[LEAPSECS] Bio cycles and dueling timescales (was Letters Blogatory)

Kevin Birth Kevin.Birth at qc.cuny.edu
Thu Mar 12 09:24:14 EDT 2015

You are correct to not call biological cycles "clocks."  Doing so is one
of my pet peeves, and I've recently published an article castigating the
psychophysics folks for doing so.  The reference to that is:

Birth, Kevin. 2014.  Non-clocklike Features of Psychological Timing and
Alternatives to the Clock Metaphor.  Timing and Time Perception

The bats, being mammals, have a SCN that is entrained by light/dark
cycles.  The repetition in their daily cycles is due to the interaction of
the SCN's two parts--the free-running part with a @24 period, and a
photosensitive part that resets the free-running part daily.  The
relationship of these two parts allow the bats to anticipate evening
twilight.  Most likely there are hormonal rhythms that get them up and
going that start to kick in a hour or so before twilight.  The reason why
they come out starting 7-9 minutes after sunset, despite seasonal
variability in daylight, is that the dorsal portion of the SCN is reset
each day (probably from a sunset cue), and then free-runs for @24 hours
until it is reset the next day.  The same sort of mechanism (although
involving the pineal) is is also why roosters' crows anticipate the dawn
(I also have an article on roosters if you are interested).  With roosters
I know that the hormone cycle that anticipates sunrise is a testosterone

There is one study that I know about nuclear subs.  Here is the reference:

Kelly, TL et al. 1999. Nonentrained circadian rhythms of melatonin in
sumbmariners scheduled to
an 18-hour day.  Journal of Biological Rhythms, 14: 190-196.

The Martian day is probably within the range that some people could
entrain to it--the bigger problem would probably be bureaucrats insisting
that anyone on Mars live by a UTC day, which would have them feeling like
they had jetlag within about a week.

While I know several anthropologists who have worked in Antarctica, I
don't know any chronobiological studies done there.  However, there is a
very interesting study of Eskimo that demonstrates that during the winter
months, they tend to experience day/night reversal of activity cycles
vis-a-vis UTC.  That study is:

Stern, Pamela. 2003.  Upside-Down and Backwards: Time Discipline in a
Canadian Inuit Town. Anthropologica 45:147-161.

I particularly like the Stern article because it demonstrates the tension
between what our bodies want to do and the rhythms structured by UTC + a
timezone offset.  As I said in my earlier post, what worries me somewhat
is biology's uninformed adoption of UTC as if it accurate replicates
natural cycles of light and darkness.

Unfortunately, I'm less familiar with the literature on annual cycles than
I am on circadian cycles.

If you want any of the references I mentioned but cannot get them
yourself, I can probably find copies and send you .pdf files. If that is
the case, you should email me off the list--publishers are persnickety
about distribution of electronic copies on list-servs.



Kevin K. Birth, Professor
Department of Anthropology
Queens College, City University of New York
65-30 Kissena Boulevard
Flushing, NY 11367
telephone: 718/997-5518

"We may live longer but we may be subject to peculiar contagion and
spiritual torpor or illiteracies of the imagination" --Wilson Harris

"Tempus est mundi instabilis motus, rerumque labentium cursus." --Hrabanus

On 3/11/15 6:39 PM, "Richard Clark" <rclark at noao.edu> wrote:

>I'm curious about the repeatability of natural biological cycles. I
>that most of them are actually triggered by external nonbiological cues
>rather than being 'biological clocks' in our sense of the word clock.
>Some that come to mind are annual. The swallows at Capistrano (and the
>buzzards at Hinkley). I'm not sure how precisely repeatable they actually
>are vs their popular representation.
>But one that I have directly observed is the large bat colony under the
>Campbell Ave bridge over the Rillito in Tucson. During June (Tucson
>doesn't have weather in June) they come out en mass starting 7-9 minutes
>after sunset. Very precisely, very repeatably. I imagine the cue is more
>the illumination level than an internal clock. Also some sort of social
>or aggrigate behavior may be involved. Later in the summer the mass exit
>is more diffuse.
>Some situations of humans adapting (or perhaps not adapting) to other day
>lengths that come to mind, other than shift work in general, that come to
>mind are the watch assignments on nuclear subs (repeats after 18 hours on
>US subs) and mission control operators for the first few months of a newly
>arived Mars lander (24h 39m). In the case of the Mars operators it's
>tempting to try to actually adapt to the 24.65 hr day. There can even be
>enough of them to form a group with some social identity, overlayed on
>their home life. Talk about problems of where to draw the line between two
>different timescales! The submariners actually are an isolated social
>group but 18 hr isn't a period humans are likely able to adapt to.
>What studies of these groups (and maybe South Pole winterovers too) have
>there been?
>Richard Clark
>Tucson, Az.
>On Wed, 11 Mar 2015, Kevin Birth wrote:
>> Solar time is good for humans, but as everyone on this list knows,
>>solar time is not the same as mean time or UTC.
>> From a chronobiological perspective, mammals have a small cluster of
>>neurons at the base of the hypothalamus called the suprachiasmatic
>>nucleus (SCN).  There are two parts to this structure.  The medial
>>portion has a robust free-running rhythm of around 24 hours plus or
>>minus about 15 minutes.  The two ventral portions connect to the optic
>>nerve and have no strong rhythm.  Instead, the ventral portions work to
>>reset the dorsal part so that the @24 hour rhythm always anticipates the
>>next sunrise regardless of seasonal variations in the length of the
>>daylight period (or the equation of time).  One could say that the SCN
>>is an evolutionary adaptation to Earth's foibles.
>> The SCN then operates quite differently from representations of solar
>>time, mean or apparent, which chart the rotational day.  In fact, the
>>SCN works much like some old forgotten systems of timekeeping like
>>Bohemian or Italian time, which reset every day.
>> The features of UTC that we celebrate--continuity, uniformity and
>>standardization--are features that are useful for measuring biological
>>cycles but warp our understanding of those cycles if we begin to think
>>of those cycles as having the same features of uniformity as UTC.  This
>>is true whether or not there are leap seconds.  One of the shortcomings
>>of modern chronobiology and psychophysics of time perception is that as
>>they move more and more into laboratory settings from field settings the
>>cycles are clock controlled, i.e., uniform.  As a result, a lot of
>>current biological science of timing is actually studying how well
>>organisms adapt to humanly created time cycles rather than environmental
>>cycles tied to the Earth's rotation and weather conditions.
>> Since many human activities are now structured by UTC and not circadian
>>rhythms, many of those activities are, in fact, unhealthy.  In a sense,
>>with regard to what Folkman worries about in his blog, the horse has
>>left the barn and galloped to the border, cleared customs, and now is in
>>another country and most people still don't know the barn door is open
>>much less the horse is gone.  The disconnect between social rhythms,
>>human biology, and apparent solar time began hundreds of years ago when
>>preference in timekeeping shifted in favor of mean time and 24 hour days
>>beginning at midnight, and this disconnect has been exacerbated by
>>artificial lighting.
>> Cheers,
>> Kevin
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