We asked this open question and we got a lot of answers that were set to private. So here are the responses we got.

1-5 Biological differences between men and women

Heat

1. Blood flow in a man’s body is more even than a woman’s body. In females, blood flows more around the core and the baby making zones, which explains why women’s hands and feet get colder than men. Also, due to this, women will survive longer in cold temperatures before succumbing to hypothermia than men will. Source

2. Guys have a bulge of the urethra at the tip of the penis, called the navicular fossa, that causes the urine to spin and make a straight stream. This also has the effect of cleaning the external urethral meatus (where the urine exits the body) in men. The lack of an equivalent mechanism in the female urethra partly explains why urinary tract infections occur so much more frequently in females and why they end up with a less organized stream of pee. Source

3. Collagen fibers under the skin of men are more criss-crossy than in women, which both explains why women are more prone to cellulite and also why men have an easier time opening jars. The criss-crossing means that the upper part of the skin will slide around less. That means you get a better grip. Source

4. Men are more prone to stutter. Moderate stutter is three times more likely in men. A severe stutter ten times more likely.

5. Most babies born with birth defects are male. That has to do with XY chromosomes in comparison to XX chromosomes. If a woman has a deliberating defect on an X-chromosome, they’ve got a copy to cover it. If a man has a deliberating defect on his X-chromosome… they’re fu*ked.

6-10 Biological differences between men and women

Long Eyelashes

6. Males have longer eyelashes than females do. So technically using mascara isn’t making you look more feminine it’s making you look more masculine.

7. Women are better at discerning colors than men. This is taken advantage of in a number of industries, including pearl grading. Pearls are graded by various properties, including color on a spectrum going from a dark pink to a brilliant snow white. All men, and indeed most women, don’t have the visual acuity or color sensitivity to accurately pick apart pearls belonging to the different higher-end grades. In fact, only girls between about 18-22 years old can. Seems insane. This online test can estimate your color sensitivity score, and women will far outperform men on average. Going back to the pearls, if you get 100% in under four minutes, you’d be a Tier 4 grader. Apparently there are 3 tiers above that.

8. Men are 4 times more likely to be Autistic than women.

9. The ability to break down alcohol (Alcohol dehydrogenase) is stronger in young men compared to young women but the relation reverses around the middle ages.

10. Women and men can have different symptoms when having a heart attack. Men have the classic crushing chest tightness, left arm and jaw pain. Women have less specific symptoms such as back pain or epigastric pain, frequently misdiagnosed as heart burn.

11-15 Biological differences between men and women

Neck

11.  According to a nurse at the ER, women have longer necks, as far as the sizing of neck braces goes. Men have more muscle on top of their shoulders, which makes the neck seem shorter. I’m just about 6′, yet had to wear a small-sized brace.

12. It’s called sexual dimorphism and it’s a very touchy topic even in many academic circles. There’s even research to say that there are some differences in brain structure, and to me that’s a really good explanation of transgenderism considering these differences tend to match gender rather than biological sex. Personally I think sex differences should be researched and celebrated rather than pretending they don’t exist. It just might be that on average, women are better at some things and men are better at others.

13. A few differences in the skeleton I learned in a forensics course:

  • Female foreheads tend to run vertically, while male foreheads are sloped.
  • The top edge of female eye sockets are sharper than those of males.
  • Male jaw bones are considerably heavier than those of females.
  • Female pelvis bones are much wider than those of males.
  • Female forearms make more angled connection to the upper arm than do those of males. If you turn your palm face up and extend your arm, and then compare it to someone of the opposite sex, you’ll see the difference.

14. The classic stereotypical “female handwriting” appears to have a scientific basis. Girls develop fine motor skills earlier than boys and also have a tendency to grip pens and writing implements differently (apparently due to nails) which affects their motor skills when writing.

15. “Women and girls with Asperger syndrome may be better at masking their difficulties in order to fit in with their peers and have a more even profile of social skills in general.” Source. This quote explains why it can be harder to diagnose in girls/women.

16-20 Biological differences between men and women

Frowning Woman Looking at Man

16. Women can read minds and think men can as well. Men can’t read minds and get sh*t for it. I am not joking. There is some reality to this, but its not so much the gender but the hormones. Estrogen makes the brain more receptive to not only your own emotions, but other people’s emotions as well. If you reach out to the trans community and ask how hormones affected them, trans women will often cite that they became better at reading other’s emotions, as well as feeling their own emotions stronger. Testosterone on the other hand, is why it seems men can shove their emotions inside and focus less on them, they may not pick up other’s emotional cues well, but they can put their own aside to focus on a single task. Source

17. Our vision is different. Women have a wider peripheral vision, making them able to spot something more quickly. Men have tunnel vision, giving them better depth perception. Source

18. There are ~1,000 differentially-expressed genes between male and female liver. This means that many of the drugs and chemicals that we put into our bodies are processed very differently between the sexes. I think most people remember from college that males and females process alcohol at different rates, but it also effects things like Tylenol, antibiotics, and other more serious drugs. Source: My thesis.

19. In each of the cells of a developing female embryo one of the 2 X chromosomes deactivates at random. All the cells descending from those cells share the same inactive X chromosome as their parent. The result of this is the adult female body is a patchwork of 2 slightly different genetic codes. Men have an X and a Y, and both remain active. It’s apparent in the patchwork coat pattern of tortoiseshell and calico cats, which are nearly all female. It’s also for this reason that some X-linked genetic disorders have milder, patchier presentation in women than in men.

20. Only women can pass on mitochondrial DNA to their children, so if you’re a male with a mitochondrial defect of some kind, the disease will end with you. In contrast to that, if you’re a woman with a mitochondrial disease, every single one of your offspring will have it too. The good news is that through nuclear transfer, mitochondrial disease has been experimentally cured in monkeys.

21-25 Biological differences between men and women

Fat Deposits

21. Fat is deposited differently in men and women. In men, fat tends to surround and coat the organs, so everything in the abdomen basically get further away from everything else as the person get larger. In women, fat is largely deposited like a ring around the abdomen, with little fat deposition between the organs. Because of this, you can tell a person’s gender by looking at a abdominal CT or MRI if you know what you’re looking for. It is also why liposuction is easier in females.

22. Men are better able to pick up on and focus on a singular sound than women. It’s really not all that useful anymore, now that we’ve moved away from our hunter/gatherer roots; but if your child is a musician in an orchestra, dad has a better chance of being able to single them out and listen to them more individually than mom.

23. The male and female brain differ significantly starting way back from early development. Male brains have to be “defeminized.” In a developing female, a special binding protein called alpha-fetoprotein binds estradiol (organic estrogen) and subsequently prevents defeminization. This allows something called the “surge center” to develop in the female brain. It houses a group of neurons responsible for releasing signaling molecules from the brain (GnRH, if you’re curious) to control female reproductive development and onwards. Males don’t have this surge center. But don’t worry, you guys still have something called a “tonic center” that is responsible for pumping out GnRH in a way that drives sexual development (females actually have a tonic center too, so we have both a “surge” and a “tonic center”–in conjunction with the pituitary gland, they play a leading role in orchestrating the menstrual cycle). ANYWAY, the recognition of which of these hormones are circulating occurs in a part of the brain that’s called the “preoptic area”, which houses GnRH-secreting neurons that are important for reproductive development and throughout life, both in males and females. The preoptic area in males is larger than it is in females. Interestingly, there was actually a controversial study in the 80s that looked at the brains of gay men and found that their POAs were smaller than the average male’s, more closely resembling those of females. Link to full text of POA study.

24. Men have roughly 10% faster reaction time during adrenaline rushes.  Men have more adrenaline receptors on key organs which means men respond more quickly but men’s adrenaline is also used up quickly. Although there are no studies I’ve seen comparing the two, it is fair to say that women’s adrenaline response happens over a longer period of time and starts slowly but lasts longer.

25. The mechanisms for chronic pain in women are different to those in men; they’re not caused by different hormones, or different structures of proteins, or different enzyme levels, but by different cells. As far as I’m aware, this is the only non-sex/reproduction mechanism that is different between sexes that is mediated by a different cell.

You can hypersensitize mice to pain by causing inflammation, or by ligating (tying off) a nerve; when this happens, it requires a much smaller stimulus (a smaller pinprick) to cause the mouse to react negatively (withdraw a paw, for example). If you inactivate a type of immune cell in the central nervous system called a microglia; this sensitivity goes away. But only in male mice. In female mice, blocking microglia has no significant effect on the hypersensitivity. Instead, female mice rely on a type of T-cell from the periphery to invade the CNS across the blood-brain barrier to acquire hypersensitivity to pain.Original research is here.

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Last Update: April 25, 2016

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