Message-Id: <3.0.5.32.19990426092022.0080abb0@rongenet.sk.ca>
Date: Mon, 26 Apr 1999 09:20:22 -0600
To: memetics@mmu.ac.uk, "'memetics@mmu.ac.uk'" <memetics@mmu.ac.uk>
From: Lloyd Robertson <hawkeye@rongenet.sk.ca>
Subject: RE: Darwin and Lamarck
In-Reply-To: <2CDFE2C8F598D21197C800C04F911B200CAF6B@DELTA.newhouse.akzo
In essense, how is this different from breeding dogs for a particular trait?
(nothing new below)
At 09:05 AM 26/04/99 +0200, Gatherer, D. (Derek) wrote:
>
>Chris:
>
>'.......then I saw
>some research on fruit flies which Lynn Margolis had ( don't know who did
>it) which
>showed very clearly that changes to an adult fly caused by environmental
>factors
>where then somehow transmitted through subsequent generations, and not via
>the conventional DNA etc.I don't recall much of the detail.'
>
>I think this must be Margolis referring to the experiments Waddington did
>back in the mid-1950s. Fruit fly eggs were treated with ether and it was
>found that the flies that were born from these eggs had cross-veins in
>unusual places on their wings. Waddington found that there was a dose
>response curve: more ether, more cross-veins. This is a teratological
>effect, rather like administering thalidomide to human mothers causes birth
>defects etc.
>
>But then Waddington lowered the dose to a level where very few flies
>developed cross-veins. These were deemed to be ether-sensitive flies.
>Breeding them together for several generations, and maintaining the
>selection pressure, it was possible to get ether-super-sensitive flies.
>Eventually Waddington obtained flies that were born cross-veined without
>exposure to ether.
>
>This is genetic assimilation. The initial cross-veined phenotype was a
>cellular response to an environmental toxin. But within the fly population
>there is genetic variation which can contribute to a a greater tendency to
>display that cellular response. Continued selection for the 'learned'
>response, increases the frequencies of the appropriate alleles, so that the
>degree of environmental insult required to produce the response becomes less
>and less as the generations pass. Eventually the response is constitutitve.
>
>As far as I'm aware there aren't too many other examples of genetic
>assimilation that are as well studied as this. The relevance of the idea to
>memetics is that in situations where learned behaviours are very necessesary
>to survival, there will be selection for any genetic variation which either
>
>a) makes production of the learned behaviour easier
>b) can make production of the learned behaviour instinctive, thus avoiding
>the need for learning at all.
>
>So what begins as memetic ends up as genetic (but only if the selection
>pressure is sustained for long enough, and only if there is the required
>genetic variation in the population)
>
>The question is: has this really happened in human evolution??? I struggle
>to think of an original example. Dennett has some in Consciousness
>Explained.
>
>Derek
>
>===============================================================
>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 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