Yeah that's (to me) a more accurate framing, also evolution is bad at revisions so even if there are minor disadvantages to a setup so long as it's not affecting your ability to have and raise kids it's basically completely absent as far as evolution is concerned. For example there are some wild inefficiencies in body layout left over from fish body patterns where the nerve from the brain to the voice box wraps down around your aortic arch because the relative position of the throat, brain, and heart were very different in fish so the path it took then was more direct. It happens in humans and most hilariously in giraffes where it goes all the day down their enormous necks.
and not even that, I'd narrow it further to not detrimental before and during the prime reproductive periods of a species. After that period, detrimental traits are totally fair game and more dependent on technology, culture, and family care dynamics. Heart disease later in life caused by genetic predisposition to high cholesterol isn't something people generally select for or against in a partner, but its effects happen later in life well after people have children so it passes on.
They can be detrimental too, especially if they're linked to beneficial traits. The test is ultimately whether or not the harm done is sufficiently disadvantageous that it interferes with reproductive fitness. Baldness is arguably detrimental, but it's linked to a bunch of recessive genes that function in other ways, and it doesn't impact us until we're likely to have already reproduced.
Peacocks with their giant tail feathers are my favorite example. They make flying really difficult, but they make attracting female mates much easier. The reproduction need wins.
Even if yawning in public affected sexual fitness: how long has it been socially impolite to yawn in public? Evolution takes a rather long time in species with long reproductive cycles. Almost all mammals yawn, it would take significant genetic changes to breed that out of us. That doesn't happen overnight.
Is that the right criteria? A trait must be completely, 100% disqualifying as a mate or else it sticks around?
Our ancestors used to have tails. We no longer have tails. Plenty of people wear artificial tails today and get laid, it's not a 100% disqualifying trait
Yawing seems like it must be adventurous, the contagious part not so much.
Even the mention of a yawn can trigger it.
Perhaps we are almost always in a state of needing a yawn, but the trigger is seldom met, and seeing or hearing about it is enough to make our brain go "oh yeah I forgot about that".
Perhaps yawning is actually underdeveloped and an ideal human would yawn at regular intervals without any prompting.
Just about all our behaviors are contagious. Scratching, deep breath, emotion, looking in a certain direction, sudden alertness. If yawning were different, that would be weird.
Most of those can also be done consciously though. Yawning is different. It is more inline with flatulence, crying, or vomiting. Actions that are in many ways, outside of our direct control.
> If an animal is drowsy or bored, it will be less alert than when fully awake and less prepared to spring into action. "Contagious" yawning could be an instinctual signal between group members to stay alert.
> Anecdotal evidence suggests that yawning helps increase a person's alertness.
> Paratroopers have been noted to yawn during the moments before
they exit their aircraft.
> yawning is not simply an intensified breath but a distinct cardiorespiratory manoeuvre that reorganizes neurofluid flow
Brilliant, I'll use that next time I yawn somewhere inappropriately.
The contagious nature of yawning is so weird. It has to be evolutionarily advantageous because it's so wide spread, but it's also non-obvious.
I literally yawned as I clicked on this article from my RSS reader. The contagious nature at the mere idea of a yawn is wild.
I yawned as I read the title on the frontpage. Smiled a bit when I read the rest of the comments. Contagious beyond physical proximity sure is wild.
I yawned when I read your comment.
Me too but I also wonder how much I'm influenced by knowing that that is supposed to happen.
A trait doesn’t have to be advantageous to persist just non-detrimental.
Yeah that's (to me) a more accurate framing, also evolution is bad at revisions so even if there are minor disadvantages to a setup so long as it's not affecting your ability to have and raise kids it's basically completely absent as far as evolution is concerned. For example there are some wild inefficiencies in body layout left over from fish body patterns where the nerve from the brain to the voice box wraps down around your aortic arch because the relative position of the throat, brain, and heart were very different in fish so the path it took then was more direct. It happens in humans and most hilariously in giraffes where it goes all the day down their enormous necks.
and not even that, I'd narrow it further to not detrimental before and during the prime reproductive periods of a species. After that period, detrimental traits are totally fair game and more dependent on technology, culture, and family care dynamics. Heart disease later in life caused by genetic predisposition to high cholesterol isn't something people generally select for or against in a partner, but its effects happen later in life well after people have children so it passes on.
They can be detrimental too, especially if they're linked to beneficial traits. The test is ultimately whether or not the harm done is sufficiently disadvantageous that it interferes with reproductive fitness. Baldness is arguably detrimental, but it's linked to a bunch of recessive genes that function in other ways, and it doesn't impact us until we're likely to have already reproduced.
That's a simplification, but you get the idea.
Peacocks with their giant tail feathers are my favorite example. They make flying really difficult, but they make attracting female mates much easier. The reproduction need wins.
It is detrimental though. It is socially impolite to yawn in public.
Edit: why am I being downvoted for this?
Even if yawning in public affected sexual fitness: how long has it been socially impolite to yawn in public? Evolution takes a rather long time in species with long reproductive cycles. Almost all mammals yawn, it would take significant genetic changes to breed that out of us. That doesn't happen overnight.
400-500 years minimum (15-20 generations), although point taken
I wonder if that has always been the case or if it is a modern thing (modern in the sense of our evolutionary history).
is it so detrimental that it leads to a person never finding a mate and reproducing? Maybe for a totally extreme outlier, but probably not
Is that the right criteria? A trait must be completely, 100% disqualifying as a mate or else it sticks around?
Our ancestors used to have tails. We no longer have tails. Plenty of people wear artificial tails today and get laid, it's not a 100% disqualifying trait
Natural selection doesn't require 100% disqualifying, it just needs a slight preference and a shit load of time.
Yes that is more along the lines I was thinking
>Plenty of people wear artificial tails today and get laid
…Do they? What did I miss?
Yawing seems like it must be adventurous, the contagious part not so much.
Even the mention of a yawn can trigger it.
Perhaps we are almost always in a state of needing a yawn, but the trigger is seldom met, and seeing or hearing about it is enough to make our brain go "oh yeah I forgot about that".
Perhaps yawning is actually underdeveloped and an ideal human would yawn at regular intervals without any prompting.
It's a bit like laughing. Synchronise the mood of the group. I assume other mammals have contagious yawns too?
Cats certainly do.
Strangely, dogs sneeze to show deference.
African wild dogs use sneezes to "vote" to make decisions. https://royalsocietypublishing.org/rspb/article/284/1862/201...
Is yawning contagious between species?
just reading the title made me yawn for real.
same here
It is strange how well yawning is conserved, even as far back as in reptiles, since it doesn't really seem to do anything.
Just about all our behaviors are contagious. Scratching, deep breath, emotion, looking in a certain direction, sudden alertness. If yawning were different, that would be weird.
Most of those can also be done consciously though. Yawning is different. It is more inline with flatulence, crying, or vomiting. Actions that are in many ways, outside of our direct control.
I can yawn on command. Rumbling my ears and edging swallowing it triggers a yawn 100% of the time
> If an animal is drowsy or bored, it will be less alert than when fully awake and less prepared to spring into action. "Contagious" yawning could be an instinctual signal between group members to stay alert.
> Anecdotal evidence suggests that yawning helps increase a person's alertness.
> Paratroopers have been noted to yawn during the moments before they exit their aircraft.
https://en.wikipedia.org/wiki/Yawn
https://archive.is/lTghJ
https://www.biorxiv.org/content/10.64898/2025.12.17.695005v1
Is that the paper in question?
> “Each individual seems to have what looks like an individual yawning signature”
I’m looking forward to “yawn to unlock”.
Also, what’s the deal with that article image?
paywall