Received: by alpheratz.cpm.aca.mmu.ac.uk id GAA09541 (8.6.9/5.3[ref pg@gmsl.co.uk] for cpm.aca.mmu.ac.uk from fmb-majordomo@mmu.ac.uk); Thu, 9 Aug 2001 06:38:12 +0100 Date: Wed, 08 Aug 2001 22:36:05 -0700 From: Bill Spight <bspight@pacbell.net> Subject: Re: Convergence To: memetics@mmu.ac.uk Message-id: <3B722145.FC00CFD2@pacbell.net> Organization: Saybrook Graduate School X-Mailer: Mozilla 4.72 [en]C-CCK-MCD {Yahoo;YIP052400} (Win95; U) Content-type: text/plain; charset=us-ascii Content-transfer-encoding: 7BIT X-Accept-Language: en References: <3B708804.8677.7A8E14@localhost> <002b01c12046$1ab2a780$6787b2d1@teddace> Sender: fmb-majordomo@mmu.ac.uk Precedence: bulk Reply-To: memetics@mmu.ac.uk
Dear Ted,
> It's well known that atavistic traits commonly pop up among developing
> organisms. A feral pig is liable to develop tusks. Horses occasionally
> grow extra toes. Humans are sometimes born with a small tail. Such things
> can be expected if we do indeed resonate with past forms. But they can also
> be explained according to the genetic model. What can't be explained
> genetically is parallel evolution, or "convergence."
Convergent evolution is in fact a major support of the theory of
evolution.
> Among plants and
> animals, we continually find new examples of organisms widely separated in
> their phylogenetic derivation which nonetheless develop remarkably similar
> forms. In New Zealand we find many kinds of leaves common to Eurasia which
> serve to fend off herbivores that don't exist in New Zealand. There seems
> to be no reason why marsupials and mammals would develop such incredibly
> similar forms.
Don't be silly.
> Why should butterflies or fish of different species in
> different locations develop almost identical color patterns on their wings
> or scales? In some cases animals mimic others that are poisonous to
> predators and are thus avoided by predators along with the poisonous
> varieties. But this explanation fails to apply in the vast majority of
> cases.
>
> Dawkins discusses this dilemma in The Blind Watchmaker: "It is vanishingly
> improbable that the same evolutionary pathway should ever be followed twice.
> And it would seem similarly improbable, for the same statistical reasons,
> that two lines of evolution should converge on the same endpoint from
> different starting points. It is all the more striking... that numerous
> examples can be found in real nature, in which independent lines of
> eovlution appear to have converged, from very different starting points, on
> what looks very like the same end-point."
>
From which Dawkins draws the inference of morphic resonance. Right! ;-)
> According to Sheldrake's model, organic systems resonate with similar
> systems. We resonate with ourselves individually, with our species, and
> with any other species which is similar enough to our own. If flying
> squirrels, jerboas, and moles are all emerging in both Australia and
> Eurasia, they will be drawn into similar evolutionary pathways due to their
> resonance with each other. Outside of this model, there's no explanation
> for convergent evolution.
>
Puleaze!
First, there is the simple explanation of similarity of environments.
Aquatic mammals and fish provide a basic example.
Second, there are physical and chemical constraints that impose
structure. Example: similarities in structure of sunflowers, pine cones,
snail and nautilus shells.
Third, there is coincidence.
You need to find characteristics that do not contribute to the fitness
of the organism, and are not similar for physical or chemical reasons
(such as minimizing the use of resources), and then compare their
occurrence with a model that indicates how often such convergences occur
at random, and show that they occur too often. Otherwise, don't waste
your time.
The advent of computers has enabled us to see, by simulation, how
frequent random coincidences are. It is human nature to seek
explanations, and statistical argument alone leaves nagging doubts. Thus
people can easily believe that Design, whether by supernatural or by as
yet undiscovered natural means, is necessary to explain coincidences. It
appears that morphic resonance is one such principle of Design. It is
invoked without much consideration at all of other, scientific
explanation. And it assumes that there is no coincidence.
Even if there are patterns and structures in convergent evolution that
are not explained by general physical or chemical constraints nor by
fitness in similar environments, the phenomena that are to be explained
rely on human judgements of similarity. We make such judgements at the
drop of a hat. They should occur quite frequently for randomly arising
patterns. Without a model that predicts how often they occur for random
coincidences, there is no way to tell whether they occur too often for
that explanation.
Ciao,
Bill
===============================================================
This was distributed via the memetics list associated with the
Journal of Memetics - Evolutionary Models of Information Transmission
For information about the journal and the list (e.g. unsubscribing)
see: http://www.cpm.mmu.ac.uk/jom-emit
This archive was generated by hypermail 2b29 : Thu Aug 09 2001 - 06:42:28 BST