Fighter Pilots Seem to Have More Daughters — Why?

Fighter Pilots Seem to Have More Daughters — Why?

[♪ INTRO] Fighter pilots and astronauts have really
intense jobs, and they put their bodies under extreme amounts of physiological stress. Just watch five minutes of Apollo 13 or Captain
Marvel, and you will know exactly what I’m talking about. This kind of stress — especially the high
gravitational forces — is so significant that some people believe it can affect their
kids. More specifically, there’s this common idea
in flying communities that if someone who produces sperm wants to be a fighter pilot
and an amazing parent, they should prepare for a household full of daughters. The idea is that a sperm carrying a Y chromosome
is smaller and more fragile than one carrying an X, so it’s more easily disrupted by things
like high gravitational forces. But before you go start switching careers
or anything, you might want to look at the research. Typically, making a baby is pretty straightforward
— at least, on a cellular level. In most cases, you start with an egg cell
carrying an X chromosome. And then that egg combines with a sperm cell
carrying either an X or a Y chromosome. And ultimately, you get an XX or XY kid. Although there is plenty of nuance, most females
are XX, most males are XY. For most of the population, the odds of a
sperm cell contributing an X or a Y is about 50/50. But if you look at certain studies, it seems
like that might not hold true for pilots. Take a 1987 study published in the journal
Aviation, Space, and Environmental Medicine. It looked at the number of sons and daughters
of 62 male tactical pilots and astronauts. Then, it compared those numbers to those of
222 men who had regular day jobs or were pilots with a lower exposure to gravitational forces. The analysis found that the tactical pilots
and astronauts tended to have more daughters than the average Joes they were compared to. Now, to be clear, the researchers just pulled
this data from biographies; it’s not like they ran genetic tests or anything. But it’s likely that in this paper and in
the others we mention, daughters were XX, and sons were XY. Still, one paper is rarely enough to prove
anything. There might be more going on here, so it’s
important to look at other research. There have been several other studies about
this, but in 2009, an especially large one was published in the journal Military Medicine. It compared the families of more than 500
naval aviation officers to those of the general population. And on average, it found almost no difference
in the kind of kids each group had. The one significant difference it did find
was among pilots who flew in extreme environments about two months before they conceived. That group was more likely to have daughters. In human reproduction, timing is everything. So maybe this was a sign that the stress of
flight was damaging Y sperm right before conception. Still, it’s hard to take that answer and
run with it, because scientists can’t actually explain why this would happen. Many people used to believe that Y sperm were
smaller, which would make them more susceptible to damage. But that was based on research from the 1960s,
and today, we know that isn’t true. As far as we can tell, there is actually no
meaningful size difference between X and Y sperm. So it’s hard to figure out what’s going
on with those pilots. There are plenty of hypotheses floating around,
but at this point, it’s too soon to say anything for sure. At the end of the day, though, individual
pilots probably shouldn’t be worried. As that 2009 paper pointed out, even if the
odds are skewed toward XX kids on a population level, that doesn’t mean they are for every
individual. Ultimately, if you’re a pilot, you probably
can’t predict what kind of kids you’re going to have any better than the rest of
us here on the ground. So… welcome to the club. [♪ OUTRO]

100 thoughts on “Fighter Pilots Seem to Have More Daughters — Why?

  1. The participants of the study were all men pilots I presume? Would the results vary if they researched women pilots with non-pilot partners? This is fascinating!

  2. If anyone is wondering why Hank says MOST females are XX and MOST males are XY instead of ALL, Turner's Syndrome (XO female) and Kleinfelter's Syndrome (XXY male) are a thing. Kleinfelter's Syndrome can also end up resolving immediately and resulting in Identical Male/Female twins in ultra rare cases.

  3. Maybe this female/male ratio unbalance with fighter pilots who just came back from combat is not due to how the man’s reproductive system reacts, but rather to how their partners/wives’ reproductive system reacts — the women suffer a lot of stress while waiting for the fighters to come back from their missions. There’s research to support this idea:

  4. Interesting. I teach on a master naval jet base. Not all our students are children of pilots only. I would agree agree that pilots have same chance as everyone else when I think about the families I have taught over the years. My sex Ed unit is coming up. Maybe my admin will let me share this video.

  5. pretty well known that more females are born in times of hardship, something to do with the stress levels of the womb and sperm.

  6. Also men make fresh sperm all the time… so if they were to umm… dispose of the sperm they had during the extreme flight a fresh batch would be made and this shouldn't be effected by the flight conditions… I find it hard to believe that the pilots didn't dispose of said sperm for the 2 months after the flight until conception occurred… this has to be down to something else, production of fresh sperm has to be effected somehow for a period of time after the extreme flight and not just the sperm already available during the flight.

  7. Hey Hank. It's radiation. Fighter pilots sit right behind all the antennae in the radome of the aircraft. Aircraft maintainers such as myself also seem to have more daughters per capita, particularly those that work in high-tempo environments. Higher tempo bases test the radar more often and from my anecdotal observations the trend tracks. Maybe look into that?

  8. What about the higher amounts of radiation pilots experience from being so high up in the atmosphere all the time?

  9. Males are more vulnerable than female in the womb. This is nature’s way of making sure that there is enough female to carry on off springs. In times of famine you can see that more girls are born. In the womb, females are more likely to survive any atrocities. Such as if the mother is starving or giving birth prematurely. Most likely to survive? African American daughters. Most likely to not survive? Caucasian make.

  10. Obviously this is an environmental response that is triggered by a stressful environment, just think about it. is it better to have more male or more female offspring in hard times? More Females being conceived in hard times is a way for the population to be boosted when things are tough because multiple females can be impregnated by one male where as if you had a bunch of males and one female all the men would fight each other over her… This is looking at things like people are animals though so don't hate me for saying this.

  11. Easy, male sperms swim so fast, when fighter pilots are traveling so fast, the male sperms end up traveling the speed of light and they end up folding space and time. Its my story and im sticking to it.

  12. In rural communities there is an old saying that " the sorriest man gets the most help" meaning the man who works and worries little about his work will have many boys to help on the farm. Related?

  13. "Watch 5 minutes of [good movie] or Captain Marvel, and you'll know what I am talking about."
    Lol. Nice try. But the movie was not made for you either. Your skin color and sex determines that your opinion doesn't matter.
    No matter how much of an "ally" you try to pretend to be. Hank.

  14. Look, I'm just a Chemist, but, maybe the increased of physical and mental stresses is triggering some sort of physical response akin to significant environmental / food supply changes, and that as such, the Male pilots bodies are actually producing more sperm with X chromosomes to skew the population balance towards Females as they can carry children and continue the society in which they live? As in some sort of long term genetic survival mechanism?
    But yeah, interesting study. I wonder if there is a cross over in the data with F1 / Le Mans / Isle of Mann TT drivers / riders?

  15. In the US Navy we joked about certain rates (jobs) having more girl kids. We blamed it on exposure to communications signals and radars.

  16. I didn’t know I didn’t know about this! Thanks for laying out the evidence.

    Slightly disappointed at the underlying assumption that pilot = male though, guys. A couple of small changes to the script could have sorted that but it seems to have gone largely unnoticed.

  17. Dafuq you mean by there being "a lot of nuance" and "most with XY are male and XX are female"? It's all of them, or like 99,9%.

  18. I love how every single time he mentions XX being girl and XY being boy, he has a mini social-justice seizure and starts splurging out qualifiers 'In the majority of cases, it's complicated…'

  19. the same is true of men in the US Navy submarine community. those guys have WAY more girls than boys while on sea duty.

  20. Isn't sex selection possible by sorting sperm with a centrefuge?
    Could that possibly have something to do with it?
    This is an interesting question. Pretty strange.

  21. Twin study time… Or they need to take regular sperm samples of pilots and measure how they change over time and in extreme conditions..

  22. Did anyone else feel kind of awful to see one of their favorite presenters talk about having female babies like it was something bad?

  23. You just taught me something about sperm size and stress' relevance to progeny outcome and then immediately told me to disregard what you just said…and I still have that 'yay, I learned something. Scishow is so cool' feeling anyway…wtf?

  24. DID YOU ASSUME THE CHROMOSOMES OF THOSE "DAUGHTERS" WTF, be more woke it's 2019 and science should NOT be teaching biological facts. YOU ARE A MONSTER. JK of course go science.

  25. 2:30 Sperm cells are renewed on a 90 day cycle on average, so the extreme G forces within a 2-month window of conception is plausible from the medical standpoint. This timing could explain why outside the 90 day window, observed M/F rates are normal.

  26. I've noticed that whoever is less stressed during a pregnancy then that's the sex of the baby. I know it seems too simple but give it a try anyway… 😉

  27. Its because females are more important for reproduction (you can have one male to multiple females) so therefore when bodies are under stress girls are more likely this happens throughout the animal kingdom and its also seen in people between mothers in extremely calm relaxed environments versus the women in stressful ones

  28. When the environment is stressful don’t humans tend to have more daughters than sons? Could that be the factor causing this?

  29. Anecdotally if you are in Spech Opps you are more likely to have girls than boys, same goes for frountline troops returning from a long deployment for the first few months after coming home.

    I'd herd their where some formal studies in to the matter but never heard back on the results.

  30. If size isn't a factor, mass could be. The average human Y chromosome contains about 59 million base pairs, compared to the X chromosome's 156 million base pairs. This mass difference could be negligible, but may be an important factor in setting up models in the future for why this phenomenon occurs. A bit off topic: It is observed that in some populations, the true sex ratio is not 1:1, but slightly favours male-born babies, This could be because a a Y-containing sperm cell can generate more velocity with its tail-whipping, due to its slightly lowered mass, therefore reaching the female gamete slightly faster than a X-containing chromosome. Maybe this isn't the case at all, and a deeper epigenetic effect is taking place.

  31. I wonder if something is happening on the mother's side of things. There's this episode of MinuteEarth that talks about how stressed would be mothers tend to carry daughters to term more often than sons. The video used lack of food as the stressor but perhaps if the women were stressed with worry for their husbands?

    I've also heard that the way you have sex could affect the gender of the baby. But I don't have any proof to back that up.

  32. Maybe as an aside we could possibly maybe say that there's nothing all that wrong about having female children?

  33. So, I love SciShow and watch it all the time. I won’t stop as a result of what I’m about to say, but…

    Children are almost, by definition, sexually transmitted. Wording like that at about 3:25 in the video makes daughters seem like they are similar to chlamydia, though. Not sure why someone would “be worried” about having daughters. 100% of my progeny are girls and they’re amazing.

  34. Haha this immediately interested me cause my dad flew F-16s back in the day, and three of his four kids (me included) are XX!

  35. Well, generally speaking, females tend to have an advantage prebirth and males post birth. It's hypothetically the reason why plastics have been linked to more female children being born than male ones. Likewise, it is also hypothesized that stress can be inherited, as well as affect fertility. If you combine these hypotheses, it would make sense that pilots are more likely to have daughters.

    Evolutionary speaking, it checks out. A low birth rate directly after a crisis allows for the offspring to have a better chance at survival. More resources to go around and all that. However, once the danger is passed, having more women than men would maximize the ability to repopulate if the environment improves.

  36. I'm guessing it has something to do with a centripetal effect on the sperm.

    Nope. Females are just tougher. lol

  37. And naval aviation we have a similar thing where people of the avionics Fields have more females than those of non avionics fields

  38. Seems easy enough to test: find some volunteers and start centrifuging them while they're trying to conceive.

    Well, how about a couple hours before they try to conceive, anyway. High gee sex could end rather badly.

  39. I have heard that in times of stress (famine, poverty, violence) more daughters are born and that in times of prosperity more sons are born. I have heard this is a result of males being less likely to reproduce than females and males consuming more resources and having higher mortality rates, yet a reproductively successful male can father more children in less time with less cost than females.
    This is all evolutionarily speaking. Maybe stress hormones, be it generated due to psychological or physical experiences, might affect chances of producing more or less Y or X spermatozoids?

  40. I was expecting male fighter pilots having XYY chromosomes. The psychopatj and thrill seaking chromosome makeup.

  41. I am surprised that this was reported as only pilots. For those of us who work around high power RF radiation (Satellite, wide-band microwave radio, etc…) It has long been known that our chosen carrier path leads to only girls being born. It isn't the measly 60% shown in the video. It's more like 85-90%. I suspect that the fighter pilots that fly at higher altitudes will have a much higher level of background radiation exposure and thus will fall into the same category that we do.

  42. So basically… presenting a skewed piece of information with no reliable data to back it up? C'mon!

  43. Before watching this video, I am leaving this answer. Yes. My father used to fly high altitudes. His friends all had daughters. My Dad did bring 3 boys and 2 girls. But it was odd that it held true.Navy pilots are one thing but Air Force have different type of missions? Maybe you should conduct a list of them. And other types also. Just navy? How can that be unbiased? Exposure to more radiation at higher altitudes , can it cause it?

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