I read somewhere that humans, if placed in a situation where they can’t tell what time it is, will revert to a 25 hour cycle. Right now we accomodate to a 24 schedule. A newsmagazine feature last week showed a grandmother that was actually on a 23 hour schedule, one of the fastest ever recorded. She went to bed at 5 in the evening and woke at 2 in the morning. Her daughter and granddaughter are the same way. They’re using this family in studies on sleep disorders, etc. because they’ve basically proven that their problem is genetic in nature.
A number of questions arise from this:
Is it possible to breed in a different sleep cycle that could change the entire life of humans? Can we find ways to reduce the amount of sleep we need?
Is our needing 25 hours linked in any way to the fact that Earth’s rotation is very close to that? Why aren’t we on, say, a 32 hours on, 16 hours off sequence rather than a 16/8 like now?
Would we be more comfortable on Mars, where there’s an extra 37 minutes to each day?
If we lived on Jupiter, where days are ~10 hours long, would humans be genetically predispositioned towards shorter sleep cycles?
Interesting. I have never heard that. If you think of the reference, let me know. I’d be curious to see whether it’s true or not.
No idea, but it sounds possible, doesn’t it? But I would guess that there is some lower limit (minimum number of hours needed).
Again, we’ll need to confirm the 25 hours claim, but I’d definitely say that our sleep pattern is linked to evolutionary history. A day-night sequence seems easier to get into than a 32-16 hour sequence. Hunt/gather during the daylight hours when things are visible and rest at night when things are not.
I’d certainly appreciate the extra sleep! That’s about how long I use the “snooze” button anyway! So, I could snooze and still be on time.
Perhaps we’d be really good at taking cat-naps instead of long sleeps.
Not much help here, but it’s an interesting question I wanted to chime in on.
Makes sense. Many millions of years of evolution on Earth would genetically adapt us into it’s day and nite cycle.
As to whether we would adapt into other planets day and nite cycles that’s a good question. I would generally tend to think not since we evolved under Earth’s cycle. However say Mars or some other planet with a similar cycle to Earth’s I think the adjustment could be made. But take an extreme difference where a cycle is 12 hours - I think we’d get pretty messed up as a result and adjustment would likely be nil.
Actually, Podkayne, when she was deprived of the ability to tell time, that’s exactly what happened. Why it’s different out in the real world, I have no idea. Possibly the same reason why humans with 25 hour days can adapt as well.
http://www.cbt.virginia.edu/tutorial/SLEEPWAKE1.html
gives information on the 25 hour day, which was originally proposed by the research of Jurgen Aschoff. Recent studies have apparently shown that it might not really be a 25 hour day after all.
I’ve been mulling a bit, and you pose some really interesting questions. We’re diurnal creatures, and before artificial lighting, we functioned best during the day, but why do we have to sleep every night? Obviously we tend to do stuff at night, and sleep during daylight hours, since the length of the day varies by time of year and latitude.
If we lived on a planet with a 10 hour period, would we stay awake for 15 hours (through a day and a night and a day) and sleep for just 5 hours during one of those nights? (And, I’m sure Ender knows, but perhaps casual readers do not: Nobody could live on Jupiter, since it’s a gas giant.)
I have a feeling that people vary widely in their natural cycles of arousal, and that the artificial constraints we place on ourselves are counterproductive.
I’ve been reading Are We Hardwired? by William R. Clark and Michael Grunstein lately, a pretty interesting account on current findings on the genetic basis of behavior and such. Coincidentally, the section I’m on is on circadian (and infra- and ultradian) rhythms.
Researchers have isolated genes that govern the circadian (“circadian” literally means “about a day” when you look at the etymology of it) rhythms of drosophila flies. The gene in question governs the steady production of a protein; at a certain level of it, the protein itself triggers the gene to shut off, whereupon the protein levels begin dropping. Under a lower threshold, you guessed it, the gene expression turns on again, and the cycle renews–about a day in length. This runs like clockwork when the flies are kept away from external day/night exposure.
Safe bet the same general governing mechanism is at work in humans–and no, not everyone runs on a 25 hour cycle, or a 23 hour cycle–our rhythms simply fall in the about-a-day range, and slippage is reset by exposure to sunlight.
Given that it’s genetic at the base, different cycles can certainly be bred in. The book I’m reading even makes mention of specific lab strains that have been selected to not express any circadian rhythm whatsoever–it’s not that they don’t sleep or whatnot, they simply don’t follow a regular pattern of it.
My guess is there’s subtle evolutionary benefit to having regular cycles and rhythms that mach fairly closely with day and night–and not a benefit to having those cycles locked in at a specific length. Circa is good, precisely either not good, or too much hassle without enough benefit to have evolved. Too far away is probably a bad thing.
If earth had a different rotational period, my firm bet is, yup, our rhythms would still be…about a day. However long the day we evolved in was.
That’s about how long I use the “snooze” button anyway! So, I could snooze and still be on time.