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Re: Paleo Find ("Millennium Man")



> >> Flight evolving neither from the trees or from the ground??
> >
> >Er... through the water. Sounds like pseudoscience or like the hardly
> >supported hypothesis that humans had semiaquatic ancestors, but it is
better
> >than both. I got the idea from
>
> Yeah, the Oreopithecus theory.  I had a chance to see the type specimen in
Florence.  It's a nice specimen...but I don't really buy the
semiaquatic-ancestor theory.

*Oreopithecus* was fully terrestrial and bipedal convergently to humans,
according to the popular article I read about it, and the latest paper on
semiaquatic ancestors for humans (which I still don't buy) in New Scientist
doesn't mention it.

> >Klaus Ebel: On the origin of flight in *Archaeopteryx* and in pterosaurs,
N.
> >Jb. Geol. Paläont. Abh. 202(3), 269 -- 285 [Dezember 1996].

Someone asked for this reference.

> >The arboreal hypothesis has a few big problems. One is the transition
from
> >parachuter to glider (not actually necessary) and the transition from
glider
> >to flyer (necessary). Why don't birds have ordinary patagia? Pterosaurs
had
> >hair (or was it dinofuzz???) and developed patagia instead of wing
feathers.
>
> Oh, I didn't say that the arboreal hypothesis doesn't have problems :-)  I
challenge anybody to find a hypothesis regarding >the evolution of avian
flight that doesn't have any problems.  However, to me, flight evolving from
the trees down makes >more sense ecologically and biologically.  Chiappe et
al. (I believe it was them) did come out with a paper last year showing
>mathematical evidence that Archaeopteryx could generate enough lift to fly
simply by running.  That's great, but I still think it >would have been much
easier for flight to evolve from the trees down.  I don't think that the
transition from glider to flier was >that impossible...and I certainly think
that it may have been easier, biologically, than the transition from runner
to flier.

I don't support the ground-up hypothesis. The aforementioned paper (p.
274f.) contains the following paragraphs:

"Arguments against the cursorial hypothesis

    It is not so easy to find objective arguments against the cursorial
hypothesis, but certainly not because it appears more plausible than the
arboreal hypothesis. [...]
    The weakness of the cursorial hypothesis consists in its inability to
explain why flight should develop [evolve] in a bipedal runner (Peters
1985). No physical principle can be found on which such a development might
be based. [...] A selection pressure can be attributed to the exploitation
of a new food source. Recent ground dwelling birds having lost their flight
ability in part or completely demonstrate that flight itself is not worth
striving for in any case. Our domestic hen (*Gallus*) is still capable of
flying but does not like to do it unnecessarily.
    Although the hitherto debated ideas (trees-down, ground-up) cannot yield
a convincing explanation for the origin of flight they appear to be
defended, despite weak points, mainly because no alternatives are in sight,
consequently one of them should be correct. However, none of these models
can plausibly explain the perhaps most important aspect of bird flight,
namely the evolution of the wingstroke which solely can lead to a gain of
altitude (Gautier & Padian 1985)."

And then follows an alternative...