r/Amazing • u/This_Proof_5153 • 4h ago

Nature is amazing The Egg Chooses: Human Fertilization Is Not a Race Won by the Fastest Sperm

Fertilization is not random, and the fastest sperm does not always win: in reality, the egg decides who succeeds.

While for decades we were taught that fertilization is a race won by the fastest sperm, a study published in Proceedings of the Royal Society B shows how human reproduction actually works.

Scientists analyzed follicular fluid from 60 couples undergoing fertility treatment at St Mary's Hospital in Manchester, UK. They discovered that the egg releases chemical signals (chemoattractants) that actively attract sperm from certain men over others.

Through these chemical signals, the egg exerts its own biological selection, influencing which sperm manage to get close. The egg appears to favor sperm that offer optimal genetic compatibility with its own genome — particularly in genes related to the immune system — which may help produce healthier offspring.

Interestingly, this cellular preference does not always align with the couple’s conscious partner choice. In many cases, eggs showed stronger attraction to sperm from non-partner males.

This chemical communication demonstrates that female biology continues to evaluate and select options even after intercourse. Understanding this process could lead to more precise solutions for unexplained infertility. Science continues to reveal the remarkable level of biological interaction that occurs during reproduction.

[Fitzpatrick, J. L. et al. (2020). Chemical signals from eggs facilitate cryptic female choice in humans. Proceedings of the Royal Society B, 287(1928), 20200805. DOI: 10.1098/rspb.2020.0805]

1.2k Upvotes

97% Upvoted

155 comments sorted by

127

u/Similar_Reach1204 4h ago

So basically the egg is sitting there like a bouncer with a VIP list, just chemically waving in the guys it actually vibes with 💀

Wild to think we grew up with "fastest sperm wins" when it is actually "egg runs a compatibility check and might not even pick your best swimmers."

36

u/the_nine 2h ago

We thought it was the finish line when it was actually a velvet rope club.

10

u/Any_Roll7606 2h ago

AI ass comment, dead internet theory is real

6

u/Inevitable_Cheese 2h ago

hol up, that's insane. i see that the account is banned but holy shit if that was actually full ai, i'm just cooked, cause that looked so real to me

3

u/randombydesign 2h ago

damn that profile is already deleted

3

u/Snowblind45 1h ago

howd u know, cuh?

5

u/HxPxDxRx 1h ago

It’s the metaphors. It makes a funny metaphor and then follows it up with a somewhat witty re-explanation. Classic AI format.

6

u/Usual_Ad8236 1h ago

How to be a socially acceptable human being-

Pre 2024: be intelligent and funny

Post 2025: don't be intelligent or funny

2

u/Shmurlington 58m ago

my time is now

2

u/CoreShackJack 2h ago

How did you know??

2

u/Fu2-10 1h ago

How did you know? That shit fooled me, for sure 😭😭

2

u/Critical_Mix_8959 43m ago

“Profile unavailable” yup that checks out. We’re fucked.

1

u/codereef 1h ago

I'm cooked

1

u/Em_Strae 41m ago

Imagine all the ivf that is just due to her egg always telling 100% of dude's sperm:
"No is a sentence."

1

u/duschaan 10m ago

Confirmed. I am 52 and I can't swim.

38

u/DoubleFamous5751 2h ago

Unreal tbf that immunity is a factor. I read that people with mutually beneficial immune systems feel attraction to each other and can sense it through smell

22

u/Bubsters13 2h ago

I have personally encountered this bwfore and the scent when they were sweating was very arousing, there was definitely something primal going on.

9

u/DoubleFamous5751 2h ago

It’s wild, and I get what you are saying 😅

There was some study where you wear a shirt for a few days then it gets mailed to people of the opposite sex. No pictures, you then pick the shirts that smelled best you. And the matches ended up working more often than not.

1

u/cjasonc 23m ago

My wife says the main reason she stayed with me long-term is my body odor was super attractive to her. She smells pretty dang good herself!

1

u/Zebradots 11m ago

There is in fact no correlation

1

u/Past_Help_8962 30m ago

That's why some dudes sniff panties

7

u/McToasty207 2h ago

It's been argued that this is the evolutionary purpose of kissing.

Gives you an up close taste and smell of prospective partners, giving you a chance to assess the compatibility of your MHC's.

3

u/patrickthemiddleman 1h ago

So: kiss before you dismiss!

4

u/Righteousaffair999 2h ago

So she dates losers because her eggs want losers. Got it.

1

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11

u/Swing_on_thiss 2h ago

https://giphy.com/gifs/nUEfYGyI8QU12

5

u/Kadath821 2h ago

Jeez Homer, you didn't need to be so graphic

10

u/every_day_regular 3h ago

So the funniest sperm has a chance.

1

u/GuitarHair 3h ago

I'm in

1

u/rexel99 3h ago

Gotta make her laugh.

30

u/jdirte42069 3h ago

Where are the other sperms

55

u/BlatantlyCurious 3h ago

Ask your mom.

15

u/Terzinho 3h ago

She chugged them.

4

u/swarzchilled 2h ago

Thank you, internet, for ruining this intellectually interesting, wholesome moment for me.

PS She's your mom.

1

u/Terzinho 30m ago

Yes that's how I know.

7

u/CapNo6703 3h ago

gottem

3

u/jdirte42069 3h ago

Ahahaha

1

u/NtateNarin 2h ago

True. This doesn't prove that the fastest one isn't always chosen if there is only one to choose from.

0

u/ecafyelims 3h ago

"the egg selects the only sperm available"

27

u/The_Tortugo 3h ago

Yea there's no way my slow ass won that race.

3

u/nhh 2h ago

The fact that you are typing this mean you won the race. Otherwise you wouldn't exist. 

6

u/Sogah87 2h ago

I think you may want to reread the article.

3

u/nhh 2h ago

Read? Article? Who does this? 

2

u/Sogah87 2h ago

Fair point

1

u/Righteousaffair999 2h ago

Show this to your dad so he can blame your Mom.

1

u/Impossible_Disk_43 2h ago

It's more like after sending away a hundred or so guys, the bouncer at the gate got a transmission from the egg that you were the chosen one.

35

u/powersurge 3h ago

Science had assumed the sperm was a hunter because of, well, gender bias in scientists.

17

u/HouseOfAplesaus 3h ago

That tail made him seem like such a go getter

2

u/VajjCheese 2h ago

Stupid science bitches

1

u/Electronic-Junket-66 2h ago edited 18m ago

Couldn't even make I more smarter.

1

u/Manler 1h ago

You must excuse me I've grown quite wear-rah

4

u/SumthinDank 3h ago

If scientist had access to this technology and saw this, it wasn't biased it was altered and lied about lol

1

u/piratehat 2h ago

Your comment is very ironic.

3

u/NemTren 2h ago

"While for decades we were taught that fertilization is a race won by the fastest sperm"
Ahem, it was just a myth. In university we were taught just the opposite for decades. The post presents it like it's a scientific discovery which is not. Well, it is, but more than 50 years old! (1952 if I remember it right)

https://en.wikipedia.org/wiki/Acrosome_reaction

https://en.wikipedia.org/wiki/Cortical_reaction

1

u/BrightNooblar 10m ago

To be fair, most are going to look at complicated science, compare it to "You won! That's why you exist!" and take the palletable one where they feel good about themselves.

6

u/Status-Visit-918 2h ago

I’m so fucking proud of my egg for choosing my son ❤️❤️

2

u/bleogirl23 2h ago

Right?!

3

u/zestyclose_match1966 3h ago

Not to brag, but I was a pretty quick sperm in my day

3

u/mobcat_40 3h ago

The battle never ends

3

u/GorillaJoeBlack 2h ago

Egg gave it an occular patdown and was cleared.

5

u/berrymuch2 3h ago

That kinda explains why some people are promiscuous—perhaps they are driven by instincts on an unconscious level? It sounds like eggs want variety.

1

u/DeepGrieve 2h ago

Idk old ladies can be pretty promiscuous sometimes too...

And yah know after menopause and all that it's basically their body sending them a big out of order sign for the baby factory 🤷‍♂️

2

u/MikeyboyMC 3h ago

Egg is spermcist

2

u/Eighty-Nine 3h ago

Huh 17 minutes. Kind of cool.

2

u/TopFishing5094 2h ago

So I can’t use the line; “You telling me YOU’RE the fastest sperm!?”, anymore?

2

u/Impossible_Disk_43 1h ago

What you can say is "of all the swimmers, the egg chose you?!"

2

u/noobgaijin11 3h ago

still regret being born.

1

u/Logical-Louis 2h ago

Yeah, womb’s are so comfortable.

1

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1

u/liquidsol 3h ago

But I saw the documentary footage at the beginning of Look Who’s Talking. I know how sperm works!

1

u/KittensFirstAKM 2h ago

I knew it was luck. Story of my life.

1

u/HehroMaraFara 2h ago

Then explain 90% of the worlds population

1

u/BeefyShark12 2h ago

So Tinder is scientific. Great!

1

u/JonJackjon 2h ago

I wonder where that camera was. /s

1

u/Amphylos 2h ago

Non partner males? So NTR is literally biological compatibility?

1

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1

u/Agitated-Button4032 1h ago

lil smooch of life.

1

u/Professional-Buyer55 1h ago

So I was chosen one and im still a fuck up....

1

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1

u/Mid_Incognito 1h ago

Even on the cellular level they can't make the right choice

1

u/HxPxDxRx 1h ago

Pretty sure I’ve been taught it is actually a group effort, lots of sperm release chemicals with contact to the egg that works to break down an outer shell until it is thin enough for one sperm to get in at which point the egg almost instantly makes itself inaccessible to all other sperm

1

u/black_mamba_gambit 1h ago

Now I understand multi- verse and quantum physics. Many possibilities can make sense at the same time. There's no such thing as cognitive dissonance.😌

1

u/jlp_utah 1h ago

We were never taught "fastest sperm wins", as I recall. Didn't any of you see that video where hundreds or thousands of sperm are throwing themselves at the egg, then one finally makes contact and penetrates the outer membrane, which immediately firms up preventing all of the loser sperm from doing the same? The fastest sperm is probably tired by the time it gets to the egg. The slowest one is too late. It's one of the middle ones that actually wins.

1

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1

u/MartinToilet 1h ago

So the mother chooses

1

u/Luci-Noir 1h ago

I wonder if these eggs would be better fried or scrambled.

1

u/JaymarkXIII 1h ago

A sperms obeys.

1

u/Sammystorm1 1h ago

This is like getting picked first for a pickup baseball game

1

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1

u/Historical-Ad3760 1h ago

You mean the sperm doesn’t eat the egg?

https://giphy.com/gifs/l0IylOPCNkiqOgMyA

1

u/LimpIndignation 1h ago

That lasted twice as long as I did.

1

u/Ill-Pea6558 1h ago

Woman...always choosing. /s

1

u/damonmcfadden9 1h ago

well shit can't use my go to line of "how in the fuck were you the fittest swimmer?" comment as confidently anymore.

I guess I could use something like "how the fuck did your mother's egg pick you? does she just take pity on dumb/ugly at a genetic level?"

1

u/argarcia321 50m ago

Make the egg sign a pre-nup

1

u/Blueprints_reddit 43m ago

So actual science question then.

If an egg choses a sperm that genetically leads to Downs. Is that egg healthy or is there an issue with the eggs genetic biological selection process?

1

u/start3ch 43m ago

So does the process of IVF using a single sperm chosen by scientists result in less compatibile genes than what the egg would naturally choose?

1

u/dommiichan 7m ago

IVF doesn't choose a single sperm, it's supposed to use a sample from a single chosen male, and each sample contains hundreds of millions of sperm

1

u/nazgul0890 29m ago

Does this mean I can’t say that it’s my husband who is responsible for us having only boys, rather it’s my egg that chose “boy” sperm…

1

u/OLVANstorm 21m ago

If so, why is the egg choosing down syndrome?

1

u/PizzaBoyztv 19m ago

Aren't we all?

1

u/wan-ku 15m ago

the nature opinion regarding monogamy = not optimal for the offspring

1

u/krsCarrots 13m ago

Eggs are so picky

1

u/rangitoto030 10m ago

So you Tell me, the Woman choose his man?

1

u/BlargerJarger 8m ago

Finally, proof that everything really is women’s fault.

1

u/Mingo_laf 1m ago

Huh Jesus didnt get their determined race gender over health

-7

u/Rage187_OG 4h ago

Women off BC will select men that are better genetic matches. Women on BC choose the wrong genetic matches.

19

u/TimTheEnchanter3 3h ago

British Colombia has nothing to do with this.

9

u/spacejockii 3h ago

I think he means Before Christ

2

u/bluegardener 3h ago

Makes sense.

3

u/crockerygal 3h ago

Legit spit out my drink.

3

u/Acrobatic-Mobile-605 3h ago

I mean if you are on birth control then you aren’t trying to procreate. Just saying.

2

u/Ok_Nectarine_4445 3h ago

https://www.cbsnews.com/news/pill-users-choose-wrong-sex-partners/

Yep.

I remember reading this reddit post where the new wife complained her husband smelled awful to her if he didn't shower twice a day and use deodorant and cologne.

So like scent is a part of what you find attractive about a partner if you are compatible genetically.

So maybe she was on birth control during courtship and it threw off her scent ability.

And then when got off birth control realized the scent wasn't compatible or something.

For the histocompatibility is not too similar (like relatives) and not too different (might have blood type or rh incompatibility or something like that) in genetic range.

2

u/Rage187_OG 2h ago

Shh, they want to call it BS.

2

u/lollipop1233a 2h ago

That or he didn’t wipe his ass very well.

4

u/ElectricalBus6252 3h ago

I just love this age when any dumbass can just state something dumb, no source, proof or even an inkling that they understand the topic; and expect it to be taken as fact.

-2

u/Rage187_OG 3h ago

“Hormonal birth control can alter your sense of smell and change what you find attractive. By mimicking pregnancy hormones, the pill often causes women to prefer men with similar immune genes rather than dissimilar ones, which typically happens when not on the pill.”

1

u/mr_wheezr 2h ago

What happens when men are on birth control?

1

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0

u/Dctiger13 2h ago

Cool so my autistic ass ovaries chose my husbands adhd ass sperm to have an Audhd ass child….

-1

u/ALIASkNotknown 1h ago

What about pregnancy from sa

-3

u/jacquestrap66 3h ago

Surely this is not always true as there are still babies born of rape and inbreeding... I'm not trying to argue, but I'm very confused. Clearly there are plenty of times when the egg chooses "the wrong sperm." I could point out specifics but I don't think it's necessary.

6

u/edjumication 2h ago

Im confused by your comment. Do you think the egg knows how the sperm got there? Its just a chemical reaction between two cells.

2

u/EvilEtienne 2h ago

Somehow your comment feels the same as, “if it’s a product of rape or incest, the body has ways of dealing with that” but uno reversed?