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Or - a change in those fluids makes me yawn?
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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
When the woods in eastern Africa changed into savannah, we shifted to two legs and adopted a persistence hunting strategy. The tail became useless, even a liability, and mutations that resulted in reduced tails were not selected against anymore.
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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…
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.
> 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.
Distinctly remember being outraged.
Makes more sense I suppose if yawning isn't just signalling sleepiness to do it even while asleep!
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 assumed it was a kind of warning system: "Another member of the tribe detected impairment/fatigue and took measures to become more alert, perhaps you should raise alertness also."
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.
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.
Same goes for sneezing, actually that's even worse for driving, I literally don't see anything for a second at least. Sometimes can be blocked, sometimes not so much.
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It is detrimental though. It is socially impolite to yawn in public. Edit: why am I being downvoted for this?
> It is socially impolite to yawn in public. No, it isn't. It can be socially impolite to yawn unexcused , when someone is talking to you , as it has come to be interpreted as boredom rather than tiredness or similar. But it isn't inherently impolite to, for instance, yawn when walking down the street, or in a setting where someone isn't talking to you.
What you describe is in my opinion true for western cultures. In Brazil they are not so relaxed about it. Asia even less so.
Reminds me of a recent finding that attention lapses in a sleep-deprived brain correlate with flushing of cerebrospinal fluid (almost a garbage collection pause). https://news.ycombinator.com/item?id=45771636
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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
>Plenty of people wear artificial tails today and get laid …Do they? What did I miss?
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> It is socially impolite to yawn in public. No, it isn't. It can be socially impolite to yawn unexcused , when someone is talking to you , as it has come to be interpreted as boredom rather than tiredness or similar. But it isn't inherently impolite to, for instance, yawn when walking down the street, or in a setting where someone isn't talking to you.
In my (limited) experience it is quite culturally dependent. What you describe is in my opinion true for western cultures. In Brazil they are not so relaxed about it. Asia even less so.