jrg13 at psu.edu
Wed Sep 16 23:28:27 EDT 1998
In response to my comment that
>> I don't think history has to be necessarily less scientific,
Rikki Hall said
>Sure it does. History can not be repeated nor directly observed.
This fact just means that the science of history cannot be evaluated by the
same criteria as direct observation or repeated experiments
(manipulations), not that its less scientific.
>> but in this
>> case I would agree as the particular causes invoked here are pure
>> speculation without any empirical basis that I am aware of. Primarily,
>> the invokation of predation pressures is simply an extrapolation of
>> selection as it is observed in the present.
>1. Extant mayflies, and many other insects as well, form mating swarms.
>2. Insects and arthropods of all sorts are heavily exploited food
>3. Numerous studies have demonstrated the validity of sexual selection,
>or a correlation between the possession of some trait and mating
>4. Dispersal is a fundamental trait of anything that grows, reproduces,
>Unless you want to assume that the past was radically different from the
>present, then it is fair to extrapolate these empirical facts backwards
Maybe, maybe not. These empirical (and not so empirical - number 4
fundamental is a theoretically very loaded term) observations may certainly
be used in making extrapolations, but these extrapolations are themselves
subject to assumptions that themselves reflect theoretical bias, so I still
feel my statement that the speculations made about these particular events
no empirical basis.
Truly, we should assume time invariance unless we have reason
>to think otherwise. The fossil evidence from the time of insect
>emergence strongly suggests that the stage was the same as it is today,
>with only the players being different.
>Do you have any reason to think that the planet was radically different
>back then? That is a huge supposition, and I would need a whole lot of
I'm not macking any such suggestion, just pointing out the speculative (and
theory based) reasoning was not empirically based (i.e. there is no direct
inference that such predation pressures were operative, even if they
may theoretically have.
>I'm having a hard time understanding this objection. I think that your
>understanding of natural selection is different than mine, so I will try
>to explain mine briefly. Forget the phrase "survival of the fittest",
>please, everyone: never utter it again. Natural selection is a positive
>force better described by the phrase "persistence of the fecund". It
>deals with reproductive success, with death or failure to mate being
>merely the null case of zero reproductive success. Natural selection
>says that existence will follow the vector of maximum reproductive
No problem with that description. It agrees with my understanding I think.
>The gilled members were not wiped out
they had to be within the population upon which selection was supposed to
have been taking place, at least as I would understand it.
They are the larval stage.
>Wings evolved in the adult, reproductive stage, but they are made of the
>same genes as those which make gills.
Are you familiar with the term
>"serial homology"? "gene duplication"?
yes. The question with this is still whether selection was necessarily the
operative factor in the evolution of these characters.
>Once the abdominal and thoracic gills became independent by virtue of
>this duplication mutation, you essentially have a new structure, not yet
>a wing, but a protowing. It didn't have to become a wing at this point,
>but it did, and flight did evolve.
No problem with that
>> > Were the insects necessarily "invaders"?
>OK, let's just say that they colonized a new environment, specifically
>an aquatic environment which was less oxygenated and less saline. I'm
>not sure why it matters whether this colonization was passive or active.
It has different implications for how selection may work in evolution
Sincerely, John Grehan
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