Received: by alpheratz.cpm.aca.mmu.ac.uk id MAA01478 (8.6.9/5.3[ref pg@gmsl.co.uk] for cpm.aca.mmu.ac.uk from fmb-bounces@mmu.ac.uk); Fri, 24 Aug 2001 12:56:51 +0100 Message-ID: <2D1C159B783DD211808A006008062D3101746043@inchna.stir.ac.uk> From: Vincent Campbell <v.p.campbell@stir.ac.uk> To: "'memetics@mmu.ac.uk'" <memetics@mmu.ac.uk> Subject: FW: Dawkins & Convergent Evolution- the final word (?) Date: Fri, 24 Aug 2001 12:40:09 +0100 X-Mailer: Internet Mail Service (5.5.2650.21) Content-Type: text/plain; charset="iso-8859-1" X-Filter-Info: UoS MailScan 0.1 [D 1] Sender: fmb-bounces@mmu.ac.uk Precedence: bulk Reply-To: memetics@mmu.ac.uk
Again, for Ted (and anyone else who missed it).
> ----------
> From: Vincent Campbell
> Sent: Wednesday, August 15, 2001 11:25 am
> To: 'memetics@mmu.ac.uk'
> Subject: Dawkins & Convergent Evolution- the final word (?)
>
> Hi everyone,
>
> Before the Joe/Ted dispute gets too personal (too late...) I though I'd
> check out Ted's use of Dawkins to show that convergent evolution can't be
> explained by genes alone, offering a hole for MR to fill. I should say I
> don't believe Ted ever claimed Dawkins believes in MR. But, this is the
> way Ted quoted Dawkins from 'The Blind Watchmaker':
>
> <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.">
>
> This mis-represents what Dawkins was saying significantly. The passage is
> from a chapter in the book where Dawkins is going through various aspecys
> of natural selection- such as its gradual nature (he does the classic 5%
> of the eye argument), and immediately prior to the couple of paragraphs
> Ted quotes, he's talking about "Dollo's Law" which says that evolution is
> irreversible- that is it is highly statistically improbable that exactly
> the same evolutionary trajectory could be followed twice in either
> direction (p. 94). He concludes the paragraph with the sentence 'It
> [Dollo's Law] follows simply from the elementary laws of probability'.
>
> He goes on:-
>
> 'For just the same reason, it is vanishingly improbable that exactly the
> same evolutionary pathway should ever be travelled twice. And it would
> seem improbable, for the same statistical reasons, that two lines of
> evolution should converge on exactly the same endpoint from different
> starting points.
>
> It is all the more striking a testimony to the power of natural selection,
> therefore, that numerous examples can be found in real nature, in which
> independent lines of evolution appear to have converged, from very
> different starting points, on what looks very like the same endpoint.
> When we look in detail we find- it would be very worrying if we didn't-
> that the convergence is not total. The different lines of evolution
> betray their independent origins in numerous points of detail. For
> instance, octopus eyes are very like ours, but the wires leading from
> their photocells don't point forwards towards the light, as ours do.
> Octopus eyes are, in this respect, more 'sensibly' designed. They have
> arrived at a similar endpoint, from a very different starting point. And
> the fact is betrayed in details like this.
>
> Such superficially convergent resemblances are oftene extremely striking,
> and I shall devote the rest of this chapter to some of them. They provide
> impressive demonstrations of the power of natural selection to put
> together good designs. Yet the fact that the superficially similar
> designs also differ, testifies to their independent evolutionary origins
> and histories. The basic rationale is that, if a design is good enough to
> evolve once, the same design principle is good enough to evolve twice,
> from different starting points, in different parts of the animal kingdom.
> This is nowhere better illustrated than in the case we used for our basic
> illustration of good desing itself- echolocation.'
>
> [nb: original emphasis]
>
> He goes on to talk about echolocation in two unrelated species of bird,
> whales and dolphins; about electrolocation used by a couple of unrelated
> species of weak electric fish- the remarkably similarity between is spoilt
> by the rather obvious difference that the African variety has a fin alll
> the way along it's back, the South American variety, all along its belly;
> about periodical cicadas who all have either 13 or 17 year long juvenile
> stages (he says no-one knows exactly why, although the fact that 13 and 17
> are prime numbers may allow the cicadas to exploit gaps in the
> reproductive cycle of would be predators); he gets broader in comparing at
> length the development of the Old World, South America and Australia,
> comparing different 'trades' (e.g. anteating) that produced similar
> animals independently in these regions; he finishes with talking about
> similarities and differences between ants and termites, and then driver
> ants and army ants.
>
> Dawkins seems to me to be very clear on the matter, and there's nothing to
> suggest here that there's some mystery over convergence that needs a
> theory like MR to explain it.
>
> Sheldrake is equally clear (just visit his website) that he thinks dogs
> are psychic and people can tell when they're being stared at. Sheldrake
> seems to me be offering one of the most important lessons, particularly
> for those of us in academia, that people who successfully enter academia
> are not necessarily any more credible as a result. Indeed they can be
> just as looney as anyone else. He seems to me to be suffering from a very
> common problem, personal incredulity at the wonder of the natural world
> stemming from such a simple process that he has to believe there's
> something more to it. I suppose at least he's come up with his own
> 'Answer', and not just followed the the other true believer herds.
>
> [An aside- the recent tribute to Douglas Adams on the BBC, included a
> sequence from an interview with Adams where someone had said that the
> answer to 'What is 6 times 9' did equal 42 in base 13... Sheldrake strikes
> me very much as thinking in ways that characters in Adams' books tend to.]
>
> Vincent
>
-- The University of Stirling is a university established in Scotland by charter at Stirling, FK9 4LA. Privileged/Confidential Information may be contained in this message. If you are not the addressee indicated in this message (or responsible for delivery of the message to such person), you may not disclose, copy or deliver this message to anyone and any action taken or omitted to be taken in reliance on it, is prohibited and may be unlawful. In such case, you should destroy this message and kindly notify the sender by reply email. Please advise immediately if you or your employer do not consent to Internet email for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of the University of Stirling shall be understood as neither given nor endorsed by it.=============================================================== 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 : Fri Aug 24 2001 - 13:01:26 BST