[–] Medusa91 28 points Edited

I got in a full blown raging argument with some idiot on Instagram about this the other day. You can’t see the sexes characteristics for a few weeks but it’s literally determained when your conceived.

But it makes me think about how cool the X chromosome is.

Because a woman is born with all her eggs and they’re created whilst her mother is pregnant with her, determained from the moment she’s conceived.

She carries those eggs with her her whole life, and may even choose to never use one.

If she gets pregnant and has a daughter, her body constructs the eggs and uterus that her daughter will one day use. And that X chromosome that’s given to her daughter through the sperm, can only come from her male partners mother. All that information contained in that X was the egg that was the foundation that built his body.

Sperm regenerates every few days, women are born with their eggs, when your pregnant with your daughter you create the foundation of your granddaughters. When the sperms X is passed along it’s passed from that same egg that was carried inside of a woman, from when she was inside her mother until she had her son.

Everytime I start thinking about it I fall down a big woo woo spiritual hole of just how cool and matriarchal we are.

Everytime I start thinking about it I fall down a big woo woo spiritual hole of just how cool and matriarchal we are.

I do, too. I think its phenomenal that my life technically started when my grandmother was carrying my mother

[–] ProxyMusic 5 points Edited

I got in a full blown raging argument with some idiot on Instagram about this the other day. You can’t see the sexes characteristics for a few weeks but it’s literally determained when your conceived.

I dunno what you mean by "see" and "sex characteristics" there, but cell biologists have observed and documented clear sex differences in the blastocysts of various mammals including humans just days after fertilization prior to when blastocysts reach the stage of development where they implant in the wall of uterus.

Numerous sex differences have also been found in the placental cells of males and females of different mammal species starting from the time the blastocyst implants in the uterus and starts growing a placenta and thus first becomes an embryo.

(During fertilization, the sperm and egg unite in one of the fallopian tubes to form a zygote. Then the zygote travels down the fallopian tube, where it becomes a morula. Once it reaches the uterus, which usually happens 3-5 days after fertilization, the morula becomes a blastocyst. The blastocyst then burrows into the uterine lining — a process called implantation. The implantation typically starts about 6 days after fertilization.)

It's true that by looking at the external morphology of embryos from the outside, "you can't see sex characteristics" such as gonadal differentiation until weeks following fertilization (6 weeks in humans, to be precise). But by zooming in closer and looking at cells with the kinds of microscopes, imaging technology and research methods that scientists in cell biology have been using for years, sex differences are visible within days of fertilization/conception. Sex differences are probably there from the get-go, it's just that scientists haven't documented them yet due to technical limitations - limitations that no doubt will be overcome in due course.

The big takeaway of cell biology research done in the past 30 years, and especially in the era of human stem cell research that began in the late 1990s, is that sex differentiation in mammals including humans occurs and can be seen by scientists long before the gonads differentiate and the genitals begin developing - indeed, sex differences can be seen and have been documented by scientists just days after fertilization.

This and other research done in the past 30 years completely refutes the theory in vogue for most of the 20th century which posits that physical sex differences are mainly the result of differences in male and female sex hormones that occur following gonadal differentiation and development - which also just happens to be the theory that transgenderism is based on. As it turns out, the importance of sex hormones appears to have been way over-estimated because the vast majority of the thousands of physical sex differences between males and females seem to be much more the result of genetics than of sex hormones.

In mammals... male blastocysts develop more quickly than female blastocysts [1, 2], and expression of several genes, such as murine Xist [4, 5], bovine G6PD [6, 7], ZFX [7], HPRT [6] and INF–t [8], and murine Zfy and Sry [9], is different in each sex. However, there is no report on global differences in gene expression in male and female blastocysts, largely because of the technical difficulty in sexing many blastocysts quickly and accurately.

In eutherian mammals, male preimplantation embryos develop more rapidly than females in a number of species, such as the mouse [1, 2], cow [16, 17], human [18], sheep [19], and pig [20]. These differences precede gonadal sex commitment. Here we found minor but statistically significant sex differences in the expressions of nearly 600 genes. These may have arisen from slight differences in developmental stages between the male and female blastocysts, so we cannot conclude that all are associated with sex differentiation. However, we have demonstrated here that at least four genes are certainly expressed differently, not by stage but by sex. We presume that the actual number of genes involved in such sex differences is likely to exceed the small number of previously reported genes [4–9].


The apparent male-specific growth phenotype has been observed as early as the pre-implantation period in several mammalian species, including humans. In vitro pre-implantation studies have identified that XY bovine and human embryos have an overall increase in total cell mass, when compared with XX embryos.

The mechanisms that contribute to these sex-specific differences in growth rates prior to implantation and establishment of the feto-placental unit may be, in part, the result of chromosome X-inactivation [3,22]. This female-specific alteration during early development may have implications for transcript expression and subsequent cellular function.

gene ontology analysis of differentially expressed transcripts identified male trophoblast cells had enriched protein translation and certain mitochondrial and ribosomal functions, whereas female trophoblast cells had an enrichment in transcripts involved in immune function and responses to various compounds and stimuli. Overall, the pre-implantation male embryo and the early gestation male placentae preferentially increase transcripts involved in growth regulatory pathways, whereas age-matched females appear to prioritise alternative pathways. These sex-specific differences likely contribute to an observed increase in male growth rates and outcomes during early gestation in placental mammalian species including humans [1,27], but are also thought to contribute to the observed sex-specific differences in growth trajectories and outcomes during the second and third trimesters [12](Figure 1).


Both in vitro and in vivo bovine female blastocysts are known to produce more interferon tau (maternal recognition signal in ruminants) than male blastocysts (Kimura et al., 2004; Larson et al., 2001), suggesting that female blastocysts have a greater ability to signal their presence to the mother than male embryos. Sexual dimorphism in amino acid utilization has been suggested in both in vitro cultured and in vivo bovine blastocysts (Sturmey et al., 2010). Further, bovine conceptuses exhibit sex-specific differences in amino acid utilization in vivo during the peri-implantation period, with less asparagine, histidine, glutamine, arginine, tryptophan, methionine, phenylalanine, isoleucine, and lysine present in uterine flushings associated with female conceptuses compared to male conceptuses on GD19 (Forde et al., 2016). These findings were accompanied by greater expression of mRNAs encoding amino acid transporters SLC6A19 and SLC1A35 in female conceptuses compared to male conceptuses on GD19. Greater abundances of these amino acids in uterine flushings from male pregnancies may be indicative of less uptake by the male conceptus, which suggests less utilization of these nutrients by male conceptuses during the peri-implantation period of pregnancy.

Staggeringly, transcriptomic analyses revealed sex-specific expression of approximately one-third of all actively expressed genes in the Day 7 bovine blastocyst (Bermejo-Alvarez et al., 2009). This continues throughout the peri-implantation period, with sex-specific expression of >5000 transcripts by Day 19 bovine conceptuses (Forde et al., 2016); this highlights the critical importance of embryonic sex during early conceptus development and


I’d send you the link to the video but it was on Instagram and you might not be able to access it, I might have just explained myself poorly in my original comment

The video was of a TIM insisting that all embryos and foetuses start as female and then at some mystical time have some decision making where they decide to be a boy or a girl and that’s why he can feel like a woman and he was assigned male at birth

I basically said that, no, your sex was determined at conception because the sperm only carries an X or a Y chromosome that determines your gender. You might not be able to see it immedietly (I didn’t know until your comment that it can be observed in cells so early) but your fate has already been sealed

I hope that made sense? I can be a bit of a baffoon sometimes

Thankyou for your comment though it’s super interesting

It’s been a while, but if I remember correctly isn’t it which chromosome the egg accepts, versus which chromosome the sperm “decides”?

That's interesting I'll look into that later. I edited the title for now, I wanted to post this because the people who claim their gender was incorrectly assigned at birth are full of shit. The sex of the fetus can be learned by parents at just a couple of months, millions of female fetuses are aborted in the world because the family would rather have boys, and if I remember correctly IVF is now on the level where parents can even select the physical traits including sex of the embryo.

(Sending this reply to you directly as well since I think it's important)

IVF is not a "fast food menu for children". It is a procedure for many women who want children but can't have them the "old fashioned way" used for various reasons, including health reasons (some women for instance don't ovulate normally), lesbian women using donor sperm, etc.

It sounds like what you're referencing is the CRISPR controversy where one scientist in China actually edited the genes of embryos, he went to jail and the whole thing is wildly controversial and not at all done as a general practice.

Due to the way IVF works, they do select embryos that are viable to proceed with a pregnancy, which means checking chromosome irregularities. This does filter out Down's syndrome in particular which I concede is its own ethical set of questions, but generally it just filters out cases where either no pregnancy would happen whatsoever (embryo would fail to implant) OR it would lead to a chemical pregnancy/miscarriage/etc -- the female human body is already "aborting" non viable pregnancies in those instances, it just saves the woman of the emotional hardship of implanting an embryo that literally would never be compatible with life and having to go through a miscarriage.

The side effect of testing chromosomes is that the embryology lab does indeed find out which embryos will lead to a female vs male fetus. A lot of countries (including the biggest offenders of sex selective abortions, such as China and India) outright ban informing the patient of the sex of the embryo or letting them choose the sex of the baby, though weirdly the USA does not, in my experience from IVF support groups, most women ask to not know the sex of the baby anyway.

Beyond that, there is no "selection of physical traits". I mean, I suppose if you want to get into semantics, you could argue a lesbian couple choosing a sperm donor is selecting for whatever genetic traits, but then you might as well argue that straight couples when choosing a spouse are selecting for whatever traits, sounds like a reach to me.

IVF is not a "fast food menu for children". It is a procedure for many women who want children but can't have them the "old fashioned way" used for various reasons, including health reasons (some women for instance don't ovulate normally), lesbian women using donor sperm, etc.

Just to be clear: IVF is not synonymous with "artificial insemination" or insemination through unconventional means. It's not even synonymous with "assisted reproduction technology." IVF is a procedure whereby doctors, scientists and/or lab technicians join egg and sperm in a lab dish, then grow the zygotes into blastocysts and embryos in the lab. Hence, IVF used to be known as "test tube babies." If viable embryos are created, the embryos created in the lab are implanted inside a woman in hopes that one (or more) will implant and she will become pregnant as a result. In IVF, additional embryos are frozen and stored for future use, often many years later.

IVF is not automatically necessary for lesbians or anyone else using donor sperm. IVF is only for women with specific infertility issues.

A great many women who use donor sperm do not use IVF. Same goes for women who use sperm contributed by their partners but for various reasons needs some kind of assistance. Instead, fertilization is attempted and occurs within these women's bodies by using a syringe or pipette to introduce the sperm into the women's vaginas - and then nature is allowed to run its course by letting the sperm swim towards the Fallopian tubes in the normal way as happens in "natural insemination." Intra-vaginal artificial insemination can be done by a doctor or medical technician, or it can be done at home in DIY fashion.

Alternatively, some women who use artificial insemination will have the sperm introduced into their uterus with medical assistance in a process whereby a thin pipette or needle is put through the cervix known as IUI (intra-uterine insemination). Only some women who get pregnant by "artificial insemination" use IVF.

Thanks for the explanation! I read years ago that it is now possible to not only select healthy embryos but also determine physical traits like intelligence, eye colour etc. even though it's ethically questionable whether it should be made legal in the future.

the female human body is already "aborting" non viable pregnancies in those instances, it just saves the woman of the emotional hardship of implanting an embryo that literally would never be compatible with life and having to go through a miscarriage.

No, the female human body is not aborting non-viable pregnancies in those instances. Zygotes and blastocysts that naturally self-destruct instead of implanting, or fail to implant because they can't grow a proper placenta, are following instructions encoded in their own DNA - nearly half of which comes from the father. The bodies of the women these clumps of cells are inside at the time are not terminating or aborting them. Women's bodies are not to blame here!

It's very common for fertilization to occur in its normal customary place in one of the Fallopian tubes without implantation in the uterus and thus viable pregnancy resulting. Zygotes/blastocysts that "fail to take" and naturally die or self-destruct due to genetic issues encoded within their own cells because of their own DNA are not the same as aborted embryos or fetuses. These are not pregnancies done in, killed off or aborted by the female bodies of the women within whose reproductive systems these totally natural, normal processes occur.

When zygotes/blastocysts fail to make the journey from the Fallopian tube to the uterus following fertilization and they instead implant and start growing a placenta inside the tube - as happens in ectopic pregnancies - it's not the fault of the female human body, either.

Yeah parents can select the sex of the embryo - and put it into another woman

I don’t like IVF, I know lots of people argue with me about it on this site but I’ve come to the conclusion that I just don’t agree with it

[–] Luckystar 4 points Edited

Not all or even a majority of IVF uses a surrogate mother though. You're welcome to not choose it for yourself or even personally dislike it, but it's definitely a part of reproductive freedom for women in general to be able to conceive, the most obvious example I can think of being that IVF means lesbian women can conceive without having to have sex with a man.

[+] [Deleted] -1 points

Just tell them to go shit in their hats. They know full fucking well the scam they’re trying to pull. Sometimes the only response to an argument that insults one’s intelligence is a simple “fuck off”.

That is why parthenogenetic females (like the crayfish) can only bear daughters, because there is no male to contribute a male gene. Lower evolutionary species may have differently arranged genetics but essentially the same principle.