Re: Convergence leaves the evolutionist completely dumbfounded
- From: John Harshman <jharshman.diespamdie@xxxxxxxxxxx>
- Date: Mon, 19 Sep 2005 01:28:35 GMT
Steven J. wrote:
> "Kant" <Kant@xxxxxxxx> wrote in message
> news:AdnXe.32$mI6.904@xxxxxxxxxxxxxxxxxx
>
>>Since both the creation and evolutionary frameworks attempt to explain
>>biological convergence, an analysis of this feature of nature can be used
>>to evaluate the two paradigms. When critically assessed, the evolutionary
>>paradigm is found to be woefully inadequate when accounting for all the
>>facets of biological convergence. On the other hand, biological
>>convergence is readily explained by an origins model that evokes a single
>>Creator.
>>
>
> Note that "convergence" is often invoked to explain *dissimilarities* among
> superficially similar adaptions. The very different ways in which
> vertebrate forelimbs are modified to form the wings of pterosaurs, birds,
> and bats is a common example, as are the "box camera" eyes of vertebrates
> (with the infamous "inverted retina") and those of cephalopods (with their
> very different retina). One might expect a single Creator, if He is minded
> to re-use designs in different "kinds" (e.g. dolphins and cattle) to use the
> same design for octopus eyes and dolphin eyes, or for fruit bat and
> pterodactyl wings. Or, conversely, one might expect Him, if He sees fit to
> give pandas and people different thumb designs, to use different thumb
> designs for different "kinds" of primate. But one does not see this. The
> patterns of homology and convergence (analogy) ought to leave creationists
> dumbfounded.
>
>>One of the challenges that convergence creates for the evolutionary
>>paradigm is the frequency with which it occurs throughout life's history.
>>Convergence is a common characteristic of life. This commonness makes
>>little sense in light of evolutionary theory. If evolution is indeed
>>responsible for the diversity of life, one would expect convergence to be
>>extremely rare. The mechanism that drives the evolutionary process
>>consists of a large number of unpredictable, chance events that occur one
>>after another. Given this mechanism and the complexity and fine-tuning of
>>biological systems, it seems improbable that disparate evolutionary
>>pathways would ever lead to the same biological feature.4
>>
>
> Mutations are "unpredictable chance events." Natural selection is not.
> There is nothing at all odd (at least to any evolutionist) that no matter
> what mutations may occur in a bacterial colony in a penicillin-laced
> environment, the mutations that will spread through the population and
> become "fixed" (if they occur at all) are those that produce penicillin
> resistance. Different mutations (modifying bacterial metabolism in
> different ways) can and have conveyed such resistance; this is a simple
> example of "convergence." By the same token, similar selective pressures
> can favor different mutations to different starting structures to yield
> analogous results, whether wings, or eyes, or other structures.
>
>>Two remarkable examples of complex biological features recently recognized
>>as being convergent are bat echolocation (the ability of an organism to
>>orient itself based on perceiving reflections of sound it emits) and
>>parrot, songbird, and hummingbird forebrain structure. A recent DNA
>>sequence analysis has just confirmed two earlier studies that, from an
>>evolutionary perspective, requires echolocation in bats to have evolved
>>independently in two separate groups (microchiroptera and
>>megachiroptera).5, 6, 7 This study, along with previous analyses also
>>indicate that the strikingly similar limb structures of bats and flying
>>lemurs used for flying, likewise, must have evolved independently, when
>>the data is interpreted from an evolutionary perspective.
>>
>
> Any animal with the ability to make sounds and hear them can use a crude
> form of echolocation; echos of your own voice can give you a rough estimate
> of the size of some room or cave in the dark, for example. Sonar, like so
> many other features (e.g. wings, eyes, camoflage mimicry, etc.) is not an
> "all or nothing" phenomenon. If echolocation is sufficiently important to
> an organism's chances for survival, incremental improvements to it can be
> selected, until something quite sophisticated is reached. Note, by the way,
> that bats and flying lemurs presumably started from very similar beginning
> points (a primitive, generalized small eutherian mammal); similar selective
> pressures working on similar starting points should not surprise us if they
> produce similar outcomes.
>
>>Another recent study, employing behavioral differences in gene expression
>>in brain tissue, has demonstrated that the brain structure of
>>hummingbirds, songbirds, and parrots responsible for vocal learning (the
>>ability to "learn" vocalizations by imitation rather than by instinct) is
>>essentially identical.8, 9 This is surprising, since these three birds
>>are unrelated to one another. That is, the seven distinct structures in
>>the forebrain of these three groups of birds that are responsible for
>>vocal learning are convergent. From an evolutionary perspective, these
>>structures must have evolved independently of one another on three
>>separate occasions.
>>
>>http://www.reasons.org/resources/fff/2000issue04/index.shtml#convergence_evidence_for_a_single_creator
>>
>
> Certainly hummingbirds, songbirds, and parrots are related; all are neognath
> birds, more closely related to each other than to, e.g. ostriches. Is it
> the case that these brain structures are not found in birds that are, e.g.
> more closely related to songbirds than to parrots?
There may not be any such birds. For all we know, songbirds and parrots
form a clade.
> If not, shared
> inheritance from a common ancestor with these traits seems more plausible
> than convergence (indeed, even if some birds closely related to songbirds
> don't have all these features, could their relatives have lost them since
> the last common ancestor?). If none of these explanations suffice, then I
> would have to fall back, again, on the argument that similar selective
> pressures working on similar precursor structures can produce similar
> outcomes.
>
> -- Steven J.
>
>
.
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