 ...
3
votes
1answer
475 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 ...
3
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1answer
509 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?
3
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1answer
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 ...
3
votes
1answer
184 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 ...
3
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2answers
2k views

Are gametes determined by the sex of an organism?

In the Wikipedia article for biological sex, I read the following sentence. "The gametes produced by an organism are determined by its sex:..." However, is it not through the gametes produced by ...
3
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0answers
161 views

Do ovaries produce estrogen before menarche?

It is traditionally taught that estrogen is produced by the granulosa cells of the follicle. But before menarche, where does the estrogen come from? Is it from the thin layer of granulosa cells lining ...
3
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0answers
100 views

Which scallops change their sex from male to female?

Tonight it occurred to me to look up what scallops are like when they are alive (beyond their culinary role) and it blew my mind. This post regards one detail about which I was unable to find specific ...