[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)
don ohmes wrote:
Perhaps "competitive exclusion" has some modern meaning I am
unfamiliar with, so I will substitute the term 'competitive
superiority' in it's stead.
That would be a different situation altogether. Competitive exclusion
simply refers to the expectation that the coefficient of competition
and the coefficient of selection will be negatively correlated over a
given time interval for a specific interaction set. Tests of this
expectation have met with mixed results. It clearly matters in many
cases, but may not dominate in others.
It is an essential component of the natural selection concept, and a
reality familiar to everyone.
Familiarity does not equate with applicability. Besides, I never said
exclusion was unimportant (in fact, I stated the opposite).
Mechanics are only relevant to evolution from the perspective of
natural selection, so it is considerably more accurate to say
"Mechanics are notoriously difficult to demonstrate, in fact, and it
is still uncertain how important they are in determining specific
Not true - mechanical constraints are often easy to quantify, are very
dependable metrics for certain problems, and have been demonstrated
convincingly to be a major aspect of biological evolution both in
modern populations and through evolutionary history.
True, but sometimes theory is misleading. Solar thermal power is more
"efficient" than photovoltaic panels (PV), for example. So when Google
funded (partially) a 720 acre solar power plant in the Mojave they
naturally went w/ solar thermal. However, the concentrators must be
washed w/ water twice a week to maintain that "efficiency"!!!
Yes, sometimes expectations are not met. If you can demonstrate where
I (and others) have made an error regarding the expected breakdown of
vorticity from flapping in most obligate glider planforms, then go for
it. The fluid dynamic equations are pretty robust, though.
No flying squirrel will ever increase glide length by waving it's paws
in mid-flight, but it is possible for selection to enhance control
motions that occur at the end of the glide.
Quite possible. There are also possibilities related to scrambling,
launching, and prey capture that could introduce flapping modes. It's
also quite possible that ancestral bats differed in critical details
from flying squirrels, in terms of planform and airfoil anchoring.
Until we have more information on the base of Chiroptera, these are
idle speculations at best.
I did not say that there was no competition. I continue to assume that
the competitive barriers faced by proto-birds as they achieved
lift-off were less than they would face in an environment filled w/
real birds. And bats.
Heh. Oh, do you have an example of "terrestrial origins for flight"?
As mentioned before, birds may very well be an example.
Or not. There is debate about that... :D
Question: if you were going to attempt to falsify an arboreal origin
for flight in a given group, how would you go about it? Your argument
that Archaeopteryx could maybe, possibly climb things and use them for
elevated leaps is fine - but it's also a sort of special pleading. The
outgroups to birds are terrestrial, the most basal birds appear to have
limited arboreal adaptations (if any), and birds have several exapted
traits that could make terrestrial launch possible (not to mention the
work on incline running). There might still be a mosaic of arboreal
and terrestrial stages mixed into the origin of avian flight (incline
running models, especially, suggest this), but that seems about as far
as we can go with it.
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181