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RE: new aspect of extinction
This is an interesting theory.
There is presumably more than one way to disrupt the photoperiod. I
tend to doubt that a near miss asteroid could induce enough wobble to do
this, however this is easily checked by calculating the size of asteroid
necessary to do this.
However, the main point of isn't the mechanism for disruption, the key
is that any sufficiently long term disruption of the correlation of
light and seasons would do it. I'm not an expert on how various
animals sense what Mr Pelly is calling photoperiod.
Plants grown in greenhouses are often manipulated in this way to induce
out of season blooming. Broadly speaking, most plants can be fooled via
one of two techniques - the spectrum of the light, or the length of the
day. Spectrum shifts toward red in winter (away from the equator)
because the sun is lower in the sky on average. Conversely to convince
them it's summer you need to use more bluish light. Other plants seem
to sense the duration of the day, and go into winter mode when the days
start to get shorter. Animals which are photoperiod sensitive could
sense these, and perhaps other cues.
The light spectum certainly would shift to the red after a impact, or
volcanic eruption due to dust in the atmosphere. This was noticible
with Mt St. Helens and Mt Pinatubo. Changing the day duration could
also be simulated - if dust clouds blocked enough light, you'd think
you were getting less.
This mechanism should have a strong correlation away from the equator,
because there is no photoperiod and no seasons to speak of near the
> -----Original Message-----
> From: Mike Brett-Surman [SMTP:MNHPB018@SIVM.SI.EDU]
> Sent: Monday, February 03, 1997 4:52 AM
> To: email@example.com
> Subject: new aspect of extinction
> From: David Pelly
> To: M.Brett-Surman, Smithsonian Institution.
> Date: Thu, 30 Jan 1997 23:03:54 -0800
> From: <firstname.lastname@example.org>
> Subject: another aspect of extinction theory
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
> I have been given permission to post this file to the DinoNet. please
> respond to Mr. Pelly Off-line at <email@example.com> with the phrase
> TO MR.PELLY in the subject line. Thanks.
> My name is Dave Pelley, and I am a supervisor in the Education
> Department at Sea World of Florida. I hate to take any of your
> time, but I could use your advice.
> Quite by accident roughly two years ago I stumbled upon something
> may be signifigant regarding the Cretaceous extinction, and I have
> quietly researching it on my own time (out of both curiosity and
> boredom!) since then. Its kind of crazy, and it had absolutley
> to do with dinosaurs originally, but I have come to the realization
> there is the slightest possibility that there may be some validity to
> this idea.
> Before I go any further, let me state clearly that I have no
> other than the satisfaction of my own curiosity, and that if anything
> were ever to come of this at this point I really wouldn't want
> to do with it.
> <snip> ,let me give it to you in a nutshell:
> I believe that for some reason (asteroid near miss perhaps), the
> seasonal photoperiod lengths of the Cretaceous period were suddenly
> drastically altered 65 million years ago, such that all organisms
> directly affected by photoperiod or those that lived in a
> food chain with organisms directly dependant on photoperiod could not
> adapt and were therefore selected against (talk about a run on
> <snip> let me explain my reasoning.
> I actually came across this idea one day while thinking about
> and their dependancy upon photoperiod. Being the odd biological type
> that I am, I was wondering to myself how much someone could "monkey
> around" with the penguin's photoperiod before they would finally
> exhibiting reproductive behavior. From there, it just kind of dawned
> me that this might be the crucial link that explains why certain
> and animals were selected against at the Cretaceous Extinction, while
> others were not. In fact, by creating a simple chart representing
> broad terms) the organisms alive today, a drastic and sudden change
> seasonal light cycles would result in an almost identical mass
> extinction. This explains why some seemingly hardy species went
> (dinos), and why other "delicate" species (like tropical frogs) did
> As we both know, being dependant upon seasonal light cues is not a
> "weakness" at all, it in fact makes good evolutionary sense. If you
> the seasons dictate when you do certain high-energy activities, you
> alot of extra time to save/store/obtain energy the rest of the year.
> Its a great strategy that should work because seasonal light cycles
> relatively fixed. What are the chances of an asteroid near misiing
> planet and changing our light cycles anyway? A billion to one? It
> is a
> good strategy that many ectotherms utilize, but it really cost them
> million years ago when the "impossible" happened. Obviously, I am
> of biased at this point, but no other theory explains the selectivity
> the marine and plant extinctions as well as this idea. Organisms
> were not sensitive to photperiodic cycles were fairly unscathed by
> mass extinctions, while the sensitive species were wiped out.
> a change in photoperiod would not neccessarily involve a signifigant
> temperature change, either (although it probably did).
> <snip> I think
> that the iridium layer is evidence of a meteor/asteroidal
> Although most have pointed to an impact as the cause of the
> (and I have no doubt of the bombardment), I feel that it was the one
> that missed us that actually did the damage. The gravitational
> of a really big asteroid just missing us would be enough to cause a
> slight "wobble" of the earth on it's axis, which would explain the
> sudden and drastic change in the seasonal light cycles. The effects
> this, of course, would be catastrophic. Dinosaurs would be waiting
> light cues cues to induce migration and/or breeding that would never
> come, or they would have had a total change literally overnight of
> seasons as they knew them (thus disrupting nesting, migration, etc.).
> Photoperiod change explains the "fern spike" at the end of the
> Cretaceous, and the temporary decline in angiosperms. It explains
> corals were selected against, but most fish were not.
> Ok, that's it. This is the simple, condensed version and I
> you taking time to look at it. If there is anything to this idea,
> please advise me as to what to do. I have amassed a large file of
> but I'm done with it and ready to "move on" to other things that I am
> interested in. Do I just file it away as a neat hobby that gave me
> something to do in my spare time for a couple of years, or is there
> validity to this? If it would help someone out, they are more than
> welcome to have what I have compiled from my resources.
> Again, thanks for your time, I realize you probably get stuff like
> all the time, so I appreciate your patience.
> This theory has spurred some lively
> debates with all my biologist-crony friends down here, but most were
> pretty open to it. Hope it made for some good reading!
> Dave Pelley
> Mike Brett-Surman firstname.lastname@example.org
> or at email@example.com
> Smithsonian Institution (not "institute" ;-)