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Re: Airbagged(was Dive!Dive!Dive!)

In a message dated 96-11-06 16:06:14 EST, znc14@ttacs1.ttu.edu (Jonathan R.
Wagner) writes:

>   I do not see how the natural:unnatural dichotomy is related to the
> quadrapedality:bipedality dichotomy.  To me the word "unnatural" (quotes
> notwithstanding) indicates something that is "against the natural order", or
> "not found in the natural system", "artificial", or "sinful".  I guess it
> has to do with some use of quotation marks which was never taught to me...
>         Would you care to elaborate on exactly what the relationship you
> were attempting to connote was? >>

Here's the definition of "unnatural" I had in mind: "at variance with the
character or nature of a person, animal, or plant" (from the Random House
Dictionary 2nd unabridged edition). Since quadrupedality is apomorphic for

[That's twice you've done that... I think you mean plesiomorphic
 because bipedality is apomorphic relative to quadrupedality.  Or do
 you mean relative to other Crossopterygians or something? -- MR ]

tetrapods, bipedality, the derived state, can be considered unnatural--at
variance with the "nature" of tetrapods. Perhaps not the best choice of word,
but not entirely off the wall, either. In this sense, incidentally, snakes
and caecilians could be considered even more "uunatural" than bipedal
tetrapods such as humans, birds, and kangaroos.

> It sure sounded to me like you were executing another
> terse-yet-inflammatory "bipedality cannot be explained except by my theory"
> snipe.  At the time, I could see no other reason for either a) restating the
> obvious, or b) using the word "unnatural".  Please accept my most sincere
> apologies for misjudging you.

Apologies accepted. The only point I was trying to make here was that
bipedality is a character state or condition peculiar enough among tetrapods
to justify requiring an explanation. I wasn't even trying to push the BCF
explanation. LN Jeff said, "The largest runners alive today are all
quadrapeds. If they trip with one set of legs, they have another set of legs
to keep them from falling." This very clearly describes the heightened danger
faced by a large bipedal cursorial animal--something that, I think, evolution
would "naturally" select against rather than for. Since we know that bipedal
tetrapods >have< evolved, however, we can infer that there did exist
circumstances or lifestyles, likely rare and unusual, in which the evolution
of bipedality is selected for, in spite of the danger of having only two legs
instead of all four for running. Can you now see why I chose to use the word
"unnatural" in this context?