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Re: AW: The Karate New Papers



-- On Sat, 6/12/10, evelyn sobielski <koreke77@yahoo.de> wrote:

> > Padian, K., and Horner, J.R. 2010. The evolution of
> > 'bizarre structures' in dinosaurs: biomechanics,
> sexual
> > selection, social selection or species recognition?
> Journal
> > of Zoology. doi: 10.1111/j.1469-7998.2010.00719.x.
> > 
> > ABSTRACT: 'Bizarre structures' in dinosaurs have four
> main
> > traditional explanations: mechanical function, sexual
> > selection, social selection and species recognition.
> Any of
> > these can be plausible for individual species, but
> they fail
> > to be persuasive when other lines of evidence cannot
> > adequately test them. The first three also fail as
> general
> > propositions when phylogenetic analyses based on
> other
> > characters do not support scenarios of selective
> improvement
> > of such functions in their clade (or the explanation
> simply
> > does not apply to any other species in the clade).
> Moreover,
> > the hypothesis of sexual selection requires
> significant
> > sexual dimorphism, which has never been conclusively
> > established in dinosaurs.
> >      We propose instead that species
> > recognition may have been a more general force that
> drove
> > the evolution of bizarre structures in dinosaurs. That
> is,
> > the bizarre structures communicate to other
> individuals a
> > variety of possible associational cues, including
> species
> > identification, potential protection and social habits
> and
> > the appropriateness of potential mates. In other
> words,
> > bizarre structures amount to an advertisement for
> positive
> > association. Neither species recognition nor any
> other
> > hypothesis should be a 'default' explanation.
> Although
> > direct observation is impossible, we propose two
> tests.
> > First, contrary to adaptive, social or sexual
> selection,
> > under the species recognition model morphology should
> be
> > expected to evolve without obvious directional
> trends,
> > because the only objective is to differ from one's
> > relatives. Hence, patterns of e
nd
> > non-directional. Second, several contemporaneous
> species
> > should overlap in geographic range (sympatric,
> parapatric,
> > peripatric). Fossil species often show evidence of
> this
> > pattern in the past by 'ghost ranges' of related taxa.
> These
> > tests together could reinforce or weaken an argument
> for
> > species recognition.

> That's pretty interesting. Species recognition via
> morphology - particularly when such extreme anatomical
> features are involved - indicates against more easily
> achieved means of species recognition, namely those found in
> extant dinos: color and voice. 

Perhaps "extreme anatomical features" weren't so difficult to achieve, if one 
assumes that dinosaur hatchlings were "imprinted" at hatching, something like 
baby ducks. 

Imagine a species that is generic in shape. Assume for simplicity that there 
are 10 adult "characters" imprinted on the young of that species at hatching 
that serve as "positive advertisements". Then assume that a heritable mutation 
appears infrequently that is visually obvious, perhaps a bump on the forehead. 
The young of these individuals now have 11 "identifiers" imprinted on their 
brains. Conspecifics imprinted w/ only 10 identifiers will still find all 10 
identifiers in the "bump" mutation group, so there might be no selection 
whatsoever *against* bumps. Those imprinted w/ 11 ids would still find 10 out 
of 11 ids in "non-bump" individuals and so might not shun non-bump individuals 
in the absence of bumped individuals, but still might show preference to bumped 
individuals when they are present. Therefore -- bumps are not selected against 
by those that do not have them, but bumps are preferred by those that do have 
them, or whose parents had them. It
 seems likely that "soon" everyone would have bumps.

Obviously, this assumes some parent/hatchling association at hatching, and also 
that the presence of a single anomalous visual character would not negate the 
presence of pre-existing positive identifiers, whether they were visual, 
auditory, tactile or olfactory...

> A hollow crest may still be
> involved in species-specific sound production, but spine,
> sails, massive crests etc for which a species-recognition
> function is the best hypothesis would imply that the animal
> was (perhaps apart from the recognition feature) cryptically
> colored, and not very vocal (perhaps apart from
> ULF-frequency vocalizations).
> 
> Particularly significant for restorations/CGI
> reconstructions. Dinos (and other -sauri) have become quite
> colorful in the last decade's artwork, and they have been
> walking the Mesozoic landscape hollering and bellowing ever
> since the first stop-motion movies. Always struck me as odd;
> living animals take care not to vocalize needlessly either,
> and for those that do vocalize much, it is usually related
> to species recognition.

Must have been a very intense cacophony at sunrise, though, judging by birds...